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The purpose of this study was to investigate the effects of a 120 km desert running race (5 stages over 4 days) on the main physiologic parameters related to the individual aerobic work capacity. Incremental treadmill tests were carried out on 7 recreational long-distance runners (age: 50.4±11.8 years; body mass: 76.0±8.5 kg; mean±SD) before and 3–5 days after the competition. Maximal oxygen consumption ( $$ \dot VO_{2max} $$ ), ventilatory threshold and heart rate were obtained by standard methods; the mean energy cost of running (Cr) above resting was calculated during the same protocol from the slope of the oxygen consumption versus running speed. After the race, the subjects exhibited significant ( p<0.05) reductions only in $$ \dot VO_{2max} $$ (averaging 7%; from 46.7±5.1 to 43.2±4.4 ml · kg−1 · mm−1) and in maximal heart rate (averaging 3%; from 172.4±14.1 to 166.7±14.5 beats · min−1). Knowledge of Cr (3.78±0.31 J · kg−1 · m−1 and 3.74±0.48 J · kg−1 · m−1, before and after the race respectively) allowed us to estimate the overall daily energy requirement, about 20 850 kJ. $$ \dot VO_{2max} $$ and the maximal heart rate seem to be the main variables affected by prolonged strenuous runs followed by insufficient rest periods. [ABSTRACT FROM AUTHOR]