Changes in mitochondrial DNA (mtDNA) abundance (top), MOTS‐c protein (middle), and mitochondrial‐encoded proteins (bottom) in female Sprague–Dawley rat plantaris muscle after long‐term voluntary aerobic training. Group comparisons were made between sedentary (SED) and 4‐ (EX4; n = 10), 6‐ (EX6; n = 6), and 8‐week (EX8; n = 8)‐trained rats as well as detrained rats that were trained for 4 or 6 weeks followed by 4 (DETR4; n = 9) or 6 (DETR6; n = 6) weeks of detraining, respectively. The mtDNA‐to‐nuclear DNA (nDNA) ratios determined using mitochondrial genes ATP synthase subunit 6 (ATP6) and NADH Dehydrogenase 1 (ND1) and the nuclear housekeeping gene, actin beta (ACTB). Expression of cytochrome c oxidase subunit I (COX1), ATP6, cytochrome b (CYTB), and humanin (HN) proteins are shown; representative protein and ponceau‐stained membranes as a loading control are shown. Values show mean ± S.E. *Statistically different from SED (p < 0.05); †Sig from EX6 (p < 0.05); ‡Sig from EX4 (p < 0.05).