Blood Flow Restriction: Application to Rehabilitation.
Introduction The use of blood flow restriction (BFR) training is a novel concept originally developed in Japan by Yoshiaki Sato, and referred to as Kaatsu training in the early 90’s. It involves the use of either pressure cuffs or tight wraps applied as high above the target muscle (proximal to the body) as possible (Wilson et al., 2013). The aim of this is to maintain arterial inflow while occluding venous return of blood when exercising (Scott et al., 2015). BFR training has been typically used during a range of exercise modes including resistance training, cycling and walking. Typically, blood flow restriction can be performed across different types of resistance training exercises, utilising relatively light loads between 20-30% of individuals 1RM, with the application of tight cuffs or wraps. When using cuffs, the pressure is typically set between 160-230mm/hg. With no available reading when using wraps it is recommended to aim for a perceived tightness level of 7 out of 10 (Loenneke et al. 2013b; Loenneke et al. 2014c; Sugaya et al. 2011; Manimmanakorn et al. 2012).
How it works
During the contraction of skeletal muscle there are a number of bi-products that are produced. Normally blood flow will flush out and remove these bi-products, however, due to blood flow restriction inhibiting venous return, these metabolic products localise within the target muscle producing a peak within concentration. The bi-products are anabolic in nature and include Insulin-like Growth Factor (IGF-1) (Takarada, Tsuruta, & Ishii, 2004). Work by DeVol et al. (2009) concluded that the production of IGF-1 increases in response to the overload of skeletal muscle. Besides testosterone, IGF-1 is the main positive regulator of skeletal muscle mass. IGF-1 is a growth hormone (GH) that is predominantly produced at a local level within skeletal muscle (in addition to the liver) with its key role being protein synthesis. It does this through various methods including stimulating the proliferation satellite cells (generating new muscle fibres) and inhibiting muscle atrophy – both of which are essential requirements for the increase of skeletal muscle mass (Fujita et al, 2007). A study by Takarada et al. (2000) found IGF-1 to be elevated 290 times above baseline levels following 5 sets of bilateral knee extensions at 20% 1-RM with the incorporation of blood flow restriction in a fully occluded state (pressure cuff set to 214 mmHg). This concentration of growth hormone is approximately 1.7 times higher than previous studies which investigated the use of unrestricted high intensity resistance training coupled with short rest periods (Kraemer et al, 1990, Kraemer et al, 1991). Similarly, Takano et al. (2005) reported that partial occlusion (1.3 times greater than systolic pressure) at 20% 1-RM elevated GH levels to 100 times baseline measures. Both these studies found that exercising at the same intensity without blood flow restriction failed to result in similar GH responses. Therefore, it works two-fold in the up-regulation of protein synthesis as well as inhibiting protein degradation.
Muscle fibre recruitment
Skeletal muscle consists of both slow twitch fibres, usually referred to as type I and fast twitch fibres, of which two variations are present in humans (type IIa and IIx). Type I fibres are referred to as slow twitch due to their slow rate of contraction and are oxidative in nature, meaning that they utilise oxygen and are therefore highly resistant to fatigue. However, due to their slow rate of contraction they produce low amounts of force, meaning they are more commonly suited to endurance type events. On the other hand, Type IIx fibres have a fast contraction speed causing them to produce large amounts of force and are glycolytic in nature. This means that they are activated via anaerobic metabolism and as a result fatigue easily. However, it is type IIx fibres that possess the greatest potential for growth. Research into skeletal muscle physiology has established that when muscle is recruited to perform work, the order of recruitment of these fibres is determined by size i.e. I → IIa → IIx (Fujita et al., 2007). This suggests unnecessary fatigue can be prevented. When oxygen is limited via BFR, even though the load of the exercise is low, type I fibres are unable to cope with the increasing physical demands of the work, resulting in the recruitment of type II fibres at a faster rate. Therefore, with BFR, fast twitch fibres are able to be trained with a lower intensity workload. Studies looking into the effect of BFR training on muscle activity through the use of electromyography (EMG) have shown an increase within muscle recruitment, denoting that there is an increase in motor unit recruitment with blood flow restriction. This EMG data also suggests that there is no difference between low intensity BFR training and high intensity exercise (Takarada, Tsuruta & Ishii, 2004; Wernbom et al., 2009). This implies that regardless of the lighter load, the muscle recruitment potentially mimics that of heavier resistance training. This suggests that the regular implementation of BFR training will result in gains within muscular hypertrophy.
After injury, individuals will experience disuse atrophy of the affected limb due to insufficient training stimulus to prevent muscle wastage (Kubota et al, 2008). In general, training recommendations prescribe that a training intensity of 70% and greater of 1-RM is required in order to achieve substantial development within muscle hypertrophy and strength. On the contrary, exercise with an intensity of <65% of 1-RM is generally viewed to induce an improvement within muscular endurance with no substantial increases in either muscular size or strength (Kraemer & Ratamess, 2004). This poses a problem in the fact that the athlete requires loading in order to regain and develop lost muscle and strength but cannot tolerate the required loading parameters. The research is currently mixed with regard to blood flow restriction training with studies by Karabulut et al. (2010, 2011) and Martin-Hernandez et al. (2013) finding conventional training at loads of 80% 1RM to produce greater increases within knee extension strength than training at lighter loads (20% 1RM) with BFR. Whereas work by Clark et al. (2011), Thiebaud et al. (2013) and Libardi et al. (2015) shows no significant differences in strength gains between the two groups. In the above studies, it would appear that the use of heavier loads provides greater than or equal to gains in strength when compared to BFR training. However, during early stage rehabilitation athletes will not be using loads anywhere near 80% and above of their 1RM, which would more likely be prescribed during late stage rehabilitation. In addition to this, the population groups for the above studies mostly consisted of untrained older populations aged 50 and over, suggesting any training stimulus would promote improvements within base line strength. In order to determine performance benefits, BFR training must be compared to traditional resistance training at matched loads.
The above studies show that when training loads are matched between BFR training and conventional resistance training, BFR training was found to produce greater improvements within strength development (between 10 – 28%) within as little as 14-19 days. Once again the population groups within these studies consisted of a mixture of untrained, older females or recreationally active individuals, therefore it cannot be assumed this training protocol would have a significant performance improvement within an athletic or highly trained population group. There are a small number of studies that have looked into the application of matched load BFR training within athletically trained population groups:
The above studies are more directly applicable to those working with athletic populations and help to support the findings found by previous studies which used an untrained or recreationally trained population group. Interestingly, the findings by Godawa, Credeur and Welsch (2012) showed no significant differences between the groups. Looking deeper into the methodology, BFR was not achieved through the use of cuffs or wraps but through the application of supportive powerlifting suits and shirts, which may have affected restriction due to the spread of material over a larger area as opposed to the localised pressure of a cuff or wrap. In addition, there is no mention of standardisation of compressive suits as differences in suit size will impact upon total compression. Conclusion
The use of blood flow restriction (BFR) training using low intensity resistance is an innovative method that is effective at substantially increasing muscular growth and strength. By implementing loads between 10-30% 1RM it has been shown to produce greater adaptations in strength and hypertrophy in comparison to traditional resistance training of similar loads, making it an appropriate training modality during early stage rehabilitation (Loenneke et al. 2012; Wilson et al. 2013; Yamanaka, Farley & Caputo,2012). However, more research is required to ascertain its effectiveness during traditional training or late stage rehabilitation when implementing loads at or above 70%. 1RM. Reference Clark, B.C, Manini, T.M., Hoffman, R.L., Williams, P.S., Guiler, M.K., Knutson, M.J., McGlynn, M.L., & Kushnick, M.R. (2011). Relative safety of 4 weeks of blood flow-restricted resistance exercise in young, healthy adults. Scandinavian Journal of Medicine and Science in Sports, (5):653-662 Cook, C.J., Kilduff, L.P., & Beaven, C.M. (2014). Improving strength and power in trained athletes with 3 weeks of occlusion training. International Journal of Sports Physiology and Performance, 9(1):166-172 DeVol, D.L., Rotwein, P., Sadow, J.L., Novakofski, J., & Bechtel, P.J. (1990). Activation of insulin-like growth factor gene expression during work-induced skeletal muscle growth. American Journal of Physiology, 259, E89-E95 Fujita, S., Abe, T., Drummond, M.J., Cadenas, J.G., Dreyer, H.C., Sato, Y., Volpi, E., & Rasmussen, B.B. (2007). Blood flow restriction during low intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. Journal of Applied Physiology, 103: 903-910 Godawa, T.M., Credeur, D.P., & Welsch, M,A. (2012). Influence of compressive gear on powerlifting performance: role of blood flow restriction training. Journal of Strength and Conditioning Research, 26(5):1274-1280 Karabulut, M., Abe, T., Sato, Y., & Bemben, M.G. (2010). The effects of low-intensity resistance training with vascular restriction on leg muscle strength in older men. European Journal of Applied Physiology, 108(1):147-155 Karabulut, M., Bembenm D.A., Sherk, V.D., Anderson, M.A., Abe, T., & Bemben, M.G. (2011). Effects of high-intensity resistance training and low-intensity resistance training with vascular restriction on bone markers in older men. European Journal of Applied Physiology, 111(8):1659-1667 Kraemer, W., Marchitelli, L., Gordon, S., Harman, E., Dziados, J., Mello, R., Frykman, P., McCurry, D., & Fleck, S. (1990). Hormonal and growth factor responses to heavy resistance exercise protocols. Journal of Applied Physiology, 69: 1442–1450 Kraemer, W., Gordon, S., Fleck, S., Marchitelli, J., Mello, R., Dziados, J., Friedl, K., Harman, E., Maresh, C., & Fry, A. (1991). Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females. International Journal of Sports Medicine, 12, 228–235 Kraemer, W.J., Ratamess, N.A. (2004). Fundamentals of resistance training: progression and exercise prescription. Medicine and Science in Sports and Exercise, 36, 674–688 Kubota, A., Sakuraba, K., Sawaki, K., Sumide, T., & Tamura, Y. (2008). Prevention of disuse muscular weakness by restriction of blood flow. Medicine and Science in Sports and Exercise, 40(3), 529-534 Libardi, C.A., Chacon-Mikahil, M.P., Cavaglieri, C.R., Tricoli, V., Roschel, H., Vechin, F.C., Conceição, M.S., & Ugrinowitsch, C. (2015) Effect of concurrent training with blood flow restriction in the elderly. International Journal of Sports Medicine. 36(5):395-399 Loenneke, J.P., Wilson, J.M., Marín, P.J., Zourdos, M.C., & Bemben, M.G. (2012). Low intensity blood flow restriction training: a meta-analysis. European Journal of Applied Physiology, 112(5): 1849-59 Loenneke, J.P., Fahs, C.A., Rossow, L.M., Tiebaud, R.S., Mattocks, K.T., Abe, T. & Bemben, M.G. (2013). Blood flow restriction pressure recommendations: a tale of two cuffs. Frontiers in Physiology, 4, 249- 262 Loenneke, J.P., Thiebaud, R.S., Abe,T., & Bemben, M.G. (2014). Blood flow restriction pressure recommendations: the hormesis hypothesis. Medical Hypotheses, 82(5), 623-636. Luebbers, P.E., Fry, A.C, Kriley, L.M,, & Butler, M.S. (2014). The effects of a 7-week practical blood flow restriction program on well-trained collegiate athletes. Journal of Strength and Conditioning Research, 28(8):2270-2280 Madarame, H., Neya, M., Ochi, E., Nakazato, K., Sato, Y., & Ishii, N. (2008). Cross-transfer effects of resistance training with blood flow restriction. Medicine and Science in Sports and Exercise. 40(2):258-263
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