Exercise promotes IL-6 release from legs in older men with minor response to unilateral immobilization

Physical inactivity is a major contributor to low-grade systemic inflammation. Most of the studies characterizing interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) release from exercising legs have been done in young, healthy men, but studies on inactivity in older people are lacking. The impact of 14 days of one-leg immobilization (IM) on IL-6 and TNF-α release during exercise in comparison to the contralateral control (CON) leg was investigated. Fifteen healthy men (age 68.1 ± 1.1 year (mean ± SEM); BMI 27.0 ± 0.4 kg·m(2); VO2max 33.3 ± 1.6 ml·kg(‒1)·min(‒1)) performed 45 min of two-leg dynamic knee extensor exercise at 19.5 ± 0.9 W. Arterial and femoral venous blood samples from the CON and the IM legs were collected every 15 min during exercise, and thigh blood flow was measured with ultrasound Doppler. Arterial plasma IL-6 concentration increased with exercise (rest vs. 45 min, main effect p < .05). IL-6 release increased with exercise (rest vs. 30 min, main effect p < .05). Furthermore, IL-6 release was borderline (main effect, p = .085, effect size 0.28) higher in the IM leg compared to the CON leg (288 (95% CI: 213-373) vs. 220 (95% CI: 152-299) pg·min(‒1), respectively). There was no release of TNF-α in either leg and arterial concentrations remained unchanged during exercise (p > .05). In conclusion, exercise induces more pronounced IL-6 secretion in healthy older men. Two weeks of unilateral immobilization on the other hand had only a minor influence on IL-6 release. Neither immobilization nor exercise had an effect on TNF-α release across the working legs in older men.