This study examined the effect of environmental heat stress on repeated jump performance after elite competitive soccer games. Male elite soccer players (n = 19) from 2 Scandinavian teams participated (age: 26.7 ± 1.0 years, height: 181.7 ± 1.1 cm, body mass: 75.8 ± 1.0 kg). The players had a Yo-Yo IR2 performance of 1,032 ± 42 m (range: 920-1,400 m). The players took part in the Champions League Qualification, where 6 games (3 home and 3 away) were played. The home games took place at an average ambient temperature of 12.2 ± 0.5° C (control game; CON) and the away games in hot conditions (30.0 ± 0.3° C; HOT). In the resting condition (Baseline) and immediately after CON and HOT, the players performed a repeated countermovement jump (CMJ) test consisting of 5 jumps separated by 5 seconds of recovery. Game-induced body mass loss was determined based on change in body mass after correction for fluid intake. The net loss of body mass was 3.1 ± 0.3% in HOT, which was higher (p < 0.05) than in CON (1.7 ± 0.2%). Mean CMJ performance after HOT was 37.9 ± 1.1 cm, which was 6.0% lower (p < 0.05) than Baseline (40.3 ± 1.1 cm) and tended (p = 0.08) to be lower than in the CON (39.6 ± 1.2 cm). The mean CMJ performance after CON was not different from Baseline. Peak CMJ performance after HOT was 41.1 ± 1.1 cm, which was not different from either Baseline or CON (42.0 ± 1.1 and 41.7 ± 1.2 cm, respectively). The relative decline in repeated CMJ performance from Baseline to after HOT correlated (r = 0.60; p < 0.05) to relative net loss in body mass during HOT. This study demonstrates that repeated CMJ performance deteriorates after a soccer game played in warm environmental settings, which is partly associated with severe dehydration.
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