Changes of the ECG features in response to effort

Cardiopulmonary exercise tests are widely used in patient populations for diagnosis, treatment monitoring, and disease severity assessment. Controlled effort levels in trials can be applied for experiments in which cardiac responses are monitored simultaneously with energy costs of exercise. Effortinduced changes of oxygen uptake area point of interest in exercise intolerance. Its source is often discussed and explained by exercise ECG morphology changes. We support this analysis by assessing the ECG features (RR intervals, ST segment, and QT interval) in a metabolic equivalent relation. Fourteen healthy females performed exercise on a cycle ergometer in three submaximal workloads. We found that the relation between parameters and energy cost is linear for moderate effort, but for ${\gt}6$ MET, a crossover is possible. We believe thatthis methodology can be expanded to patients with reduced myocardial oxygen demands and to the analysis of patterns of QT vs. RR interval relation in exercise.