Takada, S., Okita, K., Suga, T., Omokawa, M., Kadoguchi, T., Morita, N., Horiuchi, M., Takahashi, M., Yokota, T., Hirbayashi, K., Kinugawa, S., & Tsutsui, H. (June 03, 2010). High metabolic stress during resistance exercise might provide muscle hypertrophy and strength increase even with low-mechanical stimulus. Presentation 2072 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

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This study attempted to elucidate whether metabolic stress during resistance exercise with blood flow restriction correlated with training effects. Metabolic stress (as indicated by phosphocreatine and intramuscular pH decrease) was evaluated during two-minute low-intensity resistance exercise (unilateral plantar-flexion at 20% per 1 RM) with blood flow restriction in healthy untrained Ss (N = 14) at baseline. Blood flow was restricted by a pneumatic cuff around the thigh with 130% systolic blood pressure. In the training period, Ss performed two sets of the same exercise with a 30-second rest between sets, twice per day (with at least four hours between each session), three days per week, for four weeks. Muscle cross-sectional area of plantar flexors and 1 RM were measured at baseline and after two and four weeks of training.

Muscle cross-sectional area and 1 RM were significantly increased after two and four weeks. Phosphocreatine and intramuscular pH at baseline were significantly correlated with muscle-cross-sectional area increases at two and four weeks and with 1 RM at two weeks.

Implication. Metabolic stress of exercising muscle is closely related to muscle hypertrophy and strength increase. Enhanced metabolic stress by blood flow restriction during exercise is an important mechanism for the favorable effects in this type of training manner even with low mechanical stimulus.

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