Aging‐related loss of skeletal muscle strength: the role of muscle quality (863.8)

Abstract

Objective: Skeletal muscle aging is associated with a progressive loss of mass and strength. In this process, the loss of muscle quality has been suggested to cause a disproportionate loss in muscle strength compared to the loss in mass. This study aimed at investigating the role of changes in muscle quality in the loss of muscle strength with aging.Methods: Ten young (24±3 yo) and 9 old (72±4 yo) active men were recruited and matched for physical activity levels. Body composition (DXA and MRI) and knee extension strength (KES) were assessed. Muscle quality indexes (quadriceps mass/KES, volume/KES and CSA/KES) were then calculated. Muscle biopsies were performed in the vastus Lateralis to assess fiber type proportion and size, and intracellular lipid content (Oil Red O).Results: KES, quadriceps mass, volume and CSA were lower in old vs. young adults (p<0.05). Fat mass percentage was higher in old vs. young adults (p<0.05), while total body weight was similar. No differences were observed between young and old men in muscle quality indexes, intracellular lipid content, fiber size and type proportion. However, type IIa fibers tended to be smaller in old than in young adults (p=0.052).Discussion: Our results suggest that, in active old men, the loss in muscle strength is mainly attributable to a decrease in muscle mass. Physical activity may contribute to the preservation of the quality of contraction per unit of muscle.