Cognitive and Autonomic Effects of a Single HRV Biofeedback Session During a Time-Pressured Chess Task: A Randomized...

Heart rate variability (HRV) biofeedback (HRVBF) is a non-invasive intervention that enhances vagal tone and autonomic regulation. While its benefits for stress reduction are well established, the acute effects of a single short-term HRVBF session on psychophysiological and cognitive functions prior to performance remain insufficiently investigated. This randomized controlled pilot study examined the effects of a 10-minute HRVBF session on autonomic markers, anxiety, and problem-solving accuracy during a time-pressured chess task. Twenty chess players (10 females, 10 males; mean age = 17.55) were randomly allocated to either a biofeedback (BFB) group or a passive control group (n = 10 per group). The BFB group completed a single HRVBF session guided by 0.1 Hz paced breathing, while the control group engaged in seated spontaneous breathing. Anxiety levels were measured using the state-trait anxiety inventory (STAI). Participants completed a 5-minute chess problem-solving task before and after the intervention. Physiological signals were continuously recorded using photoplethysmography (PPG) and respiratory sensors, from which standard HRV indices including physiological stress index (SI) were derived. Results indicated that a single short HRVBF session was accompanied by within-group reductions in heart rate (HR) and respiratory rate (RSP), along with a transient increase in LF/HF ratio, and modest improvements in cognitive accuracy. Although tendencies toward changes in NN50, and LF power were observed, these did not reach post-hoc significance. Moreover, no significant changes were found in RMSSD or high-frequency (HF) power. Overall, these findings provide preliminary evidence that short HRVBF sessions may acutely influence selected autonomic markers and potentially support cognitive performance under time pressure. However, their effects on vagal tone and subjective anxiety appear limited, underscoring the need for cautious interpretation and further investigation.