Résumé
Abstract only This study aimed to determine the relationship between the individual heat acclimatization and field performance in 19 semi professional soccer players. A soccer match was played in a hot environment after a week of training in hot ambient conditions (environmental temperature: 38–43ºC). At the beginning and end of the week, all players performed a heat‐response test (30 min walk at 5 km.h‐1 + 30 min seated; 44ºC, 44% RH). Results from the heat response test showed an improvement (P < 0.05) in the physiological markers of heat acclimatization (sweat rate +34%, sweat sodium concentration −18%, plasma volume +4.3%). Despite these adaptations, the mean amount of activity during the match in hot was lower than during a control game played in thermo‐neutral conditions the week before (−6.0%, P < 0.05). The decrement in total distance during the game in the heat was correlated to the plasma volume expansion (r = 0.75, P < 0.05) and the players with the highest plasma volume expansion were able to maintain the same level of activity in the heat as in thermo‐neutral environment. These data suggest the existence of ‘responders’ and ‘non/slow ‐ responders’ to heat acclimatization that could be identified by a heat‐response test.