in vivo Oxidative Capacity Vs. Mitochondrial Volume Density in Skeletal Muscle of Age-Matched, Elderly Athletes and Sedentary Subjects a Matter of Function and Content

Andreas Boss¹, Nicholas Thomas Broskey², Roland Kreis¹, Francesca Amati, ¹², Chris Boesch¹

We assessed oxidative capacity using the rate k of phosphocreatine recovery in age-matched elderly (60-80y) endurance-trained (N=11) and sedentary subjects (N=13). Mitochondrial volume density (MitoVD) was determined from muscle biopsies using electron microscopy. k was significantly increased (p=0.01) in the trained, which was paralleled by a ~50% greater MitoVD (p=0.02). Furthermore, k was significantly correlated with MitoVD (r2=0.46, p<0.003), and the ratio k to MitoVD was similar between trained and sedentary. This indicates that in age-matched elderly subjects, the greater muscle oxidative capacity in trained is due to increased mitochondrial volume, but not necessarily enhanced function per mitochondrial volume.