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Accueil du site → Doctorat → États-Unis → 2001 → Metabolic recovery following activity in the desert iguana, Dipsosaurus dorsalis

University of Colorado (2001)

Metabolic recovery following activity in the desert iguana, Dipsosaurus dorsalis

Hancock, Thomas Vincent

Titre : Metabolic recovery following activity in the desert iguana, Dipsosaurus dorsalis

Auteur : Hancock, Thomas Vincent

Université de soutenance : University of Colorado at Boulder

Grade : Doctor of Philosophy (Ph. D) 2001

Short, vigorous activities in ectotherms provoke a long excess post-exercise oxygen consumption (EPOC) representing large metabolic recovery costs. Dipsosaurus was used to examine these costs in a variety of activity types, measuring O2 uptake, EPOC, and distance traveled. Cost of activity (Cact) was calculated as the total increase in metabolism per unit distance traveled, a measure of economy. Initial studies examined single bouts of variable duration (<5 min) and intensities ranging from maximal to a range of submaximal intensities. EPOC increased with activity duration and activity intensity. Cact decreased with activity duration due to proportionally larger increases in distance traveled relative to EPOC. Cact was independent of activity intensity over submaximal ranges, but was higher when intensity was maximal. From these data, the predicted locomotor strategy to minimize costs would utilize low intensities and extended durations. Inclusion of recovery provides an ecologically relevant estimate of locomotor impact and may impact energy budget analyses where single bout costs were as high as 7.4% of average daily energy expenditure. Intermittent activity was also examined. Animals ran for varying activity and pause durations until fatigued, but ran furthest when duration was short and pauses long. Total costs and Cact increased with pause duration indicating a tradeoff such that short pauses were most economical but fatigued the animal most rapidly. Long pauses were least economical due to energetically expensive pauses with no additional gains in distance, but also extended endurance likely due to further repletion of metabolites or removal of end products. The various components contributing to these large recovery costs are unknown in terrestrial ectotherms. To address this, EPOC was examined for a 15 sec maximal intensity bout. This activity was supported primarily by glycolysis and PCr hydrolysis, with only a small contribution from aerobic metabolism. The two primary causes of EPOC were PCr repletion and lactate gluconeogenesis. Four other components played increasingly smaller roles : ATP repletion, elevated ventilatory activity, elevated cardiac activity, and oxygen store resaturation.

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