Changes in spring-mass model parameters and energy cost during track running to exhaustion
Résumé
The purpose of this study was to determine whether exhaustion modifies the stiffness characteristics, as defined in the spring-mass model, during track running. We also investigated whether stiffer runners are also the most economical. Nine well-trained runners performed an exhaustive exercise over 2000 meters on an indoor track. This exhaustive exercise was preceded by a warm-up and was followed by an active recovery. Throughout all the exercises, the energy cost of running (Cr) was measured. Vertical and leg stiffness was measured with a force plate (Kvert and Kleg, respectively) integrated into the track. The results show that Cr increases significantly after the 2000-meter run (0.192 ± 0.006 to 0.217 ± 0.013 mL·kg− 1·m− 1). However, Kvert and Kleg remained constant (32.52 ± 6.42 to 32.59 ± 5.48 and 11.12 ± 2.76 to 11.14 ± 2.48 kN·m− 1, respectively). An inverse correlation was observed between Cr and Kleg, but only during the 2000-meter exercise (r = −0.67; P ≤ 0.05). During the warm-up or the recovery, Cr and Kleg, were not correlated (r = 0.354; P = 0.82 and r = 0.21; P = 0.59, respectively). On track, exhaustion induced by a 2000-meter run has no effect on Kleg or Kvert. The inverse correlation was only observed between Cr and Kleg during the 2000-meter run and not before or after the exercise, suggesting that the stiffness of the runner may be not associated with the Cr.