Myokine secretion during moderate‐intensity physical activity: Dose–response of interleukin 6 to walking duration

Abstract

AbstractDuring vigorous physical activity, contracting muscles secrete a variety of immunomodulatory and metabolic factors called myokines that perform a variety of functions. Foremost among these is interleukin 6 (IL‐6), which increases fatty acid mobilization and stimulates anti‐inflammatory cytokine release. Despite being well characterized in vigorous exercise contexts, whether IL‐6 is secreted during moderate‐intensity activities such as walking is unclear. This is especially pertinent as regular walking is one of the oldest and most common forms of physical activity and comes with a variety of health benefits, which may be coordinated in part by IL‐6 signaling. To test the hypothesis that IL‐6 release occurs during evolutionarily normal physical activity contexts like long distance walking, we performed a dose–response experiment to test the effect of walking duration on IL‐6 secretion. Thirteen participants completed four moderate‐intensity walking trials (55% HRmax) of varying durations (30 min, 1 h, 2 h, and 3 h) in a randomized order with intervening washout periods of at least 1 week. Using a linear mixed effects model, we found that IL‐6 levels modestly increased during only the 2 h and 3 h walking trials. These results suggest that small frequent increases in IL‐6 signaling may be an important mechanism underlying the health benefits of regular walking. Furthermore, this finding raises the possibility that IL‐6 secretion is an adaptation to fuel physical activity, especially during periods of negative energy balance.