Exercise to Exhaustion in the Second-Wind Phase of Exercise In A Case of McArdle's Disease with and without Creatine Supplementation

Abstract

The cardio-pulmonary and biochemical changes observed in a case of McArdle's disease, exercising with increasing work rates to exhaustion in °the “second-wind” phase of exercise are reported for the first time. A °work rate of 2 75–325 °watts was achieved. Venous blood lactate remained unchanged throughout. The plasma ammonium level reached a plateau of approximately 400 °mmol/l at 100 °watts. At a work rate of 150–175 watts the ratio of O₂ consumption to CO₂ production increased, the inverse of an anaerobic threshold. Maximal cardio-pulmonary responses were achieved at 200 watts. During the final periods of exercise from 200 to 275/325 °watts pulmonary ventilation did not significantly change but there was a decrease in the venous blood H⁺ concentration, and pO₂ and in increase in the pCO₂ Creatine supplementation at 25 °g/day for five days did not improve exercise performance.