Abstract
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°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°C and 42.5 ± 3.9%RH). In both studies, each trial was preceded by 30 min of CWI (~22°C), ICE or no cooling (CON). Rectal temperature (Tre), skin temperature (Tsk), thermal sensation, and sweat responses were measured. In study 1, ICE decreased Tre-Tsk gradient versus CON (p = 0.005) during first 5 min of exercise, while CWI increased Tre-Tsk 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 ~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 Tre-Tsk gradient by CWI improved MPO while ICE reduced Tre but did not confer any ergogenic effect. Both precooling treatments attenuated the thermal efferent signals until a specific body temperature threshold was reached.
Highlights
MethodsParticipantsThe experimental procedures were approved by Edith Cowan University ethics committee for human research and were conducted according to the principles expressed in the Declaration of Helsinki
The present study aimed to examine the differences in some thermoregulatory parameters and muscle perfusion (NIRS parameters) during cold water immersion (CWI) and ice slushy (ICE) versus a no cooling control condition (CON), and the consequential influence on thermoregulatory behavior as indicated by total work output during exercise in the heat
A significant effect was present for baseline body mass (p = 0.006) with post-hoc analysis revealing that baseline body mass was lower in CON versus ICE (p = 0.008), but no difference was observed between CWI and CON (p = 0.195) or between CWI and ICE (p = 0.979, CON: 77.3 ± 9.7 kg, CWI: 77.6 ± 10.2 kg, ICE: 77.8 ± 9.9 kg)
Summary
ParticipantsThe experimental procedures were approved by Edith Cowan University ethics committee for human research and were conducted according to the principles expressed in the Declaration of Helsinki. Minimum of 7 participants were required to identify significant difference in whole body sweat loss between conditions. 13 men were recruited for study 1; only 11 men completed all trials (mean ± SD; age: 27 ± 6 y, body mass: 77.5 ± 10.5 kg, height: 177.1 ± 7.9 cm, sum of 4 skinfolds: 58.1 ± 25.7 mm, Peak O2 uptake (V_ O2peak): 43.9 ± 11.4 mL kg-1 min-1, peak aerobic power: 288 ± 64 W). A minimum of 7 participants were required to identify significant difference between conditions with an α of 0.05 and a β of 0.2. Eleven out of 13 participants completed the study (mean ± SD; age: 30 ± 6 y, body mass: 80.6 ± 12.8 kg, height: 1.8 ± 0.1 m, V_ O2peak: 51.1 ± 8.2 mL.kg-1.min-1, sum of 7 skinfold: 131.2 ± 52.6 mm). Participants were asked to: 1) avoid strenuous exercise and alcohol consumption during the 24 h before each trial; 2) avoid caffeine during the 12 h before each trial; and 3) keep their diet, physical activity and sleep habits consistent before each trial, assisted by a 1-d dietary intake and physical activity record
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