Core Temperature Responses and Match Running Performance During Intermittent-Sprint Exercise Competition in Warm Conditions

Duffield, R, Coutts, AJ, and Quinn, J. Core temperature responses and match running performance during intermittent-sprint exercise competition in warm conditions. J Strength Cond Res 23(4): 1238-1244, 2009-This study investigated the thermoregulatory responses and match running performance of elite team sport competitors (Australian Rules football) during preseason games in a warm environment. During 2 games in dry bulb temperatures above 29°C (>27°C wet bulb globe temperature), 10 players were monitored for core temperature (Tcore) via a telemetric capsule, in-game motion patterns, blood lactate ([La−]), body mass changes, urine specific gravity, and pre- and postgame vertical jump performance. The results showed that peak Tcore was achieved during the final quarter at 39.3 ± 0.7°C and that several players reached values near 40.0°C. Further, the largest proportion of the total rise in Tcore (2.1 ± 0.7°C) occurred during the first quarter of the match, with only small increases during the remainder of the game. The game distance covered was 9.4 ± 1.5 km, of which 2.7 ± 0.9 km was at high-intensity speeds (>14.4 km·h−1). The rise in Tcore was correlated with first-quarter high-intensity running velocity (r = 0.72) and moderate-intensity velocity (r = 0.68), second-quarter Tcore and low-intensity activity velocity (r = −0.90), second-quarter Tcore and moderate-intensity velocity (r = 0.88), fourth-quarter rise in Tcore and very-high-intensity running distance (r = 0.70), and fourth-quarter Tcore and moderate-intensity velocity (r = 0.73). Additional results included mean game [La−] values of 8.7 ± 0.1 mmol·L−1, change in body mass of 2.1 ± 0.8 kg, and no change (p > 0.05) in pre- to postgame vertical jump. These findings indicate that the plateau in Tcore may be regulated by the reduction in low-intensity activity and that pacing strategies may be employed during competitive team sports in the heat to ensure control of the internal heat load.