2007, Piran, Slovenia

Acute and chronic heat exposure
2.2 ±6.3 and -2.4 ±6.3% for CON, 1-Hand and 2-Hand, respectively (P>0.05) with sweat rates
of 1.2 ±0.4, 1.2 ±0.4, and 1.4 ±0.3 l.hr -1 (P>0.05). Although there were no differences in the
performance trial duration between trials (14 ±6; 15 ±4; 17 ±6 sprints) six subjects completed
most sprints during 2-HC than in any other trials, one subject completed most sprints during
1-HC and two subjects completed most sprints during CON.
DISCUSSION
Although 2-HC reduced Taur significantly when compared to CON this decrease was lower
than that observed by House et al. (1997) using the same water temperature over the same
time period. The smaller decrease in the present study is most likely to have been due to the
participants having a smaller increase in core temperature prior to cooling. This would not
only reduce the demand for heat loss but also reduce the drive for blood flow to the hands,
which is the mechanism by which hand cooling is reported to work. Consequently, the
subjects were not at a level of hyperthermia where hand cooling would be affective. However,
the results of the present study in conjunction of those with House et al. (1997) suggest that
the effectiveness of hand cooling is proportional to the initial core temperature.
It is possible that the lack of core temperature reduction is due to vasoconstriction in the
hands and a reduced heat dissipation potential. However, the amount of heat lost via the
hands, the increase in the water temperature during cooling, and the tendency to lower core
temperature all suggest that vasoconstriction did not occur. This agrees with previous hand
cooling studies that reported Thand remained greater than the temperature of the water during
cooling demonstrating that vasoconstriction did not occur, and constant blood flow to the
hands was maintained (Livingstone et al., 1989, House et al., 1997). Interestingly, although
the same Thand was achieved during the cooling procedure for both 1-HC and 2-HC greater
heat loss was facilitated during 2-HC. This is most likely due to the coolant being stirred and
the smaller loss of heat from the body when compared to previous studies. If a greater core
temperature had been achieved pre-cooling and a greater cooling duration employed
differences between one and two handed cooling may have been observed as the capacity for
the water to store heat decreased.
The subjects in the present study fatigued at lower core temperatures than previously reported
(Nybo and Nielsen, 2001). It is possible that the lower level of aerobic fitness of the
participants in the present study contributed to this affect. Elite athletes are more likely to
push themselves to physiological extremes where thermoregulation limits performance.
Consequently, hand cooling may be more affective for well trained or elite populations.
The results of this study showed that although there was a significant difference between 2-
HC and CON for Taur after the cooling period and that 2-HC facilitated greater heat loss from
the hands than 1-HC this did not translate into improved performance. The onset of fatigue
during the intermittent exercise protocol was most likely related to factors other than
hyperthermia such as muscle fatigue and training status.
REFERENCES
House, J.R., Holmes, C., Allsopp, A.A. 1997. Prevention of Heat Strain by Immersing the
Hands and Forearms in Water. Journal of the Royal Naval Medical Service. 83(1):26 –
30.
Livingstone, S.D., Nolan, R.W., Cattroll, S.W. 1989. Heat Loss caused by Immersing the
Hands in water. Aviation, Space, and Environmental Medicine. 60(12):1166 – 1171.
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