PURPOSE: External counterpulsation (ECP) has previously been used to treat cardiac patients via compression of the lower extremities during diastole to increase venous return and coronary perfusion. However, the effects of ECP on exercise performance and markers of recovery in elite athletes is largely unknown. METHODS: On two separate occasions, 48 h apart, seven elite National Rugby League players performed an identical 60 min field-based conditioning session followed by a 30 min period of either regular ECP treatment or placebo. Power measures during repeated cycle bouts and countermovement jump height and contraction time derivatives were measured at rest, and 5 h post-exercise. Saliva samples and venous blood samples were taken at rest, post-exercise, and 5 h post-exercise to assess stress, inflammation and muscle damage. RESULTS: Post ECP treatment, cycling peak power output (p=0.028; 11%) and accumulated peak power (p=0.027; 14%) increased compared to the placebo condition. Post-exercise plasma Interleukin 1 receptor (IL-1ra) only increased after ECP (p=0.024; 84%) and concentrations of IL-1ra tended to be higher (p=0.093; 76%) 5 h post-exercise. Furthermore, testosterone to cortisol ratio was increased above baseline and placebo 5 hours post-exercise (p=0.017 to 0.029; 24 to 77%). Post-exercise salivary alpha amylase to Immunoglobulin A ratio decreased after treatment (p=0.013; 50%), compared with the placebo control. CONCLUSIONS: Exercise performance and hormonal indicators of stress were improved, and inflammation markers were reduced following acute ECP.