International Journal of Human Movement and Sports Sciences Vol. 11(2), pp. 398 - 410
DOI: 10.13189/saj.2023.110217
Reprint (PDF) (452Kb)

Heart Rate Variability-Established Thresholds to Determine the Ventilatory and Lactate Thresholds of Endurance Athletes

Ninette Thiart , Ben Coetzee ^*, Christo Bisschoff
Faculty of Health Sciences, North-West University, Potchefstroom Campus, Potchefstroom, 2520, South Africa

ABSTRACT

This study aimed to determine the use of heart rate variability (HRV)-established thresholds to accurately estimate endurance athletes' ventilatory threshold 1 (VT₁), respiratory compensation point (RCP) and lactate threshold 2 (LT₂). Eleven cyclists (aged: 23.7 ± 3.1 years) from the African Continental Development Cycling team and ten middle- and long-distance athletes (age: 21.2 ± 1.8 years) from a South African university participated in this study. Before the start of an incremental cycling or running maximal oxygen consumption (V̇O_2max) test each participant was fitted with a Fixed Polar HR Transmitter Belt and Monitor to determine the R-R intervals of the last 60 seconds of each stage. The Kubios HRV Premium software package was used to analyze the R-R-intervals. Blood samples were taken 30 seconds before the end of each stage and analyzed for blood lactate. Ventilatory threshold points were identified using the criteria of an increase in V̇_E/V̇O₂ with no increase in V̇_E/V̇CO₂ (VT₁) and an increase in both V̇_E/V̇O₂ and V̇_E/V̇CO₂ (RCP). The LT₂ was identified as the second increase in blood lactate concentration from one increment to the next. Concerning HRV thresholds, VT₁ was determined at a DFAα1 value of 0.75, the first breakpoint in the standard deviation of the instantaneous (SD₁) and continuous long-term RR interval (SD₂) curves, the visual deflection in the squared root of the mean squared differences between successive R-R intervals (RMSSD) curve, and the first abrupt increase in high-frequency (HF) power x HF frequency. The RCP was detected at a DFAα1 value of 0.5 and the final abrupt increase in HF. The Bland-Altman plots revealed that the absolute power outputs at VT₁SD₁ and VT₁RMSSD showed significant agreements with the absolute power outputs at VT₁. Large paired-sample correlations were also found between the absolute power outputs at VT₁SD₁, VT₁RMSSD and VT₁. In conclusion, coaches, sport scientists and other professionals are encouraged to use SD₁ and RMSSD to determine the VT₁-related training program workloads of endurance-trained athletes, especially in areas where laboratories are not available.

KEYWORDS
Ventilatory Threshold, Lactate Threshold, Heart Rate Variability, Heart Rate Variability Thresholds

Cite This Paper in IEEE or APA Citation Styles
(a). IEEE Format:
[1] Ninette Thiart , Ben Coetzee , Christo Bisschoff , "Heart Rate Variability-Established Thresholds to Determine the Ventilatory and Lactate Thresholds of Endurance Athletes," International Journal of Human Movement and Sports Sciences, Vol. 11, No. 2, pp. 398 - 410, 2023. DOI: 10.13189/saj.2023.110217.

(b). APA Format:
Ninette Thiart , Ben Coetzee , Christo Bisschoff (2023). Heart Rate Variability-Established Thresholds to Determine the Ventilatory and Lactate Thresholds of Endurance Athletes. International Journal of Human Movement and Sports Sciences, 11(2), 398 - 410. DOI: 10.13189/saj.2023.110217.