Heterogeneous Effects of Old Age on Human Muscle Oxidative Capacity in Vivo: A Systematic Review and Meta-Analysis

Despite intensive efforts to understand the extent to which skeletal muscle mitochondrial capacity changes in older humans, the answer to this important question remains unclear. To determine what the preponderance of evidence from in vivo studies suggests, we conducted a systematic review and meta-analysis of the effects of age on muscle oxidative capacity as measured noninvasively by magnetic resonance spectroscopy. A secondary aim was to examine potential moderators contributing to differences in results across studies, including: muscle group, physical activity status, and sex. Candidate papers were identified from PubMed searches (n=3,561 papers) and the reference lists of relevant papers. Standardized effects (Hedges’ g) were calculated for age and each moderator using data from the 22 studies that met the inclusion criteria (n=28 effects). Effects were coded as positive when older (≥55 years) adults had higher muscle oxidative capacity than younger (20-45 years) adults. The overall effect of age on oxidative capacity was positive (g=0.171, pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author