Effects of 10min vs. 20min passive rest after warm-up on 100m freestyle time-trial performance: A randomized crossover study.

OBJECTIVES: The aim of this study was to compare the effect of 10min vs. 20min passive rest post warm-up on performance in a 100m freestyle time-trial.

DESIGN: Randomized crossover.

METHODS: Eleven competitive male swimmers performed two experimental trials on different days, consisting of 100m freestyle time-trials following 10min or 20min passive rest after a standard 1200m warm-up. Performance (time-trial), biomechanical (stroke length, stroke frequency, stroke index, propelling efficiency), physiological (blood lactate concentrations, heart rate, core and tympanic temperature), and psychophysiological (perceived effort) variables were assessed during both trials.

RESULTS: Time-trial performance was faster after 10min as opposed to 20min passive rest (58.41±1.99s vs. 59.06±1.86, p<0.01). This was supported by strong effect sizes (d=0.99) and the qualitative indication of "likely" positive effects. Heart rate before the time-trial was also higher after 10min passive rest (89±12bpm vs. 82±13bpm; p<0.01). Furthermore, net core temperature and oxygen uptake values before the time-trial were substantially lower after 20min passive rest.

CONCLUSIONS: These data suggest that the 10min post warm-up passive rest enhances 100m freestyle performance when compared to a 20min period. An improvement that appears to be mediated by the combined effects of a shorter post warm-up period on core temperature, heart rate and oxygen uptake.