AbstractIntroduction: Individuals, who are required to wear personal protective clothing (PPC), are more susceptible to suffer from heat strain. This is due to the clothing impeding heat exchange through sweat evaporation to the surrounding environment therefore causing core temperature (Tcore) to increase (Holmér 1995). The continued rise in Tcore and inability to lose heat creates a micro-environment within the PPC results in the individual suffering from uncompensable heat stress (UHS). The submersion of the hands or feet in cool water has been shown to improve exercise tolerance by reducing UHS whilst wearing PPC (Livingstone et al. 1989; 1995). Hand cooling has been found to be effective at reducing core temperature however; the effectiveness at different levels of core temperatures due to different durations or of exercise while wearing PPC has not been reported.
Aim: The primary aim of this study was to determine the effectiveness of hand cooling at different durations of exercise whilst wearing a bomb disposal suit. A secondary aim was to determine whether having periods of ‘mid’ cooling during exercise is effective at reducing heat strain in comparison to having no cooling periods.
Methods: Eight healthy, males (mean age = 21.6 ± 1.5 years, mean body mass = 79.8 ± 12.6 kg) volunteered for this study. The test protocol required the participants to perform stepping exercise at 12 steps•min-1 for 15 minute intervals. During each trial subjects undertook either one, two or three 15 minute bouts of exercise. Each bout was separated by a 15 minute rest period. At the end of each trial a 30 minute rest period was undertaken where cooling was applied. A further trial was undertaken where three 15 minute bouts were undertaken with cooling applied after each bout. During each rest period participants remained in the full Explosive Ordinance Disposal (EOD) ensemble. During hand cooling the participants immersed both hands up to the wrist in 15 litres of water at an initial temperature of 10oC. Tcore (rectal, aural), skin temperature (Arm, Back, Chest, Thigh, Hand and Finger), Heart rate (HR), Blood lactate (Bla), RPE and TS were measured continuously with VO2 being measured during the last minute of each bout of exercise. Heat extraction from the hands was calculated during each immersion period. Data were expressed as mean and standard deviation and analysed by analysis of variance with repeated measures (trial × time) on both factors. Where significance was achieved (P<0.05) Tukey post-hoc comparisons were undertaken.
Results: There was no significant interaction for rectal temperature (Trec) between any of the trials (p>0.05), although there was a significant main effect for trial (15 MIN vs. 45 MIN and 45 MIN vs. MID-COOLING (p<0.05). There was no significant interaction for aural temperature (Taur) (p>0.05), although there was a significant main effects for time and trial (15 MIN vs. 45 MIN and 45 MIN vs. MID-COOLING) (p<0.05). A significant interaction was observed for hand skin temperature between 45 MIN vs. MID-COOLING trials (p<0.05). There were no significant differences for heat flow (P>0.05).
Discussion: Significant main effects were found between trials for Trec and Taur, although there was no significant interaction. The reduction in Tcore during cooling periods was not as much as has been previously reported, however this may be a result of Trec and Thand not being above thresholds required for hand cooling to be effective (Allsopp and Poole 1991 and Greenfield 1963). The use of MID-COOLING may not reduce Tcore greatly, however it is maintained at lower levels and therefore may be a more relevant structure for work : rest in the field as it would irradiate the need to continually monitor Tcore which is not always possible.
|Date of Award||2011|
|Supervisor||Mike Price (Supervisor)|