AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 3 450-R456, Copyright © 1987 by American Physiological Society
Effects of endurance training and captivity on activity metabolism of lizards
T. Garland Jr, P. L. Else, A. J. Hulbert and P. Tap
Two groups of Amphibolurus nuchalis, an Australian agamid lizard, were
maintained in captivity for 8 wk. The "trained" group was given submaximal
exercise at 1 km/h on a motorized treadmill, 30 min/day, 5 days/wk; the
treadmill was inclined 10% for the last 5 wk. The "sedentary" group was not
exercised. Endurance capacity did not change significantly in either group,
but sprint speed decreased in trained lizards. The sedentary group
exhibited significant decreases in maximal O2 consumption, standard
metabolic rate, and heart mass, but an increase in liver mass. Trained
lizards exhibited significant decreases in heart and thigh muscle masses,
but significant increases in liver mass, hematocrit, liver pyruvate kinase,
and heart citrate synthase activities. It is concluded that the adaptive
response to endurance training, typical of mammals, does not generally
occur in lizards. Moreover, levels of chronic activity that would elicit
adaptive responses in mammals may be excessive for lizards and may induce
pathological effects in joints and skeletal muscle. The ecological and
evolutionary significance of these conclusions is discussed.
