Abstract des Autors

Problems during the deceleration phase of running include muscle trauma and eccentric force deficits caused by a maladaptation within the nervous system. Eccentric muscle dysfunction should be greater in runners than in cyclists because cycling does not involve weight-bearing repetitive deceleration. Therefore, we compared the endurance of runners and cyclists for eccentric torque production across velocities to determine if the eccentric torque-velocity relationship of cyclists was different than that of runners. Ten endurance runners and 10 endurance cyclists were tested for isokinetic eccentric and concentric knee extension peak torque (PT) at 30, 90, 150, and 210 deg/sec (0.52, 1.57, 2.62, and 3.66 rad/sec). The cyclists produced (p</=0.05) greater concentric and eccentric PT. Eccentric and concentric PT were different across velocities (p</=0.05), but the type of exercise by velocity interaction was not different (p>/=0.05). In addition, a significant linear trend (p</=0.05) was noted across velocities for concentric PT for both runners and cyclists. Thus, as velocity increases, a significant decrease is seen in concentric PT. No increase or decrease in eccentric PT (p>/=0.05) across the four velocities was observed in either runners or cyclists. We conclude that eccentric PT is greater than concentric PT and that eccentric PT does not change as velocity increases. Therefore, the type of exercise, whether highly decelerative or not, does not influence the shape of the eccentric torque-velocity relationship. The lack of change in eccentric PT with increasing velocity may be due to a neural mechanism that is activated during maximal contractions to help ensure a safe maximum tension level. Verf.-Referat