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 (Qmax). Purpose: The purpose of this study was to assess body composition, 2000-m run time trial, VO2max, and Qmax effects of run SIT versus ET. Methods: 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. Results: Training improved (P < 0.05) body composition, 2000-m run time trial performance, and VO2max 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). VO2max increased 11.5% with SIT (46.8 ± 1.6 to 52.2 ± 2.0 mL/kg·min) and 12.5% with ET (44.0 ± 2.0 to 49.5 ± 2.6 mL/kg·min). 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). Conclusions: Despite a fraction of the time commitment, run SIT induces similar body composition, VO2max, 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.
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