In recent years it has been reported that increases in muscle size and strength equivalent to those with high intensity load can be achieved even with low intensity loads (20-40% of 1RM) using blood flow restriction (BFR) together with resistance training. The resistance training with BFR generally consists of multiple sets, during which the exercise protocol is for continuous BFR during exercise and rest. However, there is also a possibility that continuous BFR will markedly increase cardiovascular stress. There are also reports showing a very high rating of perceived exertion (RPE). However, they can be mitigated by performing this exercise intermittently, such as by releasing the BFR during the exercise period or rest period. The aim of this study was to investigate the effectiveness of intermittent BFR during low-intensity resistance exercise. Seven healthy men were recruited and performed 3 sets of low-intensity (20% of one repetition maximum, 1-RM) unilateral plantar-flexion (30 repetitions/min for 2 min) with 1-min resting interval. The exercise protocols were as follows: natural blood flow, BFR during rest periods, BFR during exercise periods, and continuous BFR during both exercise and rest periods. BFR was applied by 130% of the subject’s resting blood pressure. Muscular metabolic stress, defined as phosphocreatine and intramuscular pH decrease by using ³¹P-magnetic resonance spectroscopy. The intramuscular metabolic stress is significantly increased with continuous BFR compared with intermittent BFR in the exercise and rest periods. Intermittent BFR reduced subjects’ RPE but could not raise metabolic stress to a level at which a sufficient training effect was obtained in previous intervention studies we conducted. In a comparison of the two methods of intermittent BFR, the metabolic load was equivalent with BFR in either the exercise or rest period.

DESCENTE SPORTS SCIENCE Vol.36/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE