PURPOSE: It t is hypothesized that chronic systemic inflammation is influenced by physical activity level and is involved in the age-related decline in muscle function. The impact of physical activity behaviours on the level of C-reactive protein (CRP) and tumour necrosis factor alpha (TNF-α) in elderly women is investigated. The impact of chronic systemic inflammation on muscle mass and the cellular and molecular mechanisms behind the putative inflammation-mediated action on human muscle cells are explored.
METHODS: Total amount of sedentary time, 30-minute periods of sedentary time and breaks in sedentary behaviour and time spent in moderate-to-vigorous physical activity (MVPA) were assessed using accelerometry in a cohort of 89 elderly women. Serum HsCRP and TNF-α are were measured. The proliferative and metabolic capacity of human muscle cells obtained from vastus lateralis and exposed to CRP are assessed.
RESULTS: No variables of sedentary behaviour were significantly associated with the level of CRP or TNF-α. In contrast, time spent in MVPA was inversely associated with the level of CRP, independently of sedentary behaviour and waist circumference, but not TNF-α. Serum CRP levels were inversely associated to skeletal muscle mass. Elevated serum CRP levels were associated to reduced proliferative rate of human muscle cells and changes in the regulation of the size muscle cells.
CONCLUSIONS: Elevation in the inflammatory status in elderly is influenced by the amount of time spent in MVPA and exerts detrimental effects on skeletal muscle mass.