Estimated aerobic performance and energy cost of severe exercise of 24 h duration

Abstract

The maximal aerobic performance ([Vdot]O₂max) and energy cost of running at various speeds of two ultra-distance athletes were measured in the laboratory on a motor driven treadmill and the results related to observations made during a 24 h race. The athletes finished 1st and 2nd in the event and covered distances of 251·46 km and 234·56 km respectively during the 24 h period. From the measurements in the laboratory it was calculated that the average speeds sustained by the athletes during the competition were equivalent to an O₂ cost of 36·4 ml kg^?1 min^?1 and 35·3 ml kg^?1 min^?1 which represented approximately 50% of their [Vdot]O₂max. During the race the winner expended an estimated 77,829 kJ (18.595 kcal) which is three times the highest recorded value in the most severe industrial work. By the nature of the activity this figure must be regarded as at or near the upper limit of sustainable energy expenditure by man during a complete uninterrupted 24 h circadian cycle.