Effect of ice slushy ingestion and cold water immersion on thermoregulatory behavior

Two studies were conducted to examine the effects of ice slushy ingestion (ICE) and cold water immersion (CWI) on thermoregulatory and sweat responses during constant (study 1) and self-paced (study 2) exercise. In study 1, 11 men cycled at 40-50% of peak aerobic power for 60 min (33.2 +/- 0.3 degrees C, 45.9 +/- 0.5% relative humidity, RH). In study 2, 11 men cycled for 60 min at perceived exertion (RPE) equivalent to 15 (33.9 +/- 0.2 degrees C and 42.5 +/- 3.9% RH). In both studies, each trial was preceded by 30 min of CWI (similar to 22 degrees C), ICE or no cooling (CON). Rectal temperature (T-re), skin temperature (T-sk), thermal sensation, and sweat responses were measured. In study 1, ICE decreased T-re-T-sk gradient versus CON (p = 0.005) during first 5 min of exercise, while CWI increased T-re-T-sk gradient versus CON and ICE for up to 20 min during the exercise (p<0.05). In study 2, thermal sensation was lower in CWI versus CON and ICE for up to 35-40 min during the exercise (p<0.05). ICE reduced thermal sensation versus CON during the first 20 min of exercise (p<0.05). In study 2, CWI improved mean power output (MPO) by similar to 8 W, compared with CON only (p = 0.024). In both studies, CWI (p<0.001) and ICE (p = 0.019) delayed sweating by 1-5 min but did not change the body temperature sweating threshold, compared with CON (both p>0.05). Increased T-re-T-sk gradient by CWI improved MPO while ICE reduced T-re but did not confer any ergogenic effect. Both precooling treatments attenuated the thermal efferent signals until a specific body temperature threshold was reached.