Intro to Blood Flow Restriction

In today’s blog post, I am excited to introduce a piece of technology that is new to Our clinic and to the Canadian Physiotherapy world in general. It’s called Blood Flow Restriction (BFR) and it just might be the Holy Grail of rehab exercise. Although it is new to Physiotherapists here in Canada, it has gained serious momentum in the US and around the globe (click the link for a list of sports teams and clinics currently using BFR in North America http://www.owensrecoveryscience.com/certified-providers/ ). I will use today’s post as a general overview of BFR and future posts to discuss in greater depth, all of its potential uses and benefits.

The American College of Sports Medicine (ACSM, 2009) states that in order to build muscle strength and size, it is necessary to lift greater than 70% of your 1-rep max (the maximum amount of weight you can lift for a single repetition). However, as I’m sure you can guess, there are many cases in which it is unfeasible or unsafe to be lifting this heavy. For example, if you’ve just had your ACL replaced, the new graft is too fragile to begin squatting at 70% of your 1 rep max a week or two after surgery. Therefore, Physiotherapists will typically start you on much lower resistance exercises for the first 6-8 weeks. But if we are being honest with ourselves, it is quite clear that working against a theraband or light ankle weight is not building muscle effectively. It is at best slowing muscle atrophy. So wouldn’t it be great if there was some way of amplifying the effects of light resistance exercise to promote more muscle growth? This is where BFR comes in...

Blood flow restriction training involves the application of a pneumatic tourniquet to an exercising limb and inflating it to partially restrict the blood flow in that limb (primarily the venous blood coming back to the heart) (Scott et al., 2015). A large volume of research has shown that training under these conditions produces significantly greater gains in muscle strength and size compared to light resistance exercise alone (Loenneke et al., 2011; Scott et al., 2015; Loenneke et al., 2012a). Even more exciting is the fact that these benefits have come while training at only 20-30% of the 1 rep max! Suddenly those light theraband exercises for a patient coming off surgery are much more effective. So how does it work?

In simple terms, light resistance exercise under BFR tricks the body into thinking it is exercising at high intensity. The blood flow restriction causes pooling of venous blood in the exercising limb, which creates an environment metabolically similar to that seen during high intensity exercise. There are a few biochemical pathways that have been proposed as specific mechanisms for the gains seen with BFR. For example, Takarada et al. (2000) found that low intensity exercise + BFR increased acidity within the exercising muscles to an extent similar to or even greater than high intensity exercise. This increased acidity triggered a signalling pathway resulting in increased Growth Hormone release. Gundermann et al. (2014) confirmed that BFR produces gains in muscle strength and size by, at least in part, activating a protein complex known as mTORC1. This is significant because mTORC1 is a key player in the strength and size gains produced by high intensity exercise, suggesting that low-intensity BFR training activates some of the same pathways as traditional heavy lifting. Additionally, mechanisms involving muscle stem cell activation (Nielsen et al., 2012), cellular swelling (Kubota et al., 2008; Loenneke et al., 2012b) and increased recruitment of fast twitch muscle fibres (Pearson and Hussain, 2015) appear to play a role in the gains seen with BFR. It is not known if one of these mechanistic pathways is more important than the others and in all likelihood they are synergistic in nature.

A recent review and meta-analysis (Hughes et al., 2017) was published in the prestigious British Journal of Sports Medicine, which evaluated the usefulness of low-load exercise with blood flow restriction (LL-BFR). The authors sifted through the relevant literature and selected 20 articles that looked at the effects of LL-BFR on muscle strength in patient populations with recent ACL reconstruction, knee osteoarthritis and elderly individuals demonstrating sarcopenia (the gradual loss of muscle bulk). After analyzing the results of these studies Hughes et al., reached the conclusion that LL-BFR is more effective at building muscular strength than low-load resistance exercise alone. They also concluded that LL-BFR is more tolerable for patients who may find typical exercise painful (those with osteoarthritis for example). Compared to traditional high intensity exercise, though, LL-BFR is not quite as effective at increasing muscle mass and strength. Therefore, the take home message of this article is that low load exercise under blood flow restriction is more effective than low load exercise alone, making it the optimal substitute for high intensity exercise in individuals who are unable to lift heavy. This is just a brief summary of the potential benefits of BFR, I will describe other examples in more detail in future posts, so stay tuned!

It is my hope that what you have read here today stokes your interest in this novel piece of technology and that some of its beneficial applications have become apparent. One of the common, logical questions that most people have at this point is in regards to the safety of exercising with reduced blood flow to a limb. This is a great question and one that has been investigated in depth. Therefore, you can look forward to a discussion revolving around the safety of blood flow restricted exercise in my next post. See you then!

References

ACSM. American College of Sports Medicine position stand. (2009). Progression models in resistance training for healthy adults. Med Sci Sports Exerc, 41: 687-708.

Gundermann, DM, Walker, DK, Reidy, PT, Borack, MS, Dickinson, JM, Volpi, E., Rasmussen, BB. (2014). Activation of mTORC1 signaling and protein synthesis in human muscle following blood flow restriction exercise is inhibited by rapamycin. Am J Phsyiol Endocrinol Metab, 306: E1198-1204.

Hughes, L, Paton, B, Rosenblatt, B, Gissane, C., Patterson, SD. (2017). Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis. Br J Sports Med, 51: 1002-1011.

Kubota, A, Sakuraba, K, Sawaki, K, Sumide, T, Tamura, Y. (2008). Prevention of disuse muscular weakness by restriction of blood flow. Med Sci Sports Exerc, 40: 529-34

Loenneke, JP, Wilson, JM, Marin, PJ, Zourdos, MC, Bemben, MG. (2011). Low intensity blood flow restriction: A meta-analysis. Eur J Appl Physiol, DOI: 10.1007/s00421-011-2167-x.

Loenneke, JP, Abe, T, Wilson, JM, Theibaud, RS, Fahs, CA, Rossow, LM, Bemben, MG. (2012a). Blood flow restriction: An evidence based progressive model. Acta Physiologica Hungarica, 99(3): 235-250.

Loenneke, JP, Fahs, CA, Rossow, LM, Abe, T, Bemben, MG. (2012b). The anabolic benefits of venous blood flow restriction training may be induced by muscle cell swelling. Medical Hypotheses, 78: 151-54.

Nielsen, JK, Aargaard, P, Bech, RD, Nygaard, T., Hvid, LG, Wernborn, M, Suetta, C., Frandsen, U. (2012). Proliferation of myogenic stem cells in human skeletal muscle in response to low-load resistance training with blood flow restriction. J Physiol, 590(17): 4351-61.

Pearson, JP & Hussain, SR. (2015). A Review on the Mechanisms of Blood-Flow Restriction Resistance Training-Induced Muscle Hypertrophy. Sports Med, 45: 187-200.

Scott, BR, Loenneke, JP, Slattery, KM, Dascombe, BJ. (2015). Exercise with Blood Flow Restriction: An Updated Evidence-Based Approach for Enhanced Muscular Development. Sports Medicince, 45(3); 313-25.

Takarada, Y., Nakamura, Y, Aruga, S, Onda, T, Miyazaki, S, Ishii, N. (2000). Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion. J Appl Physiol, 88: 61-65.