Changes in serum concentration of markers associated with energy metabolism and fatigue. (A–D): serum levels of GLU, NEFA, LA, and LDH in rats with acute exercise-induced fatigue following interventions with peppermint essential oil at different dosages (this investigation was the acute experiment intended to screen the optimal dose of peppermint oil for chronic experiment). (n = 5–7). (E–H): serum levels of GLU, BUN, LA, and LDH in rats with chronic exercise-induced fatigue (n = 7–10). Data are presented as mean ± SEM. Data were analyzed using one-way analysis of variance followed by the Bonferroni multiple comparison test. GLU, glucose; NEFA, nonestesterified fatty acid; LA, lactate acid; LDH, lactate dehydrogenase; BUN, blood urea nitrogen. Values of 95%CI and effect size (Cohen’s d) are in Appendix A, Table A3.