What is blood flow restriction?

Blood flow restriction or BFR has become popular in the last few years in the training and physical therapy field. BFR consists in applying pressure (usually using an inflatable cuff) on the proximal part of the lower or upper limbs to block the venous return without blocking the arterial flow. Among other processes, BFR has proven to increase the metabolic stress, which has been suggested as one of the mechanisms that could facilitate muscle hypertrophy. As a matter of fact, possibly due to an increase in metabolites and hydrogen ions, BFR has been proven to stimulate the release of anabolic hormones, such as growth hormone or IGF-1,^1,2 as well as an increase in muscle protein synthesis.³

How is blood flow restriction applied?

As Dr. Loennekke, one of the greatest experts in this field, commented in an interview. BFR must be applied considering the cuff being used (especially its width, as the wider the cuff, the less pressure is needed to restrict blood flow) and the individual to whom the cuff is being applied, as those with wider limbs are more likely to need more pressure than those with thinner limbs. However, an objective way of controlling the necessary pressure can be finding the arterial occlusion pressure, that is the lowest pressure required to stop the arterial blood flow completely (when there is no distal pulse) and establishing the necessary pressure as a percentage of this arterial occlusion pressure (40-80% of this pressure is usually recommended). Nevertheless, when there is no access to tools such as the Doppler ultrasonography to measure arterial pulse, with healthy individuals, determining the pressure trying to obtain 7 over 10 on a perceived exertion scale might be enough,⁴ although we wouldn’t be very precise and the safety and effectiveness of the procedure might be compromised.

The benefits of blood flow restriction for injury recovery

Due to its efficacy to promote muscle anabolism, BFR is more and more used for physical therapy, to speed up recovery after suffering an injury. In fact, a meta-analysis published in the prestigious British Journal of Sports Medicine which included 20 studies, concluded that although it is less effective than training with high loads, the combination of BFR with low-intensity training is effective to increase muscle strength in patients undergoing physical therapy (for example, after the restoration of the anterior cruciate ligament, or in patients with osteoarthritis).⁵ Therefore, in patients who cannot lift heavy loads or make great efforts yet, BFR can be a good alternative. Even the application of BFR with a high pressure (~200 mmHg) on its own, i.e. without training concomitantly, has been proven to be effective in some studies to mitigate muscle atrophy and strength loss in patients who are immobilized after an operation.^6,7 However, whenever possible, BFR must be applied in combination with exercise. A recent study showed that BFR can increase protein synthesis when applied simultaneously with exercise, but not at rest.⁸ In this sense, applying BFR together with low-intensity aerobic exercise during 15 minutes has been proven to be even more beneficial to increase muscle mass and strength than aerobic exercise without BFR during 45 minutes.⁹ Likewise, other authors have observed that applying BFR together with low-intensity strength training provides benefits similar to those of high-intensity strength training without BFR.¹⁰ Hence, BFR allows us to obtain results similar to training with high loads, but using low ones. However, it is convenient to do it progressively, starting with the application of BFR at rest, and then combining it with low or high intensity training.

The benefits of blood flow restriction for performance

Besides its possible benefits for injury rehabilitation, it has been suggested that BFR could also maximise the benefits of training for healthy athletes. Different meta-analyses show that this strategy is effective to increase muscle mass and strength for the general population.^11,12 For example, a study carried out with Rugby players showed that strength training (70% RM) with BFR increases strength gain in comparison to the same training without BFR.¹³ Moreover, another study performed with trained individuals showed that sprinting at 60-70% of maximum intensity in combination with BFR brought greater benefits in sprint performance and muscle mass and strength than the same type of training without BFR.¹⁴ Furthermore, recent studies show that training (pedalling) with BFR in active individuals improves performance, the antioxidant process, the glycolytic metabolism, blood flow, and the oxygen supply and usage compared to the same type of training without BFR.^15–17 However, there is not enough evidence for healthy athletes in the physical therapy field, and, for example, a study carried out with semi-professional Australian football players showed that combining low-intensity training with BFR on a 5 week training programme that already included high-intensity training did not improve performance in comparison to the same type of exercise without BFR (Scott, 2017).

Conclusions

In summary, BFR is an effective strategy for maximising gains in muscle mass and strength, being able to obtain benefits with low intensity training similar to the ones obtained with higher training loads without BFR. These results are especially relevant, as it is not always possible to subject athletes to high loads. Also, for healthy athletes, the addition of blood flow restriction to training (e.g., strength exercises or sprints) could also maximise the benefits when compared to the same exercises without BFR, although the evidence for this is insufficient.

Pedro L. Valenzuela

References

1. Inagaki Y, Madarame H, Neya M, Ishii N. Increase in serum growth hormone induced by electrical stimulation of muscle combined with blood flow restriction. Eur J Appl Physiol 2011;111:2715–21. https://doi.org/10.1007/s00421-011-1899-y.
2. Takano H, Morita T, Iida H, Asada KI, Kato M, Uno K, et al. Hemodynamic and hormonal responses to a short-term low-intensity resistance exercise with the reduction of muscle blood flow. Eur J Appl Physiol 2005;95:65–73. https://doi.org/10.1007/s00421-005-1389-1.
3. Wernbom M, Apro W, Paulsen G, Nilsen TS, Blomstrand E, Raastad T. Acute low-load resistance exercise with and without blood flow restriction increased protein signalling and number of satellite cells in human skeletal muscle. Eur J Appl Physiol 2013;113:2953–65. https://doi.org/10.1007/s00421-013-2733-5.
4. Wilson J, Lowery R, Joy J, Loenneke J, Naimo M. Practical blood flow restriction training increases acute determinants of hypertrophy without increasing indices of muscle damage. J Strength Cond Res 2013;27:3068–75.
5. Hughes L, Paton B, Rosenblatt B, Gissane C, Patterson SD. Blood flow restriction training in clinical musculoskeletal rehabilitation: A systematic review and meta-analysis. Br J Sports Med 2017;51:1003–11. https://doi.org/10.1136/bjsports-2016-097071.
6. Takarada Y, Takazawa H, Ishii N. Applications of vascular occlusion diminish disuse atrophy of knee extensor muscles. Med Sci Sports Exerc 2000;32:2035–9.
7. Kubota A, Sakuraba K, Sawaki K, Sumide T, Tamura Y. Prevention of disuse muscular weakness by restriction of blood flow. Med Sci Sports Exerc 2008;40:529–34. https://doi.org/10.1249/MSS.0b013e31815ddac6.
8. Nyakayiru J, Fuchs CJ, Trommelen J, Smeets JSJ, Senden JM, Gijsen AP, et al. Blood Flow Restriction only Increases Myofibrillar Protein Synthesis with Exercise. Med Sci Sports Exerc 2019;51:1137–45. https://doi.org/10.1249/MSS.0000000000001899.
9. Abe T, Fujita S, Nakajima T, Sakamaki M, Ozaki H, Ogasawara R, et al. Effects of low-intensity cycle training with restricted leg blood flow on thigh muscle volume and VO2max in young men. J Sport Sci Med 2010;9:452–8. https://doi.org/10.1097/JPT.0b013e3181d07a73.
10. Ladlow P, Coppack RJ, Dharm-Datta S, Conway D, Sellon E, Patterson SD, et al. Low-load resistance training with blood flow restriction improves clinical outcomes in musculoskeletal rehabilitation: A single-blind randomized controlled trial. Front Physiol 2018;9:1–14. https://doi.org/10.3389/fphys.2018.01269.
11. Loenneke JP, Wilson JM, Marín PJ, Zourdos MC, Bemben MG. Low intensity blood flow restriction training: A meta-analysis. Eur J Appl Physiol 2012;112:1849–59. https://doi.org/10.1007/s00421-011-2167-x.
12. Slysz J, Stultz J, Burr JF. The efficacy of blood flow restricted exercise: A systematic review & meta-analysis. J Sci Med Sport 2016;19:669–75. https://doi.org/10.1016/j.jsams.2015.09.005.
13. Cook CJ, Kilduff LP, Beaven CM. Improving strength and power in trained athletes with 3 weeks of occlusion training. Int J Sports Physiol Perform 2014;9:166–72. https://doi.org/10.1123/IJSPP.2013-0018.
14. Behringer M, Behlau D, Montag JCK, McCourt ML, Mester J. Low-Intensity Sprint Training with Blood Flow Restriction Improves 100-m Dash. J Strength Cond Res 2017;31:2462–72. https://doi.org/10.1519/JSC.0000000000001746.
15. Christiansen D, Eibye KH, Hostrup M, Bangsbo J. Blood flow-restricted training enhances thigh glucose uptake during exercise and muscle antioxidant function in humans. Metabolism 2019;98:1–15. https://doi.org/10.1016/j.metabol.2019.06.003.
16. Christiansen D, Eibye KH, Rasmussen V, Voldbye HM, Thomassen M, Nyberg M, et al. Cycling with blood flow restriction improves performance and muscle K+ regulation and alters the effect of anti-oxidant infusion in humans. J Physiol 2019;597:2421–44. https://doi.org/10.1113/JP277657.
17. Christiansen D, Eibye K, Hostrup M, Bangsbo J. Training with blood flow restriction increases femoral artery diameter and thigh oxygen delivery during knee-extensor exercise in recreationally trained men. J Physiol 2020;598:2337–53. https://doi.org/10.1113/JP279554.