Journal of Applied Physiology, Vol 51, Issue 1 14-18, Copyright © 1981 by American Physiological Society
Energy expenditure during load carriage at high altitude
A. Cymerman, K. B. Pandolf, A. J. Young and J. T. Maher
To determine the applicability of a prediction equation for energy
expenditure during load carriage at high altitude that was previously
validated at sea level, oxygen uptake (Vo2) was determined in five young
men at 4,300 m while they walked with backpack loads of 0, 15, and 30 kg
at treadmill grades of 0,8, and 16% at 1.12 m.s-1 for 10 min. Mean +/- SE
maximal Vo2, determined on the cycle ergometer, was 42.2 +/- 2.3 at sea
level and 35.6 +/- 1.7 ml.kg-1 .min-1 at altitude. There were no
significant differences in daily Vo2 at any specific exercise intensity on
days 1, 5, and 9 of exposure, nor were there any differences in endurance
times at the two most difficult exercise intensities. Endurance times for
15- and 30-kg loads at 16% grade were 7.3 and 4.2 min, respectively.
Measured energy expenditure was compared with that predicted by the formula
of Pandolf et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol.
43: 577-581, 1977) and found to be significantly different. The differences
could be attributed to measurements at metabolic rates exceeding 730 W or
2.1 1.min-1 Vo2. These data indicate that the prediction equation can be
used at altitude for exercise intensities not exceeding this upper limit.
The observed deviations from predicted values at the high exercise
intensities could possibly be attributed to the occurrence of appreciable
oxygen deficits and the inability to achieve steady-state conditions.
