Journal of Applied Physiology, Vol 40, Issue 1 85-90, Copyright © 1976 by American Physiological Society
Metabolic and cardiovascular adjustment to work in air and water at 18, 25, and 33 degrees C
W. D. McArdle, J. R. Magel, G. R. Lesmes and G. S. Pechar
By use of successive increments of discontinuous work with an arm-leg cycle
ergometer the VO2, Q, SV, and HR were studied in six male subjects at rest
and during exercise in air and in water at 18, 25, and 33 degrees C. The Q
values obtained by CO2 rebreathing were reproducible. VO2 was linearly
related to work with the plots for air and 33 degrees C water being
similar. However, during work in 25 and 18 degrees C water, the VO2
averaged 9.0% (150 ml) and 25.3% (400 ml) higher, respectively, than values
observed in 33 degrees C water, with the largest differences observed in
leaner subjects. The plot of HR-VO2 was linear and almost identical during
work in air and 33 degrees C water, but shifted significantly to the right
in cooler water. VO2 averaged 250-700 ml higher in cold water compared to
air and 33 degrees C water at a given mean heart rate. The Q vs. VO2 line
was similar during work in air and in water with no effect of water or
temperature. At similar levels of VO2, SV was significantly larger (P less
than 0.05) in 25 and 18 degrees C water than in air or 33 degrees C water.
Consequently, the reduction in heart rate during work in cold water was
entirely compensated for by a proportionate increase in the SV of the
heart. Q was therefore maintained at similar levels of energy expenditure
in air and in 18, 25, and 30 degrees C water.
