Abstract

Objective: The purpose of this study was to determine whether moderate water loss (~ 1.5 - 2% of body mass) represents a significant impairment to soccer match- play and the related fitness variables.

Methods: Eleven moderately active male soccer players (age: 24.4 ±3 years, body mass: 74.03 ±10.5 kg, [Vdot] O₂ peak: 50.91 ±4.0 ml kg ^-1min^-1 volunteered to participate. The experimental procedure comprised: 1) a 45-min pre-match period of cycle ergometry exercise (90% of individual ventilatory threshold), 2) the completion of a 45-min soccer match, and 3) the immediate post-match performance of sport-specific and mental concentration tests. The subjects completed the procedure on 3 occasions each in a different experimental condition (fluid-intake, no-fluid, mouth-rinse) in an individually randomised order. Core temperature (T_c),heart rates, plasma and urine osmolalities, body mass, sweat rates, and heat storage were all measured.

Results: The only condition-dependent difference during the match-play element of the protocol was a significantly elevated T_c in the no-fluid condition compared to the fluid-intake condition (39.28°C±0.35 and 38.8°C±0.47;P<0.05). The immediate post- match performance of a sport specific fitness test was significantly impaired where fluid intake had been denied (P<0.01). Post-test evaluation of RPE and thirst indicated that the no-fluid condition was perceived to be the most challenging (P<0.05).

Conclusions: The condition-dependent differences in match-play and post-match performance tests demonstrate that moderate dehydration is detrimental to soccer performance. However, it remains unclear whether this could be attributable to water loss per se or the negative psychological associations derived from a greater perception of effort in that condition.