At Issue: Blood flow restriction
Question: Is there sufficient evidence that blood flow restriction after ACL surgery aids pain control and strength recovery to warrant its regular use? If so, why?
Findings support consistent use of blood flow restriction in various patient populations
by Corbin Hedt, PT, DPT, SCS, CSCS
We have entered an era in which the divide between rehabilitation, strength and conditioning has evolved.
This former dichotomy now blends into a symbiotic understanding that exercise and activity are vitally important in injury prevention and recovery. Today’s physical therapist appreciates the delicate balance that exists between optimizing strength and muscle quality while avoiding undue stress, which may hamper rehabilitation efforts. These stressors, however, are all too common when engaging in physical activity which can limit a patient’s productivity while participating in physical therapy. Enter blood flow restriction (BFR) — a powerful tool that allows us to circumvent these challenges while improving strength, endurance and function, and mitigating pain.
As research elucidates the potential benefits of BFR with various patient populations, clinical use becomes increasingly popular. One of the major purported benefits seems to be the ability to modulate pain. Pain is a significant limiting factor for patients undergoing rehabilitation and, many times, is the primary cause for seeking physical therapy services in the first place. Whether acute injury, chronic disorders or post-surgical cases, reducing or preventing a patient’s pain is typically a main objective for the treating clinician. Interestingly, moderate-intensity exercise has proven to induce what is known as an “analgesic effect” — the temporary reduction in pain and symptoms. Once this effect takes place, we can potentially expect patients to achieve higher levels of function and capacity and gain more from their session in physical therapy. However, what happens when their specific injury or procedure precludes their ability to perform such exercise? Typically, one would have to resort to utilizing much lower-level activities to prevent pain or adverse stress and to achieve some sort of therapeutic effect. Unfortunately, this means more time and a prolonged recovery while working around the issues at hand.
However, recent studies have utilized BFR in cohorts of injured and painful populations and found some promising results, even with the more mundane and simplified exercises. We have seen acute and longer-lasting reductions in pain, which allow for greater compliance and consistency with physical therapy activities. Several mechanisms are being explored to help explain why these findings are occurring. Most seem to mirror those effects that we appreciate with reduced pain signaling during higher-level activities. Future studies should help to build on our understanding of the use of BFR to modulate pain levels.
Additionally, one of the most common reasons for using BFR in a clinical setting is to improve muscular strength. Early studies of BFR used with some of the larger, distal muscle groups have shown tremendous benefit when using low-load exercise with BFR vs. control groups that perform the same activities without BFR. In recent years, we’ve come to understand more about the effect on smaller, more proximal muscles, as well. The potential for muscle growth across the board is extremely valuable for physical therapists and their patients. Interestingly, even exercises which are not typically used as “strengthening” activities have still shown promise in improving muscle strength and endurance. Several studies have examined the effects of BFR with something as simple as walking on the treadmill. Not only is an improvement seen in the patients’ overall endurance with the activity, but a notable increase is seen in maximal oxygen consumption or VO2 max, as well. Many researchers will indicate that improved muscle mass and work capacity are to thank for these improvements. Ultimately, a majority of experts in the specialty and prevailing data will indicate that higher loads and exercise intensities will generally produce the most favorable results; however, in instances where loading and resistance are inappropriate, BFR allows for similar gains with less risk.
In rehabilitation and injury prevention, efficacy is key. While much is still to be learned about BFR in a clinical sense, current findings indicate its use is well-served and worthy of consistent utilization for a multitude of populations. Of course, safety should remain paramount when considering substantial new methods of exercise. This requires skilled and knowledgeable practitioners and devices that appropriately measure occlusion pressures to maximize the benefits and limit adverse effects.
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Timing, resistance used with blood flow restriction are important, data indicate
by Nathan P. Fackler, MS; and Edward S. Chang, MD
Yes, there is sufficient evidence to warrant the regular postoperative use of BFR in patients who undergo ACL reconstruction.
Postoperative quadriceps atrophy is a challenging problem patients face following ACL reconstruction (ACLR). Exercises directed toward building muscle mass can be achieved by loading muscle groups with at least 70% of the patient’s one-rep maximum. Unfortunately, patients cannot safely undergo these loads in the acute postoperative period due to the potential adverse effect on the surgical reconstruction. The main benefit of BFR comes from its ability to stimulate hypertrophy in the occluded limb at loads lower than the 70%, one-rep maximum, usually between 20% and 50% of patients’ one-rep maximum. This low-load (LL) exercise, coupled with BFR, can help safely resist muscle atrophy and encourage hypertrophy in the early postoperative period.
A systematic review by Mark Colapietro, MS, LAT, ATC, and colleagues published in February 2022 found six clinical trials that examined outcomes of BFR in post-ACLR patients. Since that review was conducted, an additional RCT was published on the topic. Three studies compared the effect of LL exercises on strength of the operative limb vs. BFR to LL exercises without BFR. Both Alan Kacin and colleagues and Haroyasu Ohta and colleagues began the BFR training they performed in the acute postoperative phase (0 to 2 weeks) and found the BFR cohort showed significant increases in quadriceps strength compared with the non-BFR cohort. The third group, Matthew A. Kilgas and colleagues, found no difference between the two groups. However, patients in this study underwent ACLR years prior to the trial, which is not the optimal time point for use of BFR.
Of the remaining four studies, two utilized high-load (HL, >70% one rep max) training for the control group. L. Hughes and colleagues and MT Curran and colleagues found no difference between the two groups with respect to strength. Finding no significant difference in strength between BFR and non-BFR groups at high load training makes sense conceptually, as both groups can achieve hypertrophy in their training. The remaining two studies, by E. Iversen and colleagues and Y. Takarada and colleagues did not measure strength.
The study by L. Hughes and colleagues highlights the importance of BFR with respect to strength and pain. Starting at postoperative week 2, the control group started performing HL workouts while the BFR group performed LL workouts. Both groups achieved similar increases in strength, however the BFR group had significantly lower pain as demonstrated by increases in KOOS-pain score by postoperative week 8 (67 vs. 39 for BFR and control, respectively). This study concluded that starting BFR with LL training can improve skeletal hypertrophy similar to HL training with a greater reduction in knee joint pain and effusion.
A randomized controlled trial by Flavio Fernanes Bryk and colleagues demonstrated similar findings to that of L. Hughes and colleagues, but these were found in a cohort of women with knee osteoarthritis. The patients in the control group underwent training at 70% of their one rep max and the BFR group underwent training at 30%. Both groups demonstrated similar increases in strength. Again, the BFR group showed lower levels of pain and effusion in the affected knee. Furthermore, a study Vasileios Korakakis and colleagues demonstrated that even a single physiotherapy session with BFR can provide pain relief for anterior knee pain. These studies demonstrate the wide applicability of BFR for knee pain and further support that BFR can help with postoperative pain control.
The existing data highlight the importance of timing and resistance used with BFR in patients postoperatively. For optimal effect, BFR is best utilized with LL training in the acute postoperative period, which helps patients achieve hypertrophy while reducing pain in a more efficient manner than the traditional rehabilitation protocol. These data, combined with the low risk of complications with the application of BFR, warrant the consideration of regular postoperative use of BFR in patients who undergo ACLR.
Bryk FF, et al. Knee Surg Sports Traumatol Arthrosc. 2016;doi:10.1007/s00167-016-4064-7.
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Curran MT, et al. Am J Sports Med. 2020;doi:10.1177/0363546520904008.
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Iversen E, et al. J Sport Health Sci. 2016;doi:10.1016/j.jshs.2014.12.005.
Kacin A, et al. Scand J Med Sci Sports. 2021;doi:10.1111/sms.13968.
Kilgas MA, et al. Int J Sports Med. 2019;doi:10.1055/a-0961-1434.
Korakakis V, et al. Phys Ther Sport. 2018;doi:10.1016/j.ptsp.2018.05.021.
Ohta H, et al. Acta Orthop Scand. 2003;doi:10.1080/00016470310013680.
Takarada Y, et al. Med Sci Sports Exerc. 2000;doi:10.1097/00005768-200012000-00011.