Life-long endurance exercise in humans: Circulating levels of inflammatory markers and leg muscle size

•Endurance training is associated with higher skeletal muscle mass in elderly.•Physical training counteracts age-related changes.•CRP and IL-6 are lower with training in both young and elderly.•Life-long exercise may reduce aging-related inflammation and maintain muscle mass.

Human aging is associated with a loss of skeletal muscle and an increase in circulating inflammatory markers. It is unknown whether endurance training (Tr) can prevent these changes. Therefore we studied 15 old trained (O-Tr) healthy males and, for comparison, 12 old untrained (O-Un), 10 Young-Tr (Y-Tr) and 12 Young-Un (Y-Un). Quadriceps size, VO2 peak, CRP, IL-6, TNF-α and its receptors, suPAR, lipid profile, leucocytes and glucose homeostasis were measured. Tr was associated with an improved insulin profile (p < 0.05), and lower leucocyte (p < 0.05) and triglyceride levels (p < 0.05), independent of age. Aging was associated with poorer glucose control (p < 0.05), independent of training. The age-related changes in waist circumference, VO2 peak, cholesterol, LDL, leg muscle size, CRP and IL-6 were counteracted by physical activity (p < 0.05). A significant increase in suPAR with age was observed (p < 0.05). Most importantly, life-long endurance exercise was associated with a lower level of the inflammatory markers CRP and IL-6 (p < 0.05), and with a greater thigh muscle area (p < 0.05), compared to age-matched untrained counterparts. These findings in a limited group of individuals suggest that regular physical endurance activity may play a role in reducing some markers of systemic inflammation, even within the normal range, and in maintaining muscle mass with aging.