Baroreflex and autonomic responses to two equated isometric resistance exercise protocols in females

Abstract

Different resistance exercise sessions/set configurations seem to lead to distinct hemodynamic, baroreflex, and autonomic responses. Nevertheless, the baroreflex and autonomic reactivities to an equated impulse-to-rest ratio (I:R) isometric exercise (IE) session in females must be clarified. Thus, we investigated the autonomic and baroreflex responses of two equalized I:R isometric exercise sessions in females. Nine healthy females (25 ± 3 years) performed two isometric protocols equalized in I:R with 30% 1 RM: long set protocol (LSC): 4 sets x 2 min isometric x 2 min rest; Short set protocol (SSC): 16 sets x 30 s isometric x 24s rest. Blood pressure (BP) and cardiac intervals were monitored by photoplestimography and electrocardiogram pre-, during, and after (immediately, 30 and 60 min) exercise. Time and frequency domain parameters of the heart rate variability and baroreflex gain and effectiveness were calculated. Two-way ANOVA for repeated measures was applied. Both RT protocols evoked a reduction in baroreflex gain, whereas the LSC gain reduction lasted longer (30 and 60 minutes). Only the SSC decreased RMSSD during exercise compared to pre-values (p < 0.05). SDNN increased during exercise in LSC protocol (p<0.05). HF band reduced only in the SSC protocol during exercise (p < 0.05), while LF/HF ratio also augmented only in the SSC during exercise (p<0.05). LSC evoked more prolonged reductions in baroreflex gain, while SSC protocol caused a greater disturbance in cardiac autonomic modulation.

Keywords

• Parasympathetic Nervous System
• Baroreflex
• Isometric Exercise