Battista, RA, Foster, C, Andrew, J, Wright, G, Lucia, A, and Porcari, JP. Physiologic responses during indoor cycling. J Strength Cond Res 22: 1236-1241, 2008-During the last decade, there has been active interest in indoor cycling (e.g., spinning) as a method of choreographed group exercise. Recent studies have suggested that exercise intensity during indoor cycling may be quite high and may transiently exceed V̇o2max. This study sought to confirm these findings, as the apparent high intensity of indoor cycling has implications for both the efficacy and the risk of indoor cycling as an exercise method. Twenty healthy female students performed an incremental exercise test to define V̇o2max and performed 2 videotaped indoor exercise classes lasting 45 minutes and 35 minutes. V̇o2, heart rate (HR), and rating of perceived exertion (RPE) were measured during the indoor cycling classes, with V̇o2 data integrated in 30-second intervals. The mean %V̇o2max during the indoor cycling classes was modest (74 ± 14%V̇o2max and 66 ± 14%V̇o2max, respectively). However, 52% and 35% of the time during the 45- and 35-minute classes was spent at intensities greater than the ventilatory threshold (VT). The HR response indicated that 35% and 38% of the session time was above the HR associated with VT. In 10 of the 40 exercise sessions, there were segments in which the momentary V̇o2 exceeded V̇o2max observed during incremental testing, and the cumulative time with exercise intensity greater than V̇o2max ranged from 0.5 to 14.0 minutes. It can be concluded that although the intensity of indoor cycling in healthy, physically active women is moderate, there are frequent observations of transient values of V̇o2 exceeding V̇o2max, and a substantial portion of the exercise bouts at intensities greater than VT. As such, the data suggest that indoor cycling must be considered a high-intensity exercise mode of exercise training, which has implications for both efficacy and risk.