Cold drink attenuates heat strain during work-rest cycles.

There is limited information on the ingestion of cold drinks after exercise. We investigated the thermoregulatory effects of ingesting drinks at 4°C (COLD) or 28°C (WARM) during work-rest cycles in the heat. On 2 separate occasions, 8 healthy males walked on the treadmill for 2 cycles (45 min work; 15 min rest) at 5.5 km/h with 7.5% gradient. Two aliquots of 400 mL of plain water at either 4°C or 28°C were consumed during each rest period. Rectal temperature (T re ), skin temperature (T sk ), heart rate and subjective ratings were measured. Mean decrease in T re at the end of the final work-rest cycle was greater after the ingestion of COLD drinks (0.5±0.2°C) than WARM drinks (0.3±0.2°C; P<0.05). Rate of decrease in T sk was greater after ingestion of COLD drinks during the first rest period (P<0.01). Mean heart rate was lower after ingesting COLD drinks (P<0.05). Ratings of thermal sensation were lower during the second rest phase after ingestion of COLD drinks (P<0.05). The ingestion of COLD drinks after exercise resulted in a lesser than expected reduction of T re . Nevertheless, the reduction in T re implies a potential for improved work tolerance during military and occupational settings in the heat.

Ice slurry on outdoor running performance in heat.

The efficacy of ingestion of ice slurry on actual outdoor endurance performance is unknown. This study aimed to investigate ice slurry ingestion as a cooling intervention before a 10 km outdoor running time-trial. Twelve participants ingested 8 g · kg (- 1) of either ice slurry ( - 1.4°C; ICE) or ambient temperature drink (30.9°C; CON) and performed a 15-min warm-up prior to a 10 km outdoor running time-trial (Wet Bulb Globe Temperature: 28.2 ± 0.8°C). Mean performance time was faster with ICE (2 715 ± 396 s) than CON (2 730 ± 385 s; P=0.023). Gastrointestinal temperature (Tgi) reduced by 0.5 ± 0.2°C after ICE ingestion compared with 0.1 ± 0.1°C (P<0.001) with CON. During the run, the rate of rise in Tgi was greater (P=0.01) with ICE than with CON for the first 15 min. At the end of time-trial, Tgi was higher with ICE (40.2 ± 0.6°C) than CON (39.8 ± 0.4°C, P=0.005). Ratings of thermal sensation were lower during the cooling phase and for the first kilometre of the run ( - 1.2 ± 0.8; P<0.001). Although ingestion of ice slurry resulted in a transient increase in heat strain following a warm up routine, it is a practical and effective pre-competition cooling manoeuvre to improve performance in warm and humid environments.