Effects of Blood Flow Restriction Rehabilitation After Bone Patellar Tendon Bone Anterior Cruciate Ligament Reconstruction
Phase: NA
Conditions: ACL Tear
Sponsor: The Methodist Hospital Research Institute

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PROTOCOL TITLE: 
 
1) Protocol Title Effects of blood flow restriction rehabilitation after bone patellar tendon bone 
anterior cruciate ligament reconstruction 
 
2) Investigator Patrick McCulloch, MD 
 
3) Objectives  
Athletes commonly experience a significant amount of muscular atrophy following ACL 
reconstruction surgery associated with an increased risk of re-injury and an increase in time of 
recovery and return to sport participation.  A combination of low intensity resistance exercise 
and blood flow restriction (BFR) therapy has been shown to elicit responses similar to high 
intensity resistance exercise with regards to reduced risk.  We hypothesize that chronic low 
intensity resistance exercise combined with BFR will improve muscular strength, reduce skeletal 
muscle atrophy, and will enhance recovery.  Therefore, the specific aims of this study are as 
follows: 
 
1. Determine if BFR added to standard post-operative rehab will prevent skeletal muscle 
atrophy and promote skeletal muscle growth during 12-weeks of rehab training compared to 
traditional rehab alone. The working hypothesis, founded on previous literature, is that 
combined rehab and BFR will enhance skeletal muscle growth and prevent atrophy to a greater 
extent than rehab alone. 
2. Determine if BFR added to standard post-operative rehab will improve muscular strength 
following surgery compared to traditional rehab alone.  Because strength can be attributed to 
skeletal muscle mass, the working hypothesis, founded on previous literature, is that combined 
rehab and BFR will enhance skeletal muscle strength and fatigue resistance to a greater extent 
than rehab alone. 
3. 
Determine if BFR added to standard post-operative rehab will improve functional 
outcomes following surgery compared to traditional rehab alone.  The working hypothesis, 
founded on previous literature is that BFR will improve functional outcomes over rehab alone. 
 
The expected outcome of the proposed work is the identification of a novel therapy that can 
overcome muscle atrophy and decrease recovery time following surgery. The findings of the 
proposed study will have a positive impact, because they will allow us to translate this 
information into evidence-based clinical interventions to improve functional outcomes with 
reductions in risk during rehab and upon returning to sport participation. 
 
 
4) Background  
Athletes who undergo ACL reconstruction are known to experience quadriceps atrophy with 
resulting decreased strength in their injured extremity.  This is likely due to their inactivity 
following injury and also to disuse atrophy during initial post-operative period.  It has been 

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shown that some patients may continue to have atrophy even 9 years post ACL reconstruction 
[1].  As a result, there is an increased risk of re-injury and an extended timeline for recovery and 
return to athletic participation.  Current intensive rehabilitation programs accelerate return to 
play timelines, however, the initial quadriceps atrophy prior to beginning formal rehabilitation is 
still not addressed.  Therefore, the need for more effective rehabilitation methods is of great 
interest to clinicians and physical therapists.  
 
Blood flow restriction (BFR) exercise training, has been shown to induce skeletal muscle 
hypertrophy (growth) even when using low resistance loads (<30% One-repetition maximum).  It 
has also been shown that BFR significantly improves fatigue resistance and greater strength 
gains compared to traditional resistance training alone [6,7].  In a recent study involving Division 
IA athletes, low resistance BFR training was shown to increase strength and muscle size as 
compared with traditional high resistance training in as little as four weeks [8].  Strikingly, blood 
flow restriction alone has been observed to decrease atrophy of the quadriceps following ACL 
reconstruction [10].  Thus, this type of training may be promising for ACL reconstruction 
patients who are unable to partake in heavy weight training post-operatively.    
 
While the mechanisms that promote recovery and an increase in skeletal muscle hypertrophy are 
not well understood, it has been hypothesized that BFR elicits a stress response associated with 
decreases in intramuscular pH, accumulation of metabolites, increases in the ratio of carbon 
dioxide to oxygen, and changes in osmotic pressure [11].  In laymen’s terms, these effects are 
similar to high volume / high intensity exercise but achieved with minimal resistance and 
reduced risk to the patient following surgery.  Similar to high intensity resistance exercise, BFR 
exercise with low resistance levels elicits significant elevations in protein synthesis and 
associated changes in anabolic signaling within skeletal muscle cells (14).  Encouragingly, BFR 
exercise does not show increase in markers for muscle damage such as myoglobin or creatine 
kinase [2].  
 
Much effort has been made to optimize BFR training in terms of optimal cuff size, occlusion 
pressures, and training weight or resistance.  Scott et al have provided a guideline for BFR 
therapy [18]. The generally agreed upon low resistance weight amount should be 20-30% of the 
maximum repetition (1RM) for the given exercise [7,18,19].  However, optimal training 
durations have yet to be determined.  Additionally, functional assessments following chronic 
BFR training and association between changes in leg muscle mass and performance have yet to 
be thoroughly evaluated.   In light of the present literature, we hypothesize that 12 weeks of 
combined low intensity leg exercise and BFR therapy will mitigate post-operative muscular 
atrophy, improve muscular strength, and improve functional outcomes in athletes following ACL 
reconstruction surgery compared to a traditional rehabilitation program in men and women 
athletes (age 18-35yr).     
 
 
5) Setting of the Human Research  
The study will start for each subject in the clinic setting.  Consent for the study will be obtained 
after explaining all aspects of the study.  The subject will undergo their scheduled procedure in 
the operating room with no differences between the control group and study group.  Physical 
therapy will take place at two locations in Houston, two times per week for 12 weeks.  

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Questionnaires will be conducted before surgery, prior to physical therapy instructed BFR 
exercises at week two, two months, six months, and one year post-operatively.  Questionnaires 
will take 20 minutes to complete.   
 
6) Resources available to conduct the Human Research  
DEXA (Dual Xray Absorptiometry) Scanner 
Automated Electronic Blood Flow Restriction Cuffs (used for physical therapy) 
Rehabilitation exercise equipment. 
Rehabilitation facility.   
 
7) Study Design  
The study will be a prospective randomized control trial consisting of subjects requiring ACL 
reconstruction with BTB autograft. Subjects will be randomly divided into two groups following 
their inclusion in the study. One group will undergo the normal ACL rehab protocol as 
determined by Drs. Harris and McCulloch.  The study group will undergo normal ACL rehab 
modified by use of a tourniquet for blood flow restriction during selected exercises. 
 
On the day of the procedure, the surgeon will measure the subject’s thigh circumference 1/3 
distance from the superior pole of the patella to the inguinal crease.  The subject will then 
undergo the normal BTB autograft ACL reconstruction procedure.  A subject will be excluded 
from the study if a meniscal repair is performed.  At the subject’s two week post-operative clinic 
visit, the physician will measure thigh circumference at 1/3 distance from the superior pole of the 
patella to the inguinal crease. Study group subjects will begin physical therapy instructed BFR 
exercises at two weeks post operatively. Study group subjects will be taken through normal ACL 
rehab protocol as well as BFR exercises. Control group subjects will do the same exercises and 
formal physical therapy rehab protocol as the study group without BFR. 
 
The BFR exercises will consist of: bilateral leg press week 3-10, eccentric leg press weeks 4-10, 
hamstring curl week 4-6, eccentric hamstring curl weeks 7-10, straight leg press weeks 6-10.  
The pressure used will be elevated to occluded blood flow by 80% (80% occlusion pressure) 
which will be determined for each individual subject.   Subjects will do exercises at 20% of 1RM 
in 4 sets of 30-15-15-15 repetitions separated by 30 seconds of rest. Repetition maximum (1RM) 
will be determined by the contralateral leg, using the greatest amount of weight with full range of 
motion and proper form. This will be done over three separate tries, separated by one minute 
breaks.  Resistance loads will be adjusted every 2 weeks as strength improves.  During the 
exercise protocol, if patients are unable to complete the prescribed amount of repetitions, rest 
periods between sets will be increased as needed.  The control group will do these exercises 
without BFR.  Both study and control groups will also do the surgeons’ standard post-ACL 
reconstruction physical therapy protocol. 
 
Cuff pressures will be determined using the Loenneke et al outline, based off of thigh 
circumference and estimated cuff pressure for 50% artery occlusion [19].  
Body composition (DEXA), bone density (DEXA), IKDC and Tegner Lysholm scores will be 
recorded at first rehabilitation visit, two weeks, eight weeks and 12 weeks following the 
initiation of rehab (1 wk following surgery).  Y- balance, single leg squat distance, and single leg 

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step down will be measured at 8 weeks and 12 weeks of rehab.  Return to play will be recorded 
as the number of months after the day of operation until subject returns to sport. 
a) Recruitment Methods  
Patients will be informed of study after counseled in the clinic on their need for the 
procedure.  Patients will be recruited at the Houston Methodist Hospital by either Dr. 
Patrick McCullouch, Dr. Joshua Harris, or Dr. Robert Jack.    Patients will be asked if 
they would like to be included in the study before leaving clinic. If the patients agree to 
participate they will complete all necessary paperwork in the clinic. 
 
.  
b) Inclusion and Exclusion Criteria  
Subjects. We will test our central hypothesis in 70 healthy adults (18-35 yr) who are  
participating in athletics or are recreationally trained.  Exclusion criteria include subjects 
that demonstrate any of the following: 
• 
Concomitant meniscal tear or additional ligamentous injury to the knee 
• 
Obesity (BMI>30) 
• 
Diabetes 
• 
Cardiovascular, renal, liver or pulmonary disease 
• 
Active infections 
• 
Cancer (current or treated within the past 2 years) or coagulation disorder 
• 
Rapid weight change within the past year 
• 
Physically unable to participate in the intervention 
• 
Are not currently taking, or recently (w/in 1month of participation) taken  
prescribed or over the counter ergogenic aids or compounds known to be banned 
by the NCAA.  The NCAA banned substances list can be viewed from:  
http://www.ncaa.org/health-and-safety/policy/2014-15-ncaa-banned-drugs 
• 
Unable to complete a minimum of 85% of the assigned rehabilitation sessions. 
 
These conditions are excluded as they can impact muscle protein metabolism and training 
responses which would yield confounding the results.  
 
Criteria for stopping treatment: 
-Exorbitant pain (VAS >8/10) related or unrelated to exercise -Numbness, tingling, paresthesias 
>2 hours following any BFR session -Instability preventing safe, quality exercise -Nausea, 
severe headache, vomiting, fainting within 2 hours of BFR session 
 
 
e) Data management  
The PI will be responsible for all data collected, its confidential storage, and deletion 
after the study is completed. 
 
f) Withdrawal of subjects  
N/A 
 

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8) Risks to subjects  
Minimal risks of thigh pain at tourniquet site and deep venous thrombosis.  Minimal radiation 
exposure from DEXA scan measurement.  However, the radiation is comparable to participating 
in a long plane flight.  Minimal risk of injury to patients as they will be treated with the current 
standards of care during rehabilitation under close supervision from the physical therapy team.   
 
 9) Potential benefits to subjects  
Subjects in the BFR group may experience quicker quadriceps/hamstring strength recovery as 
well as earlier return to play. 
 
 
 
10) Provisions to protect the privacy interests of subjects  
PHI information will not be used or published in the study as all information will be used to form 
aggregate data. The data will be kept on a secure password protected, hospital server and will be 
deleted after the study is complete. 
 
11) Provisions to maintain the confidentiality of data  
See #10 
  
12) Cost to subjects  
The cost of a routine clinic visit, ACL reconstruction, and physical therapy sessions will be 
involved in this study.   No additional costs to the patient will be accrued with regards to the 
additional research portions of the evaluation. 
  
13) Consent process  
The subjects will then be asked in private, after explanation of the bone patellar tendon bone 
autograft ACL reconstruction procedure if they wish to participate in the study.  The consent will 
be read and either accepted/obtained or declined. Participants will also be asked if they are taking 
oral contraceptives or if they have a history of blood clots or pulmonary embolus in order to 
determine exclusion for oral contraceptives, blood clots, and pulmonary embolus. The 
participants will be told that they may opt out of the research study at any time- even after they 
have signed the consent to participate in the study.   
 
14) Process to document consent in writing  
The standard consent form for this project will be explained and if the subject wishes to 
participate the consent will be signed prior to the patient leaving the clinic on the day a BTB 
ACL reconstruction is decided upon as the treatment.  The PI will explain and obtain the consent 
for each participant in the study. 
 
 
 
 
 
 
 

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