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 degrees C (COLD) or 28 degrees C (WARM) during work-rest cycles in the heat. On 2 separate occasions, 8 healthy males walked on the treadmill for 2 cycles (45min work; 15min rest) at 5.5km/h with 7.5% gradient. Two aliquots of 400mL of plain water at either 4 degrees C or 28 degrees 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 degrees C) than WARM drinks (0.3 +/- 0.2 degrees 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.