ABSTRACT.The purpose of this study was to determine the relative importance of the factors intensity and distance in interval training on maximal aerobic power (max&OV0312;O2). Three programs were used: (1) high‐intensity, short‐distance sprints (Group S); (2) low‐intensity, long‐distance runs (Group L): and (3) a combination of both (Group M). Following 7½ weeks of training 5 days per week, significant increases in max&OV0312;O2(liters/min) and significant decreases in maximal and submaximal heart rates were found within each group; increases in max&OV0312;O2, (ml/kg‐min) were significant only for Groups S and M. There were no significant differences among groups before or after training. A significant (p < .05) relationship was found between the change in max&OV0312;O2and training intensity indicating that intensity rather than distance is the more important factor in improving max&OV0312;O2. It is proposed that differences in training intensities were due mainly to differences in tissue hypoxia, and that such a relationship is based on proportional differences in the oxidative capacity of skeletal muscle caused by the hypoxic stimulus.