J Appl Physiol 94: 1039–1044, 2003. First published November 8, 2002; 10.1152/japplphysiol.00720.2002.
Metabolic, thermoregulatory, and perceptual responses during exercise after lower vs. whole body precooling
ANDREA T. WHITE,1 SCOTT L. DAVIS,1 AND THAD E. WILSON2 1Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah 84112; and 2Department of Biomedical Sciences, Southwest Missouri State University, Springfield, Missouri 65804
Submitted 5 August 2002; accepted in final form 31 October 2002
White, Andrea T., Scott L. Davis, and Thad E. Wilson. Metabolic, thermoregulatory, and perceptual responses dur- ing exercise after lower vs. whole body precooling. J Appl Physiol 94: 1039–1044, 2003. First published November 8, 2002; 10.1152/japplphysiol.00720.2002.—The purpose of this investigation was to compare the thermoregulatory, meta- bolic, and perceptual effects of lower body (LBI) and whole body (WBI) immersion precooling techniques during sub- maximal exercise. Eleven healthy men completed two 30-min cycling bouts at 60% of maximal O2 uptake preceded by immersion to the suprailiac crest (LBI) or clavicle (WBI) in 20°C water. WBI produced significantly lower rectal temper- ature (Tre) during minutes 24–30 of immersion and lower Tre, mean skin temperature, and mean body temperature for the first 24, 14, and 16 min of exercise, respectively. Body heat storage rates differed significantly for LBI and WBI during immersion and exercise, although no net differences were observed between conditions. For WBI, metabolic heat pro- duction and heart rate were significantly higher during im- mersion but not during exercise. Thermal sensation was significantly lower (felt colder) and thermal discomfort was significantly higher (less comfortable) for WBI during im- mersion and exercise. In conclusion, WBI and LBI attenu- ated Tre increases during submaximal exercise and produced similar net heat storage over the protocol. LBI minimized metabolic increases and negative perceptual effects associ- ated with WBI.
body temperature; water immersion; metabolic heat produc- tion; body heat storage
EXERCISE-INDUCED INCREASES in metabolic heat load con- siderably challenge temperature homeostasis and may ultimately impair physical work performance (20). Pre- cooling is a strategy used to decrease the temperature of a large tissue mass, thereby creating a “heat sink” before exercise and/or environmentally induced ther- mal exposure. The beneficial effects of precooling in- clude thermoregulatory, circulatory, and performance b e n e fi t s ( 4 , 1 2 , 1 6 , 2 1 ) . B y c r e a t i n g a g r e a t e r b o d y h e a t ˙ storage (S) capacity, precooling delays the onset of heat
dissipation mechanisms by lengthening the time re- quired to reach sweat threshold (21). In effect, precool- ing increases the reserve for heat storage, allowing
more work to be accomplished before a given increase in core temperature (Tc) is reached (25, 26). As a consequence of reducing or delaying the need to dissi- pate heat, precooling may result in less competition for blood flow between the skin and working muscles dur- ing exercise in the heat, thus resulting in less cardio- vascular strain.
Several investigators have demonstrated clear ben- efits of precooling as a means to improve exercise performance in healthy individuals (4, 12, 16, 21), whereas other investigators have reported that pre- cooling had no effect or actually decreased performance (2, 3, 7, 15). Lower body cool water immersion before physical activity has also been helpful in minimizing heat-related decrements in physical function and fa- tigue in heat-sensitive individuals with multiple scle- rosis (MS) (25). Discrepancies in the precooling litera- ture are likely due to varying cooling methods and experimental ambient conditions and to differing exer- cise loads and population characteristics.
The most effective precooling strategy would maxi- mize the physiological benefits of decreased body tem- perature (Tb) (creation of a heat sink, delay of heat dissipation mechanisms) while minimizing the disad- vantages of an “adverse” ˙environment [increased met- abolic heat production (M), physical discomfort]. The purpose of this investigation was to compare the effects of two water immersion precooling techniques on ther- moregulatory and metabolic responses during exercise- induced heat stress. We hypothesized that lower body immersion (LBI), a treatment that our laboratory has shown to be well tolerated, would be as effective a precooling treatment as whole body immersion (WBI) by delaying the time until a given temperature in- crease is reached during subsequent submaximal exer- cise (25). Although there have been several studies that have examined thermoregulatory responses to whole body precooling as well as physiological re- sponses to maximal exercise after precooling, we are aware of no direct comparisons of WBI and LBI pre- cooling techniques on thermoregulatory and metabolic responses during a constant submaximal work rate. A
Address for reprint requests and other correspondence: A. T. White, Dept. of Exercise and Sport Science, University of Utah, 250 S. 1850 E., Rm. 241, Salt Lake City, UT 84112-0920 (E-mail: email@example.com).
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