Estimating maximum performance: effects of intraindividual variation

Abstract

SUMMARYResearchers often estimate the performance capabilities of animals using a small number of trials per individual. This procedure inevitably underestimates maximum performance, but few studies have examined the magnitude of this effect. In this study we explored the effects of intraindividual variation and individual sample size on the estimation of locomotor performance parameters. We measured sprint speed of the lizard Sceloporus occidentalis at two temperatures (20°C and 35°C), obtaining 20 measurements per individual. Speed did not vary temporally, indicating no training or fatigue effects. About 50% of the overall variation in speed at each temperature was due to intraindividual variation. While speed was repeatable, repeatability decreased slightly with increasing separation between trials. Speeds at 20°C and 35°C were positively correlated, indicating repeatability across temperatures as well. We performed statistical sampling experiments in which we randomly drew a subset of each individualʼs full set of 20 trials. As expected, the sampleʼs maximum speed increased with the number of trials per individual; for example, five trials yielded an estimate averaging 89% of the true maximum. The number of trials also influenced the sample correlation between mean speeds at 20°C and 35°C; for example, five trials yielded a correlation coefficient averaging 90% of the true correlation. Therefore, intraindividual variation caused underestimation of maximal speed and the correlation between speeds across temperatures. These biases declined as the number of trials per individual increased, and depended on the magnitude of intraindividual variation, as illustrated by running sampling experiments that used modified data sets.

A performance-based cost to honest signalling in male green anole lizards (Anolis carolinensis)

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Fitness Consequences of Infection by Batrachochytrium dendrobatidis in Northern Leopard Frogs (Lithobates pipiens)

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Behavioural and kinematic components of the fast-start escape response in fish: individual variation and temporal repeatability

“…This was done for three reasons: (1) to determine whether a decline in performance would occur over subsequent short-term tests; (2) to ensure that maximum performance was elicited in at least one repetition, to avoid any potential confounding effects from underestimating maximum performance (Adolph and Pickering, 2008); and (3) to permit assessment of short-and medium-term repeatability of maximum performance. We found no decline or habituation effect in any of the fast-start components.…”