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The present study compared the effects of aerobic endurance training at different intensities and with different methods matched for total work and frequency. Responses in maximal oxygen uptake (V˙O2max), stroke volume of the heart (SV), blood volume, lactate threshold (LT), and running economy (CR) were examined.Forty healthy, nonsmoking, moderately trained male subjects were randomly assigned to one of four groups:1) long slow distance (70% maximal heart rate; HRmax); 2)lactate threshold (85% HRmax); 3) 15/15 interval running (15 s of running at 90-95% HRmax followed by 15 s of active resting at 70% HRmax); and 4) 4 × 4 min of interval running (4 min of running at 90-95% HRmax followed by 3 min of active resting at 70%HRmax). All four training protocols resulted in similar total oxygen consumption and were performed 3 d·wk−1 for 8 wk.High-intensity aerobic interval training resulted in significantly increased V˙O2max compared with long slow distance and lactate-threshold training intensities (P < 0.01). The percentage increases for the 15/15 and 4 × 4 min groups were 5.5 and 7.2%, respectively, reflecting increases in V˙O2max from 60.5 to 64.4 mL·kg−1·min−1 and 55.5 to 60.4 mL·kg−1·min−1. SV increased significantly by approximately 10% after interval training (P < 0.05).High-aerobic intensity endurance interval training is significantly more effective than performing the same total work at either lactate threshold or at 70% HRmax, in improving V˙O2max. The changes in V˙O2max correspond with changes in SV, indicating a close link between the two.