Belief drives physiology: A wearable device expectancy study in healthy young adults

Abstract

Wearable devices are widely used in health and performance settings, yet it is unclear whether belief in a device can influence physiological or performance outcomes independent of its function. Expectancy effects have been documented in sport and exercise contexts, but findings on objective strength outcomes are mixed. This study tested whether the presence of an inactive smart ring, with or without an expectancy-oriented script, was associated with changes in maximal strength or cardiovascular arousal during acute assessment. Twenty healthy adults completed a randomized, placebo-controlled, within-subject crossover trial with three conditions: control (no device), ring-only (inactive smart ring), and ring-plus-script (inactive ring paired with a standardized expectancy statement). Handgrip strength and resting heart rate (HR) were recorded under standardized conditions. Strength did not differ across conditions (p = 0.21), indicating that a single expectancy exposure did not increase maximal voluntary force production. HR differed significantly across conditions in the subset of participants with complete HR data (n = 14; p < 0.001), with higher HRs observed in both the ring-only (p = 0.005) and ring-plus-script (p = 0.006) conditions compared with control, and no difference between the two ring conditions. The overall effect was large and observed in fourteen participants with complete HR data. These findings suggest that expectancy associated with a wearable device can influence cardiovascular arousal during early exposure, while not improving maximal strength. The dissociation between arousal and strength may reflect an initial stage of expectancy-related physiological response. Understanding how belief relates to physiological markers may be important for interpreting wearable-derived outcomes in research and applied sport settings.