Ingestion of carbohydrate and reducing core body temperature pre-exercise -- either separately or combined -- may have ergogenic effects during prolonged intermittent exercise in hot conditions.

The aim of this investigation was to examine the effect of carbohydrate ingestion and pre-cooling on the physiological responses to soccer-specific intermittent exercise and the impact on subsequent high-intensity exercise performance in the heat.

Twelve male soccer players performed a soccer-specific intermittent protocol for 90 min in the heat (30.5°C and 42.2% r.h.) on four occasions. On two occasions, the participants underwent a pre-cooling manoeuvre. During these sessions either a carbohydrate-electrolyte solution (CHOc) or a placebo was consumed at (PLAc). During the remaining sessions either the carbohydrate-electrolyte solution (CHO) or placebo (PLA) was consumed.

At 15-min intervals throughout the protocol participants performed a mental concentration test. Following the soccer-specific protocol participants performed a self-chosen pace test and a test of high-intensity exercise capacity.

The period of pre-cooling significantly reduced core temperature, muscle temperature and thermal sensation (P < 0.05).

Self-chosen pace was greater with CHOc (12.5 ± 0.5 km h(-1)) compared with CHO (11.3 ± 0.4 km h(-1)), PLA (11.3 ± 0.4 km h(-1)) and PLAc (11.6 ± 0.5 km h(-1)) (P < 0.05). High-intensity exercise capacity was improved with CHOc and CHO when compared with PLA (CHOc; 79.8 ± 7 s, CHO; 72.1 ± 5 s, PLAc; 70.1 ± 8 s, PLA; 57.1 ± 5 s; P < 0.05). Mental concentration during the protocol was also enhanced during CHOc compared with PLA (P < 0.05).

These results suggest pre-cooling in conjunction with the ingestion of carbohydrate during exercise enhances exercise capacity and helps maintain mental performance during intermittent exercise in hot conditions.