Heart rate variability estimates ventilatory threshold regardless body mass index in young people

Agreement Between Heart Rate Variability - Derived vs. Ventilatory and Lactate Thresholds: A Systematic Review with Meta-Analyses

BACKGROUND

Determining thresholds by measuring blood lactate levels (lactate thresholds) or gas exchange (ventilatory thresholds) that delineate the different exercise intensity domains is crucial for training prescription. This systematic review with meta-analyses aims to assess the overall validity of the first and second heart rate variability - derived threshold (HRVT1 and HRVT2, respectively) by computing global effect sizes for agreement and correlation between HRVTs and reference - lactate and ventilatory (LT-VTs) - thresholds. Furthermore, this review aims to assess the impact of subjects' characteristics, HRV methods, and study protocols on the agreement and correlation between LT-VTs and HRVTs.

METHODS

Systematic computerised searches for studies determining HRVTs during incremental exercise in humans were conducted. The agreements and correlations meta-analyses were conducted using a random-effect model. Causes of heterogeneity were explored by subgroup analysis and meta-regression with subjects' characteristics, incremental exercise protocols, and HRV methods variables. The methodological quality was assessed using QUADAS-2 and STARDHRV tools. The risk of bias was assessed by funnel plots, fail-safe N test, Egger's test of the intercept, and the Begg and Mazumdar rank correlation test.

RESULTS

Fifty included studies (1160 subjects) assessed 314 agreements (95 for HRVT1, 219 for HRVT2) and 246 correlations (82 for HRVT1, 164 for HRVT2) between LT-VTs and HRVTs. The standardized mean differences were trivial between HRVT1 and LT1-VT1 (SMD = 0.08, 95% CI -0.04-0.19, n = 22) and between HRVT2 and LT2-VT2 (SMD = -0.06, 95% CI -0.15-0.03, n = 42). The correlations were very strong between HRVT1 and LT1-VT1 (r = 0.85, 95% CI 0.75-0.91, n = 22), and between HRVT2 and LT2-VT2 (r = 0.85, 95% CI 0.80-0.89, n = 41). Moreover, subjects' characteristics, type of ergometer, or initial and incremental workload had no impact on HRVTs determination.

CONCLUSION

HRVTs showed trivial differences and very strong correlations with LT-VTs and might thus serve as surrogates. These results emphasize the usefulness of HRVTs as promising, accessible, and cost-effective means for exercise and clinical prescription purposes.

Effects of Breakfast Omission on Resting, Exercise, and Postexercise Autonomic and Hemodynamic Profile in Men

Purpose: The acute effects of fasting interventions on metabolic dynamics have been widely investigated. However, knowledge about the acute effect of overnight fasting on hemodynamic and cardiac autonomic modulation is limited, especially during and after exercise. Our objective was to investigate the effects of breakfast omission on hemodynamic and cardiac autonomic modulation during different stress conditions. Method: Twenty-one young men [age: 20.3 (20.1, 26.5 years); body mass index: 22.7 (21.4, 24.4 kg/m²)] underwent resting and postexercise blood pressure assessments and heart rate variability (HRV) analysis, using the SD1 and SD2 indices of Poincaré plots, at rest in supine and standing positions, every 10 minutes during moderate cardiorespiratory training and every 10 minutes throughout the postexercise recovery phase, for a total of 30 minutes for each phase (exercise and recovery). All measurements were performed in a randomized order after overnight fasting or 60 minutes after a breakfast containing ~20% of the total recommended daily calories. The normality hypothesis was rejected, and the Wilcoxon test was conducted to compare the interventions (p < .05). Results: No differences between interventions were observed for resting and postexercise blood pressures (p = .21 to 0.87) or for resting, exercise, and postexercise SD1 (p = .10 to 0.82) and SD2 indices (p = .14 to 0.71). Conclusions: We concluded that overnight fasting does not promote significant changes in resting and postexercise blood pressures or cardiac autonomic modulation in young men at rest (in supine and standing positions), during 30 minutes of moderate cardiorespiratory training and throughout a 30-minute postexercise recovery phase.

Reliability of the Heart Rate Variability Threshold During Treadmill Exercise

The heart rate variability threshold (HRVT) is a clinical parameter used to gain insight into autonomic balance. Prior validation of the HRVT has been with cycle ergometry, with no studies examining the viability of treadmill exercise. The purpose of this study was to examine the reliability of the HRVT during treadmill exercise, and to compare the HRVT to the ventilatory threshold (VT). Ten healthy, college‐aged males completed two maximal graded exercise tests on a treadmill. A Polar RS800CX watch was used for heart rate and HRVT data. The HRVT was determined from three HRV variables including the root mean square of successive differences of continuous R−R intervals (RMSSD), the standard deviation of normal R−R intervals (SDNN) and the standard deviation of instantaneous beat intervals (SD1). A metabolic cart was utilized to determine the VT. Results showed no difference between the HRVT (2.4 ± 0.6 and 2.2 ± 0.3 for RMSSD, 2.8 ± 0.5 and 2.7 ± 0.5 for SDNN and 2.4 ± 0.6 and 2.3 ± 0.6 for SD1) or the VT (3.0 ± 0.3 and 3.1 ± 0.3) between trials. When compared to the VT, averaged HRVT values for RMSSD (2.3 ± 0.3) and SD1 (2.3 ± 0.5) were lower than averaged VT (2.8 ± 0.4, p < 0.05). The averaged HRVT from SDNN (2.8 ± 0.5) did not differ from the VT. These results suggest that treadmill is a viable mode for HRVT determination, and that HRVT determined by SDNN may be a better comparison to the VT.

Ambulatory heart rate variability in overweight and obese men after high-intensity interval exercise versus moderate-intensity continuous exercise

Despite the growing evidence for the beneficial effects of high-intensity interval exercise (HIIE) on vascular health of overweight and obese individuals, it is not clear whether the autonomic stress promoted by HIIE during the ambulatory period is higher than that by moderate-intensity continuous exercise (MICE). Therefore, this study compares the 24 hour (h) ambulatory heart rate variability (HRV) following HIIE and MICE in young overweight and obese men. Eleven untrained men aged 23.2 ± 1.9 years, with average body mass index (BMI) of 31.6 ± 3.9 kg/m² (three overweight and eight obese), underwent three exercise sessions: HIIE, MICE and Control (CT). HRV was recorded in the laboratory and for the next 24 h following laboratory recovery. There were no differences in HRV indices in the rest period between the sessions (p > .05). During the ambulatory period, the area under the curve (AUC) of the low-frequency band transformed into natural logarithm (Ln-LF) during sleep was higher after HIIE than after CT (43.31 ± 8.59 vs. 41.11 ± 7.28 ms²*h, p = .034). The HRV followed by MICE did not differ from other sessions (p > .05). In conclusion, the 24 h ambulatory HRV did not differ after HIIE and MICE. However, despite the small effect, HIIE increased the cardiac autonomic modulation during the sleep period, as a protector of cardiovascular system. Highlights24 h ambulatory HRV could add important information about the cardiovascular safety of the exercise protocols in overweight and obese individuals.There was no disturbances in the cardiac autonomic modulation during the awake period, regardless of the exercise protocol.LnLF index was higher in HIIE compared to CT in the sleep period.24 h ambulatory HRV did not differ between the HIIE and MICE sessions.

Obesity does not Impair Ambulatory Cardiovascular and Autonomic Responses Post-exercise

This study aimed to assess whether obesity and/or maximal exercise can change 24 h cardiac autonomic modulation and blood pressure in young men. Thirty-nine men (n: 20; 21.9±1.8 kg·m^-2, and n: 19; 32.9±2.4 kg·m^-2) were randomly assigned to perform a control (non-exercise) and an experimental day exercise (after maximal incremental test). Cardiac autonomic modulation was evaluated through frequency domain heart rate variability (HRV). Obesity did not impair the ambulatory HRV (p>0.05), however higher diastolic blood pressure during asleep time (p=0.02; group main effect) was observed. The 24 h and awake heart rate was higher on the experimental day (p<0.05; day main effect), regardless of obesity. Hypotension on the experimental day, compared to control day, was observed (p<0.05). Obesity indicators were significantly correlated with heart rate during asleep time (Rho=0.34 to 0.36) and with ambulatory blood pressure(r/Rho=0.32 to 0.53). Furthermore, the HRV threshold workload was significantly correlated with ambulatory heart rate (r/Rho=- 0.38 to-0.52). Finally, ambulatory HRV in obese young men was preserved; however, diastolic blood pressure was increased during asleep time. Maximal exercise caused heart rate increase and 24h hypotension, with decreased cardiac autonomic modulation in the first hour, regardless of obesity.