Figure 5. Mitochondrial capacity and functional performance.

Recovery time of creatine phosphate (PCr) after plantar flexion exercise (PFE) is longer (A), and maximum oxidative capacity is reduced (B) in frail older individuals. The rate of PCr decline during PFE correlates with reduced maximum oxidative capacity (C, P < 0.02). Correlations between 6MW and maximum oxidative capacity (D), between peak VO₂ and maximum oxidative capacity (E), and between PFE time and maximum oxidative capacity (F). Data are individual points and shown as mean ± SEM. CONT (n = 11, black triangles), NFO (n = 12, dark-gray circles), FO (n = 11, open squares). (A) Kruskal-Wallis with Mann-Whitney U tests, (B) ANOVA with multiple comparisons tests, and (C–F) Spearman’s correlations were used. *P < 0.05, **P < 0.02, ***P < 0.005, ****P < 0.001.