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ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Sprint performance-duration relationships are set by the fractional duration of external force application

¹Locomotion Laboratory, Kinesiology Department, Rice University; and ²Center for Human Performance, Texas Medical Center, Houston, Texas

Submitted 1 August 2005 ; accepted in final form 18 October 2005

We hypothesized that the maximum mechanical power outputs that can be maintained during all-out sprint cycling efforts lasting from a few seconds to several minutes can be accurately estimated from a single exponential time constant (k_cycle) and two measurements on individual cyclists: the peak 3-s power output (P_{mech max}) and the maximum mechanical power output that can be supported aerobically (P_aer). Tests were conducted on seven subjects, four males and three females, on a stationary cycle ergometer at a pedal frequency of 100 rpm. Peak mechanical power output (P_{mech max}) was the highest mean power output attained during a 3-s burst; the maximum power output supported aerobically (P_aer) was determined from rates of oxygen uptake measured during a progressive, discontinuous cycling test to failure. Individual power output-duration relationships were determined from 13 to 16 all-out constant load sprints lasting from 5 to 350 s. In accordance with the above hypothesis, the power outputs measured during all-out sprinting efforts were estimated to within an average of 34 W or 6.6% from P_{mech max}, P_aer, and a single exponential constant (k_cycle = 0.026 s^–1) across a sixfold range of power outputs and a 70-fold range of sprint trial durations (R² = 0.96 vs. identity, n = 105; range: 180 to 1,136 W). Duration-dependent decrements in sprint cycling power outputs were two times greater than those previously identified for sprint running speed (k_run = 0.013 s^–1). When related to the respective times of pedal and ground force application rather than total sprint time, decrements in sprint cycling and running performance followed the same time course (k = 0.054 s^–1). We conclude that the duration-dependent decrements in sprinting performance are set by the fractional duration of the relevant muscular contractions.

locomotion; cycling; running; anaerobic; aerobic; skeletal muscle; fatigue

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