title: Trade-offs between speed and endurance in the frog Xenopus laevis: a multi-level approach.
abstract: One of the most interesting trade-offs within the vertebrate locomotor system is that between speed and endurance capacity. However, few studies have demonstrated a conflict between whole-animal speed and endurance within a vertebrate species. We investigated the existence of trade-offs between speed and endurance capacity at both the whole-muscle and whole-animal levels in post-metamorphs of the frog Xenopus laevis. The burst-swimming performance of 55 frogs was assessed using a high-speed digital camera, and their endurance capacity was measured in a constant-velocity swimming flume. The work-loop technique was used to assess maximum power production of whole peroneus muscles at a cycle frequency of 6 Hz, while fatigue-resistance was determined by recording the decrease in force and net power production during a set of continuous cycles at 2 Hz. We found no significant correlations between measures of burst swimming performance and endurance capacity, suggesting that there is no trade-off between these two measures of whole-animal performance. In contrast, there was a significant negative correlation between peak instantaneous power output of the muscles at 6 Hz and the fatigue-resistance of force production at 2 Hz (other correlations between power and fatigue were negative but non-significant). Thus, our data support the suggestion that a physiological conflict between maximum power output and fatigue resistance exists at the level of vertebrate muscles. The apparent incongruence between whole-muscle and whole-animal performance warrants further detailed investigation and may be related to factors influencing both whole-muscle and whole-animal performance measures.
authors.affiliation: Laboratory of Functional Morphology, Department of Biology, University of Antwerp, Universiteitsplein 1, Wilrijk B-2610, Belgium. rwilson@uia.ua.ac.be
authors.forename: Robbie S
authors.initials: RS
authors.lastname: Wilson
authors.forename: Rob S
authors.initials: RS
authors.lastname: James
authors.forename: Raoul
authors.initials: R
authors.lastname: Van Damme
mesh_terms: D000818:Animals; D001835:Body Weight; D066298:In Vitro Techniques; D008124:Locomotion / Q000502:physiology*; D008954:Models, Biological; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010781:Photography; D012044:Regression Analysis; D013550:Swimming; D013997:Time Factors; D014982:Xenopus laevis / Q000502:physiology*