Adaptation to Exercise in the Rat: Lack of Associative Control

A procedure in which female Long-Evans rats were swum to a criterion of fatigue was utilized to assess the contextual determinants of adaptation to exercise. In Experiment 1, it was observed that rats given four exercise exposures demonstrated significant adaptation to the treatment, as indicated by reliably longer swimming times over the course of exercise exposure. Furthermore, the change in swimming times reflected in these subjects was not due to maturation or growth over the course of the experiment, as their body weights before and after the experiment did not reliably differ. Experiment 2 addressed whether adaptation to swimming exercise was susceptible to a context shift effect, as is tolerance to drugs and adaptation to other homeostatic disturbances (e.g., hypothermia). Using a within-subject design, Experiment 2 demonstrated that a shift in contextual stimuli (a procedure that reliably disrupts drug tolerance and hypothermia adaptation) failed to disrupt established adjustment to exercise. The results of these experiments suggest that adaptation to exercise may be mediated by different mechanisms than adaptation to other disturbances (e.g., drugs, hypothermia), since an alteration in contextual stimuli did not appear to be detrimental to established exercise adaptation with this paradigm.