Energetic costs of performance in trained and untrained lizards.

The energetic costs of performance constitute a non-trivial component of animals' daily energetic budgets. However, we currently lack an understanding of how those costs are partitioned among the various stages of performance development, maintenance and production. We manipulated individual investment in performance by training lizards for endurance or sprinting ability. We then measured energetic expenditure both at rest and immediately following exercise to test whether such training alters the maintenance and production costs of performance. Trained lizards had lower resting metabolic rates than controls, suggestive of a maintenance saving associated with enhanced performance as opposed to a cost. Production costs also differed, with sprint-trained lizards incurring a larger energetic performance cost and experiencing longer recovery times compared with endurance trained and control animals. Although performance training modifies metabolism, production costs are probably the key drivers of trade-offs between performance and other life-history traits in this species.