Application of Blood Flow Restriction in Resistance Exercise Assessed by Intramuscular Metabolic Stress

Background: Skeletal muscle bulk and strength are becoming important therapeutic targets in exercise therapy. However, in standard resistance training intensive loads are placed on muscles, which make it difficult for weak subjects. Recently, studies have reported that low-intensity resistance training with blood flow restriction (BFR) effectively increased muscle bulk and strength equivalent to those of high-intensity resistance training despite using a lower mechanical load, although the exact mechanism and its generality have not yet been clarified. Methods and results: We investigated the intramuscular metabolism during low-intensity resistance exercise with BFR and compared it with that of high-intensity and low-intensity resistance exercises without BFR using 31 P-magnetic resonance spectroscopy. We found that metabolic stress in skeletal muscle estimated as the phosphocreatine depletion and intramuscular pH decrease during low-intensity resistance exercise with BFR were significantly greater than those in low-intensity resistance exercise without BFR, but were significantly lower than those in high-intensity without BFR. The recruitment of fast-twitch fiber evaluated by inorganic phosphate splitting occurred less in low-intensity resistance exercise with BFR compared to high-intensity without BFR. Conclusions: The metabolic stress in skeletal muscle during low-intensity resistance exercise was significantly increased by applying BFR, but did not generally reach that during high-intensity resistance exercise. Therefore, we also argued about several important points concerning the optimization of a protocol for resistance exercise with BFR. In this mini review, we introduced the effectiveness and optimization of low-intensity resistance training with BFR based on our previous studies.