The single most important decision in any interval workout isn't the exercise. It's the ratio between how long you work and how long you rest. Get this wrong and you're either undertraining or burning out. Get it right and the results take care of themselves.
Here's the complete reference. Bookmark this page. Come back to it every time you build a new workout.
Different goals need different rest lengths. Fat loss, endurance, power, and recovery all live at different points on the work:rest spectrum. There is no single "best" ratio — only the right one for what you're training today. 📄 Buchheit & Laursen 2013 — Sports Medicine
The 5 Ratios You'll Ever Need
Research confirms that work:rest ratio is the primary variable determining the metabolic pathway stressed during HIIT. Shorter rest creates more anaerobic demand; longer rest preserves power output and aerobic quality. 📄 Buchheit & Laursen 2013 — Sports Medicine
The simplest decision framework: If you're new or returning to exercise, start at 1:2. When rest feels comfortable, move to 1:1. If you want maximum time efficiency and can handle the intensity, try 2:1 (Tabata) for short sessions. If you're training for endurance events, use long intervals with moderate rest (3:1 or 4x4). 📄 MacInnis & Gibala 2017 — J. Physiology
Matching Ratio to Goal
A 2014 meta-analysis found that even low-volume HIIT (sessions under 15 minutes) produced clinically meaningful improvements in cardiovascular fitness across all ratios tested — the key was consistency over weeks, not the perfect ratio on any single day. 📄 Weston et al. 2014 — Sports Medicine
The One Rule That Matters Most
Can you maintain effort quality across all rounds? If your power collapses by round 4, your rest is too short. If you feel barely challenged by the final round, your rest is too long. The right ratio keeps you working at 80%+ effort from the first round to the last. 📄 Milanović et al. 2015 — Sports Medicine
What This Means for Your Workout
Pick your goal. Find the ratio above. Set it in your timer. That's your workout structure for the next 2-4 weeks. When it starts feeling manageable, adjust one variable (shorter rest, more rounds, or harder exercise) and stay at the new level for another 2-4 weeks.
SUPER INTERVAL TIMER — THE APP
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SOURCES (5 peer-reviewed studies)
- Buchheit M, Laursen PB. High-intensity interval training, solutions to the programming puzzle: Part I & II. Sports Medicine. 2013;43(5):313-338 & 43(10):927-954.
- MacInnis MJ, Gibala MJ. Physiological adaptations to interval training and the role of exercise intensity. The Journal of Physiology. 2017;595(9):2915-2930.
- Weston M, Taylor KL, Batterham AM, Hopkins WG. Effects of low-volume high-intensity interval training on fitness in adults. Sports Medicine. 2014;44(7):1005-1017.
- Milanović Z, Sporiš G, Weston M. Effectiveness of HIIT and continuous endurance training for VO2max improvements. Sports Medicine. 2015;45(10):1469-1481.
- Tabata I, et al. Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Medicine & Science in Sports & Exercise. 1996;28(10):1327-1330.
