Knee Extensor-Focused Biomechanical Intervention for Pain, Posture, and Disability in Non-Specific Low Back Pain: A Randomized Controlled Trial
Phase: NA
Conditions: Non Specific Low Back Pain
Sponsor: Lincoln University College

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Official Title of the Study: 
Knee Extensor-Focused Biomechanical Intervention For Pain, Posture, and Disability in Non-
Specific Low Back Pain: A Randomized Controlled Trial 
 
NCT Number: 
Pending 
 
Date: 
01 November 2025 
 
 
 
 
 
 
 

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Contents 
CHAPTER I .................................................................................................................................. 4 
INTRODUCTION......................................................................................................................... 4 
1. 
Introduction to the chapter............................................................................................. 4 
1.1- 
Background ...................................................................................................................... 4 
1.3. 
Research Objectives ........................................................................................................ 8 
1.3.1 
General objective ............................................................................................................. 8 
1.3.2 
Secondary objectives ....................................................................................................... 8 
1.5 
Research Hypotheses ....................................................................................................... 9 
1.6 
Research Significance .....................................................................................................11 
1.7 
 Scope of the study ......................................................................................................... 12 
1.8 
Definition of terms ......................................................................................................... 12 
1.9 
Summary ........................................................................................................................ 13 
CHAPTER 2 ................................................................................................................................ 14 
LITERATURE REVIEW ........................................................................................................... 14 
2. 
Introduction to chapter ................................................................................................. 14 
2.1 
Lumbar Spine ................................................................................................................ 14 
2.1.1 
 IVD and facet joints ..................................................................................................... 15 
2.4 
Assessment for LBP ....................................................................................... 19 
2.4.1 
Low Back Pain (LBP) Intensity ....................................................................... 19 
2.4.2 Lumbar Posture .................................................................................................. 19 
2.4.3  
Muscle Strength ............................................................................................. 20 
2.4.4 
 Functional Ability and Health-related Quality of Life ...................................... 22 
2.5 
Exercise-Based Interventions for Non-Specific Low Back Pain (NLBP) ................. 22 
2.6 
Knee extensor training (Open kinetic chain versus Closed kinetic chain) ............... 23 
CHAPTER 3 ................................................................................................................................ 28 
METHODOLOGY ..................................................................................................................... 28 
3 
Introduction ................................................................................................................... 28 
3.1 
Research Design ............................................................................................................. 28 
3.2 
Research Setting ............................................................................................................ 28 

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3.3 
Research population and sampling techniques. .......................................................... 29 
3.3.1 
Research population ...................................................................................................... 29 
3.3.2 
Sampling technique ....................................................................................................... 29 
3.3.4 
Randomization ............................................................................................................... 30 
3.4 
Selection criteria ............................................................................................ 30 
3.4.2 
Exclusion criteria: ......................................................................................................... 30 
3.5. 
Data collection procedure ............................................................................................. 31 
3.6- Flow of the Study ................................................................................................ 33 
3.7 
Outcome Measures ........................................................................................................ 34 
3.7.1 
Primary outcome: .......................................................................................................... 34 
3.7.2 
Secondary outcome: ...................................................................................................... 34 
3.8 
Rehabilitation protocol (8 weeks)................................................................................. 37 
3.9 
Description of variables. ............................................................................................... 40 
3.9.1 
The independent variables ............................................................................................ 40 
3.9.2 
The dependent variables: .............................................................................................. 41 
3.10 
Data Analysis Process .................................................................................................... 41 
3.10.1 Exploratory data analysis ............................................................................................. 41 
3.10.2 Data analysis approach ................................................................................................. 41 
3.11 
Ethical considerations ................................................................................................... 42 
3.12 
Limitations of the study ................................................................................................ 42 
3.13 
Summary ........................................................................................................................ 42 
3.14 
Research Gantt Chart ................................................................................................... 43 
References .................................................................................................................................... 45 
Appendix I ................................................................................................................................... 57 
Appendix II .................................................................................................................................. 59 
Appendix III ................................................................................................................................ 61 
 

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CHAPTER I 
INTRODUCTION 
 
1. Introduction to the chapter  
The following chapter will provide a concise background on low back pain especially 
nonspecific low back pain (NLBP), including its prevalence and impact. Additionally, it will 
clarify the relationship between the spinal column and the lower extremities, discussing how they 
are considered a single entity. Furthermore, this chapter will outline the research problem, aim, 
significance, objectives, research questions, and hypotheses. 
1.1- 
Background  
Low back pain is defined as pain in the back of the body that is severe enough to prevent 
the individuals from engaging in daily activities for more than a day, extending from the lower 
edge of the twelfth ribs to the lower gluteal folds, with or without pain in the lower extremities 
(Hayden et al.,2019). It lasts for at least a day and spreads from below the costal margin to the 
gluteal folds, with or without referred pain in one or both legs (Elmannan et al., 2021). Pain in the 
lumbar region, sacral spine, or S1 to sacrococcygeal junction region is referred to as axial 
lumbosacral back pain. Due to nerve or dorsal root ganglion compressions, radicular leg pain 
spreads along the dermatomal distribution to the lower extremity. In contrast, referred pain is felt 
in a location separate from its source, following a non-dermatomal route (Urits et al., 2019). 
LBP is a common musculoskeletal problem worldwide. Between 1990 and 2017, the 
number of people with LBP increased from 377.5 million to 577 million. In 2017, LBP remained 
the primary cause of disability worldwide (Wu et al., 2020). Approximately 619 million 
individuals worldwide were impacted by LBP in 2020 (with a 95% uncertainty interval of 554–
694 million), and projections estimate 843 million (ranging from 759 to 933 million) cases by 
2050 (Ferreira et al., 2023).  
Most individuals who experience LBP are diagnosed with NLBP which is considered a 
diagnosis of exclusion. This term encompasses diverse symptoms and presentations that cannot be 

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attributed to a specific, recognizable pathology, such as fractures, rheumatoid arthritis, infections, 
neoplasms, or metastases (Hayden et al., 2019).  
The prevalence of LBP ranged from 63.8% to 89% in Saudi Arabia. Approximately 80% 
to 90% of all cases of low back pain are NLBP, which most likely results from the interplay of 
biological, psychological, and social variables (Aldera et al., 2020). The prevalence and 
complexity of LBP can affect any age which included young children, teenagers, and adults 
(World Health Organization, 2023). Age-related changes in both the structure and physiology of 
the body contribute to high disability rates among those with NLBP (Özsoy & İlçin, 2021) 
geriatric adults who aged 80 years and above. It was discovered that females were more likely 
than males to have LBP and was observed to increase with age. Women are more prone than men 
to LBP, with peak rates between the ages of 50 and 55 years (Vos et al., 2019).   
Several modifiable risk factors are associated with NLBP, particularly occupationnal 
hazard such as prolonged standing and manual labor involving lifting heavy weights (Chiarotto 
& Koes, 2022). For instance, a study in Saudi Arabia reported a high prevalence (46.3%) of 
physical disability related to NSLBP among male soldiers (Sidiq et al., 2021). Similarly, 65.6% 
nurses in Qassim, Saudi Arabia reported experiencing NSLBP (Elmannan et al., 2021). 
Physiotherapists were the most prevalent healthcare professionals with LBP (89%), whereas 
teachers were the least prevalent (63.8%) (Aldera et al., 2020). Additional adjustable variables 
were sedentary lifestyle (including obesity), psychological variables (including depression and 
anxiety), and previous LBP episodes (Chiarotto & Koes, 2022).  
Earlier literature indicated that patients with NLBP frequently have problems in social life, 
prefer to avoid employment, which ultimately impacts their quality of life (QOL) (Keeley et al., 
2008; Zou et al., 2019). Nieminen et al. (2021) noted that untreated NLBP may lead to bad 
prognosis and disability.  
Moreover, LBP may cause considerable economic losses. The treatment costs, as well as 
other expenditures on LBP in healthcare, are very high. In a study by Al Amer (2020), 15.3% of 
Saudi Arabian LBP workers missed work, 29.2% of them reported limited work activity, and 
24.1% reported a reduced working hours. The consequences of LBP for health workers include 
limited social, leisure, and daily activities, as well as requesting medical care, and even surgical 
intervention (Aseri et al., 2019). Previous studies have demonstrated a strong correlation between 

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recurrent LBP and a higher likelihood of leaving salaried employment for health-related reasons 
(Kim et al., 2019). Additionally, LBP can lead to several psychological and physical issues as well 
as affect the healthcare system, especially concerning increased healthcare expenses and work 
absences (Kim et al., 2019). So, early detection and treatment of nonspecific LBP can greatly lower 
medical expenses and employee absenteeism. 
Rehabilitation of LBP depends mainly on exercise and behavioral interventions with 
medication coming as the second option for intervention (Chiarotto & Koes, 2022). However, there 
was no single exercise that was shown to be more effective than another in decreasing the 
symptoms and recurrent episodes of LBP (Essman & Lin, 2022). In systematic reviews (N> 200 
randomized trials) reported that most exercises had helpful effects on relieving pain and 
developing functioning (Hayden et al, 2021).  
Common interventions for LBP include walking, aerobic exercise, yoga, and Pilates. 
However, no single exercise modality has demonstrated superior effectiveness in reducing 
symptoms or preventing recurrence of LBP (Essman & Lin, 2022). Walking has been explored as 
a cost-effective alternative to structured trunk muscle exercise programs for managing low back 
pain (LBP), with studies reporting no significant differences in pain and disability outcomes 
between the two approaches (Vanti et al., 2019). Variations in walking duration or modality may 
influence outcomes, suggesting the need for further research. 
Aerobic exercise prescriptions for individual with LBP specifically engage weight-bearing, 
low-impact, moderate-intensity activities- defined as 40%–60% of heart rate reserve, performed 5 
to 7 days per week. For those with low baseline activity levels, shorter sessions of 10 to 15 minutes 
may be initiated, with gradual progression toward the recommended 150 minutes per week. In the 
case where weight-bearing exercise is contraindicated or poorly tolerance, aquatic exercises 
including swimming have demonstrated effectiveness in managing chronic pain. It is essential to 
evaluate the individualized’ s baseline fitness to appropriately tailor exercises intensity and 
duration (Pocovi et al, 2022). 
1.2 
Statement of the Problem  
Most rehabilitation protocols for NLBP primarily focus on the axial body, which includes 
the spine, shoulder girdle, and pelvic girdle (Kwok et al, 2021). Most of the NLBP studies focus 

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on lumbar stabilization, core stabilizer or hip musculature, with limited exploration of distal kinetic 
chain elements like the knee extensors training (Li et al, 2023).  
With reference to the biomechanical linkage between the knee and lumbar spine, the distal 
joints of the lower limb play a critical role in maintaining mechanical balance and functional 
alignment of proximal joints and the spine (Escamilla et al., 2010; Youdas et al., 2024). While open 
kinetic chain (OKC) and closed kinetic chain (CKC) exercises are widely compared in orthopedic 
and sports rehabilitation, few studies have analyzed their differential effects on kinetic chain 
function in populations with NLBP (Sadeghi et al., 2024).  
In past exercise programs, trunk and core muscle activities have not frequently incorporated 
lower limb involvement to overall movement synergy and load distribution (Grooten et al., 2022). 
Furthermore, the transfer effects of lower limb training on trunk control are not well understood, 
and little evidence is available on the potential impact of strengthening the knee extensors, 
especially in the context of different kinetic chains, on posture, pelvic control, or lumbar spine 
stability of individuals with NLBP (Lindblom et al., 2023; Escamilla et al., 2010).  
The knee extensor muscles, like the quadriceps, contribute to the upright posture, body 
weight support, and ground reaction force absorption (Escamilla et al., 2010). Compensatory 
loading patterns in the lumbar spine can result from dysfunctional lower limb biomechanics. 
Investigating the impact of interventions, including corrective exercises to enhance the knee 
position, can be helpful to clinicians to understand the factors of LBP management and prevention 
strategy of chronicity and recurrent LBP (Abbasi et al., 2024). Thus, with no clinical comparisons 
between OKC and CKC training being conducted in the NLBP setting, the present study design 
was intended to investigate how two alternative approaches might affect the intensity of pain, 
lumbar posture and quality of life (QOL) of patients with NLBP. The study is committed to offer 
important insights and knowledge that can support the designing of future interventions of this 
population. It is worth considering the knee during NSLBP rehabilitation since it will help to 
maximize the alignment of the kinetic chain, reduce lumbar strain, and improve overall movement 
patterns. 

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1.3.       Research Objectives 
1.3.1 
General objective 
To examine the impacts of open kinetic chain (OKC) and closed kinetic chain (CKC) knee 
extensor strengthening activities on pain, postural control, lumbar lordosis and core stabilizer, as 
well as functional disability in adults with NLBP. 
1.3.2 
Secondary objectives  
1.3.1 To contrast the outcomes of open and closed kinetic chain knee extensor strengthening 
training with conventional training (lumbar stabilization training) on pain, lumbar 
curvature, postural control, and disability in patients with non-specific low back pain. 
1.3.2.  To compare the effects of open kinetic chain knee extensor strengthening on pain, lumbar 
curvature, postural control, and disability compared to closed kinetic chain exercises in 
individuals with non-specific low back pain? 
1.3.3  To compare the effects of open kinetic chain knee extensor strengthening on pain, lumbar 
curvature, postural control, and disability compared to conventional lumbar muscle 
exercises in individuals with non-specific low back pain? 
1.3.4  To compare the effects of closed kinetic chain knee extensor strengthening on pain, lumbar 
curvature, postural control, and disability compared to conventional lumbar muscle 
exercises in individuals with non-specific low back pain? 
1.3.5 To investigate the effects of open kinetic chain knee extensor strengthening on pain, lumbar 
curvature, postural control, and disability in individuals with non-specific low back pain? 
1.3.6 To investigate the effects of closed kinetic chain knee extensor strengthening on pain, 
lumbar curvature, postural control, and disability in individuals with non-specific low back 
pain? 
1.3.7 To investigate the effects of conventional lumbar extensor strengthening on pain, lumbar 
curvature, postural control, and disability in individuals with non-specific low back pain? 

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1.4 
Research Questions  
1.4.1 What are the comparative effects of open and closed kinetic chain knee extensor 
strengthening exercises versus lumbar stabilization exercises on lumbar curvature, postural 
control, and disability in individuals with non-specific low back pain? 
1.4.2. How does open kinetic chain knee extensor strengthening affect pain, functional capacity, 
and lumbar spine stability compared to closed kinetic chain exercises in individuals with 
non-specific low back pain? 
1.4.3 What is the effect of open kinetic chain knee extensor strengthening on pain, functional 
capacity, and lumbar spine stability compared to conventional lumbar muscle exercises in 
individuals with non-specific low back pain? 
1.4.4 What is the effect of closed kinetic chain knee extensor strengthening on pain, functional 
capacity, and lumbar spine stability compared to conventional lumbar muscle exercises in 
individuals with non-specific low back pain? 
1.4.5 What is the effect of post open kinetic chain knee extensor strengthening on pain, functional 
capacity, and lumbar spine stability in individuals with non-specific low back pain? 
1.4.6 What is the effect of post close kinetic chain knee extensor strengthening on pain, functional 
capacity, and lumbar spine stability in individuals with non-specific low back pain? 
1.4.7 What is the effect of post conventional lumbar extensor strengthening on pain, functional 
capacity, and lumbar spine stability in individuals with non-specific low back pain? 
1.5 
Research Hypotheses 
1.5.1. H0: There are no significant differences in lumbar curvature, postural control, or disability 
outcomes among individuals with non-specific low back pain following closed kinetic chain, 
open kinetic chain, or lumbar stabilization exercises. 
 
H1: There will be significant differences in lumbar curvature, postural control, or disability 
outcomes among individuals with non-specific low back pain following closed kinetic chain, 
open kinetic chain, or lumbar stabilization exercises. 

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1.5.2- H0: Open kinetic chain knee extensor strengthening does not lead to greater improvements 
in lumbar curvature, postural control, and disability compared to close kinetic chain or 
lumbar stabilization exercises in individuals with non-specific low back pain 
 
H1: Open kinetic chain knee extensor strengthening will lead to greater improvements in 
lumbar curvature, postural control, or disability compared to close kinetic chain or lumbar 
stabilization exercises in individuals with non-specific low back pain 
1.5.3- H0: Open kinetic chain knee extensor strengthening does not lead to greater improvements 
in lumbar curvature, postural control, and disability compared to conventional lumbar muscle 
exercises in individuals with non-specific low back pain 
 
H1: Open kinetic chain knee extensor strengthening will lead to greater improvements in 
lumbar curvature, postural control, or disability compared to conventional lumbar muscle 
exercises in individuals with non-specific low back pain 
1.5.4- H0: Closed kinetic chain knee extensor strengthening does not lead to greater improvements 
in lumbar curvature, postural control, and disability compared to conventional lumbar muscle 
exercises in individuals with non-specific low back pain 
 
H1: Closed kinetic chain knee extensor strengthening will lead to greater improvements in 
lumbar curvature, postural control, or disability compared to conventional lumbar muscle 
exercises in individuals with non-specific low back pain 
1.5.5- H0: There are no significant improvements in lumbar curvature, postural control, and 
disability post open kinetic chain knee extensor strengthening in individuals with non-
specific low back pain 
H1: There are significant improvements in lumbar curvature, postural control, and disability 
post open kinetic chain knee extensor strengthening exercises in individuals with non-
specific low back pain 
1.5.6 H0: There are no significant improvements in lumbar curvature, postural control, and 
disability post close kinetic chain knee extensor strengthening in individuals with non-
specific low back pain 

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H1: There are significant improvements in lumbar curvature, postural control, and disability 
post close kinetic chain knee extensor strengthening exercises in individuals with non-
specific low back pain 
1.5.7 H0: There are no significant improvements in lumbar curvature, postural control, and 
disability post conventional lumbar muscle exercises in individuals with non-specific low 
back pain 
 
H1: There are significant improvements in lumbar curvature, postural control, and disability 
post conventional lumbar muscle exercises in individuals with non-specific low back pain 
1.6 
Research Significance  
 1.6.1  New knowledge 
 Previous research often treats spine and lower limb problems as separate entities, but 
emerging models (e.g., “knee–spine syndrome”) suggest an integrated biomechanical relationship. 
This present study's finding helps to bridge this gap by investigating how open vs closed kinetic 
chain knee exercises affect lumbar alignment. Exploring the neuromuscular and postural linkage 
between the knee extensors and lumbopelvic control. Hence, it contributes novel insights into 
kinetic chain rehabilitation, which is underexplored in NLBP populations. It evaluates a novel, 
functional intervention with potentially wide clinical applicability. 
1.6.2    Clinical Relevance 
This present study targets a non-spinal intervention (knee training) to address a spinal 
condition (NLBP)—which is novel and clinically relevant. The finding of present study may 
inform that knee chain extensor training improves lumbar lordosis and postural control, it offers a 
non-invasive, low-cost alternative or adjunct to conventional back-focused therapies. Results may 
inform whether CKC or OKC is more beneficial for improving functional outcomes. The clinicians 
could better tailor lower limb strengthening interventions that may indirectly affect spinal posture 
and improve functional disability and QOL. 
1.6.3  Future research 
This study highlights the need for long-term kinetic chain effects and cross-joint 
rehabilitation strategies in larger multicentre trials.  

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1.7 
 Scope of the study 
This clinical trial will be conducted among adult male participants aged 40 to 60 years 
diagnosed with NSLBP, in the western region of Saudi Arabia, specifically in Taif. The primary 
objective is to investigate the effect of incorporating knee extensor strengthening exercises into 
the rehabilitation program for adult patients with non-specific low back pain (NSLBP). The 
intervention will utilize knee chain training and conventional lumbar muscle training techniques 
targeting the knee extensors to determine the most effective approach for improving the 
aforementioned outcomes. The study will focus on the following outcome measures: lumbar spine 
posture, assessed via X-ray using the Cobb angle method, pain intensity, measured using the 
Numerical Pain Rating Scale (NPRS); quality of life (QOL) evaluated using the validated Arabic 
version of the Oswestry Disability Index (ODI); and lastly isometric knee extensor strength, 
measured using a handheld dynamometer. 
1.8 
Definition of terms 
1.8.1 Non-specific low back pain: Back pain without a distinct nociceptive reason, with or 
without leg pain (Hayden et al., 2019). 
1.8.2  Isometric strength: Isometric contractions are performed without joint motion and the 
muscle length remains constant (Dunleavy & Slowik, 2019) 
1.8.3  Cobb angle for lumbar lordosis:    
A line is drawn through the first lumbar vertebra's superior endplate on a lateral lumbar 
radiograph, followed by a second line parallel to the fifth lumbar vertebra's inferior 
endplate. Perpendicular lines are then created, and the angle formed at their intersection is 
measured (Furlanetto et al., 2018). 
1.8.4  Ten repetition maximum: the greatest load for which 10 consecutive repetitions could be 
completed (Monteiro et al. 2019). 
1.8.5  Functional disability: refers to limitations or impairments in a person’s ability to perform 
everyday activities that are essential for independent living (Baradaran et al., 2020). 
1.8.6  Quality of life: the individual's overall well-being, encompassing physical, psychological, 
and social aspects of their life (Cieza et al., 2021). 

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1.8.7 Lumbar extensor exercises: strength-training or rehabilitation movements that specifically 
target the lumbar extensor muscles to improve spinal stability and function (Raza et al., 
2021). 
1.8.8  
Core stabilizer training: exercises aimed at activating and strengthening the deep muscles 
of the trunk, such as the transversus abdominis and multifidus, to enhance spinal control 
(Akuthota & Ferreiro, 2020). 
1.8.9  
Closed kinetic chain exercise: are movements where the distal segment (e.g., foot or hand) 
is fixed, and multiple joints move simultaneously. These exercises promote joint stability 
and functional movement (Nagai et al., 2020). 
1.8.10  Open kinetic chain exercise: are those in which the distal segment is free to move, 
typically targeting a specific muscle group in non-weight-bearing positions (Delgado-
Payán et al., 2019). 
1.8.11 Knee extensor training: Knee extensor training is a set of exercises that helps to 
strengthen the quadriceps, which is crucial in the process of knee extension and lower limb 
function (Krupa et al., 2023). 
1.9 
Summary 
This chapter briefly introduces the purpose of the current study, which is to incorporate 
knee extensor training as a new intervention in the rehabilitation program for adult patients with 
NLBP. It also emphasises the need to incorporate lower limb training in spinal rehabilitation. 
Emergent models (e.g. "knee-spine syndrome") imply a biomechanical interaction.  
 
 
The research design focuses on a biomechanical connection that has been ignored in the 
conventional management of back pain. It fills an existing evidence gap about the importance of 
knee extensor kinetic chain training on enhancing spinal outcomes.  
 
 
 

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CHAPTER 2 
LITERATURE REVIEW 
 
2. 
Introduction to chapter 
This chapter will lay the theoretical groundwork for the current project by addressing all 
necessary aspects to support the study's concept and aid in completing the practical component. It 
will review previous research that has examined fundamental topics related to the current study. 
Key subjects to be discussed include the lumbar spine, LBP, the interaction between the lower 
limbs and the spine, mechanical alterations in the knee joint of patients with LBP, and protocols 
for strengthening knee extensors. 
2.1 
Lumbar Spine  
The lumbar spine is an important part of the human body, which includes both active and 
passive components to support a person in maintaining a posture, allowing motion, and carrying 
significant loads during the daily routine. Active structures, primarily muscles, regulate movement 
and coordination, whereas passive features, including bones, ligaments, and intervertebral discs, 
provide stability to the spine, limit ROM, and protect the neural structures within the spinal canal 
(Widmer et al., 2020). 
Its strong structure helps withstand huge mechanical loads, such as frequent blows of 
walking, jumping, and lifting (Desmoulin et al., 2020). It undergoes great stresses and strains when 
performing heavy load activities, such as carrying heavy things (Frost et al., 2019). In addition, it 
provides stability needed without functional mobility loss, particularly in the trunk and in the 
pelvic region. 
The lumbar spine is practically held accountable to support the weight transmitted by the 
upper body and adapt to various postural and dynamic loads (Frost et al., 2019). It provides a 
maximum flexion-extension range of over 50 degrees, and each of its vertebral segments provides 
about 7°–7.5° of rotational motion (Pourahmadi et al., 2021; Haughton et al., 2002). This type of 
biomechanical feature ensures the spinal cord security and mobility in different physical activities. 

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2.1.1  IVD and facet joints  
The human spine is composed of a series of anatomical structures that make it both stable 
and mobile. The most important of these are the intervertebral discs (IVDs) that exist between the 
vertebral bodies and a system of supporting ligaments. Important spinal ligaments are the anterior 
longitudinal ligament connecting the anterior surfaces of the vertebral bodies, the posterior 
longitudinal ligament connecting with the posterior vertebral cortex and the ligamentum flavum 
that connects the laminae of the adjacent vertebrae. Other stabilizing structures are the 
intertransverse ligaments, which connect the transverse processes, interspinous and supraspinous 
ligaments, which are found along the dorsal spinous processes. 
Functionally, the spinal motion segment (known as the articular triad or three-joint 
complex) consists of an intervertebral disc and two facet (zygapophyseal) joints. This three 
dimensional articulation forms the basis of biomechanical versatility of the spine. The IVD, which 
is surrounded by cartilaginous end plates, gives segmental mechanical stability, limits movement 
between the vertebrae, and maintains facet joint alignment (Mohd Isa et al., 2022a). The facet 
joints, which are created by the articular cartilage and are surrounded by fibrous capsules, provide 
passive mechanical resistance and limit excessive movement, especially during axial rotation and 
extension (Widmer et al., 2020). The combination of the disc and facet joints allows the 
physiological movement of the spine, reduces the likelihood of mechanical injury and helps to 
protect against low back pain (Han et al., 2023). 
All passive spinal structures of ligaments, discs, and joints have a particular part in 
maintaining a stable spine, determined by their anatomy and biomechanical characteristics. 
Nevertheless, long-term mechanical stress and aging are identified as the causes of progressive 
wear and tear of these components, weakening their performance and frequently causing 
dislocation or pain (Widmer et al., 2020). It is important to note that IVD degeneration, which is a 
major cause of low back pain in 26-42% of patients, is associated with decreased nucleus pulposus 
(NP) progenitor cell and impaired intrinsic regenerative ability (Mohd Isa et al., 2022b). The 
degenerative changes, including the loss of disc height, may change the transmission of axial loads 
and cause the inferior articular process to compress the adjacent structures during extension, which 
entraps the capsule and results in pain (Inoue et al., 2020). Furthermore, facet joint degeneration, 
which often progresses concurrently with disc degeneration, is implicated in conditions such as 

16 
 
degenerative spondylolisthesis and contributes to facet osteoarthritis through biomechanical 
dysfunction (Inoue et al., 2020). 
2.2  
Lumbar Spine and Lower Limb 
The spine takes the shape of an inverted pendulum, with the weight of the upper body 
resting upon a slender, standing-up column. Stability in this analogy is attained with a moving base 
of support, just like balancing a pencil on a fingertip when the pencil (the spine) starts to lean, 
stability is gained by moving the fingertip (representing the lower limbs) to place the center of 
gravity back on the base (Zeinali et al., 2008). Applying this model to human biomechanics, the 
hip, knee, and ankle joints act together in providing stability to the posture by modifying in the 
sagittal and multiplanar directions, especially during functional activities. This neuromechanical 
interaction is an effective model to explain compensatory processes and disturbed movement 
patterns in persons with low back pain (LBP) (McGregor & Hukins, 2009). 
In addition to this interdependence, Jean Felix Dubousset has proposed a cone of economy 
model that explains a dynamic balance, where the skeletal system holds an upright position with a 
minimum muscular force when the line of gravity lies within a narrow cone of movement 
(Hasegawa and Dubousset, 2022). This cone is increased in musculoskeletal dysfunctional patients 
due to compensatory muscular recruitment, which denotes the unstable posture that predisposes 
the risk of pain and functional constraints (Shu et al., 2020). 
The sagittal plane of posture position is particularly vulnerable to alterations of the center 
of gravity. The anterior shift of the gravity line can result in the following compensatory changes: 
the reduction of thoracic kyphosis, back pelvic tilt, hip extension, and knee flexion (resulting in 
LBP) (Takahashi et al., 2021). With sagittal global malalignment, individuals can also respond by 
flexion of the lower extremity, reduction of lumbar lordosis, and rearward rotation of the pelvis 
(Yagi et al., 2017). 
A significant association occurs between lower lumbar lordosis (<30°) and limited 
extension of the knee. Patients with >5° knee-extension limit are susceptible to significant lumbar 
curvature reductions (Shimizu et al., 2020; Teraguchi et al., 2021). These alterations are age-
dependent, implying a biomechanical connection between degenerative alterations in knee joints 
and spinal positioning, known as the “knee-spine syndrome” (Shimizu et al., 2020). 

17 
 
Upon surpassing the capacity for establishing pelvic retroversion as a compensatory 
mechanism, the additional compensatory mechanisms include more hip extension and knee 
flexion. This is found to be negatively correlated with lumbar lordosis, a fact that underscores the 
inter-relationship between lower limb and spinal biomechanics (Obeid et al., 2011).  
Coordinated muscular activation between the lower limbs and the trunk affects the 
lumbopelvic stability as one of the determinants of spinal health. The successful transfer of force 
along the chain of movements depends on hip strength, neuromuscular control, and lower limb 
joint mobility (De Sousa et al., 2019; Nelson et al., 2008). Disruptions in this system (lumbar spine, 
pelvis, hips, or knees) may cause changes in the load distribution and mechanical instability (De 
Sousa et al., 2019). 
Both mechanical and functional impairments of individuals with LBP have been attributed 
to abnormal lower limb mechanics. These results confirm the hypothesis that spinal and lower limb 
pathomechanics are not independent, but related (Farahpour et al., 2018; Madabi et al., 2020). 
Moreover, a lack of mobility or lower extremity weakness can enhance lumbar compensatory 
movement, which can aggravate or cause LBP. 
The etiology behind low back pain cannot be viewed as spinal condition, but rather it results 
from a local interdependence between the spine, pelvis and lower extremities (McGregor and 
Hukins, 2009). This becomes particularly applicable considering the fact that around 90% of LBP 
cases are non-specific with no concrete structural pathology by definition (Han et al., 2023). 
2.3 
Relationship Between Hip, Knee Function, and Low Back Pain (LBP) 
There is emerging evidence of a biomechanical and functional interdependence between 
the knee and hip joints and the presence or maintenance of low back pain (LBP). Whilst high-
quality studies are scarce, a few studies indicate that there is a significant relationship between 
lower limb joint alignment and LBP (Abbasi et al., 2024). Rahimi et al. (2020) established that 
LBP individuals have exhibited decreased knee flexion at the late stance phase of gait, which 
reflect changes in lower limb kinematics. Knee posture and alignment abnormalities can also cause 
muscle imbalances in the lower extremities and spinal muscles, which contributes to increasing 
LBP risks (Hira et al., 2021).            

18 
 
   
Restricted knee range of motion (ROM) and quadriceps weakness have also been shown 
to be associated with LBP (Kato et al., 2021). The strength of knee extensors is also always reduced 
among patients with LBP compared to healthy people (De Sousa et al., 2019; Jimenez-del-Barrio 
et al., 2020). It was also found that knee extensor strengthening results in more sagittal plane 
positioning and improves pelvic position, which in turn also has the potential to decrease the loads 
on the lumbar spine (Takahashi et al., 2021). 
It has also been reported that a decrease in both abdominal and knee extensor muscle 
strength occurs concurrently in the LBP populations, thereby implying that core and lower-limb 
muscle deficits can interact synergistically to the detriment of trunk-lower-limb coordination 
(Kato et al., 2021). This interrelationship is further supported by the inverse correlation between 
pain intensity and quadriceps and abdominal strength. As a result, lower-limb muscle 
strengthening interventions, especially quadriceps, can potentially improve posture in LBP groups 
and reduce symptoms (De Sousa et al., 2019). 
In athletes, especially runners with chronic LBP (CLBP), literature indicates a lowering of 
knee extensor strength that affects the eccentric action of the contraction of the quadriceps muscle 
during the initial ground contact. Such a deficit decreases shock-absorption capacity, thus making 
it easier to transfer more ground-reaction forces to the lumbar spine (Cai and Kong, 2015). 
Repeated loading may increase the load stress on the spine and worsen the pain related to this kind 
of load redistribution. 
Beyond muscular weakness, patients with NSLBP often exhibit neuromuscular deficits 
such as delayed trunk muscle recruitment, impaired lumbar proprioception, and reduced lower-
limb activation—factors that compromise balance and postural control (Berenshteyn et al., 2019). 
Quadriceps strength shows an inverse relationship with pain severity (Kocaman et al., 2023). 
Isokinetic studies provide quantitative support: LBP patients demonstrate significantly 
lower knee flexor and extensor strength than controls at 60–120°/s, with extensor torque deficits 
of 0.31 Nm/kg (De Sousa et al., 2019). Similar reductions in peak torque have been reported in 
limbs of older adults (Genc & Demircioglu, 2024) and in elderly women with LBP (Kato et al., 
2023). Moreover, erector spinae fatigue has been linked to quadriceps inhibition in golfers with 
poor spinal endurance, underscoring the functional interdependence of spinal and lower-limb 
systems (Edwards et al., 2020). 

19 
 
2.4 
Assessment for LBP 
2.4.1 Low Back Pain (LBP) Intensity 
The Numerical Pain Rating Scale (NPRS) accounts for a valid, reliable, and acceptable tool 
used in measuring the severity of LBP. It can be utilized in clinical and research contexts owing to 
its simplicity and sensitivity to changes. The NPRS is a 11 point scale, with 0 (no pain) to 10 (worst 
imaginable pain). The patients are requested to rate the intensity of their pain on it (Ostelo et al., 
2005). 
The NPRS shows strong construct validity through positive correlations with other pain 
measures (Von Korff et al., 2000) and responsiveness to meaningful changes, with a minimum 
clinically important difference of 2 points (Childs et al., 2005). Additionally, NPRS scores have 
demonstrated predictive value in determining the extent of disability that comes with LBP 
(Shafshak et al., 2021). 
2.4.2 Lumbar Posture 
2.4.2.1 Lumbar Lordosis Assessment 
Lumbar lordosis is one of the most important postural parameters and is commonly 
measured as a part of measuring spinal positioning and mechanical activity. The lumbar curvature 
should be measured accurately, both clinically and in research. Cobb angle between L1 and L5 
radiographs is considered the gold standard of all available methods (Dreischarf et al., 2016). 
Healthy populations have normal L1-L5 Cobb angles, which are between 38.1° and 45.6°, but 
these values do not necessarily remain constant across age, sex, and ethnicity (Furlanetto et al., 
2018; Dimitrijevic et al., 2022). Less invasive methods of lumbar lordosis can be provided by non-
radiographic equipment like inclinometer or flexicurves, but might not be as accurate as other 
radiographic methods. 
2.4.2.2  Pelvic Alignment 
Digital Inclinometers/Goniometers: To assess anterior/posterior pelvic tilt angles. 

20 
 
 
Pelvic tilt should be assessed correctly in order to examine lumbopelvic alignment and its 
role in postural control, lower back pain, and functional mobility. Digital inclinometers and 
goniometers are commonly used because of their portability, easy to use and find application in 
both clinical and research settings. These instruments give a quantitative measure of both anterior 
and posterior tilt of the pelvis in the sagittal plane, which offers useful information on pelvic 
positioning in the standing and actively engaged positions. According to Yudas et al. (1996), 
inclinometers are able to distinguish different degrees of pelvic tilt, with a high degree of precision, 
among asymptomatic individuals, creating the possibility to establish numeric reference values. 
Levine and Whittle (1996) showed that the tilt of the pelvis has a significant effect on the 
positioning of the lumbar spine, which makes it necessary to have valid measuring tools. Moreside 
and McGill (2011) validated digital inclinometers can be used to identify clinically significant 
changes in pelvic angle after hip intervention to record subtle compensatory changes that are often 
not visually obvious. Owing to their precision, the digital inclinometers and goniometers have been 
confirmed as reliable tools to measure pelvic tilt in healthy subjects and patients with 
musculoskeletal disorders such as NLBP. 
2.4.3  Muscle Strength  
2.4.3.1 Knee Muscle Strength Using Hand-Held Dynamometer (HHD) 
The hand-held dynamometer (HHD) makes up a practical and economical instrument to 
assess knee extensor strength. It has been shown to have reliability, validity, and responsiveness, 
even when compared with more sophisticated electromechanical devices (Kittelson et al., 2020). 
It is a particularly beneficial measure for monitoring quadriceps strength before and after total 
knee arthroplasty in clinical studies.  

21 
 
According to Baron et al. (2024), the HHD is considered to be a valid technique for 
measuring the knee strength during various joint positions in healthy individuals. Measurement 
accuracy is increased with the use of the mean of two repeated trials. Pinto et al. (year) showed 
that the HHD is clinically useful in testing Knee extension strength and should be included in 
musculoskeletal assessment protocols. 
2.4.3.2 Lumbar Muscle Strength Using Hand-Held Dynamometer (HHD) 
Measuring the lumbar muscles' strength is the most important technique for assessing 
spinal stability, functional ability and rehabilitation progress. Recently, hand-held dynamometers 
(HHDs) have become an easily administered, inexpensive, and portable alternative to isokinetic 
devices for the assessment of isometric lumbar flexor and extensor strength in clinical and 
research settings. Studies have shown that HHDs are both reliable and valid: Tanveer et al. (2021) 
found high intra- and inter-rater reliability (ICC = 0.94--0.97) in healthy adults and have, thus, 
confirmed its usefulness for baseline and follow-up testing. Althobaiti and Falla (2023) found 
good to excellent test-retest reliability (ICC = 0.73-0.93) in patients with CLBP and healthy 
volunteers, while their correlations to isokinetic dynamometry were moderate to high (r = 0.56-
0.78), which established their criterion validity. 
Concerning responsiveness, HHDs have demonstrated usefulness in identifying the 
changes in lumbar strength over time. Althobaiti et al. (2025) conducted a follow-up to determine 
how responsive HHD was after six weeks of an exercise program in chronic LBP patients. he 
authors indicated moderate to large internal responsiveness, with effect sizes (ES) of between 
0.40 and 0.85 and standardized response means (SRM) of between 0.60 and 0.74. Nonetheless, 
the external responsiveness, which is measured by the association of the changes in the strength 
with the changes in the functional outcomes, was low (r = 0.22 -0.26), meaning that the changes 
in the strength might not necessarily relate directly to the perceived clinical improvement. 
HHDs also have been examined in athletic populations. Juan-Recio et al. (2024) examined 
the consistency of HHDs when testing the strength of seated trunk flexion and extension among 
female amateur athletes. Their results showed moderate to high reliability (ICC = 0.65 -0.87), and 
moderate correlations (r = 0.42 -0.47) between the HHD and the isokinetic testing. Nevertheless, 
the authors warned against the interchangeability of HHD and isokinetic devices because they 
have fundamental differences in the application of resistance and stabilization needs. Collectively, 

22 
 
these results imply that HHDs are a valid and reliable technique in the measurement of lumbar 
muscle strength within different communities. Although they might not completely substitute 
laboratory-quality apparatus in sophisticated strength profiling, they can provide a workable, 
reproducible, and responsive instrument in clinical use and research, especially in the areas where 
sophisticated equipment is inaccessible. 
2.4.4  Functional Ability and Health-related Quality of Life 
One of the most popular instruments that can be used to measure functional disability and health-
related quality of life in people with LBP is the Oswestry Disability Index (ODI) (Garg et al., 2020; 
Omar et al., 2023). The ODI is a self-administered questionnaire consisting of 10 items, rated 0-5 
each, with a total score being converted to a percentage (0 -100%). It can be interpreted as follows 
(El‑Hady et al., 2023):  
0–20%: Minimal disability; the patient can perform most daily activities. 
21–40%: Moderate disability; difficulties in travel and social participation, but basic self-care 
and sleep are only partially affected. 
41–60%: Severe disability; significant limitations in daily functioning due to pain. 
61–80%: Crippling disability; pain affects all aspects of life. 
81–100%: Bed-bound or possibly exaggerating symptoms. 
ODI has been confirmed to be applicable to a wide range of populations, and it is responsive to 
variation induced by treatment, which makes it a useful scale in monitoring the progress of 
rehabilitation of LBP patients. 
 
2.5 
Exercise-Based Interventions for Non-Specific Low Back Pain (NLBP) 
Exercise is recognized to be the most effective intervention for non-specific low back pain 
(NLBP) among other treatment modalities. There is solid evidence of the use of active therapy 
techniques, where patients are promoted to participate in progressive movement and functional 
activity. These are motor control training, resistance exercises, aerobic conditioning, and spinal 
stabilization exercises, which have shown clinically significant results in the reduction of pain and 
disability (Owen et al., 2020). 
Dimitrijevic et al. (2022) conducted a meta-analysis to determine the effects of corrective 
exercise programs in patients with lumbar hyperlordosis and reported that there are moderate 

23 
 
positive effects in reducing the excessive lumbar curvature. Such exercises are useful in 
hyperlordotic and normo-lordotic individuals to ensure alignment and functional changes. 
Likewise, Kim et al. (2021) showed that corrective and resistance exercise programs were 
effective in increasing lumbar muscle cross-sectional area, improving lumbar lordosis angles, 
augmenting flexibility, and diminishing ODI scores. Notably, the researchers concluded that 
corrective exercises yielded a higher rate of improvement in lumbar position and functional 
impairment than resistance training and traditional physical therapy. 
Also, integrated exercise regimens have better results. According to Woo and Kim (2016), 
a program combining lumbar stabilization and thoracic extension exercises proved more effective 
in the improvement of both the ODI and lumbar curvature than the program of lumbar stabilization. 
Likewise, Cho et al. (2015) established that lumbar stabilization exercises were superior in 
comparison to conservative treatment in terms of lumbar lordosis and functional disability scores. 
Nevertheless, the relationship between lumbar stabilization and structural spinal changes 
is not always consistent in all studies. Ko et al. (2018) determined that lumbar stabilization 
exercises could positively affect lumbar lordosis angle, but they did not have a significant effect 
on lumbar lordosis functional and symptom management. All these studies point to the fact that 
even though exercise-based interventions are imperative in the management of NLBP, the type, 
intensity, and emphasis of exercise programs can also have a significant impact on the effects of 
spinal alignment and disability. Therefore, it is suggested that the prescription of exercises based 
on the individual needs of the muscle-function and spinal-position be applied in order to achieve 
the best therapeutic effects. 
2.6 
Knee extensor training (Open kinetic chain versus Closed kinetic chain) 
Open kinetic chain (OKC) exercises refer to exercises where the distal segment such as the 
foot is free to move; examples include leg extensions and seated straight leg raises which allow 
for the selective activation of specific musculature especially the quadriceps muscle. In contrast, 
closed kinetic chain (CKC) exercises involve stabilisation of the distal segment against a surface, 
such as the ground, with exercises such as squats, lunges and step-ups involving multiple joints 
and muscle groups simultaneously (Diong et al., 2015). 

24 
 
Both OKC and CKC exercises have different biomechanical profiles, and therefore, both 
exercises play complementary roles in rehabilitation. A step-wise approach may be the best 
strategy: starting with OKC exercises to work on isolated strength in patients with high pain levels 
or poor stability followed by CKC exercises for improving neuromuscular coordination, functional 
strength, and postural control for daily and athletic activities. The integration of both OKC and 
CKC into individualized programs is particularly beneficial to patients with non-specific low back 
pain and lower limb involvement (optimizing functional outcomes). 
 
Table 2.1 Summary of Key Differences Between CKC and OKC 
Feature 
Closed Kinetic Chain (CKC) 
Open Kinetic Chain (OKC) 
Distal Segment 
Fixed 
Free-moving 
Muscle Activation 
Co-contraction, multi-joint 
Isolated muscle activity 
Joint Loading 
Higher (functional load) 
Lower (reduced axial load) 
Proprioception 
Enhanced 
Minimal 
Suitability 
Later-stage rehab, functional 
tasks 
Early-stage rehab, pain-
sensitive conditions 
Example 
Squats, lunges 
Leg extension, straight leg 
raise 
 
2.6.1  Neuromuscular and Functional Differences 
CKC and OKC exercises: Neuromuscular activation and biomechanics are different for 
both exercises. CKC exercises stimulate the ability to co-contract the agonist and antagonist 
muscles, which, in turn, stimulates joint compression and stability that can be used to enhance the 
control of proprioception and lumbo-pelvic (Kim et al., 2018). They are also useful for stimulating 
the muscle spindles and joint receptors, which promotes better neuromuscular coordination and 
postural control (Cheon et al., 2020). In contrast, OKC exercises enable isolated muscle 
strengthening with low loading of the joint, making them more appropriate for early-stage 
rehabilitation, especially in patients with pain or instability, such as NLBP (Daskapan et al., 2013). 
CKC vs OKC in neuromuscular and functional impacts 

25 
 
• 
The CKC exercises tend to promote stability and proprioception of the joints through co-
contraction, which may promote lumbar-pelvic control. 
• 
 Isolated strengthening through OKC exercises with reduced axial load can be 
advantageous in painful cases of NLBP. 
 
 
2.6.2 Functional Carryover 
CKC exercises tend to have more functional relevance, as they are close to what would be 
done in real life (such as rising from a chair, stair climbing, and running). Accordingly, they are 
commonly prescribed for functional restoration in both lower limbs and spinal rehabilitation 
programs (Kim et al., 2018). In comparison, OKC exercises might be beneficial in controlled 
strengthening situations, specifically where there are impediments to performing CKC tasks due 
to pain, range limitation or poor stability. Thus, they are often used as part of early-phase 
rehabilitation before more functional CKC movements are undertaken (Owen et al., 2020). 
2.6.3  Evidence Comparison 
Although CKC and OKC exercises are commonly used for lower limb rehabilitation in 
patients with low back pain and knee pathology, there is still a lack of definitive evidence regarding 
the effectiveness of these exercises. Goh et al. (2019) noted that although it is common practice, 
there is no consensus on the effectiveness of one modality over the other for patients who have 
both knee and low back pain conditions. Some investigations support the use of OKC in relieving 
clinical symptoms specific to the joint in knee and hip disorders (Daskapan et al., 2013), while 
others report the superior proprioceptive and functional benefits of CKC (Kim et al. 2018). For 
example, Adegoke et al. (2019) found that both OKC and CKC improved quadriceps strength and 
reduced pain in patellofemoral pain syndrome, but CKC was more efficacious. Recent systematic 
reviews reflect this uncertainty: Pamboris et al. (2024) reported inconsistent results and low 
certainty evidence when comparing OKC and CKC in anterior cruciate ligament rehabilitation and 
Ozudogru and Gelecek (2023) reported no significant differences in quadriceps strength between 
OKC, CKC and combined exercises in grade II knee osteoarthritis. Overall, CKC is likely to be 
slightly better than open surgery with regards to functional outcome. 

26 
 
2.7 Conceptual framework  
 
 
 
 
Figure 2.1 Conceptual framework of Knee Extensor Strength inrelation to NLBP 
 
2.8 Summary of literature review 
The management of non-specific low back pain (NLBP) increasingly incorporates lower 
limb-focused rehabilitation due to the biomechanical and neuromuscular interdependence between 
the lumbar spine, pelvis, hip, and knee joints. Among various approaches, Open Kinetic Chain 
(OKC) and Closed Kinetic Chain (CKC) exercises are two commonly applied strategies for knee 
extensor strengthening, each with distinct physiological and functional implications. 
Mediating variables 
Knee extensors 
muscular strength  
Postural realignment 
and neuromuscular 
control  
OKC and CKC knee 
extensor training  
o
Age. 
o
BMI 
o
Occupation 
o
Activity level 
o
Morbidity 
Independent variable 
Variables to be controlled  
Dependent variables 
o Lumbar lordosis 
cobb angle. 
o Lumbar(Numerical 
pain rating scale) 
o Lumbar extensor 
muscle strength  
o Knee extensor 
muscle strength 
o Lumbar extensor 
strength 
o Quality of Life 
(Oswestry 
disability index) 
o Postural Control 
o Pelvic alignment 

27 
 
Evidence suggests that both OKC and CKC exercises can effectively improve muscle 
strength and reduce pain in individuals with lower limb or spinal disorders. However, CKC 
exercises are frequently preferred due to the superior effect of CKC exercises on neuromuscular 
control and functional performance. Nevertheless, the literature is still contradictory, as some 
studies found no significant difference between the two modalities regarding results of quadriceps 
strength or disability, especially in populations with knee osteoarthritis or patellofemoral pain 
syndrome.  
The current literature is less clear regarding which kinetic chain approach provides a 
greater therapeutic benefit in patients with NLBP and the way in which lumbar stability, knee 
function, and global postural control influence each other. This shows a major gap in the literature 
and justifies the need for further research, especially in patient groups with combined lumbar and 
lower limb dysfunction. Further studies, especially prospective research, are needed to better 
understand these associations and to elucidate the causal pathways and mechanisms underlying 
LBP with special regard to the role of corrective exercises aimed at improving knee alignment in 
preventing chronic and recurrent cases. 

28 
 
CHAPTER 3 
METHODOLOGY 
 
3 
Introduction  
The methodology chapter describes the sequential steps of the empirical investigation, 
including a comprehensive plan of time on all research activities. It will discuss the methods and 
tools used for data collection, ensuring that their reliability and validity are demonstrated. In 
addition to describing the intervention in detail, the research design and the statistical analytical 
methods to be used are presented. 
3.1 
Research Design  
An innovative therapeutic strategy of knee extensor training will be evaluated in a four-
arm randomized controlled trial (RCT) for non-lumbar back pain (NLBP). We will use 
randomization to reduce the risk of bias and offer a valid way to study the cause-and-effect 
relationship between the intervention and the outcomes. This RCT will use a triple-blinded design 
in which the participants, outcome assessors, and statisticians will be blinded to the intervention 
assigned to each participant. 
3.2 Research Setting 
The research will be carried out in the Ministry of Health (MOH) hospitals of Taif, 
Kingdom of Saudi Arabia, for several strong reasons. First, the MOH hospitals in Taif represent 
a wide and mixed patient population, providing access to individuals representing a wide range 
of demographic, health status, and socioeconomic diversity. This diversity will increase the 
generalizability and applicability of study results to real-world clinical practice. 
Second, these hospitals have standardized medical infrastructure and rehabilitation 
services, in particular, physical therapy departments staffed by licensed physiotherapists. This 
assures the availability of critical resources (assessment tools, therapeutic equipment and 
treatment facilities) necessary for safe and effective implementation of the study protocol.  

29 
 
Additional benefits arise from the institutional review boards at the hospitals and their 
experience with regulatory mechanisms for clinical research. These factors can support ethical 
approval processes, recruitment of participants and compliance with modern standards of research 
governance.  
3.3 
Research population and sampling techniques. 
3.3.1 Research population 
Saudi male adults aged 40-60 years suffering from NLBP can participate in the current 
study. The patient records in the Ministry of Health hospitals in Taif will be the source for patients’ 
contact information. 
3.3.2 Sampling technique 
Probability of sampling with a simple random sample technique, as every member of a 
study has an equal chance of selection 
 
3.3.3 
Sample size 
The G*Power software (Kang, 2021) was utilized to calculate the required sample size 
using the following parameters: F tests for MANOVA with repeated measures within and between 
interactions, specifying Pillai’s trace of 0.16 an effect size of 0.3, an alpha error probability of 0.05, 
and a desired power of 0.85. The analysis involved eight groups and three measurement times (pre-
after 4 weeks, and after 8 weeks of intervention), resulting in a determined sample size of 120 
participants.  

30 
 
3.3.4 Randomization 
A total of 128 participants will be enrolled and randomly assigned to one of eight study 
groups using a stratified randomization method. Randomization will be stratified by age to ensure 
equal distribution across intervention and control groups. Participants will first be categorized into 
two age strata: 
• 
Group A: 40–49 years 
• 
Group B: 50–59 years 
Within each age stratum, participants will be randomly allocated to one of four intervention 
arms: 
• 
Treatment Group I (lumbar strengthening exercise and knee OKC exercise) 
• 
Treatment Group II (lumbar strengthening exercise and knee CKC exercise) 
• 
Treatment Group III (lumbar strengthening exercise and knee OKC and CKC exercise) 
• 
Control Group ((lumbar strengthening exercise) 
• 
) 
3.3.5 Blinding techniques 
The double-blinding technique will be used during the study period, in which the 
participants, assessor, and statisticians will not know the assignment. 
3.4 
Selection criteria 
3.4.1 Inclusion criteria:  
Males aged 40 to 60 years, nonsmokers, with normal body mass index of Saudi nationality, 
office workers, suffering from chronic NLBP for 12 weeks or more with a moderate disability 
according to the Oswestry Disability Index (score of 21 - 40%) and moderate activity level 
according to the Arabic version of the International Physical Activity Questionnaire short form 
(Appendix III). 
3.4.2 Exclusion criteria:  
I. 
Previous spinal surgery, fracture, deformity, or disease. 
II. 
Neurological deficit and Lower limb deformity or fracture, or disease. 

31 
 
III. 
Mental or psychological illness. The Arabic version of the Self-Reporting Questionnaire 
(SRQ-20) developed by the World Health Organization (WHO) to screen for common 
mental disorders such as depression and anxiety, uses a cut-off score to distinguish 
between individuals with and without significant psychological distress. A score of 7 or 
below is generally considered "normal", indicating no significant psychological distress 
(Al-Subaie et al., 1998).  
IV. 
Systematic chronic illnesses such as hypertension, cardiac and respiratory disorders, and 
diabetes mellitus.  
3.5. 
Data collection procedure 
3.5.1 Recruitment  
 
 
The sample of study will be selected from outpatient physical therapy and rehabilitation 
departments of Ministry of Health hospitals in Taif, Kingdom of Saudi Arabia. Two main methods 
will be used to identify and invite potential participants. Firstly, the subjects will be identified by 
conducting a systematic review of clinical databases and medical records in cooperation with 
hospital physiotherapists and attending physicians. Patients who were diagnosed with non-specific 
low back pain (NLBP) within the target age range (40-60 years) will be screened from records to 
identify those who meet the initial inclusion criteria. The identified subjects will then be contacted, 
by telephone or during clinic visits, to inform them of the study and invite them to take part. They 
will be given short and clear information about the purpose, procedures, potential benefits and 
their rights as research subjects. Second, to broaden recruitment and assure fair opportunity for 
participation, flyers, posters, and electronic advertisements will also be distributed on hospital 
waiting areas, rehabilitation units, and community health centers. These advertisements will 
contain a pithy study description, eligibility criteria, and contact information for the research team. 
Participants will be asked to voluntarily contact investigators. They will be screened initially by 
telephone or face-to-face pre-screening interview to establish eligibility. 
3.5.2 
Screening Process 
All eligible participants, whether identified through clinical records or self-referred via 
advertisements, will be invited to attend a screening visit where informed consent will be obtained, 
and a detailed eligibility assessment will be conducted. Only those who meet the inclusion and 

32 
 
exclusion criteria will be randomly allocated into one of the eight study groups, stratified by age 
and intervention type as described in the study design. Within each age stratum, participants will 
be randomly assigned to either the control group or one of three treatment groups (Group I, Group 
II, or Group III).  
The assessor who is blind to group assignment (SAA) will conduct the baseline assessment, 
4 weeks and at the end of eighth week intervention.   
All potential participants will undergo a two-stage screening process. Stage I:  an interview 
for age, BMI, medical history, occupation, other characters, low back pain intensity and Oswestry 
Disability Index and IPAQ-SF questionnaire. The interview will be conducted by a licensed 
physiotherapist to verify and questionnaire scores. Stage II : Physical measurement  comprised of 
lumbar lordosis, postural control, lumbar instability and knee extensor isometric strength. The 
measurement will be conducted by a senior physiotherapist with over five years experience in 
managing musculoskeletal condition who will be blinded to group allocation where feasible. 
Participants will attend prescheduled sessions for eight weeks. All exercise interventions 
will be delivered by licensed physical therapists with at least 5 years of clinical experience in 
musculoskeletal rehabilitation. Therapists will be trained in the study protocol and Intervention 
sessions will take place in the rehabilitation department of participating Ministry of Health 
hospitals and will follow standardized protocols for each exercise group, ensuring fidelity and 
consistency across all participants. The flow of the study is presented in Figure 3.1 
 
 

33 
 
3.6- Flow of the Study 
Eligible participants with LBP (n=150) 
 
Random allocation (N=128) 
 
 
 
 
Interview: Sociodemographic, QOL questionnaire  
Baseline assessments of primary and secondary outcomes 
 
 
 
Follow-up Assessment after 4 weeks  
 
 
 
Follow-up Assessment after 8 weeks  
 
Statistical analysis 
Descriptive analysis: Means, Standard deviations,  
Factorial analysis: MANOVA for comparing the study groups 
 
Figure 3.1 The flow of the study 
CG (40-50) (n=16) 
CG (51-60) (n=16) 
TGI (40-50) (n=16) 
TGI (51-60) (n=16) 
TGII (40-50) (n=16) 
TGII (51-60) (n=16) 
TGIII (40-50) (n=16) 
TGIII (51-60) (n=16) 
CG (40-50) (n=16) 
CG (51-60) (n=16) 
TGI (40-50) (n=16) 
TGI (51-60) (n=16) 
TGII (40-50) (n=16) 
TGII (51-60) (n=16) 
TGIII (40-50) (n=16) 
TGIII (51-60) (n=16) 
CG (40-50) (n=16) 
CG (51-60) (n=16) 
TGI (40-50) (n=16) 
TGI (51-60) (n=16) 
TGII (40-50) (n=16) 
TGII (51-60) (n=16) 
TGIII (40-50) (n=16) 
TGIII (51-60) (n=16) 
CG (40-50) (n=16) 
CG (51-60) (n=16)
TGI (40-50) (n=16) 
TGI (51-60) (n=16) 
TGII (40-50) (n=16) 
TGII (51-60) (n=16) 
TGIII (40-50) (n=16) 
TGIII (51-60) (n=16) 
Exclusion criteria (N=22) 

34 
 
3.7 Outcome Measures  
3.7.1 Primary outcome:  
i) 
Lumbar lordosis is measured by X-ray Cobb angle. 
For the Lumbar lordotic measure, a standard 36-inch lateral radiograph will be taken 
from a distance of 6 feet in a standing position. The participant's arms will be positioned 
horizontally on a support bar to eliminate shadows that could obscure the measurement of the 
spine (Hammerberg and Wood, 2003).  
The most common method of Cobbs angle calculation involves drawing a line through the 
first lumbar vertebra's superior endplate on a lateral lumbar radiograph, followed by a second line 
parallel to the fifth lumbar vertebra's inferior endplate. Perpendicular lines are then created, and 
the angle formed at their intersection is measured (Harrison et al., 2001; Russell et al., 2020). The 
method has an ICC of 0.99, with a 95% confidence interval (Harrison et al., 2001; Russell et al., 
2020). 
3.7.2 Secondary outcome:  
i) 
LBP intensity is measured by the Numeric Pain Rating Scale. 
The NPRS, a widely used 11-point scale in LBP research (Shafshak et al., 2021), will 
be used for this analysis. The participant will choose the score that best matches their 
perception of pain intensity, where 0 is no pain and 10 is maximum pain imaginable. 
The NPRS is a highly reliable instrument with an ICC of 0.991 (Yao et al., 2020) and it 
is deemed to be a valid instrument used for measuring LBP severity. It has been proven to react 
adequately both in clinical as well as research settings (Von et al., 2000). The scale has good 
construct validity (Von et al., 2000), with good positive correlation with other measures of pain 
intensity, and is easy to administer and score (Ostelo et al., 2005). 
 
ii) 
Quality of Life: Oswestry Disability Index (ODI)  
The Arabic version of the ODI (Arabic-ODI) has been tailored for the Saudi population 
and will be used for functional disability measures because it has high metrological qualities. The 
self-completed ODI includes 10 items covering the topics of pain intensity, lifting, self-care, 
walking, sitting, sexual function, standing, social life, sleep quality and ability to travel. Patients 
are asked to choose the best phrase to describe their circumstances. Each item is scored on a 5-

35 
 
point scale that ranges from 0 (no disability) to 5 (most severe disability). Subjects are free to skip 
the sexual-function question. The sum raw score from 0 to 50 is then transformed into percentile 
summary score as percentage (0% - 100%) (Cook et al., 2021).  
It has been validated in the Kingdom of Saudi Arabia (KSA), demonstrating excellent intra-
observer reliability (ICC: 0.99). Correlations of the index with the Visual Analog Scale (VAS) for 
pain (r = 0.708), the Roland–Morris Low Back Pain Disability Questionnaire (r = 0.656), and the 
Quebec Back Pain Disability Scale (r = 0.792) indicate strong construct validity (Algarni et al., 
2014). 
Among the tools specific to LBP, ODI is noted for its strong construct validity and 
reliability. The test-retest reliability values range from 0.94 to 0.99, with high inter-rater reliability 
at 0.94 and internal consistency values between 0.835 and 0.90 (Garg et al., 2020).  
 
iii) 
Muscle strength using Hand-held dynamometer (HHD) 
a) Lumbar muscle strength (Fakhro et al, 2022) 
Lumbar extensor muscle strength will be assessed using a Hand-Held Dynamometer 
(HHD) (e.g., MicroFET or Lafayette Manual Muscle Tester). The testing of participants will 
be done while in a prone position on a treatment table with the arms placed alongside the 
body and the legs extended. A standardized warm-up consisting of light dynamic stretches 
will be provided prior to testing. 
The examiner will position the HHD over the participant’s thoracolumbar junction 
(T12-L1) while stabilizing the pelvis with a strap or manual fixation to prevent compensatory 
movements. Participants will be instructed to extend their trunk maximally against the 
resistance applied by the dynamometer, maintaining a steady effort for 3–5 seconds. Verbal 
encouragement will be given to help ensure maximum effort. 
Each subject will perform three consecutive trials with a 30-second rest period 
between the repetitions, which will minimize fatigue. The maximum force in Newtons 
measured during the tests will be taken for analysis. High test-retest reliability has already 
been demonstrated for HHD in the measurement of trunk extensor strength, with an ICC 
above 0.90. All of the tests will be conducted by the same trained investigator, thus inter-
rater variability is eliminated. 

36 
 
 
b) Postural control (Sarvestan et al, 2021) 
Postural control will be assessed using the Y-Balance Test (YBT), a reliable and 
validated dynamic balance test that challenges single-leg stability in multiple directions. 
The test is based on the Star Excursion Balance Test (SEBT) and is widely used to assess 
neuromuscular control, dynamic balance, and risk of injury in clinical and athletic 
populations. Participants will perform the test barefoot to minimize shoe-related variability, 
unless footwear is standardized. The participant will be instructed to stand on the dominant 
limb at the center of a Y-shaped grid, with the other limb used to reach in three directions: 
Anterior (ANT), Posteromedial (PM), and Posterolateral (PL) 
Participants will be allowed four practice trials in each direction, followed by three 
measured trials. The reach distance in each direction will be recorded to the nearest 0.5 cm 
using a standard YBT kit or a tape grid marked on the floor. Trials will be discarded and 
repeated if the participant: Fails to maintain single-leg stance, Touches down with the 
reaching foot, or cannot return to the starting position under control. The maximum reach 
distance in each direction will be normalized to leg length (measured from anterior superior 
iliac spine to the medial malleolus) and expressed as a percentage. A composite score will 
be calculated as: 
 
This protocol provides a reliable measure of dynamic balance and postural control (ICC > 
0.85), with demonstrated sensitivity to intervention effects and neuromuscular training. 
 
c) Knee extensor strength 
Hirano et al. (2020) demonstrated that measuring knee extensor isometric strength using 
the HHD is highly reliable with the subject in the sitting position. This method shows criterion-
related validity when compared to an isokinetic dynamometer for males and exhibits acceptable 
reproducibility among different examiners. Specifically, the assessment of isometric knee strength 
using the HHD yielded high intra-rater and inter-rater intraclass correlation coefficients (ICCs), 
with values exceeding 0.950 and 0.927, respectively. Thus, using the HHD to measure knee 

37 
 
extension strength seems to be a reliable way to measure strength objectively (Pinto-Ramos et al., 
2022). 
In the current research, we will utilize a valid and reliable handheld dynamometer, 
specifically the Lafayette Instrument brand (model number 01165, Lafayette, Sagamore, USA) as 
referenced by Nepomuceno et al. (2021). Assessment procedures will adhere to those outlined by 
Pinto-Ramos et al. (2022). Patients will be seated at the edge of the bed with their feet suspended, 
arms crossed over their chests, and examined knees flexed at 60 degrees. The observer will squat 
while supporting their back against the wall, extending both arms to stabilize the patient's leg. This 
positioning minimizes the influence of strength from either the patient or observer while 
maintaining the knee flexion angle at 60 degrees.  
Each patient will have the HHD placed on their front leg, about five centimeters above the 
distal portion of the medial malleolus. Patients will exert and sustain their maximum knee 
extension strength for five seconds. To reduce the impact of fatigue, a rest period of one minute 
will be allowed between two measurements. An independent observer will register the results 
displayed on the HHD, ensuring that both the patients and observers using the HHD remain blinded 
to the readings. Strength measurements will be recorded in Newtons (N), and the higher of the two 
measurement values will be considered as the final result. 
 3.8 
Rehabilitation protocol (8 weeks). 
i. Knee extensor training. 
1. Open kinetic chain exercise (Adegoke et al., 2019) 
Quadriceps Setting 
By bringing up their patella while maintaining an extended knee, participants will perform 
an isometric contraction of the quadriceps muscle while lying supine on a plinth. After holding the 
contraction for ten seconds, they will release it and perform the exercise in ten repetitions with a 
five-second rest between them. This task will be performed throughout the exercise intervention 
protocol. 
 
 
Straight Leg Raising (SLR) 

38 
 
The participant will lift his lower extremity while isometrically contracting his quadriceps 
(quadriceps setting) in a supine position to attain about 45° of hip flexion while maintaining an 
extended knee. After ten seconds, they will lower the limb and repeat the exercise ten more times 
with a five-second rest in between. The contralateral hip and knee will be flexed to approximately 
45° and 90°, respectively, to prevent excessive strain on the lower back. Participants will begin 
performing SLR with additional weight in the third week by fastening an ankle weight equal to 
their 10-repetition maximum (10RM) to their ankle. 
Full-Arc Extension 
While the participants are in a high sitting position, a weight equal to their 10RM will be 
attached to the lower limb, approximately above the ankle. The popliteal area will be covered by 
a towel roll for protection. The load will be gradually raised through a range of 90° knee flexion 
to 0° knee extension. They will hold the position for five seconds before decreasing it again. In 
each session, participants will complete three sets of ten repetitions of this exercise, taking a 10-
second break between sets to rest their feet on a stool. This task will be performed from the fourth 
week to the eighth week. 
2. Closed kinetic chain exercise (Adegoke et al., 2019)  
Quadriceps Setting  
While Participants are sitting in a chair with backs supported, their heels resting on the 
floor, knees outstretched, they will press their thighs against the chair's seat and their heels to the 
floor and hold for a count of 10. After ten counts, they will rest. This exercise will be performed 
throughout the study. 
Mini Squats 
While the participants are in a standing position, they will bend both knees to 
approximately 30-60 degrees while keeping their trunks upright. They will hold this position for 
10 seconds. After that, they will relax and then repeat it for 10 repetitions. This exercise will be 
performed in the 2nd week of the study, after which it will be stopped when participants begin doing 
weighted mini squats. Starting in the third week, participants will use a barbell with plastic weights, 
totaling 10RM, put across their shoulders for the mini squats with weight. 
Step-Up and Step-Down 

39 
 
Participants will use a robust wooden box that is 5 cm high to do step-ups and step-downs 
in the following directions: forward, backward, and lateral. They should maintain an upright trunk, 
ensuring that their heels are the last to leave the floor and the last to return, which emphasizes the 
use of the quadriceps muscle. Each exercise will be repeated 10 times. This part of the program 
will be conducted only during the 4th week. From week 5 onward, ankle weights totaling 10RM 
will be strapped to participants' ankles for the weighted step-ups and step-downs. The knee 
extensor exercise program is illustrated in Table (3.1). 
All participants will perform the exercises three times per week, on consecutive days, for 
both lower extremities, with a five-minute rest between each extremity. They will start with the 
dominant lower extremity, followed by the non-dominant one. The knee extensor exercise program 
is detailed in Table (3.1). 
Table (3.1): knee extensor exercise program. 
 
OKC 
CKC 
W 1 
• Quadriceps sets (10 rep.)  
• Quadriceps sets (10 rep.) 
W 2 
• Quadriceps sets (10 rep.) 
• Straight leg raises (10 rep.)  
• Quadriceps sets (10 rep.) 
• Mini squats (10 rep.) 
W 3 
• Quadriceps sets (10 rep.) 
• Straight leg raises with resistance (10 RM)  
• Quadriceps sets (10 rep.) 
• Mini squats with resistance (10 RM) 
W 4 
• Quadriceps sets (10 rep.) 
• Straight leg raises with resistance (10 RM)  
•  Full knee extension exercise (10 RM as 
resistance) 
• Quadriceps sets (10 rep.) 
• Mini squats with resistance (10 RM) 
• Step up and step down 
W 5-8 
• Quadriceps sets (10 rep.)  
• Straight leg raises with resistance (10 RM)  
•  Full knee extension exercise (10 RM as 
resistance)  
• Quadriceps sets (10 rep.) 
• Wall slides with resistance (10 RM) 
• Step up and step down with resistance 
 
ii.        Lumbar Strengthening Exercise (Cai et al., 2017). 
The goal of the 8-week progressive training program for the lumbar extensor exercises is 
to induce physiological changes in the muscles. A gradual approach will be used to protect the 
participants and reduce undue mental and physical stress from their exercise routine. 

40 
 
In the first week, participants will perform leg raises in a quadruped position while 
maintaining a neutral lumbar spine during both flexion and extension of the leg. In the 2nd week, 
participants will progress to raise one leg and the opposite arm. This structured progression will 
allow participants to do about 40% of their maximum voluntary isometric contraction (MVIC) at 
the start of the 2nd week, without raising the probability of injury to the muscles of the lower back. 
For all exercises, participants will complete three sets of 10 repetitions per session, which is 
recommended for improving muscle endurance and reducing fatigability. 
At the end of each repetition, participants will include an isometric contraction which is 
essential for enhancing lumbar extensor fatigability. Before beginning the subsequent repetition, 
they will be asked to hold the end position for five seconds and take a two-second break. 
Additionally, a two-minute rest will be provided between sets.  
To achieve the counseled intensity of about 60% of MVIC for lumbar extensors, 
participants will add 0.5 kg of ankle weights in the 3rd week and 0.5 Kg of wrist weights in the 
4th week. Following this, an increment of 0.5 kg will be suggested every week for the ankle 
weights and every three weeks for the wrist weights. Starting in week 5, the prone back extension 
will replace the quadruped exercises, as this exercise produces a MVIC percentage above 65%. 
All participants will be advised that their back pain should not worsen while training. Instead, the 
body's response to exercise should be limited to feelings of "aching" or "soreness." If participants 
experience any increased discomfort, they should either reduce the exercise intensity or terminate 
the program. 
3.9 
Description of variables. 
3.9.1 The independent variables 
The independent variable in this study is the knee extensor training program, which 
consists of two levels: OKC exercises and CKC exercises. The sample will be divided based on 
the independent variable into four groups: a control group (CG) that will not be exposed to the 
knee training program, a treatment group I (TGI) that will perform OKC exercises, treatment group 
II (TGII) that will engage in CKC exercises, and a treatment group III (TGIII) that will engage in 
OKC and CKC exercises. All groups will receive lumbar strengthening exercises. 

41 
 
3.9.2 The dependent variables:  
3.5.1.1. Lumbar spine lordosis 
3.5.1.2. Oswestry Disability Index 
3.5.1.3. LBP intensity  
3.5.1.4. Isometric strength of the knee extensor 
3.5.1.5. Lumbar extensor muscle strength  
3.5.1.6. Pelvic inclination 
3.5.1.7. Postural control 
3.10 
Data Analysis Process 
3.10.1 Exploratory data analysis 
SPSS software (version 26) will be utilized to analyze the collected data. The Shapiro-Wilk 
test for normality, along with an inspection of histograms featuring normality curves, skewness, 
and kurtosis, will be employed to assess data normality. 
3.10.2 Data analysis approach 
Pre-tests and post-tests for each group will be analyzed using a mixed-design repeated-
measures MANOVA to compare different study groups through the SPSS program. The syntax 
code will allow various pairwise comparisons using the Bonferroni test. The significance level 
will be determined at p< 0.05. 
Covariate Adjustments: The study does not include covariates in the model, as participants 
have been stratified by age group before randomization, and any covariates controlled by the 
inclusion and exclusion criteria. This approach is expected to ensure baseline comparability across 
the six groups, rendering covariate adjustment unnecessary for our current design. Nonetheless, 
we will assess baseline characteristics to confirm group equivalence, and any significant 
imbalances identified will be documented and discussed. 
 
Study Design Summary: The study comprises 128 participants assigned to eight groups 
based on a combination of two age strata and four treatment arms. This factorial design facilitates 

42 
 
group comparisons utilizing MANOVA, which is appropriate given the multiple dependent 
variables involved. 
Interaction Effects: While the primary objective is to evaluate the main effects of treatment 
within each age group, we may explore potential interactions between age group and treatment in 
secondary analyses, contingent upon data structure and sample size. Such interactions will be 
interpreted with caution, acknowledging power limitations. 
 
Handling of Dropouts/Non-Adherence: As this is a controlled clinical trial, we anticipate 
possible challenges related to participant dropouts or non-adherence. To address these concerns, 
our primary analysis will adhere to the intention-to-treat (ITT) principle. In addition, per-protocol 
analyses will be conducted to further evaluate the data. 
Missing data will be examined for patterns and handled using appropriate statistical 
methods such as multiple imputation or mixed-effects models, depending on the nature of the 
missingness. 
3.11 
Ethical considerations 
Once the research plan is approved, the researcher will seek ethical approval from the 
Ethics Committee of the Ministry of Health in Taif. To confirm their agreement to engage in the 
study, all eligible participants will sign a written consent form in Arabic (see Appendix II). 
3.12 
Limitations of the study 
This study aims to investigate the impact of knee extensor strengthening on lumbar spine 
posture, pain levels, and QOL in patients with NLBP. Considering the cultural and social context 
in Saudi Arabia (KSA), the study will involve only male participants. It will specifically recruit 
individuals diagnosed with NLBP, excluding those with other underlying causes of LBP.  
3.13 
Summary 
This study, based on a randomized controlled trial, aims to explore the effects of 
strengthening the knee extensor muscles on the position of the lumbar vertebrae, the severity of 
pain, and the QOL in patients with LBP. The research plan reviewed recent literature addressing 
the relationship between the lower extremities and the spine, particularly the lumbar vertebrae. It 

43 
 
also clarified the connection between knee extensor muscle weakness and low back pain, 
highlighting the bidirectional causal relationship involved. 
After reviewing previous research, the study aims to investigate the effects of two different 
patterns of knee extensor muscle strengthening on patients with LBP. The findings are intended to 
inform the development of rehabilitation programs for these patients. Additionally, the study may 
contribute to knowledge in this area and generate research hypotheses for future investigations. 
Reliable and accurate measurement methods will be used to assess participants before and 
after the therapeutic intervention. The study also will clarify methods for collecting and analyzing 
data, ensuring that the final results can be interpreted and applied in practical contexts. 
3.14 
Research Gantt Chart 
Table (3.2): Timeline of the PhD milestones  
Task  
Start date 
End date 
Literature Review 
10/15/2024 
06/26/2025 
Proposal preparation 
01/01/2025 
07/31/2025 
Ethic approval  
08/1/2025 
08/30/2025 
Data collection 
09/01/2025 
09/30/2025 
Folow up 
10/01/2025 
01/31/2026 
Data Analysis & Interpretation 
02/01/2026 
03/31/2026 
2 publications in Scopus index 
04/01/2026 
05/31/2027 
2 Oral presentation conferences 
06/01/2027 
06/01/2028 
Submission of Thesis 
07/01/2028 
08/01/2028 
Deface preparation 
08/01/2028 
10/01/2028 
Final Defense 
10/02/2028 
11/30/2028 

44 
 
 
 
 

45 
 
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Appendix I 
Oswestry Disability Index 
 
 
 

58 
 
 
 
 

59 
 
 
Appendix II 
Informed Consent to Participate in a Research Study 
You are being asked to participate in a research study. Researchers conduct studies in 
order to answer important questions that may help change or improve the way we perform 
medical procedures in the future. 
You may choose not to participate in this study, and you may also withdraw from the study 
at any time. Your decision not to participate, or to withdraw later, will not result in any 
penalty or loss of benefits to which you are entitled, and it will not affect your relationship 
with the researchers or their institution. 
Before you agree to participate, the researcher will summarize the important information 
that will allow you to decide whether or not to take part. After that, the researchers will 
provide you with details of the study, including: 
- Why the researchers are conducting the study. 
- The number of people participating in the study. 
- What will happen during the study, including how long your participation will last and 
whether the study involves any experimental procedures. 
- Any potential risks or benefits. 
- Whether there are alternative treatment options besides participating in the study. 
- The procedures that will be taken to protect your personal information and how it may be 
used in the future. 
- How you will be informed of new findings that may affect you personally or your 
participation. 
- Who will cover the costs of treatment if you are injured during your participation in the 
study. 
- Whether there are any costs to you, and whether you will be paid for participating in the 
study. 
- What happens if you decide to stop participating, or the reasons the researchers may 
terminate your participation. 
If you have any questions about the study or about a study-related injury, please contact: 

60 
 
Name: ______________________________________________ 
Telephone Number: ____________________________________ 
 
Participant Consent 
The research study has been explained to me verbally, including the information listed 
above, and I agree to participate in this research study. I will receive a signed copy of this 
form and an English version of the informed consent statement to keep for my records. I 
agree to participate in this study. 
Participant’s Name (printed clearly and in capital letters): 
_________________________________________________________ 
Participant’s Signature: ____________________________   Date: ____________ 
Parent/Guardian/Legally Authorized Representative (if applicable): 
_________________________________________________________ 
Date: ____________________ 
 
 
 

61 
 
Appendix III 
 
 
 

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