Fig. 4. Muscle synergy merging patterns associated with increased running efficiency.

a Three efficiency-enhancing synergy patterns in adult runners (see also b) based on merging different combinations of Sedent0 synergies. Shown here for each merging combination are the Elite synergies being explained as merging (dark purple) and their reconstructions by merging their respective S0- combinations (light purple), averaged across all merging instances belonging to that combination. Arrows denote patterns of merging (magenta, S0-5 + 6 + 8, n = 15; blue, 7 + 11, n = 8; green, 5 + 6 + 12, n = 8). The percentage of Elite possessing each combination is shown in parentheses. b The merging combinations in a are potentially biomechanically relevant, in that across all adults, the subjects with (Wi) the merging pattern (n = 18, 17, 34 for S0-7 + 11, 5 + 6 + 12, and 5 + 6 + 8, respectively) had higher average running efficiency than those without (Wo) (n = 72, 73, 56) (mean ± SE; *p = 0.049; **p = 0.011; ⁺p = 0.028; 2-tailed Mann–Whitney). c The frequencies of occurrence of the combinations in a increased from the groups with the least (Sedent0) to most (Elite) running experience (*r across adults = 0.83, p = 0.021, 2-tailed t-test; **r = 0.88, p = 0.0091; ⁺⁺r = 0.90, p = 0.0058), suggesting that their emergence may be related to running training. Source data for all panels are available as a Source Data file.