Quadriceps Activation Comparative Analysis Based on Positioning of the Ankle During Supine Straight Leg Raise and Quad Set
Conditions: Quadriceps Muscle Atrophy, Leg Injury
Sponsor: Andrews Research & Education Foundation

Quadriceps Activation Comparative Analysis Based on Positioning of the Ankle during Supine Straight 
Leg Raise.  
Tyler Opitz DPT, SCS, CSCS 
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Title:   
Quadriceps Activation Comparative Analysis Based on Positioning 
of the Ankle During Supine Straight Leg Raise and Quad Set 
 
 
Principal Investigator:  
Tyler Opitz, DPT, SCS, CSCS 
 
Co-Investigators:  
 
 
Adam Anz, MD 
Chandler Bridges, MS 
Jessica Truett, BCBA 
Victoria Williams 
Joshua Cook, BS 
 
 
 
 
 
 
 
 
Funding Mechanism:   
State of Florida Grant 
 
Institution(s):   
 
Andrews Institute- Rehabilitation 
 
 
 
 
1040 Gulf Breeze Pkwy. 
 
 
 
 
Gulf Breeze, FL 32561 
 
 
 
 
(850) 934-2180 
 
 
1 
Background / Scientific Rationale 
 
Returning quadriceps neuromuscular control and preventing atrophy is an area of intense current 
interest in orthopedic rehabilitation and recovery science. It is clear that returning full 
autonomous control of the quadriceps, including the vastus medialis obliqus (VMO), at full knee 
extension is an important factor in rehab and dysfunction of the quadriceps leads to a loss of 
physical performance and self-reported function1-4. Quadriceps function is critical for optimal 
ambulation patterns and eccentric control is essential for the weight acceptance phase of gait5,6,7.   
 
Quadriceps atrophy is one of the most common post-operative side effects of anterior cruciate 
ligament (ACL) reconstruction, total knee arthroplasty, and many other surgeries including 
meniscal repairs, patella realignment procedures, and microfracture procedures1-4. Due to the 
swelling within the joint after injury or surgery to the knee, the joint inflammation cascade 
occurs and leads to the quadriceps being arthrogenically inhibited by spinal neuron inhibition as 
a protective mechanism5. These neural changes usually lead to decreased voluntary quadriceps 
contraction6. Additional contributions of inhibition from post-operative pain, patient 
apprehension, and surgical procedure requiring protection of the repaired tissue5,7,8. The sooner 
one regains control of the quadriceps muscles the less atrophy occurs, reductions in strength are 
minimized, and the more optimal the outcome is achieved for patient recovery9.  
 
Studies have shown that neuromuscular electrical stimulation (NMES), Transcutaneous electrical 
nerve stimulation (TENS), and biofeedback techniques can limit post-operative quadriceps 
atrophy and can return strength of the quadriceps back to normative values faster than without 

Quadriceps Activation Comparative Analysis Based on Positioning of the Ankle during Supine Straight 
Leg Raise.  
Tyler Opitz DPT, SCS, CSCS 
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those techniques and traditional therapeutic exercise and have better long-term outcomes based 
on pain, functional outcomes, and return to sport participation rates1,7,10-12.  
 
Irradiation effect is a proprioceptive neuromuscular facilitation technique that causes an 
overflow of neuronal energy from distal to proximal muscles to increase muscle activity of a 
targeted muscle13,14. This technique can be used to selectively recruit weaker motor units through 
the application of resistance or stimulation13-15. By inducing a stronger contractile force of the 
quadriceps, our hope is to return quadriceps function to normal quicker with less atrophy and 
greater strength3,6,12.  
 
We hypothesize that ankle positioning in maximal dorsiflexion (DF) changes the quantity of 
contraction as a percent of the reference voluntary contraction when performing a supine straight 
leg raise compared with having the foot in neutral (0°), relaxed, and plantarflexed (PF) positions. 
This may help provide insight into proper instruction and cuing for patients to return quadriceps 
neuromuscular control sooner and thus limiting quadriceps atrophy. 
 
2 
Objectives 
 
Aim 1: Determine the effects of ankle positioning on quadriceps neuromuscular activation 
during supine straight leg raises. 
 
Aim 2: Determine if there is a difference between ankle positioning on quadriceps 
neuromuscular activation during straight leg raises in supine in healthy versus post-operative 
participants. 
 
3 
Participant Eligibility 
 
All Participants 
 
Inclusion Criteria: 
 Males and females ages 18-55 
Exclusion Criteria: 
 History of diagnosed cancer, neurological disorder, peripheral nerve injury 
affecting the lower limb or injury to the lower spine with radicular symptoms, 
which may affect quadriceps activation 
 History of musculoskeletal injury to the quadriceps that may affect ability to 
maintain muscle contractions without excessive fatigue or discomfort 
 
Healthy Controls 
 
Exclusion Criteria: 
 Injury to the knee or the quadriceps muscle group within the past 12 months to the 
tested side 
 History of lower extremity orthopedic surgery in the past 12 months to the tested 
side 
 

Quadriceps Activation Comparative Analysis Based on Positioning of the Ankle during Supine Straight 
Leg Raise.  
Tyler Opitz DPT, SCS, CSCS 
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Participants with Arthroscopic Knee Surgery 
 
Inclusion Criteria:  
 Arthroscopic knee surgery including a meniscectomy, chondroplasty, 
debridement, loose body removal, and plica excision within the past 28 days 
 Scheduled for physical therapy at Andrews Institute Rehabilitation 
Exclusion Criteria: 
 Multiple ligament reconstruction 
 Total joint arthroplasty 
 Major surgical complication (infection, deep vein thrombosis, surgical revision, 
neural impairment/pathology) 
 
4 
Participant Enrollment 
 
We intend to enroll 100 volunteers. 50 participants with knee arthroscopy to be tested within the 
first 28 days after surgery and 50 healthy control participants will be recruited for this study by 
word of mouth and participants will be screened for inclusion and exclusion criteria. Healthy 
control participants will be matched by age and leg tested (dominant or non-dominant) with 
participants in the knee arthroscopy group. Dominant leg will be identified as the leg that the 
participant uses to kick a soccer ball. Potential participants will have the study described to them 
including potential risks and will be given the opportunity to read and sign an approved informed 
consent form. This process will take place prior to any study related activities. If the participant 
meets inclusion and exclusion criteria, the participant will be scheduled for a testing appointment 
at the Andrews Research & Education Foundation. 
 
5 
Study Design and Procedures 
 
Participants will be screened for all inclusion and exclusion criteria during subject recruitment 
and will be asked to refrain from heavy lifting, exercise, and any activity that may cause fatigue 
of the leg muscles 24 hours prior to the testing session. The participants who have undergone 
knee arthroscopy will be tested on a day they have not done physical activity. The participant’s 
age, date of birth, height, weight, and surgical history (if applicable) will be collected on the 
Knee History Form (attached), which has been adapted from the 2000 International Knee 
Documentation Committee Knee History Form, and participants will complete the visual analog 
scale for pain (VAS).   
 
Participants will have surface electromyography electrodes placed on the skin overlying the 
vastus medialis oblique (VMO), rectus femoris (RF), vastus lateralis (VL), and tibialis anterior 
(TA). Electrode locations will be identified through palpation of the muscle belly and electrodes 
will be placed according to SENIAM recommendations. The identified locations for electrode 
placement will be shaved, abraded, and cleaned using standard medical alcohol swabs. 
Subsequent to surface preparation, adhesive Noraxon Single Electrodes, 4cm Ag/AgCl diameter 
disk shaped, surface electrodes (Noraxon USA, INC, Scottsdale, Arizona) will be attached over 
the muscle bellies and positioned parallel to muscle fibers using previously published 
standardized methods.16 Electrodes will not be replaced or moved throughout the entire data 

Quadriceps Activation Comparative Analysis Based on Positioning of the Ankle during Supine Straight 
Leg Raise.  
Tyler Opitz DPT, SCS, CSCS 
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collection. Electromyographic data will be collected via a Noraxon myoMuscle Ultium EMG 
(Noraxon USA, INC, Scottsdale, Arizona). Surface EMG data will be visually monitored during 
the collection of data and sampled.   
 
Following the application of surface electrodes, the reference voluntary contraction 
normalization method will be utilized so that all surface EMG data can be normalized16. The 
reference posture will be a SLR performed to the height of the contralateral knee flexed to 90 
with a level to ensure appropriate height is achieved with the moving limb performing max 
dorsiflexion throughout the motion. Participants will maintain the reference posture for 5 
seconds and the middle 3 seconds of the contraction will be selected for data analysis. Two 
reference voluntary contraction trials will be performed, and the data will be averaged. 
Participants will be given 30 seconds of rest between each trial. The reference voluntary 
contraction method was chosen for normalization to account for the knee arthroscopy 
participants pain and possible weakness16. Pain and weakness post arthroscopy could hinder 
obtaining maximal isometric contractions through manual muscle testing. Several studies have 
shown that within 3 days of knee joint surgery patients can lose up to 80-90% of their quadriceps 
strength due to a phenomenon called arthrogenic muscle inhibition (AMI) that is in part due to 
surgical trauma as well as joint effusion17,18,19. 
 
Participants will then have 3 practice repetitions in each position of the foot for a total of 9 
repetitions.  Upon completion, participants will perform 5 repetitions of SLR and quad sets with 
the foot in active maximal DF, PF, and a relaxed foot position. In total there will be 15 reps 
performed. Joint angles will be measured using a goniometer and participants will be instructed 
to maintain that foot position throughout the motion of the SLR as well as being verbally cued 
throughout the duration of the task. Video tracking will be used to determine when the motion 
begins and ends for each repetition. Order of foot positioning and performance of exercises will 
be randomized. Muscle activation will be recorded for each repetition and 5 repetitions of each 
foot position will be analyzed. Healthy control participants will perform the exercises on bilateral 
limbs as will the surgical participants with randomization determining which is done first.  
 
Participants will place the foot in the desire position prior to the quad set and any motion of the 
leg and will maintain the foot position throughout the motion of the task. The participant will 
then perform a quad set holding for 1 second, then raise the leg taking approximately 1 second to 
raise the leg to the height of the contralateral limb with the knee flexed to 90 (based off 
goniometric measurements), hold for 1 second at the top and lower during the SLR taking 
approximately 1 second, then continue to hold the quad set for 1 second with the foot in the 
specified position while the leg is on the table, then relaxing. During the quadriceps set the 
participant will actively contract their quadriceps for a maximum total of 5 seconds performing 5 
repetitions in each foot positioning and the muscle activation will be recorded. The knee will be 
extended active maximally as is customary with the performance of a quadriceps set and straight 
leg raise with the participant in the supine position, and remain extended throughout the task. 
Participants will be asked to maximally contract their quadriceps for the duration of the task as 
well. There will be a minimum of 1 second duration during both the concentric and eccentric 

Quadriceps Activation Comparative Analysis Based on Positioning of the Ankle during Supine Straight 
Leg Raise.  
Tyler Opitz DPT, SCS, CSCS 
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phases of the movement. Participants will have a minimum of 60 seconds of rest between each 
repetition. 
 
Before starting each straight leg raise, a rest period of muscle activity will be recorded with the 
participants ankle in the respective testing position (active maximal DF, PF, and a relaxed foot 
position). This will allow for the option for the EMG signal to be rectified and adjusted for 
baseline noise by subtracting the mean of the rectified signal during the quiet period (before the 
start of each exercise) from the rectified signal. 
 
Analysis will be performed with the first repetition and the last repetition being omitted and the 
average of the remaining 3 repetitions will be done for each testing position for both controls and 
intervention groups. 
 
A video camera will be used to record the performance of each exercise. EMG and video 
acquisition will be synchronized. Each repetition will be sub-divided in 2 phases: concentric 
phase defined as when the participant works against gravity to actively lift their leg of eccentric 
phase defined as when the participant works against gravity to slow down the return to the 
starting point of the concentric phase. 
 
 
6 
Expected Risks and Benefits 
 
Risks and Discomforts: 
 
The risks of this study are minimal but do include quadriceps fatigue and gastrocnemius/soleus 
as well as tibialis anterior muscle fatigue. To minimize muscle soreness and fatigue, adequate 
rest breaks will be utilized between sets of contractions. The exercise is strictly designed to keep 
heart rates normal and measure strength of the quadriceps contraction. The appeal of this 
exercise regimen is that it is not strenuous and can be used during the first rehabilitation day after 
surgery while at the same time eliciting changes in quadriceps activation that can be used for 
proper instruction by therapists and trainers to their patients for optimal rehabilitation. This 
exercise is designed to keep heart rates in normal exercise ranges. There is a slight risk of 
temporary skin irritation occurring when the surface EMG electrodes are removed from the skin. 
The skin may appear to be red after the electrodes are removed. 
 
Benefits: 
 
No direct benefits are expected for the participants involved in the study, however results from 
the study should help clinicians better understand the current cutting edge in exercise technology. 
 
 
7 
Data Management Procedures 
All personal information is strictly confidential and no names will be disclosed except as 
required by law. Data sheets will have names and identifying information replaced with a 
participant code to protect the confidentiality of the participant. All information provided by the 

Quadriceps Activation Comparative Analysis Based on Positioning of the Ankle during Supine Straight 
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participant during this project will be recorded on the appropriate forms and stored in a locked 
room in the Andrews Research & Education Foundation (AREF) research facility. In addition, 
all participant data forms will be scanned and stored, along with summary information forms, 
spreadsheets, and photos, in a secure password protected folder on a laptop in which only study 
investigators will have access to and will be permanently deleted following any and all 
publications or presentations have been completed related to this research. All records related to 
this research will be retained in a secure location for a period of 3 years following the completion 
of all study related activities, at which time they will be properly destroyed.  
 
8 
Data Analysis 
 
Data will be analyzed using custom-built MATLAB Software. Rectified EMG will be smoothed 
and filtered according to standard procedures for human surface EMG. Root mean square values 
will be calculated and normalized to the reference voluntary contraction. Root mean square 
values will be calculated for each repetition of the SLR and for each of the three phases 
(isometric, concentric, and eccentric) and across the whole trial. Processed data will be exported 
to Microsoft Excel and SPSS.  
9 
Statistical Considerations 
 
Statistical analysis will be performed in excel and SAS Studio (Version 3.8 on SAS 9.4, SAS 
Institute Inc., Cary, NC). A 2 (group) x 4 (position) x 3 (phase) MANOVA will be performed for 
each muscle and appropriate post-hoc tests will be used to ascertain differences among variables. 
The alpha level will be set a priori at p < .05.  
 
10  
Quality Control and Assurance 
 
All protocols will be monitored and analyzed data will be checked for accuracy by the principal 
investigator and/or a designated research team member. All medical data will be kept in 
compliance with HIPAA guidelines.  
 
11 
Regulatory Requirements 
 
Informed Consent: 
The informed consent process will be performed by one of the study investigators or staff. All 
participants will have the study described to them and will be given as much time as they would 
like to read an approved, stamped version of the informed consent document. After signing the 
informed consent document, they will be given a copy for their records. This process will take 
place at the AREF. 
 
Participant Confidentiality: 
 
Participant confidentiality information is listed above in #7 (Data Management Procedures). All 
medical data will be recorded and stored in compliance with HIPAA guidelines. 

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Tyler Opitz DPT, SCS, CSCS 
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12 
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Leg Raise.  
Tyler Opitz DPT, SCS, CSCS 
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