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Human Performance and Protection, Defence and Civil Institute of Environmental Medicine, Toronto, Ontario, Canada M3M 3B9
Eleven women (age = 24.4 ± 6.3 yr,
mass = 65.0 ± 7.8 kg, height = 167 ± 8 cm, body
fatness = 22.4 ± 5.9%, mean ± SD) were immersed to
neck level in 18°C water for up to 90 min for comparison of their
thermal responses with those of men (n = 14) in a
previous similarly conducted protocol. Metabolic rate increased about
three times resting levels in men and women, whereas the rate of rectal temperature cooling (
Tre/
t) in women
(0.47°C/h) was about one-half that in men. With use of all data,
Tre/
t correlates with the ratio of body
surface area to size and the metabolic rate of shivering correlates
inversely to the square root of body fatness. No significant gender
differences in total metabolic heat production normalized for body mass
or surface area were found among subjects who completed 90 min of
immersion (9 women and 7 men). Nor was there a gender difference in the
overall percent contribution (~60%) of fat oxidation to total heat
production. Blood concentrations of free fatty acids, glycerol,
-hydroxybutyrate, and lactate increased significantly during the
90-min immersion, whereas muscle glycogen sampled from the right
quadriceps femoris vastus lateralis decreased (free fatty acids,
glycerol, and
-hydroxybutyrate were higher in women). When the
subjects were subgrouped according to similar body fatness and 60 min
of immersion (6 women and 5 men), no significant gender differences
emerged in
Tre/
t, energy metabolism, and
percent fat oxidation. These findings suggest that no gender
adjustments are necessary for prediction models of cold response if
body fatness and the ratio of body surface area to size are taken into
account and that a potential gender advantage with regard to
carbohydrate sparing during cold water immersion is not supported.
body cooling; shivering; prediction; model; substrate utilization
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