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Repeated maximal-intensity short-duration exercise (sprint interval training, SIT) can produce muscle adaptations similar to endurance training (ET) despite a much reduced training volume. However, most SIT data use cycling, and little is known about its effects on body composition or maximal cardiac output (Q˙max).The purpose of this study was to assess body composition, 2000-m run time trial, V˙O2max, and Q˙max effects of run SIT versus ET.Men and women (n = 10 per group; mean ± SD: age = 24 ± 3 yr) trained three times per week for 6 wk with SIT, 30-s all-out run sprints (manually driven treadmill), four to six bouts per session, 4-min recovery per bout, versus ET, 65% V˙O2max for 30 to 60 min·d−1.Training improved (P < 0.05) body composition, 2000-m run time trial performance, and V˙O2max in both groups. Fat mass decreased 12.4% with SIT (mean ± SEM; 13.7 ± 1.6 to 12.0 ± 1.6 kg) and 5.8% with ET (13.9 ± 1.7 to 13.1 ± 1.6 kg). Lean mass increased 1% in both groups. Time trial performance improved 4.6% with SIT (−25.6 ± 8.1 s) and 5.9% with ET (−31.9 ± 6.3 s). V˙O2max increased 11.5% with SIT (46.8 ± 1.6 to 52.2 ± 2.0 mL·kg·−1·min−1) and 12.5% with ET (44.0 ± 2.0 to 49.5 ± 2.6 mL·kg−1·min−1). None of these improvements differed between groups. In contrast, Q˙max increased by 9.5% with ET only (22.2 ± 2.0 to 24.3 ± 1.6 L·min−1).Despite a fraction of the time commitment, run SIT induces similar body composition, V˙O2max, and performance adaptations as ET, but with no effect on Q˙max. These data suggest that adaptations with ET are of central origin primarily, whereas those with SIT are more peripheral.