Free sprint interval timer for HIIT running workouts. 20–30 second sprint intervals with adjustable rest periods. Alarm signals each transition.
Research shows 20–30 second all-out sprints with 90–120 second rest maximize EPOC (excess post-exercise oxygen consumption), which drives fat burning for hours afterward. 6–10 sprint rounds in a session is optimal for most people.
For maximum intensity: 1:3 ratio (20 sec sprint, 60 sec rest). For conditioning with some fatigue: 1:2 ratio (30 sec sprint, 60 sec rest). Never go below 1:1 for true sprints — insufficient rest means later rounds aren't real sprints.
Yes, but be careful — treadmill belts take 2–3 seconds to reach full speed after you press the button. Start the acceleration about 5 seconds before the alarm sounds, then sprint at full belt speed for the measured interval. Use the handrails for the transition only.
Beginners: 4–6 rounds. Intermediate: 6–8 rounds. Advanced: 8–10 rounds. More rounds doesn't mean better results — if you can't hit 90%+ effort on each sprint, you've done enough. Sprint workouts should leave you feeling worked but not destroyed.
2–3 times per week maximum with at least 48 hours between sessions. Sprinting is high-impact and CNS-demanding — recovery is where adaptations happen. Combine with 1–2 lower-intensity cardio days to maintain aerobic base without over-stressing the body.