Effects of physical conditioning on cardiac autonomic function in healthy middle-aged women

The purpose of this study was to determine whether moderate exercise training affects heart rate variability (HRV) and spontaneous baroreflex (SBR) function in healthy middle-aged women. Thirty-two sedentary women aged 40-59 yr were divided into four groups depending on reproductive state (premenopausal, PrM or postmenopausal, PoM, and training group (exercise or sedentary control group). The electrocardiographic R-R interval and systolic blood pressure (finger plethysmograph) were measured at rest during paced breathing at 16 breaths/min in the left lateral decubitus, sitting, and free standing postures, and during upright cycling at 40% maximal heart rate reserve (MHRR). After initial testing, the exercise groups underwent a 12 week walking program. After training, both exercise groups (PrM and PoM) had a longer R-R interval in all conditions, a higher SBR slope in the sitting and standing posture and lower sympathetic modulation in the standing posture, than the control groups and pre-training levels. During exercise, vagal modulation was higher and sympathetic modulation was lower in both exercise groups compared to pre-training values. Vagal modulation is increased following moderate intensity aerobic conditioning in middle-aged women.