THE RELATIONSHIP BETWEEN MUSCLE ACTION AND REPETITION MAXIMUM ON THE SQUAT AND BENCH PRESS IN MEN AND WOMEN

The relationship between muscle action and fatigue is not well understood, especially in terms of potential sex-specific differences. The purpose of this investigation was to determine whether a different number of repetitions could be performed on the individual muscle actions of the bench press and squat in men and women. Ten resistance-trained men (n = 10; age, 25.2 +/- 1.2 years; height, 178.6 +/- 8.8 cm; weight, 91.4 +/- 18.1 kg; body fat, 12.7 +/- 3.6%) and women (n = 10; age, 25.4 +/- 2.4 years; height, 164 +/- 4.0 cm; weight, 58.45 +/- 3.3 kg; body fat, 20.8 +/- 1.5%) participated in this balanced and randomized within-group study. Using 85% of a 1 repetition maximum, over the course of 3 visits, subjects performed 1 eccentric (ECC), concentric (CON), or combined (COMB) set to failure on the squat and bench press. Differences in muscle action and sex-specific number of repetitions to failure were compared on the squat and bench press, where significance was p <= 0.05. Across both exercises and sex, we observed significant differences between each of the 3 muscle actions, where the number of repetitions decreased from ECC to COMB to CON. While no sex-specific differences were observed in the squat, women performed significantly more repetitions on the ECC and CON muscle actions of the bench press. Men performed more combined repetitions, however, indicating a greater reliance on the stretch-shortening cycle. Different muscle actions contribute uniquely to the successful performance of a lift and fatigue. These contributions appear to differ in men and women.