Contraction-specific differences in maximal muscle power during stretch-shortening cycle movements in elderly males and females

Elderly people (age 75 years; n = 48 males and 34 females) were studied in order to elucidate gender differences in elderly subjects on the determinan ts of muscle power (force and velocity) during a stretch-shortening cycle. All subjects performed three maximal counter-movement vertical jumps using both legs, on a force platform (Kistler 9281 B). The eccentric (Ep) and con centric (Cp) phases of the jumps were analyzed. The Ep was further divided into an acceleration phase (Ep(acc): from the start of the downward movemen t to the maximal negative velocity) and deceleration phase (EPdec: from the maximal negative velocity to the end of the downward movement). Jump heigh t for the men was higher than for the women (P < 0.001). During both Ep(acc ) and Ep(dec) no significant differences were observed between males and fe males in force and power generation. However, the men had a higher peak mus cle power during the Cp, which may be explained exclusively by the velocity determinant (P < 0.001). No specific gender-related strategy appeared to i nfluence the motor pattern of the movement. The comparable eccentric force generation of the leg extensors in both genders suggests a similar ability to cope with eccentric muscle actions during everyday activities. In contra st, the marked lower capacity for concentric contractions in women may resu lt in an impaired performance, especially in activities where intense and r apid movements are essential, for example when reversing a forward fall. Th is may be one reason why elderly women are more prone to falls than are eld erly men.