EFFECT OF HIGH INTENSITY INTERVAL TRAINING ON CARDIAC AUTONOMIC MODULATION IN MIDDLE-AGED WOMEN

Abstract

Moderate intensity continuous training increases heart rate variability (HRV) in middle-aged women, but little is known about the time-efficient potency of high intensity interval training (HIIT) for improving cardiac autonomic modulation. This study aimed to assess the effects of 12 weeks HIIT on cardiac autonomic modulation in middle-aged women. Seven healthy middle-aged women (3 postmenopausal and 4 premenopausal) performed 12 weeks of HIIT consisting of 4 x 4 min cycling at 90- 95% HRmax with 3 min active recovery at 60-70% HRmax, 3 times a week. A maximal graded continuous exercise test was performed and supine resting HRV was measured during both 5 min of spontaneous and controlled breathing (10 breaths min-1) at baseline and after the HIIT programme. HRV was analysed by frequency domain methods: total power (TP), low frequency (LF) and high frequency (HF) spectral power. HIIT increased VO2 peak (17% P < 0.01) and peak power output (14% P < 0.001). HRV TP increased from 2420 ± 1367 to 3270 ± 1444 ms2 (P = 0.042) and HF power increased from 1310 ± 944 to 1773 ± 1083 ms2 (P = 0.024) during controlled breathing. No significant differences were found between premenopausal and postmenopausal women at baseline and after HIIT. Postmenopausal women experienced significant increases in TP and HF power (P < 0.05) and a significant decrease in resting HR (P < 0.05) in response to HIIT, whilst increases in premenopausal women were not statistically significant. In conclusion, HIIT increases HRV HF power reflecting vagal modulation in middle-aged women and is particularly effective training for postmenopausal women.