Effects of age and recovery duration on performance during multiple treadmill sprints

The aim of this study was to investigate the effects of age and recovery duration on performance during multiple treadmill sprints. Twelve boys (11.7 ± 0.5 y) and thirteen men (22.1 ± 2.9 y) performed ten consecutive 10-s sprints on a non-motorised treadmill separated by 15-s (R15) and 180-s (R180) passive recovery intervals. Mean power output (MPO), mean force output (MFO), running velocity, step length, and step rate were calculated for each sprint. Capillary blood samples were drawn from the fingertip at rest and 3 min after the tenth sprint to measure the lactate accumulation (Delta [La]). With R15, all mechanical parameters decreased significantly less in the boys than in the men over the ten sprints (MPO: -28.9 vs. -47.0%, MFO: -13.1 vs. -25.6%, running velocity: -18.8 vs. -29.4%, p < 0.001, respectively). With R180, all mechanical values remained unchanged in the boys. In the men, MPO and MFO significantly decreased over the ten sprints (-7.8% and -4.6%, p < 0.05, respectively). The running velocity, however, did not decrease because the decrease in step rate (p < 0.001) was compensated by an increase in step length. For either recovery interval, Delta [La] values were higher in the men compared to the boys (R15: 12.7 vs. 7.7 mmol·L^-1, p < 0.001, R180: 10.7 vs. 7.7 mmol·L^-1 p < 0.05). To conclude, the boys maintained more easily their running performance than the men during repeated treadmill sprints with R15. Three-minute recovery periods were sufficient in the boys to repeat short running sprints without substantial fatigue. Despite the decrease in power and force outputs with R180, the young men were able to maintain their running velocity during the test.