Leg and hip muscles show muscle-specific effects of ageing and sport on muscle volume and fat fraction in male Masters athletes.

Abstract

Age-related deterioration in muscle volume, intramuscular fat content and muscle function can be modulated by physical activity. We explored whether Masters athletes, as examples of highly physically active people into old age, could prevent these age-related muscle deteriorations. Four groups of 43 men were examined: young athletes (20-35 years, n = 10), Masters athletes (60-75 years, n = 10) and two age-matched control groups (old: n = 11, young: n = 12). Volumes and fat fractions of 17 different hip and leg muscles were determined using magnetic resonance imaging. In the soleus muscle extra- and intramyocellular lipids were measured using 1H-MR-spectroscopy. Finally volumes of glutei, quadriceps and triceps surae muscles were cumulated and compared to peak jumping power. In both age groups the sum of glutei, quadriceps and triceps surae muscles showed larger volumes in athletes (young: 5758 ± 1139 ml, old: 5285 ± 895 ml) compared to the corresponding control groups (young: 4781 ± 833 ml, old: 4379 ± 612 ml) (p < 0.001). Fat fraction varied between 1.5% and 12.5% ¹H-signal across muscles and groups and was greater in Masters athletes than in young athletes (p < 0.001), but lower than that in old controls (p < 0.001) and comparable with young controls. Age and exercise-related effects on muscle fat predominantly originated from the extramyocellular lipids. Finally muscle peak power per volume was effectively halved in the combined older groups compared to the younger groups. Our findings suggest that sarcosthenia, that is, intrinsic muscle weakness, is an effective cause of age-related power declines in addition to sarcopenia and fat accumulation. KEY POINTS: Muscle volume and muscle fat fraction from 17 hip and leg muscles of Masters athletes were compared with old controls, young athletes and young controls. Muscle volume and fat fraction were determined using magnetic resonance imaging (MRI) using a six-point-DIXON sequence. Muscle volume in Masters athletes was larger than that in old controls but partially smaller than that in young athletes. Muscle fat fraction of Masters athletes was lower than that in old controls but higher than that in young athletes. Muscles of old athletes and old controls produce only 50% of jumping peak power per muscle volume compared with younger subjects. The intrinsic reduction of power loss in old muscle could not be explained by the higher fat fraction in old muscle.