Palmar cooling mitigates exercise-induced immune suppression after high-intensity training: A randomized trial

ObjectivesWe investigated whether palmar cooling alters inflammatory responses following a single session of high-intensity eccentric exercise. We hypothesized that palmar cooling during rest intervals would attenuate maladaptive inflammatory responses while preserving beneficial immune adaptations necessary for muscle repair and recovery. MethodsIn this randomized interventional study, 20 healthy adults were matched by sex and one-repetition maximum (1RM) for bicep curls. Participants performed 10 sets at 70% 1RM, receiving either palmar cooling at 14{o}C or a thermoneutral control at 30{o}C during 3-minute inter-set rest periods. Whole blood was collected at baseline, immediately post-exercise, and on post-exercise days 1, 2, and 4 for comprehensive immune profiling with mass cytometry. Blood lactate and pain scores were also recorded. ResultsExercise induced broad immunosuppression that was significantly attenuated in the palmar cooling group by 2 days post-exercise (AUC=0.79, p=0.03). The cooled group had decreased immunosuppressive activity and increased inflammatory innate immune mechanisms in the cooled group. Palmar cooling also significantly reduced lactate levels compared to controls (p=0.024). ConclusionPalmar cooling at 14{o}C during rest intervals effectively modulated the immune response to high-intensity exercise and reduced lactate accumulation. These findings suggest palmar cooling may serve as a promising intervention to mitigate exercise-induced immunosuppression and support recovery. Trial identifierNCT07215338 (retrospectively registered). Summary BoxO_ST_ABSWhat is already known on this topicC_ST_ABSHigh intensity eccentric exercise contributes to physiological heat stress which induces significant immune alterations that can lead to a transient period of immunosuppression and increased incidence of respiratory tract infections. What this study addsPalmar cooling resulted in cell-type-specific alterations in innate and adaptive immune cell signaling activity, particularly decreasing immunosuppressive cell responses while enhancing inflammatory innate immune mechanisms implicated in pathogen defense. How this study might affect research, practice or policyPalmar cooling may serve as an effective intervention for managing exercise-induced immunosuppression and supporting recovery in athletes. Integration of palmar cooling techniques into athletic training regimens and rehabilitation protocols can ultimately enhance exercise performance and reduce the adverse effects associated with high-intensity exercise.