Augmented vagal heart rate modulation in active hypoestrogenic pre-menopausal women with functional hypothalamic amenorrhoea

Compared with eumenorrhoeic women, exercise-trained women with functional hypothalamic amenorrhoea (ExFHA) exhibit low heart rates (HRs) and absent reflex renin-angiotensin-system activation and augmentation of their muscle sympathetic nerve response to orthostatic stress. To test the hypothesis that their autonomic HR modulation is altered concurrently, three age-matched (pooled mean, 24 ± 1 years; mean ± S.E.M.) groups of women were studied: active with either FHA (ExFHA; n=11) or eumenorrhoeic cycles (ExOv; n=17) and sedentary with eumenorrhoeic cycles (SedOv; n=17). Blood pressure (BP), HR and HR variability (HRV) in the frequency domain were determined during both supine rest and graded lower body negative pressure (LBNP; -10, -20 and -40 mmHg). Very low (VLF), low (LF) and high (HF) frequency power spectra (ms(2)) were determined and, owing to skewness, log10-transformed. LF/HF ratio and total power (VLF + LF + HF) were calculated. At baseline, HR and systolic BP (SBP) were lower (P0.05). At each stage, HR correlated inversely (P<0.05) with HF. In conclusion, ExFHA women demonstrate augmented vagal yet unchanged sympathetic HR modulation, both at rest and during orthostatic stress. Although the role of oestrogen deficiency is unclear, these findings are in contrast with studies reporting decreased HRV in hypoestrogenic post-menopausal women

Intra-session stability of short-term heart rate variability measurement: gender and total spectral power influence

Heart rate variability (HRV) has been increasingly analysed under numerous research settings. HRV measurement reliability is, however, still an unresolved issue. The main purpose is to carry out an intra-session stability evaluation of HRV parameters from short-term recordings by means of orthoclinostatic stimulation in a study group which is stratified by gender or Total Power (PT) magnitude. The goal is to make as homogeneous a study group as possible and investigate whether the reproducibility level could be influenced by these factors. The study group consisted of 103 participants (age 22.3 ± 1.2). Standard HRV indexes were computed: PT (total spectral power), PHF (high frequency spectral power), PLF (low frequency spectral power) and LF/HF. Absolute reliability is assessed by the standard error of measurement and 95% limits of agreement; the relative reliability is assessed by the intraclass correlation coefficient. The markedly different standard error of measurement (SEM) between the Male and Female groups was not observed for any HRV parameters. The intraclass correlation coefficient (ICC) values ranged from 0.67 to 0.95 for males and from 0.69 to 0.97 for females. According to the SEM and ICC, there is no difference between the groups of High PT and Low PT. There are not any significant differences in absolute or relative reliability between the more homogeneous study groups and we have therefore concluded that HRV measurement reliability is not influenced by gender or HRV magnitude