title: Intramuscular metabolism during low-intensity resistance exercise with blood flow restriction.
abstract: 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.
authors.affiliation: Graduate School of Program in Lifelong Learning Studies, Hokusho University, Ebetsu, Hokkaido, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Suga
authors.forename: Koichi
authors.initials: K
authors.lastname: Okita
authors.forename: Noriteru
authors.initials: N
authors.lastname: Morita
authors.forename: Takashi
authors.initials: T
authors.lastname: Yokota
authors.forename: Kagami
authors.initials: K
authors.lastname: Hirabayashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Horiuchi
authors.forename: Shingo
authors.initials: S
authors.lastname: Takada
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Takahashi
authors.forename: Masashi
authors.initials: M
authors.lastname: Omokawa
authors.forename: Shintaro
authors.initials: S
authors.lastname: Kinugawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsutsui
mesh_terms: 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
chemical_list: D010710:Phosphates; D010725:Phosphocreatine