Plantar Pressure Distribution In Relation to The Way of Carrying Backpack In Adolescents
Conditions: Healthy Participants
Sponsor: Cairo University

 
 
Plantar Pressure Distribution in 
Relation to The Way of Carrying 
Backpack in Adolescentes 
 
 
 
NCT Number
 
 ٍ
 
07161349
NCT
 
 
 
 
 
 
Date:
 
2023
-
Sept
 
 
 
 
 
 
 
 
 
 
 
  

1 
PLANTAR PRESSURE DISTRIBUTION IN 
RELATION TO THE WAY OF CARRYING 
BACKPACK IN ADOLESCENTES 
 
 
 
 
 
 
 
By 
Amira Ibrahem Mohamed Ahmed 
B.Sc. in Physical Therapy 
 
 
 
 
 
 
 
 
 
Submitted in Partial Fulfillment of the Requirement of the Master Degree 
in Physical Therapy for Pediatrics 
Faculty of Physical Therapy 
Cairo University 
2020 

1 
CHAPTER I 
INTRODUCTION 
  
     Adolescents perform a daily routine of carrying school material over 
their middle and high school years. Considering that backpacks are 
practical and are the most commonly used means of carrying school 
material (Sheir-Neiss et al., 2003). Taking care with the load and the way 
in which it is supported is fundamental for this age group. When the 
backpack load is greater than the support capacity of the muscle groups, 
there is an overload on the vertebral column, which may cause postural 
alterations, pain or dysfunctions (Rebelatto et al., 2001). Since carrying 
school material is a daily routine that is repeated over consecutive years, 
special care is needed to avoid the presence of postural alterations that 
might become established over the medium to long term, thereby bringing 
risks to this population's health (Brackley et al., 2004). 
     Several recommendations have been made in the literature regarding 
the correct way of wearing schoolbags. Most students use backpacks on 
either shoulders or on one shoulder (Sheir-Neiss et al., 2003). Some 
reports recommend that the backpack be worn high on the back with the 
shoulder straps tightened. However, school backpacks should be 
positioned with the center at waist or hip level and not high on the trunk 
(Grimmer et al., 2000). 
     There are many types of backpack designs including shoulder bags, 
traditional double strap backpacks and unilateral backpacks. Despite 
warnings issued by various professional organizations regarding the 
harmful effects of carrying unevenly distributed heavy loads, students 
continue to carry shoulder bags over one shoulder of self-selected body 
side (Perrone et al ., 2018). Decreased availability of school lockers as a 

2 
result of security concerns, increased homework, larger textbooks, and 
other objects being carried to school has prompted the increase use of 
backpacks by school students which in turn, has lead to both an increase 
in weight and duration of backpack carriage (Castellucci et al., 2016).    
     Load carriage is defined as locomotion while transporting an external 
mass supported on the upper torso by shoulder straps and\or transporting 
hip belts .Several studies concerning the carriage of heavy backpacks, are 
postural modifications are certainly among the most carefully 
investigated (Singh and Koh, 2009). The average weight of the backpack 
is about 10% to 15% of children’s body weight (Whittfield et al., 
2001and Sheir-Neiss et al., 2003). 
     The anatomical differences in foot structures must be a reason to walk 
in a different way. At birth, the skeletal tissue of the foot consists mainly 
of cartilage. During the first 6 years of life, ossification and development 
towards a mature foot structures occurs. At approximately one year of 
age, when children usually start walking, the talus, calcaneus, and some 
of the phalanges contain their primary ossification centers still surrounded 
by cartillagenous tissue (Kimmeskamp and Henning, 2001). The foot is 
the terminal segment in the lower kinematic chain; proper kinematics 
within the foot influences the ability of the lower limb to attenuate the 
forces of the weight bearing. The lower extremity should distribute and 
dissipate compressive tensile, shearing, and rotatory force during the 
stance phase of walking (Neuman, 2002).  
     In the foot there are two longitudinal arches: the medial arch consists 
of the calcaneus, the talus, the navicular, the three cuneiform bones and 
the first three metatarsal bones. It is more elastic than the lateral arch that 
consists of the calcaneus, the cubiod and the fourth and fifth metatarsal 
bones. This is flattened and in contact with the ground (Ridola et al, 

3 
2007). There are two transverse arches between longitudinal arches, 
extending from the medial to the lateral borders of the foot. The first is a 
lancet dome, between midfoot and forefoot, at the tarsometatarsal joints 
level; it consists of the bases of the metatarsal bones, the cubiod and the 
three cuneiform bones. The second is a flat dome, in correspondence of 
the forefoot at, the metatarsophalangeal joint level; it consists of the bases 
of the proximal phalanges of the toes and the head of the five metatarsal 
bones (Ridola and Palma, 2001). 
     There are three main arches of the foot which are concave in plantar 
directions. The main function of these arches is to alternate the foot 
during weight bearing from a rigid lever to a complaint series of joints 
and reverses it. Two of the foot arches are oriented longitudinally and one 
is oriented transversely, so, the foot is a biconcave structure (Richard, 
2003). 
     A foot scan is the method by which we examine the biomechanics of 
the feet. It provides a dynamic weight bearing computerized assessment 
of the biomechanics of a person’s foot. The system measures the weight 
distribution at all the contact points along the bottom surface of the feet 
(Tan, 2005). Changes of plantar pressure, force and contact area during 
lifting loads have been reported previously (Pau et al. 2011). An increase 
in plantar pressure and contact area was also demonstrated when 
backpack   loads increased up to 30% (Pau et al., 2011). Moreover, an 
increase in peak force was reported when loads carried was 15% of body 
weight (Hong and Li, 2005). Changes on the plantar pressure, force and 
contact area with loads in backpacks, using both hands have been 
extensively reported. However, information on biomechanics of body 
structures when lifting loads using one hand is limited (Lloyd et al., 
2010). 

4 
     The presence of abnormalities in the plantar force distribution and in 
the body's pressure center pathway may suggest that inadequate postures 
are being adopted when carrying school material. Over the long term, this 
would favor several vertebral column abnormalities. Such abnormalities 
may cause functional, psychosocial, work and quality-of-life constraints, 
thus justifying the need for preventive intervention (Penha et al., 2005). 
Statement of the problem: 
     Is there any effect of the way of carrying backpack on foot pressure 
distribution in adolescents? 
Purpose of the study: 
     To investigate the relationship between backpack carriage unilaterally 
as well as bilaterally and plantar pressure distribution in adolescents.  
Significance of the study:           
     Backpack use can begin at a very young age and continue until 
adulthood. Often high loads are carried over a number of years which 
may have an effect on the growing body. Students currently continue to 
require a mode of carriage for their school supplies. Although the future 
may change this with the use of lightweight laptops and other smart 
devices. Heavy items such as textbooks that may overload a bag are still 
in use and require transport at minimum between school and home 
(Qureshi and Shamus, 2012). 
     The backpack is still the most common way of carrying school items.   
Backpack users traditionally carry heavy loads, while simultaneously 
dealing with the perturbations experienced in daily living (Costello et al., 
2012). Backpack carriage places increasing demand on the musculature 
of all of the joints of the lower limb. Increasing backpack load affects the 

5 
kinematics, moments and powers at the pelvis and hip, but few changes in 
these parameters are seen at the knee and ankle (Chow et al., 2006). 
    Throughout the ages, mankind has devised a variety of techniques for 
load carriage (Wang et al., 2001). Common carrying methods used by 
adolescent teenagers are; two strapped backpack (bilateral) and one 
strapped backpack (unilateral) (Feingold and Jacobs, 2002). Researchers 
suggest that backpack introduces significant increases in overall contact 
area and in the plantar pressure peaks in midfoot and forefoot regions A 
significant shift in the average position of the center of pressure towards 
the forefoot was also observed (Massimiliano et al., 2011). 
     The feet are considered to be the base of support of the skeletal 
system, and so the feet loading mechanisms can affect the rest of body. 
The inadequate distribution of the forces of weight bearing can affect the 
normal bone growth. Presence of a load alters the physiological weight 
bearing functions and, when mechanical overloading is repeated in time, 
it can act as a co-factor in promoting foot discomfort or pain. Therefore, 
this study aimed to investigate relation between foot pressure distribution 
and way of backpack carriage in adolescents. 
Null hypothesis: 
    There is no effect of different ways of carrying backpack on plantar 
pressure distribution in adolescents. 
 
 

6 
Delimitations: 
The study will be delimited to: 
1- One hundred and ten healthy adolescents from both sexes will 
participate in this study. The sample size is based on sample size 
calculation within factors, α=0.05, β=0.2, effect size = 0.1 using G 
power statistical analysis. 
2- Their age will be ranged from 12 to 18 years 
3- All students use backpacks that represent 15% of body weight 
according to Chow et al.  (2010). 
4- Foot scan plate system will be used to assess foot pressure 
distribution.                                                                                 
Basic assumptions: 
It will be assumed that: 
1- All children will be evaluated in the same way. 
2- The methods of evaluation constitute the best objective methods to 
evaluate foot pressure distribution (Foot scan plate system). 
3- The results obtained from this study will be of value in the field of 
physical therapy. 
 
 
 
 
 

7 
CHAPTER II 
LITERTURE REVIEW 
     Backpack carriage is common in schoolchildren. More than 90% of 
schoolchildren in the developed countries are reported to carry backpack 
(Sheir-Neiss et al., 2003). Weight of the backpack appears to be strongly 
related to the occurrence of shoulder, neck, back, and extremities 
complaints in students. Although musculoskeletal discomforts are 
believed to be multifactorial in origin, the carriage and manipulating of 
heavy backpack is signally a suspected factor and may represent an 
overlooked daily physical stress for secondary students (Shamsoddin et 
al., 2010). 
     A person's carrying capacity is affected not only by the magnitude of 
the load they carry, but also by the way the load is carried, the duration of 
carriage, the frequency of carriage and the physical capabilities of the 
person. These other factors must also be considered when attempting to 
determine the overall physical demands placed on the user. Many 
backpacks have been designed specifically to improve load distribution, 
balance, stability, and organization (Stuempfle et al., 2004). 
     Load weight was clearly the most influential of the load carriage 
variables that were studied. This seems reasonable as the gravitational 
pull on the contents of the backpack because the added load would have 
the greatest effect on the forces at the shoulder straps. A more direct 
method of determining the physical demands of load carriage in students 
would be to measure the external forces that directly relate to carrying a 
backpack, such as the pressure on the shoulders that occur as a result of 
the tension in the shoulder straps of a backpack. Based on the present 

8 
findings, school students should wear their backpacks with the least 
weight possible, use the hip-belt if present, allow a reasonable amount of 
looseness in the shoulder straps and should position the heaviest items 
closest to their back (Hamish et al., 2005). 
      Most of the children adapted the proper carriage mode of strapping the 
backpack to both shoulders posteriorly. While adolescents, prefer using 
one shoulder for backpack carriage (Waston et al., 2003). The optimal 
mode of carrying a load should increase the body's stability, have the load 
close to the COM and use muscles of large mass (Fowler et al., 2006). 
The increased use of school bags has deepened our need for knowledge 
about the consequences of different modes of carriage school bag (Pau et 
al., 2016). 
     Current recommendations for school bag carriage are mainly 
concerned with reducing bag weight and optimizing bag design in order 
to minimize postural changes when carrying school bag (Yoon, 2014). 
The type of schoolbag and the way of carrying it may depend on student's 
preferences. On the other hand, students often tend to choose their   
schoolbag using fashion criteria rather than ergonomic characteristics.  
Fashion trends might be country and age specific (Skaggs et al., 2006).  
     Wearing the back pack should be over the strongest mid- back 
muscles. It is also important to pay close attention to the way the back 
pack is positioned on the back. The backpack should rest evenly in the 
middle of the back and shoulder straps should be adjusted to allow the 
child to put on and take off the backpack without difficulty and permit 
free movement of the arm. The straps should not be too loose and that the 
backpack does not extend below the low back. Carrying the backpack 
with two shoulder straps affects posture and gait less than carrying it on 

9 
one shoulder (Cottlorda et al., 2004). Back pack is one of the most 
common designs used by most children. Backpack-style bags with two 
straps were found to be the most popular style of schoolbag for both boys 
and girls (Docker et al., 2006). 
     Carrying a backpack over two shoulders is the most efficient means of 
carriage, but often backpacks are carried over one shoulder. Although 
backpacks have been shown to be most effectively used when two 
shoulder straps and hip straps are properly fitted to better distribute the 
weight of heavy backpack across the shoulders and down the back, 
backpacks often are not adjusted or worn correctly. However carrying 
backpacks on one shoulder significantly altered posture and gait 
parameters in adolescent children (Barbara et al., 2008). 
     The feet are important structures for the human body mechanics they 
are considered the base of support of the skeletal system. The feet are 
considered in normal state when they are pain free, having normal muscle 
balance, absence of contracture, a central heel, straight mobile toes and 
three sites (big toe, lateral border of foot and heel) of weight bearing 
while standing, and during stance phase of walking (Cailli, 1999). 
     The foot is a multibone structure with numerous articulations. 
Included the subtalar and midtarsal joints and several tarsometatarsal, 
intermetatarsal, metatarsophalangeal, and interphalangeal joints, together 
the bones and joints of the foot provide a foundation of support for the 
upright body position (Hall, 2003).  The normal foot is made up of 26 
bones, 33 joints, 128 ligament, 22 muscles and 49 tendons. This 
structures are all arranged in such a way as to be rigid enough to support 
the weight of the body (Kinon and Schoppe, 2001). 

10 
     Normal foot is flexible enough to conform to the contours of the 
ground and absorb shock at others during every step taken while walking 
or running, the foot switches from rigid to flexible and back to rigid 
(Kinon and Schoppe, 2001). The foot has two important functions: to 
support the body weight and to serve as a lever to propel the body 
forward in walking and running. If the foot possessed a single strong 
bone, instead of a series of small bones, it could sustain the body weight 
and serve well as a rigid lever for forward propulsion. However, with 
such an arrangement, the foot could not adapt itself to uneven surfaces 
and the forward propulsive action would depend entirely on the activities 
of the gastrocnemius and soleus muscles (Lawren et al., 2001). 
     The foot-ankle complex is generally divided into three units: the hind 
foot, the mid foot, and the forefoot. The hind foot is composed of talus 
and calcaneus and is generally the first point of contact of the foot with 
the ground in many loco motor activities, the mid foot is composed of the 
navicular, cuboid, and cuneiform bones. This system of bones forms the 
bridge between the hind foot and forefoot. The forefoot is composed of 
the metatarsals, which are referred to as rays. These rays fan out from a 
constricted beginning in the mid foot, with the relative movement 
between them increasing as they fan out. The joints of the foot has 
individual actions, these individual actions are in fact highly coordinated, 
allowing the foot to function dynamically as a unit. The actions of the 
joints are highly integrated, and action at one joint usually results in a 
functional compensatory movement in another joint. The pronation/ 
supination actions of the foot illustrate these compensatory movements 
(Sammar, 2001).  
     The muscles of the sole of the foot are conventionally described in 
four layers, interspersed with the long tendons of muscles originating in 

11 
"the posterior and lateral compartments of the leg .Functionally, however, 
it is easier and quite useful to think of the foot muscles as lateral, central, 
and medial. The lateral group includes the abductor digiti minimi and 
flexor digiti minimi brevis. These insert on the base of the proximal 
phalanx of toe number five, and they abduct and flex the fifth toe. The 
central group includes the flexor digitorum brevis, flexor digitorum 
longus, flexor hallucis longus, flexor accessorius (quadratus plantae), 
lumbricals (Basmaji and Stecko, 2003). Only one muscle is found on the 
dorsum of the foot, the extensor digitorum brevis extending, from the 
calcaneus to the proximal phalanx of the great toe and the tendons of the 
extensor digitorum longus for toes two to five. Some recognize the slip to 
the great toe as a separate muscle, the extensor hallucis brevis (Richard, 
2003).   
     The tendons of the anterolateral leg muscles may be seen through the 
thin skin of the dorsum of the foot, the otherwise thin deep fascia of the 
dorsum of the foot thickens to form two specialized structures-the 
extensor and peroneal retinacula. The extensor retinaculum has superior 
and inferior subdivisions. The superior extensor retinaculum connects the 
distal ends of the fibula and the tibia. The inferior extensor retinaculum 
begins on the calcaneus laterally and arches over the dorsum of the foot to 
attach to the tibial malleolus and the medial side of the calcaneus. It 
surrounds or covers all of the deep tendons, vessels and major nerves on 
the anterior surface of the foot. The superior peroneal retinaculum 
connects the lateral malleolus and calcaneus; the inferior peroneal 
retinaculum connects the calcaneus and plantar aponeurosis. The 
peroneus longus and brevis are enclosed in these retinacula (Thibod & 
Patton, 2000). 
 

12 
     The medial longitudinal arch (MLA) is thought to develop most 
rapidly until the age of 6 years, after which changes are less apparent. 
There is, however, much debate on MLA development during the critical 
age range of 7 to 9 years. Within this age range, some studies 
demonstrated that the MLA remained fairly stable, whereas other studies 
showed that the foot arch was becoming higher. The foot arch also was 
reported to become flatter from 7 to 8 years of age and to show a reversal 
to a higher arch from 8 to 9 years of age. Therefore, it is still uncertain at 
which point the MLA stops developing in children. In addition, it is 
currently unknown whether MLA development differs between boys and 
girls, although cross-sectional studies suggested that boys tend to have a 
flatter foot type than girls. There is a need to clarify the conflicting 
reports on MLA development in boys and girls during the critical age 
range from 7 to 9 years using a longitudinal approach. Subsequently, 
health care practitioners can make informed decisions when managing 
flexible flatfoot in children (Waseda et al., 2014). 
     The structures of the foot are anatomically such that the load is evenly 
distributed over the foot during weight bearing. Approximately 50%of 
body weight is distributed through the subtalar joint to the calcaneus, with 
the remaining 50% transmitted across the metatarsal heads. The head of 
the first metatarsal sustains twice the load borne to by each of the other 
metatarsal heads. A factor that influences this loading pattern, however, is 
the architecture of the foot. Several factors may affect the foot pressure 
distribution. Those factors may be structural (e.g. bony prominence), 
functional (e.g. restricted range of motion) and type of footwear (e.g. 
pointed shoes), body weight, and walking speed (Nurse and Nigg, 2001). 
 
 

13 
CHAPTER III 
SUBJECTS, MATERIALS AND METHODS 
 I- Subjects: 
     This study will be conducted on ninty two healthy adolescents from 
both sexes to determine the effect of different backpack carriage styles on 
plantar pressure distribution in adolescents. They will be recruited from 
public and private schools at Mansoura city.  
Inclusion criteria: 
• Their age will be ranged from 12 to 18 year.  
• Their body mass index (BMI) is within normal range according to 
BMI for age percentile score (WHO, 2007). 
• All adolescents will be free from postural deviation, the trunk 
rotation in all students is within normal degree determined by 
scoliometer (Bunnel, 1993). 
Exclusion Criteria: 
• Visual, auditory or perceptual deficits. 
• Deformities at any joint of the lower limbs and spine. 
• Surgical intervention in foot. 
• Deep sensory loss.                                    
• Musculoskeletal disorders. 
 
 

14 
II- Instrumentations: 
 -  For selection: 
    1- Weight and height scale: 
    A valid and reliable weight and height scale will be used for all 
students to measure weight in kgs and height in cm. 
     2- Body Mass Index for age percentile charts: 
    Body mass index will be calculated using BMI for age percentile score 
charts to determine BMI category  according to (Who, 2007) through the 
formula of (BMI=Body weight (Kg)\𝐻𝑒𝑖𝑔ℎ𝑡2 per meter (𝑚2) 
3-Scoliometer: 
The scoliometer is an inclinometer designed to measure trunk 
asymmetry, or axial trunk rotation (Gideon et al., 2017). Strong levels of 
evidence exist for scoliometer measurements, with a high reliability (r 
= .86–.97) and high validity (Ashleigh Prowse et al., 2016). It is hand-
held circular fluid filled disc with a weighted gravity pendulum indicator 
that remains oriented in the vertical direction (Katarzyna et al., 2018). 
 -  For evaluation:  
     1-Foot scan plate system: 
     A foot scan is the method used to examine the biomechanics of the 
foot. It provides a dynamic weight bearing computerized assessment of 
the biomechanics of a person's feet. The system measures the weight 
distribution at all contact points along the bottom surface of the foot 
(Tan, 2005).  It is valid and reliable tool for quantifying static and 
dynamic plantar pressure   (Huang et al., 2017). 
     Foot scan plate system includes the following components: 

15 
• The pressure sensors platform.  
• Computer for data acquisition, storage and retrieval for analysis. 
• Software to allow the physical therapist to divide the planter 
surface of the foot into numerous regions to permit the analysis of 
data. 
• The pressure plate containing sensors (pressure gauges), which 
convert the mechanical pressure of the foot into electrical signals 
routed to the computer system (Morag and Cavanagh, 1999). 
2-Backpack: 
     Two backpacks will be used for all students, one with unilateral 
padded shoulder strap and the other with bilateral padded shoulder straps. 
The features that were typical in the majority of school backpacks, 
comprising a soft fabric backpack with no internal framing or back 
support and no internal compartments. Different weights will be used 
inside each backpack to represent the percentage of 15% of body weight. 
III- Procedures: 
 -  For selection:  
     Scoliometer will be used to measure any asymmetry of the sides of the 
trunk in axial region in degrees. The students will be examined from 
standing position, with bare trunk, with trunk anteriorly flexed and almost 
parallel to the ground, with relaxed arms, hanging perpendicular to the 
trunk. The trunk rotation is within normal limits from 0o to 3o (Bunnell, 
1993). 
-  For evaluation:  
    The purposes and procedures will be explained in details for all 
students and their parents to obtain their interest, confidence and co-

16 
operation. All parents of students will sign a consent form approving their 
children participation in this study. 
Subject preparation: 
• The adolescent personal data (name, age, weight and height and 
shoe size) will be collected and then stored on the computer in their 
specific folder.  
• Each student stands with eyes open and looking forward.  
• Each student takes off shoes and stand with two leg stance on the 
platform of the device.  
• Each student will carry the backpack with its bottom at the level 
above the posterior iliac spine (backpack at the level of the hip) 
either during unilateral or bilateral backpack carrying (Kellis and 
Arabatzi, 2009). 
Adjustment of apparatus: 
•  Callibiration of the instrument needs the subject to stand over the 
platform by his feet then by single foot. 
• The system is activated and ready to record the pressure. 
• The software provides the calculations for the pressure values 
according to the pressure imposed on the plate.  
• It uses specified color to display the pressures acting on the planter 
surface of the foot in various preset colors the red and purple colors 
denoted graphically the highest pressure, while the green, blue and 
black colors represented the lowest pressure values. 
• The area calculated refers to the amount of surface contact between 
the planter surface of the foot and sensor.  
• The measurement will be done in the preset scanning direction 
denoted by the manufacturer. 

17 
Measurement procedures: 
- All students will be assessed during four conditions as follows; 
without carrying backpack, carrying backpack bilaterally, carrying 
backpack unilaterally on right and left sides. 
- Measurements will be taken during standing (static plantar 
pressure) and walking (dynamic plantar pressure). 
-  Analysis will be initiated by locating the second metatarsal head 
then the foot area is divided into eight zones. 
- The measured variables will represent peak pressure, average 
pressure and surface contact under the three anatomical regions of 
the foot, the fore foot including the medial fore foot (big toe and 
first metatarsal), lateral fore foot including (small toe and fifth 
metatarsal), the mid foot including (medial and lateral mid foot) 
and the heal regions (medial and lateral hind foot). 
 
 
 
 
 
 
 
 
 
 
 
 
  
 

18 
                                     Data analysis 
The data will be analyzed as follow: 
- Descriptive statistics for age, height, weight and BMI. 
- The mean value and standard deviation will be calculated for all 
measured variables. 
- Analysis of variance (ANOVA) with repeated measures will be 
used to compare measured variables at different conditions. 
- Level of significance will be determined at P<0.05. 
 
 

19 
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