Blood Flow Restriction: Useful Training Method or Meaningless Masochism?

Hybrid Performance Method
September 4, 2019
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Reading time: 9-10 minutes 

Key points: a Summary and interpretation of a recent narrative review of blood flow restriction training. the article focused on

  • Standard BFR protocols a
  • Plausible mechanisms for reported benefits
  • Remaining questions
  • Sound advice for practical application

Background


Blood Flow Restriction (BFR) training is an emerging trend in physical therapy and strength and conditioning, but its roots extend surprisingly far back. The concept is simple. Apply cuffs to partially limit the blood supply of a limb, then exercise the limb to more efficiently fatigue it all else being equal. In theory, this process should amplify the stress signals that normally occur during strenuous exercise and lead to more powerful training adaptations. The potential applications would be virtually endless. In the 1960s, Anecdotal observations about the effects of intermittent claudication in certain clinical populations and the experiences of a Japanese aspiring bodybuilder contributed to the idea that would become a cottage industry. While interested parties have purported claims about its effectiveness since its inception, little high quality supporting scientific evidence existed until recently. As trends in physical therapy and rehabilitation shift away from passive manual therapy towards an emphasis on active care, exercise, and self-management, BFR research is now a priority for rigorous study.

Recent meta analysis indicate meaningful effects, suggesting efficacy in achieving hypertrophy with low training loads equal to that of high loads (Hughes, Paton, Rosenblatt, Gissane, & Patterson, 2017). A Review in the May issue of The Journal of Orthopaedic and Sports Physical Therapy (JOSPT) appraises the current evidence around BFR including, protocols, outcomes, possible mechanisms, indications, contraindications, limitations, and directions for future research.

Methods


Whitely compiles a list of 57 articles and lays them out in a narrative, “viewpoint” form, encouraging the reader to keep in mind that commercial bias in research is ever-present. This push to publish on BFR is also driven by industry-wide interest in exploring more exercise-based therapies as clinical researchers shift focus towards studying these interventions in search of the quality clinical effect sizes that are often lacking in large manual therapy studies (Rubinstein et al., 2019).

Indications


BFR is most useful when hypertrophy and/or strength is the goal, but heavy loading isn’t an option. In a clinical rehabilitation setting, intolerable pain or injury to a joint often limit loading options early in the recovery process. BFR provides a workaround by stressing the tissue without overloading the joint.

Plausible Mechanisms


The scientific understanding of the mechanisms underlying hypertrophy is evolving quickly, and BFR research highlights some of the key drivers in that process. BFR can produce equivalent hypertrophy as heavy resistance training because of its effects on fatigue accumulation, motor unit recruitment, cortical excitability, and cellular swelling. While some of these elements may directly stimulate hypertrophy in subtle ways all of these elements contribute to fatigue in the working muscle, forcing more fibers to experience higher forces and create more mechanical tension (Schoenfeld, 2013). Mechanical tension is widely considered the primary driver of hypertrophy. These effects, based on mechanical tension, may translate to muscles proximal to the cuff. Muscles such as pecs or glutes may get targeted as recruitment in these muscles increases to compensate for distal muscle failure. BFR’s effects on strength are limited and variations in study design may explain conflicting evidence (Sieljacks et al., 2019). The ambiguity of the evidence for strength benefits from BFR is understandable given unclear relationship between strength and hypertrophy in general.  BFR seems to produce no more or less muscle soreness or damage than other loading strategies since those sensations are likely influenced by calcium overload, which is possible irrespective of loading. .(Fredsted, Gissel, Madsen, & Clausen, 2007).

Plausible Mechanisms

The scientific understanding of the mechanisms underlying hypertrophy is evolving quickly, and BFR research highlights some of the key drivers in that process. BFR can produce equivalent hypertrophy as heavy resistance training because of its effects on fatigue accumulation, motor unit recruitment, cortical excitability, and cellular swelling. While some of these elements may directly stimulate hypertrophy in subtle ways all of these elements contribute to fatigue in the working muscle, forcing more fibers to experience higher forces and create more mechanical tension (Schoenfeld, 2013). Mechanical tension is widely considered the primary driver of hypertrophy. These effects, based on mechanical tension, may translate to muscles proximal to the cuff. Muscles such as pecs or glutes may get targeted as recruitment in these muscles increases to compensate for distal muscle failure. BFR’s effects on strength are limited and variations in study design may explain conflicting evidence (Sieljacks et al., 2019). The ambiguity of the evidence for strength benefits from BFR is understandable given unclear relationship between strength and hypertrophy in general.  BFR seems to produce no more or less muscle soreness or damage than other loading strategies since those sensations are likely influenced by calcium overload, which is possible irrespective of loading. .(Fredsted, Gissel, Madsen, & Clausen, 2007).

Contraindications

Adverse events from BFR training are rare and are limited mostly to upper extremity bruising. Those with significant vascular compromise, hypertension, or clotting disorders are at higher risk of complications and should avoid occlusion training. 

Standard protocol

In an effort to standardize the application of BFR training to reduce uncertainty in clinical outcomes, the following standard protocol was established…

  1. Measure limb occlusion pressure in the body position in which the exercise will be undertaken. Set training pressure (40% to 80% of limb occlusion pressure for leg, 30% to 60% for upper limb), higher pressures may be associated with more discomfort
  2. First set: aim for voluntary failure at 30 repetitions at a rate of approximately 1 repetition every 2 to 4 seconds
  3. Second to fourth sets: same weight as first set, 15 repetitions, 30 seconds of recovery between sets. Adjust weight up or down depending on performance on the first set: harder if failure wasn’t achieved, easier if patient could not reach 30 repetitions

At first, training can be done on alternating days but eventually progress to twice a day in ideal scenario because of a dose dependent response to training volume (Schoenfeld et. Al, 2017).

As BFR undergoes more rigorous testing, it appears to hold up to scrutiny. BFR training helps therapists and coaches introduce stimulating exercise earlier in a rehabilitation program than they would otherwise. It delivers the potency of fatiguing training with easily manageable mechanical stress. Since the loading can remain low, ligaments and tendons that may be compromised are minimally stressed. It may even help potentiate future adaptations in late-stage rehab program. Because challenging exercise is fundamental to current best practice in musculoskeletal rehabilitation, the addition of BFR is a potentially effective tool to augment the effect of an exercise session for a temporarily compromised athlete or patient. 

Limitations 

BFR has demonstrated a relatively narrow range of possible applications in conventional strength training. By manipulating constraints of the exercising limb, several BFR studies have highlighted the primary role of mechanical tension in hypertrophy adaptation. Heavier resistance training tends to produce the same amount of hypertrophy with and without BFR, and lighter resistance training with BFR produces the same amount hypertrophy as heavier training as long the intensity is sufficient (close to failure) and the set volume is equated.  BFR seems to increase the rate of fatigue, thereby decreasing the volume needed at lighter loads to reach the point of reduced muscle shortening velocity and a concomitant increase in muscle force. This feature has its advantages in a rehab setting, but it may not be uniquely useful in a healthy individual. 

Additionally, some BFR data suggests an analgesic effect that might be of use in a rehab scenario to enable short term improvements in exercise tolerance. However, i analgesia is a questionable primary goal of therapy and some discomfort during exercise may be appropriate(Smith et al., 2018, 2017). Exercise selection solely based on analgesic properties is not recommended. 

 Applications for use in exercise recovery and sports performance programs are limited and largely untested. This may be an area to explore in the future.

Takeaways for Practice

  1. The standard BFR procedure involves 40-80% or 30-60% arterial occlusion for the leg and arm respectively. The standard set/rep protocol should include multiple sets following an initial set to failure. Variations in the application may lead to skew results in hard to predict ways.
  2. There is a body of evidence supporting the claim that BFR training with light loads produces similar levels of hypertrophy as training with moderate and heavier loads with or without BFR. The specific mechanisms underlying these outcomes deserve further investigation
  3. BFR has limited evidence supporting improvements in strength. Some evidence has suggested a cross-education effect might explain improvements in strength in cases where strength has been reported following BFR training on one limb. muscles proximal to the cuff may adapt to BFR to compensate for fatigue in distal muscles. increases in hypertrophy may directly yield strength benefits in some people and not in others. The way in which strength is tested may influence results since strength is highly specific.
  4. BFR is a useful tool in a rehab setting to train as a work-around to heavy loading. The ability to prevent atrophy and possibly even hypertrophy soft tissue in an affected limb may have significant long-term benefits in a rehab program. However, the goal is almost always a return to loading to support a return to performance. BFR is not yet supported as a reliable analgesic nor is it indicated for sports performance improvement. In a rehabilitation setting, as soon as an athlete is capable it’s important to resume exposure to tolerable movements and to progressively increase training loads to support strength specific adaptations. (Schoenfeld, 2018)  

BFR is a potentially useful tool in the context of a complete rehabilitation program, particularly in earlier stages when heavy loads are not well tolerated. While it has limited demonstrated uses in conventional training, some people might find it an engaging source of novelty in an otherwise repetitive hypertrophy focused training program. As long as there is a standard protocol, the risk associated with occlusion training is minimal in healthy individuals.

Article

Whiteley, R. (2019). Blood Flow Restriction Training in Rehabilitation: A Useful Adjunct or Lucy’s Latest Trick? Journal of Orthopaedic & Sports Physical Therapy, 49(5), 294–298. Https://doi.org/10.2519/jospt.2019.0608

Supporting References

Hughes, L., Paton, B., Rosenblatt, B., Gissane, C., & Patterson, S. D. (2017, July 1). Blood flow restriction training in clinical musculoskeletal rehabilitation: A systematic review and meta-analysis. British Journal of Sports Medicine, Vol. 51, pp. 1003–1011. https://doi.org/10.1136/bjsports-2016-097071

Sieljacks, P., Wang, J., Groennebaek, T., Rindom, E., Jakobsgaard, J. E., Herskind, J., … Vissing, K. (2019). Six Weeks of Low-Load Blood Flow Restricted and High-Load Resistance Exercise Training Produce Similar Increases in Cumulative Myofibrillar Protein Synthesis and Ribosomal Biogenesis in Healthy Males. Frontiers in Physiology, 10, 649. https://doi.org/10.3389/fphys.2019.00649

Fredsted, A., Gissel, H., Madsen, K., & Clausen, T. (2007). Causes of excitation-induced muscle cell damage in isometric contractions: mechanical stress or calcium overload? American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 292(6), R2249–R2258. https://doi.org/10.1152/ajpregu.00415.2006

Biazon, T. M. P. C., Ugrinowitsch, C., Soligon, S. D., Oliveira, R. M., Bergamasco, J. G., Borghi-Silva, A., & Libardi, C. A. (2019). The Association Between Muscle Deoxygenation and Muscle Hypertrophy to Blood Flow Restricted Training Performed at High and Low Loads. Frontiers in Physiology, 10, 446. https://doi.org/10.3389/fphys.2019.00446

Lixandrão, M. E., Ugrinowitsch, C., Berton, R., Vechin, F. C., Conceição, M. S., Damas, F., … Roschel, H. (2018, February 17). Magnitude of Muscle Strength and Mass Adaptations Between High-Load Resistance Training Versus Low-Load Resistance Training Associated with Blood-Flow Restriction: A Systematic Review and Meta-Analysis. Sports Medicine, Vol. 48, pp. 361–378. https://doi.org/10.1007/s40279-017-0795-y 

Rubinstein, S. M., De Zoete, A., Van Middelkoop, M., Assendelft, W. J. J., De Boer, M. R., & Van Tulder, M. W. (2019). Benefits and harms of spinal manipulative therapy for the treatment of chronic low back pain: Systematic review and meta-analysis of randomised controlled trials. BMJ (Online), 364, 689. https://doi.org/10.1136/bmj.l689

Schoenfeld, B. J. (2013). Potential mechanisms for a role of metabolic stress in hypertrophic adaptations to resistance training. Sports Medicine, Vol. 43, pp. 179–194. https://doi.org/10.1007/s40279-013-0017-1

Schoenfeld, B., & Grgic, J. (2018). Evidence-based guidelines for resistance training volume to maximize muscle hypertrophy. Strength and Conditioning Journal, 40(4), 107–112. https://doi.org/10.1519/SSC.0000000000000363

Schoenfeld, B. J., Ogborn, D., & Krieger, J. W. (2017). Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis. Journal of Sports Sciences, 35(11), 1073–1082. https://doi.org/10.1080/02640414.2016.1210197

Smith, B. E., Hendrick, P., Bateman, M., Holden, S., Littlewood, C., Smith, T. O., & Logan, P. (2018). Musculoskeletal pain and exercise – Challenging existing paradigms and introducing new. British Journal of Sports Medicine, p. bjsports-2017-098983. https://doi.org/10.1136/bjsports-2017-098983

Smith, B. E., Hendrick, P., Smith, T. O., Bateman, M., Moffatt, F., Rathleff, M. S., … Logan, P. (2017). Should exercises be painful in the management of chronic musculoskeletal pain? A systematic review and meta-analysis. British Journal of Sports Medicine, Vol. 51, pp. 1679–1687. https://doi.org/10.1136/bjsports-2016-097383

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