Valenzuela PL, et al. - Investigators quantified the acute impacts of spinal manipulative therapy (SMT) on performance and autonomic modulation in recreational athletes in this randomized, double-blind, parallel groups, sham-controlled trial. In response to actual vs sham SMT, a significant and lower value of a marker of sympathetic modulation (the stress score) was observed. With actual SMT, they noted a trend toward a significant and likely lower sympathetic: parasympathetic ratio and a likely higher natural logarithm of the root-mean-square differences of successive heartbeat intervals. They also found a significantly lower mean power output during the time trial with actual vs sham SMT. Induction of an acute shift toward parasympathetic dominance and slight impaired performance in recreational healthy athletes were reported with a single pre-exercise SMT session.