Reproducibility of Heart Rate Variability Threshold in Untrained Individuals.

The aim of this study was to evaluate the reproducibility of the heart rate variability threshold (HRVT) by different HRV indexes and determination criteria. 68 untrained participants, 17 women (24.09±4.91 years old; 21.54±1.97 kg∙m-2) and 51 men (24.52±3.52 years old; 26.51±6.31 kg∙m-2), were evaluated on 2 different days (test and retest). The HRVT was determined during an incremental exercise test using 2 indexes (SD1 and RMSSD) and criteria (HRTV1, first intensity of physical effort with index<3 ms, and HRVT2, first intensity of physical effort, in which the index presents a difference<1 ms between 2 consecutive intensities). There was no significant difference (p<0.05) between the test and retest for any of the variables evaluated. All variables, except for the rate of perceived exertion at HRVT2, presented moderate to high intraclass correlation coefficient (HRVT1: 0.55-0.85 and HRVT2:0.58-0.69). All variables at HRVT1 and the heart rate at HRVT2 showed coefficient of variation ~ 10%. The HRVT, regardless of criteria and HRV index used, showed satisfactory reproducibility. Thus, these criteria can be used to assess clinically autonomic cardiac modulation and aerobic capacity, and to analyze the effect of different interventions.

Higher blood pressure and lower cardiac vagal activity in obese young individuals in supine and seated position.

BACKGROUND: Obesity triggers alterations in hemodynamic and autonomic control. There are few studies that investigate the effects of overweight and obesity in early adulthood on hemodynamic and autonomic variables. AIM: The aim of this study was to determine whether overweight and obesity in young individuals cause alterations in hemodynamic parameters and heart rate variability (HRV) in supine and seated position, and to correlate these variables with anthropometric features. METHODS: Measurements were performed in 40 young untrained male study participants. The subjects were eutrophic (22.8 ± 0.3 kg/m2, N = 19), overweight (27.0 ± 0.5 kg/m2, N = 10), and obese (33.5 ± 0.8 kg/m2, N = 11). After 5 min in supine and seated position, the R-R intervals and blood pressure (BP) were recorded. RESULTS: The systolic blood pressure were higher in overweight (supine, 122.9 ± 2.3 mmHg) and obese (supine, 123.9 ± 2.2; seated, 121.7 ± 2.3 mmHg) individuals compared to eutrophic individuals (supine, 111.8 ± 1.64; seated, 111.3 ± 1.8 mmHg) (p ⩽ 0.05). Obese subjects exhibited lower HRV (SD1, RMSSD, pNN50) compared to eutrophic individuals when seated. In obese subjects, the heart rate (HR) increased and HRV decreased (p ≤ 0.05) when seated versus supine position. The body mass, body mass index (BMI), and waist and abdominal circumferences correlated positively with BP (r = 0.40-0.64, p ≤ 0.05), while the BMI, waist circumference, BP, and HR were negatively correlated (r = -0.32 -0.62, p ≤ 0.05) with HRV (pNN50 and HF) in both body positions. BMI, waist circumference, BP and HR correlated negat- ively with additional HRV indices (SD1, SD2, RMSSD, TP, and LF) when seated. CONCLUSIONS: Obese and overweight individuals presented higher SBP, and obese individuals had lower HRV and cardiac vagal activity, associated with anthropometric variables. RELEVANCE FOR PATIENTS: The monitoring of HRV in obese subjects in seated position allows improved prognosis of metabolic consequences to cardiac autonomic control.