Superior aerobic capacity and indices of skeletal muscle morphology in chronically trained master endurance athletes compared with untrained older adults

The study aim was to comprehensively assess physiological function and muscle morphology in chronically-trained older individuals against untrained young and older individuals. In a cross-sectional design 15 young untrained controls (YC) (20±2.7 y, 78.9±13.3kg), 12 untrained older controls (OC) (69.8±4.1 y, 77.5±14.2kg) and 14 endurance-trained master athletes (MA) (67.1±4.1 y, 68.7±6.5kg) underwent assessments of body composition, aerobic capacity, strength, muscle architecture and fibre-type morphology. Skeletal muscle index was lower and body fat greater in OC vs. MA. Estimated VO2max (ml·kg-1·min-1) was similar between MA and YC, but lower in OC. Isometric leg strength normalized to fat-free mass was similar between groups, whereas normalized isometric arm strength was greater in YC than MA. Myosin heavy chain (MHC) I fibre area was greater in MA than OC, whilst MHC II fibre area was greater in YC than OC. MHC II fibre myonuclear domain size was greater in YC than OC and MA, whereas MA had greater MHC I and MHC II fibre capilliarisation than OC and YC. Satellite cell content was similar between groups. Chronic endurance training enhances indices of muscle morphology and improves body composition and aerobic capacity in older age, with potentially important implications for healthspan extension.