It’s finally here! The article you’ve all been waiting for…or maybe just some of you. I know we’ve been waiting for and talking about this one for a while. The crew at Houston Methodist just published a study involving BFR post ACL reconstruction. This study was a little different than the other ones we’ve seen previously in that they went beyond the assessment of muscle size, muscle strength, and functional outcomes. They added the assessment of bone using a DEXA scan and the long term outcome of meeting return to sport criteria. Let's take a closer look at what they did and what they found.
Participants all underwent an ACL reconstruction with BTB autograft and were randomized into a BFR (n=17) or Routine Rehab (control, n=15) group. The intervention period started within 7 days of surgery and involved 12 weeks of progressive rehab performed twice a week. The BFR condition performed “select exercises” at 80% LOP and 20% 1RM for the commonly prescribed 30/15/15/15. Individual’s 1RM was assessed in the uninvolved limb - Brutal!. DEXA scans were done pre-surgically and at 6 and 12 weeks post-op. Assessments of lower extremity function including single leg squat, single leg step down, Y Balance, single leg leg press, and single leg hamstring curl were done at 8 and 12 weeks post op. After the 12 week intervention period, subjects were required to complete supervised PT out to at least 6 months post surgery.
What they Found:
The BFR group had better preservation of whole limb bone mass and site specific (femur, tibia, and fibula) bone mineral density (BMD) at 6 and 12 weeks post surgery
The BFR group had better preservation of lower extremity lean mass at 6 and 12 weeks post surgery
There was a similar improvement in functional measures in both groups between week 8 and week 12
The BFR group did better than the control group in the anterior Y-balance
The BFR group met return to sport criteria (cleared by a physician) 1.4 months faster than the control group
As informative as these research papers are, the description of what was done can leave things to the reader's imagination. Instead of us giving you our own interpretation of the details of this study and how it adds to our understanding of BFR in post operative care, we thought it would be helpful to sit down and have a discussion with one of the clinicians/authors on the paper. Here’s how that went down:
Ben: As with most studies, the methods leave some things open to interpretation. Can you clarify the exercise intensity and how it was determined for the BFR and the Control group?
Corbin: With the BFR group, we wanted to stick to the standard 20-30 %1RM that is used in most studies and we thought we would err on the side of 20% as the target. We decided we were going to do a 1RM on the opposite limb as long as the other limb was healthy and we did that for all of the loaded exercises other than things like quad sets and SLRs. For the control group, we didn’t do the same 1RM testing on the opposite limb but we tried to make the group as effort matched as we could. We did the 30, 15, 15, 15 and progressed the intensity or loading if all of the reps could be completed.
Ben: How did participants tolerate BFR and the exercise intensity that early after surgery? Were there any modifications needed?
Corbin: Fortunately, I don’t remember any of the participants that we had to hold off on or really modify the protocol for. We were mindful of massive effusion or leaky incisions and would have held off a couple extra days for something like that, but for the most part everyone was ready to go at the one week mark. With the BFR group, we were only doing quad sets with BFR for the first couple weeks and 80% LOP was tolerated well for everyone in the study.
Ben: How did you guys progress loading and was it the same across both groups?
Corbin: The progression of loading was left up to the treating clinician and was done session by session based on completing the prescribed volume of reps. It was set up to be similar to the load progression in routine clinical care.
Ben: What are your thoughts on the lack of difference between groups in functional outcomes at 8 and 12 weeks?
Corbin: That was a tough one for me since I was excited about the potential difference between groups. I think it may have just been too early or too short of a timeframe to see changes. Looking at the data and especially the lean mass differences between groups at that time, it looks like it was just a matter of time to see measurable functional differences between groups.
Ben: What are your major takeaways from this study?
Corbin: The biggest takeaway from this study was the difference in bone between groups. It’s something that we thought was there from what we’ve seen with BFR but it hadn’t really been measured formally or shown directly in other research. The bone side of things is definitely going to be a part of how we plan research going forward.
Ben: If you could do the study again, would you do anything differently?
Corbin: I would do more exercises to give more of a BFR stimulus to the BFR group. I would also like to see the functional outcomes taken further out and assessed at a later time point than 12 weeks.
Ben: Have the results of this study changed how you manage patients following ACLR?
Corbin: It really just confirmed what we thought all along. BFR is a safe intervention to use early after surgery without anything adverse happening and it looks like it has the potential to improve the patient outcome especially in regards to overall lean mass.
It was great to get the additional context from Corbin and we really appreciate him offering his time. We look forward to seeing additional research come from him and the group at Methodist.
Like most publications, this study doesn’t answer all of the questions we have about BFR. It does show the potential for BFR to affect more than just muscle and that applying BFR early after surgery is well tolerated without causing adverse events. Check out the paper for yourself at the journal website. We’re planning a future podcast with Corbin so send us any additional questions you want us to ask about this paper or their future projects.
Jack, R. A., 2nd, Lambert, B. S., Hedt, C. A., Delgado, D., Goble, H., & McCulloch, P. C. (2022). Blood Flow Restriction Therapy Preserves Lower Extremity Bone and Muscle Mass After ACL Reconstruction. Sports Health, 19417381221101006.