Chappell MA, Hammond KA (2004) Maximal aerobic performance of deer
mice in combined cold and exercise challenges. Journal of Comparative
Physiology B, in press.
ABSTRACT -- In nature, animals frequently must
deal with several physiological challenges simultaneously. We examined
thermoregulatory performance (body temperature stability) and maximal oxygen
consumption of deer mice (Peromyscus maniculatus) during intense
exercise at room temperature, acute cold exposure, and exercise during cold
exposure. Results with exercise and cold exposure alone were consistent
with previous results: there was little difference between maximal metabolism
elicited by exercise alone or cold exposure alone in warm acclimated mice;
after cold acclimation (9 weeks at 5 °C), maximal exercise metabolism
did not change but maximum thermogenic capacity increased by >60%.
Warm acclimated animals did not increase maximal oxygen consumption when
exercise was combined with moderate cold (0 °C) and had decreased maximal
oxygen consumption when exercise was combined with severe cold (16
°C). Combined cold and exercise also decreased thermoregulatory performance
and exercise endurance time. Cold acclimation improved thermoregulatory
performance in combined cold and exercise, and there was also a slight increase
in endurance. However, as for warm-acclimated animals, maximal exercise
metabolism did not increase at low temperatures. We interpret these results
as an indication of competition between thermoregulatory and locomotor effectors
(brown adipose tissue and skeletal muscle) under the combined challenges
of cold exposure and maximal exercise, with priority given to the locomotor
function.