Objective. Irisin is a recently identified myokine, suggested to mediate the beneficial effects of exercise by inducing browning of white adipocytes and thus increasing energy expenditure. In humans, the regulation of irisin by exercise is not completely understood. We investigated the effect of acute and chronic whole-body vibration exercise, a moderateintensity exercise that resembles shivering, on circulating irisin levels in young healthy subjects. MaterialslMethods. Healthy untrained females participated in a 6-week program of wholebody vibration exercise training. Blood was drawn before and immediately after an acute bout of exercise at baseline (week 0) and after 6 weeks of training. Results. The resting irisin levels were not different at baseline (week 0) and after 6 weeks of training. At both 0 and 6 weeks of training, an acute bout of vibration exercise significantly elevated circulating irisin levels by 9.5% and 18.1%, respectively (p = 0.05 for the percent change of irisin levels). Conclusions. Acute bouts of whole-body vibration exercise are effective in increasing circulating irisin levels but chronic training does not change levels of baseline irisin levels in humans. @ 2014 Elsevier Inc. All rights reserved.