BACKGROUND: It has been shown that recreational soccer was a highly motivating and social activity which produces large improvements in health-related indices in sedentary healthy and unhealthy subjects. The purpose of this study was to compare the acute parasympathetic reactivation after small-sided soccer games (SSG) and repeated sprints training (RST) sessions. METHODS: Eight post-pubertal untrained adolescents (age 15.8+/-0.6 years, body mass 59.1+/-3.7 kg, height 1.7+/-0.1 m) performed a RST, SSG and a control session in a counterbalanced order. Heart rate variability (HRV) indices in time and frequency domain, heart rate recovery and rating of perceived exertion (RPE) were evaluated. RESULTS: RPE was significantly lower after SSG compared with RST (P=0.02, ES=1.1). There was a significant decrease in mean R-R intervals after RST (difference: -19.6%, P<0.01, ES=1.7) and after SSG (-19.2%, P<0.01, ES=2.3). A significant decrease was also noted in SDNN after RST (-26.6%, P=0.02, ES=1.8) and SSG (-37.8%, P=0.01, ES=1.1). For RMSSD, a significant decrease was observed only after SSG (48%, P=0.01, ES=1.3). No significant change in all HRV indices after the control condition. CONCLUSIONS: SSG and RST elicited high and similar heart rates responses. A low parasympathetic reactivation during early recovery was noted after both RST and SSG. These results were important especially for clinician looking to prescribe repeated sprint or small-sided game for sedentary subjects.