Intramuscular metabolism during low-intensity resistance exercise with blood flow restriction.
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 (31)P-magnetic resonance spectroscopy. Twenty-six healthy subjects (22 +/- 4 yr) participated and performed unilateral plantar flexion (30 repetitions/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 (H(2)PO(4)(-)) levels and intramuscular pH at rest and during exercise were obtained. We found that the PCr depletion, the H(2)PO(4)(-) 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 with 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.
Suga
Tadashi
T
Graduate School of Program in Lifelong Learning Studies, Hokusho University, Ebetsu, Hokkaido, Japan.
Okita
Koichi
K
Morita
Noriteru
N
Yokota
Takashi
T
Hirabayashi
Kagami
K
Horiuchi
Masahiro
M
Takada
Shingo
S
Takahashi
Tomohiro
T
Omokawa
Masashi
M
Kinugawa
Shintaro
S
Tsutsui
Hiroyuki
H
D000328:Adult; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006984:Hypertrophy; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism* / Q000502:physiology; D009929:Organ Size / Q000502:physiology; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D010809:Physical Fitness / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D012727:Sex Characteristics; D014891:Weight Lifting / Q000502:physiology*; D055815:Young Adult
D010710:Phosphates; D010725:Phosphocreatine