Submitted on March 5, 2008
Revised on January 30, 2009
Accepted on February 10, 2009
Intramuscular Metabolism during Low-Intensity Resistance Exercise with Blood Flow Restriction
Tadashi Suga1, Koichi Okita1*, Noriteru Morita2, Takashi Yokota3, Kagami Hirabayashi3, Masahiro Horiuchi1, Shingo Takada1, Tomohiro Takahashi1, Masashi Omokawa1, Shintaro Kinugawa4, and Hiroyuki Tsutsui4
1 Hokusho University
2 Hokkaido Univ. Education
3 Hokkaido University Graduate School of Medicine
4 Hokkaido University
* To whom correspondence should be addressed. E-mail: okitak{at}hokusho-u.ac.jp.
Although recent studies have reported that low-intensity resistance training with blood flow restriction could stress the muscle effectively and provide rapid muscle hypertrophy and strength gain equivalent to those of high-intensity resistance training, the exact mechanism and its generality have not yet been clarified. We investigated the intramuscular metabolism during low-intensity resistance exercise with blood flow restriction and compared it with that of high-intensity and low-intensity resistance exercises without blood flow restriction using 31P-magnetic resonance spectroscopy. Twenty-six healthy subjects (22 ± 4 yr) participated and performed unilateral plantar flexion (30 times/min) for 2 min. Protocols were as follows: low-intensity exercise (L) using a load of 20% of one-repetition maximum (1 RM), L with blood flow restriction (LR), and high-intensity exercise using 65% 1 RM (H). Intramuscular phosphocreatine (PCr) and diprotonated phosphate (H2PO4-) levels and intramuscular pH at rest and during exercise were obtained. We found that the PCr depletion, H2PO4- increase and the intramuscular pH decrease during LR were significantly greater than those in L (p<0.001); however, those in LR were significantly lower than those in H (p<0.001). The recruitment of fast-twitch fiber evaluated by inorganic phosphate splitting occurred in only 31% of the subjects in LR, compared to 70% in H. In conclusion, the metabolic stress in skeletal muscle during low-intensity resistance exercise was significantly increased by applying blood flow restriction, but did not generally reach that during high-intensity resistance exercise. This new method of resistance training needs to be examined for optimization of the protocol to reach equivalence with high-intensity resistance training.
