Milligan, C. Louise, G.Brian Hooke & Crystal Johnson (2000). Sustained swimming at low velocity following a bout of exhaustive exercise enhances metabolic recovery in rainbow trout. J. Exp. Biol. 203:921-926
Sustained swimming at 0.9 BL s-1 following a bout of exhaustive exercise enhanced recovery of metabolite and acid-base status in rainbow trout, compared to fish held in still water. The most striking effect of an active recovery was a total absence of the cortisol elevation typically associated with exhaustive exercise. In fish swimming at 0.9 BL s-1, plasma cortisol levels averaged 20-25 ng ml-1 throughout the 6 h recovery period. In contrast, plasma cortisol increased to a peak level of 128.4±11.2 ng ml-1 in fish recovered in still water. Muscle glycogen was completely resynthesized and lactate cleared within 2 h of exercise in swimming fish compared to >6 h required in the fish held in still water. Similarly, blood lactate and acid-base status was restored more quickly in the swimming fish. These observations suggest that the prolonged recovery usually associated with exhaustive exercise in rainbow trout is due to elevations in plasma cortisol and that the stimulus for cortisol release is not exercise per se, but rather post-exercise inactivity.