Effect of activity duration on recovery and metabolic costs in the desert iguana (Dipsosaurus dorsalis)

The majority of elevated O-2 consumption associated with short and vigorous activity occurs during recovery, thus an assessment of associated metaboli c costs should also examine the excess post-exercise oxygen consumption (EP OC). This study examined O-2 uptake during exercise, EPOC and distance trav eled during 5-, 15-, 60- and 300-s sprints at maximal treadmill intensity i n Dipsosaurus (N = 10; 743 +/- 2.1 g). EPOC (0.08, 0.14, 0.23 and 0.18 ml O -2 g(-1), respectively) was large (80-99% of total elevated O-2 consumption ) and increased significantly between 5 and 60 s. The cost of activity (C-a ct; ml O-2 g(-1) (.) km(-1)), intended to reflect the total net costs assoc iated with the activity, was calculated as the total elevated O-2 consumpti on per unit distance traveled. C-act decreased with activity duration due t o proportionally larger increases in distance traveled relative to EPOC vol ume, and is predicted by the equation C-act = 14.7 x activity duration (s)( -0.24). The inclusion of EPOC costs provides an ecologically relevant estim ate of the total metabolic cost of locomotor activity. C-act exceeds standa rd transport costs at all durations examined due to the addition of obligat e recovery costs. The differences are large enough to impact energy budget analyses for ectotherms. (C) 2001 Elsevier Science Inc. All rights reserved .