Figure 1.

Performance trade-offs in elite athletes competing in combined-events sports. ‘Heat maps’ display the sign and magnitude of the correlations among performance in the 10 decathlon events (top row; n = 636) and the seven heptathlon events (bottom row; n = 733). Shown are the phenotypic correlations based on personal-best values (a) before and (b) after correcting for the total number of repeated measures (n_trial; see electronic supplementary material, figure S1). Comparing (a) versus (b) shows the extent of the bias related to the use of ‘personal bests’ when individuals differ in n_trial. Clearly, (b) shows performance trade-offs and clusters of positive correlations along the main diagonal, which correspond to functional groups (throwing, jumping, running). Correlations at the (c) among- and (d) within-individual levels using all repeated performances (n = 2830 decathlons and 3588 heptathlons) and controlling for effects of year, Julian day, wind assistance, age, and experience. Comparing panels (b) versus (c) shows that stronger trade-offs and functional clustering emerge after factoring out sources of within-individual correlations (d). Events: discus (DISC), shot put (SHOT), javelin (JAVE), pole vault (POLE), high jump (JMPH), long jump (JMPL) and hurdles (HURD). Times for running events were multiplied by −1 such that larger values indicate better performance.