Physiological and biochemical adaptations to training inRana pipiens

Summary

FifteenRana pipiens were trained on a treadmill thrice weekly for 6.5 weeks to assess the effects of training on an animal that supports activity primarily through anaerobiosis. Endurance for activity increased 35% in these frogs as a result of training (P=0.006, Fig. 1). This increased performance was not due to enhanced anaerobiosis. Total lactate produced during exercise did not differ significantly for the trained or untrained animals in either gastrocnemius muscle (2.77±0.21 and 2.82±0.13 mg/g, respectively) or whole body (1.32±0.10 and 1.47±0.06 mg/g, respectively). Glycogen depletion also did not differ between the two groups (Fig. 2c). The primary response to training appeared to involve augmentation of aerobic metabolism, a response similar to that reported for mammals. Gastrocnemius muscles of trained frogs underwent a 38% increase over those of untrained individuals in the maximum activity of citrate synthase (14.5±1.0 and 10.5±0.9 μmoles/(g wet wt·min);P=0.008). This enzyme was also positively correlated with the level of maximum performance for all animals tested (r=0.61,P<0.01) and with the degree of improvement in the trained animals (r=0.72,P<0.05). In addition to an increased aerobic capacity, the trained animals demonstrated a greater removal of lactate from the muscle 15 min after fatigue (Fig. 2b).