Comparability and repeatability of three commonly used methods for measuring endurance capacity

Abstract

Measures of endurance (time to exhaustion) have been used to address a wide range of questions in ecomorphological and physiological research, as well as being used as a proxy for survival and fitness. Swimming, stationary (circular) track running, and treadmill running are all commonly used methods for measuring endurance. Despite the use of these methods across a broad range of taxa, how comparable these methods are to one another, and whether they are biologically relevant, is rarely examined. We used Australian water dragons (Intellagama lesueurii), a species that is morphologically adept at climbing, swimming, and running, to compare these three methods of endurance and examined if there is repeatability within and between trial methods. We found that time to exhaustion was not highly repeatable within a method, suggesting that single measures or a mean time to exhaustion across trials are not appropriate. Furthermore, we compared mean maximal endurance times among the three methods, and found that the two running methods (i.e., stationary track and treadmill) were similar, but swimming was distinctly different, resulting in lower mean maximal endurance times. Finally, an individual's endurance rank was not repeatable across methods, suggesting that the three endurance trial methods are not providing similar information about an individual's performance capacity. Overall, these results highlight the need to carefully match a measure of performance capacity with the study species and the research questions being asked so that the methods being used are behaviorally, ecologically, and physiologically relevant.

Shrinking into the big city: influence of genetic and environmental factors on urban dragon lizard morphology and performance capacity

“…They are also found within several major cities and are frequently found in many human-dominated landscapes (e.g., urban greenspaces, botanical gardens, zoos, and backyards; Littleford-Colquhoun et al 2017;Baxter-Gilbert and Whiting 2018). These dragons are adept at swimming, but they are also skilled at climbing and sprinting (Baxter-Gilbert et al 2018a).…”

“…The endurance arena was constructed from a clear plexiglass box (1.1 × 0.08 m) with an open bottom placed on a human treadmill set to a fixed running speed of 1.0 km/h (Garland and Else 1987;Noble et al 2014). During the trial dragons were placed in the first third (0.36 m) of the treadmill, so that as they tired there would be enough time to pinch the base of the tail 10 consecutive times before the dragon was carried along the track and pushed off the end (Garland and Else 1987;Baxter-Gilbert et al 2018a).…”

“…We analyzed clinging ability separately for each substrate, because it was significantly lower on concrete than tree bark (Table S5). We included repeated measures of each performance trait, instead of using only maximal values, within our LMMs to account for within-individual variation in our study (Careau and Wilson 2017;Baxter-Gilbert et al 2018a).…”

“…Post-hoc assessment and treatment of the interaction effect was the same as described above. There were significant trial order effects in our data (specifically for endurance and sprint speed; Tables S7 and S8), potentially due to training effects, and inclusion of them in our models statistically controlled for this potentially confounding variable (Baxter-Gilbert et al 2018a). Models also included the random intercepts of juvenile identity, clutch, site, and rearing enclosure to incorporate dependency among observations of the same individual, clutch, location, and captive rearing enclosure, respectively.…”

Are whole‐organism performance and thermal preference linked to endo‐ and ectoparasites in a short‐lived lizard?

“…Lizards are good model systems to study the host-parasite relationship because methods of measuring their performances have been well developed (Baxter-Gilbert et al, 2017;Gomes et al, 2017;Husak & Lailvaux, 2017;Losos et al, 2002), and their whole-organism performance capacity may relate to their fitness (Irschick et al, 2008;Lailvaux et al, 2012Lailvaux et al, , 2018Noble, McFarlane, et al, 2014). Many species also rely heavily on their performance capacity to forage, irrespective of whether they are ambush predators or active foragers (Kuo et al, 2019).…”