Heart Rate Variability and Perceived Stress in Normal‐Weight Female University Students: The Role of Physical Activity Level

) were recruited. To minimise hormonal variability, assessments for naturally menstruating participants were conducted during the early follicular phase, confirmed through a cycle-tracking application and luteinizing hormone (LH) tests. For participants using hormonal contraceptives, measurements were scheduled during the first week of a new contraceptive cycle. PA was assessed (IPAQ-SF) and categorised as low-moderate or vigorous. HRV was recorded using a Polar H10 over three days for reliability (SDNN, LF, HF, LF/HF ratio) were analysed. Perceived stress used the Perceived Stress Questionnaire (PSQ). Group differences and associations were then analysed, controlling for total PA (METs). Forty-two participants completed the study. Vigorous PA was associated with higher SDNN (p = 0.099, d = -0.620) and lower LF (p = 0.045, d = -0.761) versus the low-moderate PA group, indicating more efficient cardiac autonomic modulation. METs significantly influenced SDNN, HF, LF, and pNN50. However, no significant differences were found in LF/HF ratio (p = 0.990) or perceived stress (p = 0.249) between groups, nor were significant correlations observed between PSQ scores and any HRV indices. Higher PA levels correlate with a more favourable autonomic profile (increased parasympathetic activity, reduced sympathetic drive at rest, unaltered LF/HF balance). The lack of association between PA/perceived stress and perceived stress/HRV suggests a potential dissociation between subjective stress perception and objective autonomic activity in this population.