Survival of the Fastest: The Multivariate Optimization of Performance Phenotypes

Introduction Tradeoffs are widespread in biological systems. Any investment in one trait must necessarily limit the investment in other traits. Still, many studies of physiological performance produce positive correlations between traits that are expected to tradeoff with one another. Here we investigate why predicted tradeoffs may often go unmeasured in studies of human athletes. Methods Triathletes compete in consecutive swimming, cycling, and running events as a single competition, events whose physical demands may be especially prone to generating performance tradeoffs. Performance variation in these three events interacts to explain overall variation in athletic performance. Results We show that individual variation in athletic performance can mask tradeoffs among disciplines, giving the impression that high performance triathletes are athletic generalists. Covariance in race performance across the three disciplines was positive in the most elite athletes, but became increasingly negative as race times increased. Conclusions These performance trade-offs among the disciplines preclude the realization of a generalist athlete except in the most elite triathletes, a result similar to the 'big houses, big cars' phenomenon in life history evolution. This distinction between trait combinations that are favored for optimal performance, versus constrained by trade-offs was only apparent when accounting for individual level variation in athletic performance. Our results provide further evidence that meaningful tradeoffs may be missed if individual variation in quality is ignored. Corresponding author: Ryan Calsbeek, Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, Email ryan.calsbeek@dartmouth.edu, phone: 603-646-9917 fax: 603-646-1345 Competing interests. We have no competing interests. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. Funding This project was supported by a National Science Foundation award to R.C. (DEB-1655092). and grants from Natural Science and Engineering Research Council to V.C. Accepted for Publication: 10 September 2018 © 2018 American College of Sports Medicine

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