Background: Sighing is integral to psychophysiological regulation. Volitional sighing tasks have been developed to overcome methodological issues of studying naturalistic sighing and advance research on sigh physiology. This study uses fixed-interval volitional sighing (FIVS), which rhythmically paces sighs at different frequencies, to dissect cardiovascular and autonomic responses during FIVS and explore potential sex differences in cardiovascular response dynamics. Methods: Healthy college students (n=250, 65% female) completed a baseline task and two FIVS tasks (0.033Hz and 0.066Hz) while continuous HR, BP, and respiration were measured. Using a mixed model and a priori cardiorespiratory assumptions, we isolated HR, low-frequency heart rate variability (LF-HRV), high-frequency HRV (HF-HRV), pulse transit time variability (PTTv), and mean arterial pressure (MAP) responses to sighing. Results: FIVS produced non-habituating cardiovascular responses with spectral peaks corresponding to sighing frequency. HR, LF-HRV, PTTv, and MAP increased significantly from baseline to both FIVS tasks, with greater changes observed during 0.066Hz FIVS. HF-HRV decreased only during the 0.066Hz task. Males exhibited greater increases than females in HR and PTTv, but smaller decreases in HF-HRV, from baseline to the FIVS tasks. Conclusions: Volitional sighing directly elicits graded cardiac, vascular, and autonomic responses in a frequency-dependent manner. These responses support sighing as a sympathetic challenge, which, like strenuous physical activity, may lead to longer-term improvements in autonomic balance. Sex differences in cardiovascular mobilization processes indicate potentially distinct regulatory mechanisms. This research advances our understanding of sigh physiology and suggests FIVS may serve as a valuable tool for assessing subtle variations in cardiovascular function.