An investigation into the relationship between heart rate variability and the ventilatory threshold in healthy moderately trained males
During incremental exercise, heart rate variability (HRV) has been shown to display distinct stabilization and inflection points, which have been used to indirectly detect the ventilatory threshold (VT).Methods
Ten moderately trained males (26·5 ± 5·9 years: VO2peak 48·7 ± 4·1 ml min−1 kg−1) performed an incremental test on a cycle ergometer until volitional exhaustion with both R-R intervals and respiratory indices recorded. HRV was quantified using both nonlinear (Poincare plot; short-term variability SD1) and spectral analysis of the R-R intervals (high-frequency component; HFp). The VT was identified using the V-slope method. The relationship between HRV parameters and the VT was assessed using both a paired t-test and Pearson's product correlation. In addition, Bland and Altman plots were used to quantify the mean difference along with a 95% confidence interval.Results
When expressed as the corresponding heart rate values, both the SD1 and the HFp stabilization points revealed a strong (r = 0·86 and 0·087, respectively) correlation with the VT. However, only for SD1 this relationship was different to the VT (t-test). The Bland–Altman plots supported these findings showing wide limits of agreement present for SD1 and the VT whilst the relationship between HFp and the VT revealed narrower limits.Conclusion
There does not appear to be a relationship present between the VT and the SD1 stabilization point in moderately trained healthy males, whereas the HFp stabilization point revealed a strong relationship with the VT when expressed as heart rate.