Determination of the Maximal Lactate Steady State by HRV in Overweight and Obese Subjects.

The study assessed if the maximal lactate steady state (MLSS) may be determined by HRV in overweight and obese individuals. Fourteen obese (OB) and 14 overweight (OW) participants performed an incremental exercise test and several constant-load tests on a bicycle ergometer to determine the MLSS. HRV was analysed by using time domain and non-linear parameters of the Poincaré plot. Various HRV thresholds (HRVt) were detected and compared with the MLSS. Overall, Bland-Altman plots demonstrated moderate to strong agreements between the power at the MLSS and the power at HRVt, with all HRVt overestimating the MLSS (range: - 14.6 to-19.8 W). All HRVt were detected at higher intensities (69.2-78.8%P max ) compared to the MLSS (62.6-66.8%P max ). The primarily vagally modulated parameter HRVt SD1 revealed higher correlations (r=0.66-0.76) and lower differences (16.8-19.9%) compared to the parameter HRVt SD2 (r=0.56-r=0.66; 22.4-22.9%). The data suggest a delayed vagal withdrawal during incremental exercise in obese and overweight individuals. For this population, the use of HRV to determine the MLSS seems questionable.