Background and Purpose: Skeletal muscle bulk is becoming an important therapeutic target in medicine. In order to increase muscle mass, however, intensive mechanical stress must be applied to the muscles, and such stress is often accompanied by orthopedic and cardiovascular problems. Resistance exercise with blood flow restriction（BFR）is a new training method providing significant training effects despite the use of low-intensity load. We observed that blood flow restriction（BFR） remarkably enhanced muscular metabolic stress in resistance exercise, although there was a wide range of individual differences in the responses. It is possible that these differences could be due to gender difference in muscular physiological characteristics. Therefore, we compared intramuscular metabolic stress during low-intensity resistance exercise with BFR between men and women. Methods: Twenty-six age-matched men （n=13, 22±4 yrs）and women（n=13, 21±4 yrs）were recruited and performed unilateral plantar-flexion（30 repetitions/min for 2 min）The exercise protocols were as follows: low-intensity exercise（L）with 20% of one repetition maximum（1-RM） L with BFR, and high-intensity of 65% 1-RM without BFR（H）BFR was applied by 130% of the subjects resting blood pressure. We added the three protocols of 30, 40% 1-RM with BFR and 20% 1-RM with high BFR at 200 mmHg to determine an optimal protocol. Muscular metabolic stress, defined as phosphocreatine and intramuscular pH decrease were evaluated by using ³¹P-magnetic resonance spectroscopy. Results and Discussion: Metabolic stresses were statistically similar between men and women in all protocols. Compared with L, metabolic stresses were enhanced similarly by BFR （L-BFR）in men and women, while those did not reach the levels in H. By increasing intensity to greater than 30% 1-RM, the metabolic stresses reached to those in H. Conclusions: Effects of resistance exercise with BFR on muscular stress might be similar in men and women. Optimal muscular stress in BFR exercise could be achieved by increasing mechanical intensity to 30%1-RM or greater especially in women.

DESCENTE SPORTS SCIENCE Vol.33/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE