Ventilatory thresholds determined from HRV: Comparison of 2 methods in obese adolescents

The development of personalised training programmes is crucial in the management of obesity. We evaluated the ability of 2 heart rate variability analyses to determine ventilatory thresholds (VT) in obese adolescents. 20 adolescents (mean age 14.3±1.6 years and body mass index z-score 4.2±0.1) performed an incremental test to exhaustion before and after a 9-month multidisciplinary management programme. The first (VT₁) and second (VT₂) ventilatory thresholds were identified by the reference method (gas exchanges). We recorded RR intervals to estimate VT₁ and VT₂ from heart rate variability using time-domain analysis and time-varying spectral-domain analysis. The coefficient correlations between thresholds were higher with spectral-domain analysis compared to time-domain analysis: Heart rate at VT₁: r=0.91 vs. =0.66 and VT₂: r=0.91 vs. =0.66; power at VT₁: r=0.91 vs. =0.74 and VT₂: r=0.93 vs. =0.78; spectral-domain vs. time-domain analysis respectively). No systematic bias in heart rate at VT₁ and VT₂ with standard deviations <6 bpm were found, confirming that spectral-domain analysis could replace the reference method for the detection of ventilatory thresholds. Furthermore, this technique is sensitive to rehabilitation and re-training, which underlines its utility in clinical practice. This inexpensive and non-invasive tool is promising for prescribing physical activity programs in obese adolescents.