Gender difference in ability using the stretch-shortening cycle in the upper extremities.

A gender difference in ability using the stretch-shortening cycle (SSC ability) in the upper extremities has not been studied in detail. This study aimed to devise an index to evaluate SSC ability during powerful elbow flexion and to examine its gender differences. Thirty-three men athletes (19.9 +/- 1.0 years) and 21 women athletes (20.6 +/- 1.2 years) with mastered SSC movements participated in this study. They pulled a 20% load of maximal voluntary contraction (MVC) by elbow flexion as quickly as possible with the dominant upper extremity from the following two preliminary conditions: a static relaxed muscle state (SR condition) and using a countermovement (SSC condition). The muscle power was measured accurately by a power measurement device, which adopted the weight loading method. The peak power under both conditions showed significantly higher values in men than in women. In both genders, the peak power showed significantly lower values in the SSC condition than in the SR condition (p < 0.05). The potentiation of using the SSC was not found in the peak power test. However, the initial power showed significantly higher values under the SSC condition (men: 37.2 +/- 6.4 W; women: 17.4 +/- 5.1 W) than in the SR condition (men: 18.3 +/- 4.3 W; women: 11.2 +/- 3.1 W). Hence, assuming a difference between initial muscle power outputs of the SR and SSC conditions as a difference in SSC ability, an SSC index was devised to evaluate the above ability. The SSC index showed significantly higher values in men (50.1 +/- 12.4) than in women (32.1 +/- 23.2). However, the individual difference of SSC ability was very large in women. The ability of women to use SSC in the upper extremities may be inferior to that of men.