EMG breakpoints for detecting anaerobic threshold and respiratory compensation point in recovered COVID-19 patients

INTRODUCTION: A huge number of COVID-19 patients should be referred to rehabilitation programmes. Individualizing the exercise intensity by metabolic response provide good physiological results. The aim of this study was to investigate the validity of EMG as a non-invasive determinant of the anaerobic threshold and respiratory compensation point, for more precise exercise intensity prescription. METHODS: An observational cross-sectional study with 66 recovered COVID-19 patients was carried out. The patients underwent a cardiopulmonary exercise test with simultaneous assessment of muscle electromyography in vastus lateralis. EMG breakpoints were analyzed during the ramp-up protocol. The first and second EMG breakpoints were used for anaerobic threshold and respiratory compensation point determination. RESULTS: EMG and gas exchange analysis presented strong correlation in anaerobic threshold (r = 0.97, p < 0.0001) and respiratory compensation point detection (r = 0.99, p < 0.0001) detection. Bland-Altman analysis demonstrated a bias = −4.7 W (SD = 6.2 W, limits of agreement = −16.9 to 7.6) for anaerobic threshold detection in EMG compared to gas exchange analysis. In respiratory compensation point detection, Bland-Altman analysis demonstrated a bias = -2.1 W (SD = 4.5 W, limits of agreement = −10.9 to 6.6) in EMG compared to gas exchange analysis. EMG demonstrated a small effect size compared to gas exchange analysis in oxygen uptake and power output at anaerobic threshold and respiratory compensation point detection. CONCLUSIONS: EMG analysis detects anaerobic threshold and respiratory compensation point without clinical significant difference than gas exchange analysis (gold standard method) in recovered COVID-19 patients.