Cardiorespiratory fitness response to endurance training in athletes post-COVID-19 compared to unaffected athletes.

Background: Endurance sports primarily attract recreational athletes over 35 years, who impose an exceptionally rigorous and sustained demand on their cardiorespiratory systems.

Objectives: This study aimed to determine the influence of COVID-19 on the cardiovascular, pulmonary, and skeletal muscle function of endurance athletes with exercise intolerance. Secondly, it aimed to compare the exercise response of endurance athletes post-COVID-19 to those unaffected using cardiopulmonary exercise test-related variables.

Methods: This is a prospective observational cohort study of endurance athletes. An exposure group with protracted exercise tolerance underwent a resting lung function test and maximal cardiopulmonary exercise test. These were repeated after eight weeks of endurance training and compared to the published reference values and a control group of athletes unaffected by COVID-19.

Results: The post-COVID-19 exposure group (n=57), mean age 44.5±8.1years showed a poorer ventilatory threshold (p=0.004), and workload (p=0.05), with higher respiratory exchange ratio (p=0.05) than the control group (n=34), mean age 41.8±7.7 years. Maximal inspiratory pressure improved at follow-up in the COVID-19 group compared to the controls (p=0.03). Increased odds of pulmonary and skeletal muscle limitation to aerobic capacity were found in the COVID-19 group. The COVID-19 group responded positively to endurance training with improved VO₂peak (p=0.005), maximal inspiratory pressure (p=0.04), oxygenpulse (p=0.02), and maximal workload (p<0.001).

Conclusion: COVID-19 has led to pulmonary and extrapulmonary limitations to exercise capacity. Tailored intensity and duration of physical activity are vital after COVID-19 to restore skeletal muscle health. This multidisciplinary rehabilitation approach will optimise the resumption of participation in long-distance events.