Reduced athletic performance post-COVID-19 is associated with reduced anaerobic threshold.

Detailed characterisation of cardiopulmonary limitations in patients post-COVID-19 is currently limited, particularly in elite athletes. A male elite distance runner in his late 30s experienced chest pain following confirmed COVID-19. He underwent cardiopulmonary exercise testing (CPET) at 5 months postacute illness. Subjective exercise tolerance was reduced compared with normal, he described inability to 'kick' (rapidly accelerate). His CPET was compared with an identical protocol 15 months prior to COVID-19. While supranormal maximal oxygen uptake was maintained (155% of peak predicted V̇O) anaerobic threshold (AT), a better predictor of endurance performance, reduced from 84% to 71% predicted peak V̇O maximum. Likewise, fat oxidation at AT reduced by 21%, from 0.35 to 0.28 g/min. Focusing exclusively on V̇O maximum risks missing an impairment of oxidative metabolism. Reduced AT suggests a peripheral disorder of aerobic metabolism. This finding may result from virally mediated mitochondrial dysfunction beyond normal 'deconditioning', associated with impaired fat oxidation.