A longitudinal study of exercise metabolism during recovery from viral illness.

An élite athlete engaged in a longitudinal programme of physiological assessment suffered a loss of performance that was later ascribed to an asymptomatic viral illness. In this 15-month, single subject, repeated measures study it was possible to demonstrate a severe decrease of exercise performance following viral illness. The oxygen uptake equivalent to the onset of blood lactate accumulation of 4 mmol l-1 (OBLA) decreased by 17% following viral illness, then recovered slowly, but had not returned to pre-viral levels 50 weeks later. Steady state exercise metabolism was also affected. During prolonged exercise at 70% of VO2max the proportion of energy derived from carbohydrate metabolism increased and an inability to maintain euglycaemia was observed. In both the graded and prolonged exercise tests, a pronounced tachycardia was evident after viral illness, possibly as a result of a febrile response to the infection, or, a direct effect of the virus upon myocardial performance. These data provide some preliminary and unique findings of the effects of viral illness upon the physiological and metabolic responses to exercise in an élite athlete. The data also demonstrate the sensitivity of currently used laboratory measures of exercise performance to monitor the changes in physiological function during recovery from viral illness.