Compromised heat loss leads to a delayed ice slurry induced reduction in heat storage

Compromised heat loss due to limited convection and evaporation can increase thermal strain. The aim of this study was to determine the effectiveness of ice slurry ingestion to reduce 26 thermal strain following hyperthermia in a state of compromised heat loss.

Twelve healthy males (age: 25±4y) underwent hot water immersion to elevate rectal temperature (Trec) by 1.82±0.08℃ on four occasions. In the subsequent 60-min of seated recovery, participants ingested either 6.8g·kg-1 of ice slurry (-0.6℃) or control drink (37℃) in ambient conditions (21±1℃, 39±10% relative humidity), wearing either t-shirt and shorts (2 trials: ICE and CON) or a whole-body sweat suit (2 trials: ICE-SS and CON-SS). Heat storage, Trec and mean skin temperature (Tsk) were recorded.

Heat storage was lower in ICE compared with CON at 20-40min (p≤0.044, d≥0.88) and for ICE-SS compared with CON-SS at 40-60min (p≤0.012, d≥0.93). Trec was lower in ICE compared with CON from 30-60min (p≤0.034, d≥0.65), with a trend for a reduced Trec in ICE-SS compared with CON-SS at 40min (p=0.079, d=0.60). A greater Tsk was found in ICE-SS and CON-SS compared with ICE and CON (p<0.001, d≥3.37). A trend for a lower Tsk for ICE compared with CON was found at 20-40min (p≤0.099, d≥0.53), no differences were found for ICE-SS vs CON-SS (p≥0.554, d≤0.43). 

Ice slurry ingestion can effectively reduce heat storage when heat loss through convection and evaporation is compromised. Compromised heat loss delays the reduction in heat storage, which may be related to ice slurry ingestion not lowering Tsk in this state.