Large energetic adaptations of elderly muscle to resistance and endurance training

This study determined the cellular energetic and structural adaptations of elderly muscle to exercise training. Forty male and female subjects (69.2 /- 0.6 yr) were assigned to a control group or 6 mo of endurance (ET) or re sistance training (RT). We used magnetic resonance spectroscopy and imaging to characterize energetic properties and size of the quadriceps femoris mu scle. The phosphocreatine and pH changes during exercise yielded the muscle oxidative properties, glycolytic ATP synthesis, and contractile ATP demand . Muscle biopsies taken from the same site as the magnetic resonance measur ements were used to determine myosin heavy chain isoforms, metabolite conce ntrations, and mitochondrial volume densities. The ET group showed changes in all energetic pathways: oxidative capacity (+31%), contractile ATP deman d (-21%), and glycolytic ATP supply (-56%). The RT group had a large increa se in oxidative capacity (57%). Only the RT group exhibited change in struc tural properties: a rise in mitochondrial volume density (31%) and muscle s ize (10%). These results demonstrate large energetic, but smaller structura l, adaptations by elderly muscle with exercise training. The rise in oxidat ive properties with both ET and RT suggests that the aerobic pathway is par ticularly sensitive to exercise training in elderly muscle. Thus elderly mu scle remains adaptable to chronic exercise, with large energetic changes ac companying both ET and RT.