Purpose: We examined the effect of differences in body surface area-to-lean body mass ratio (AD/LBM) on core temperature cooling rates during cold water immersion (CWI, 2°C) and temperate water immersion (TWI, 26°C) after exercise-induced hyperthermia.
Methods: Twenty male participants were divided into two groups: high (315.6 ± 7.9 cm2·kg−1, n = 10) and low (275.6 ± 8.6 cm2·kg−1, n = 10) AD/LBM. On two separate occasions, participants ran on a treadmill in the heat (40.0°C, 20% relative humidity) wearing an impermeable rain suit until rectal temperature reached 40.0°C. After exercise, participants were immersed up to the nipples (arms remained out of the water) in either a CWI (2°C) or a TWI (26°C) circulated water bath until rectal temperature returned to 37.5°C.
Results: Overall rectal cooling rates were significantly different between experimental groups (high vs low AD/LBM, P = 0.005) and between immersion conditions (CWI vs TWI, P < 0.001). Individuals with a high AD/LBM had an approximately 1.7-fold greater overall rectal cooling rate relative to those with low AD/LBM during both CWI (high: 0.27°C·min−1 ± 0.10°C·min−1 vs low: 0.16°C·min−1 ± 0.10°C·min−1) and TWI (high: 0.10°C·min−1 ± 0.05°C·min−1 vs low: 0.06°C·min−1 ± 0.02°C·min−1). Further, the overall rectal cooling rates during CWI were approximately 2.7-fold greater than during TWI for both the high (CWI: 0.27°C·min−1 ± 0.10°C·min−1 vs TWI: 0.10°C·min−1 ± 0.05°C·min−1) and the low (CWI: 0.16°C·min−1 ± 0.10°C·min−1 vs TWI: 0.06°C·min−1 ± 0.02°C·min−1) AD/LBM groups.
Conclusion: We show that individuals with a low AD/LBM have a reduced rectal cooling rate and take longer to cool than those with a high AD/LBM during both CWI and TWI. However, CWI provides the most effective cooling treatment irrespective of physical differences.
Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, CANADA
Address for correspondence: Glen P. Kenny, Ph.D., 125 University Private, Room 367, Montpetit Hall, Ottawa, Ontario K1N 6N5, Canada; E-mail: firstname.lastname@example.org.
Submitted for publication October 2013.
Accepted for publication January 2014.