Journal of Applied Physiology, Vol 70, Issue 1 371-374, Copyright © 1991 by American Physiological Society
Sweat ammonia excretion during submaximal cycling exercise
D. Czarnowski and J. Gorski
Department of Physiology, Medical School, Bialystok, Poland.
This study was undertaken to investigate whether part of the ammonia formed
during muscular exercise was excreted with the sweat. Male medical students
volunteered for the experiment. They exercised 30 min on a bicycle
ergometer at 80 and 40% of the predetermined maximal O2 uptake (VO2max).
Exercise at 80% VO2max was performed twice, at room temperature (20 degrees
C) and in a cold room (0 degrees C), whereas exercise at 40% was performed
only at room temperature (20 degrees C). Blood was collected from the
antecubital vein immediately before and after exercise. Sweat was collected
from the hypogastric region by use of gauze pads. It was shown that the
plasma ammonia level was elevated after exercise at 80% VO2max and remained
stable after exercise at 40% VO2max. The volume of sweat produced during
exercise at 80% VO2max at 20 degrees C was 428 +/- 138 ml and at 0 degrees
C 245 +/- 86 ml and during exercise at 40% VO2max was 183 +/- 69 ml. The
ammonia concentration in the sweat after exercise at 80% VO2max at 20
degrees C was 7,140 mumol/l and at 0 degrees C 11,816 mumol/l. After
exercise at 40% VO2max, it was 2,076 mumol/l. The total ammonia lost
through the sweat during exercise at 80% VO2max was similar at both
temperatures, despite the difference in the sweat volume (at 20 degrees C,
3,360 +/- 2,080 mumol; at 0 degrees C, 3,310 +/- 1,250 mumol). During
exercise at 40% VO2max, it was 350 +/- 230 mumol. These results show that
part of ammonia formed during exercise is lost with sweat. The amount lost
increases with increased work rate and the plasma ammonia concentration.
