"I don't have time to exercise." It's the most common reason people give for not working out. And for decades, the science didn't have a good answer — until a team at McMaster University decided to find out exactly how little exercise you could get away with.
The answer was absurd. Three 20-second sprints within a 10-minute session, three times per week. That's 1 minute of actual hard exercise per session. 3 minutes per week. And it matched the fitness gains of people doing 150 minutes of moderate cycling per week.
Both groups improved VO2max by 19% after 12 weeks. The sprint group did 1 minute of hard exercise per session (3×20-second all-out sprints). The endurance group did 45 minutes of continuous cycling. Same cardiovascular improvement. Five-fold less time.
📄 Gillen et al. 2016 — PLOS ONE 📄 Gibala et al. 2012 — J. PhysiologyThis study, led by Jenna Gillen in Dr. Martin Gibala's lab, is one of the most cited exercise studies of the last decade. It didn't just show that short workouts "help." It showed they're equivalent to workouts that take five times longer. Here's what that looks like in practice.
The Exact Protocol
The protocol from the Gillen 2016 study is simple enough to remember after reading it once. The entire session takes 10 minutes including warm-up and cooldown:
Total: 10 minutes. Actual hard work: 60 seconds. The original study used a stationary bike, but the principle applies to any modality — bodyweight exercises, stair sprints, hill walking, or cycling. 📄 Gillen et al. 2016 — PLOS ONE
"All-out" means all-out. The 20-second sprints in this protocol were performed at approximately 500 watts — roughly 170% of the participants' maximum aerobic capacity. This isn't "kind of hard." It's the hardest you can possibly go for 20 seconds. The protocol works precisely because the intensity is maximal. If you dial it down, the results diminish.
What Changed in 12 Weeks
The study tracked sedentary men across three groups: sprint intervals (SIT), moderate continuous cycling (MICT), and a no-exercise control. After 12 weeks:
Both training groups also showed identical improvements in insulin sensitivity and skeletal muscle mitochondrial content — the cellular machinery that produces energy. The sprint group achieved this with a five-fold lower exercise volume and time commitment. 📄 Gillen et al. 2016 — PLOS ONE
A follow-up review confirmed that protocols with as few as two 20-second sprints per session still produced meaningful VO2max improvements of 12-14%, suggesting the threshold for "enough" is far lower than anyone assumed. 📄 Vollaard et al. 2024 — Appl. Physiol. Nutr. Metab.
The Honest Caveats
Before you celebrate the end of long workouts, three important caveats:
Caveat 1: The participants were sedentary. When you start from zero fitness, almost any novel stimulus produces large gains. Trained individuals will need more volume to continue improving. 📄 MacInnis & Gibala 2017 — J. Physiology
Caveat 2: "All-out" is genuinely unpleasant. A 2015 study found that Tabata-style protocols were rated significantly less enjoyable than moderate exercise, and enjoyment declined over the course of 8 weeks. If you hate the intensity, you won't stick with it — and consistency beats perfection. 📄 Foster et al. 2015 — J. Sports Sci. Med.
Caveat 3: Short intervals don't replace everything. This protocol improves cardiovascular fitness and metabolic health. It doesn't build significant muscle mass, flexibility, or the mental health benefits that come from longer outdoor movement. Think of it as the minimum effective dose, not the whole prescription.
What This Means for Your Workout
If you have 10 minutes, you have enough time for a workout that science says is equivalent to a 50-minute jog. That's not a marketing claim — it's a peer-reviewed finding from one of the most respected exercise physiology labs in the world.
The workout above is ready to build right now. Three sprints, two minutes of recovery between each, plus warm-up and cooldown. Do it three times a week. In 12 weeks, your cardiovascular fitness will look completely different.
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SOURCES (6 peer-reviewed studies)
- Gillen JB, Martin BJ, MacInnis MJ, Skelly LE, Tarnopolsky MA, Gibala MJ. Twelve weeks of sprint interval training improves indices of cardiometabolic health similar to traditional endurance training despite a five-fold lower exercise volume and time commitment. PLOS ONE. 2016;11(4):e0154075.
- Gibala MJ, Little JP, MacDonald MJ, Hawley JA. Physiological adaptations to low-volume, high-intensity interval training in health and disease. The Journal of Physiology. 2012;590(5):1077-1084.
- Vollaard NBJ, Metcalfe RS. Reduced-exertion high-intensity interval training (REHIT): a feasible approach for improving health and fitness? Applied Physiology, Nutrition, and Metabolism. 2024;49(8):1069-1084.
- MacInnis MJ, Gibala MJ. Physiological adaptations to interval training and the role of exercise intensity. The Journal of Physiology. 2017;595(9):2915-2930.
- Foster C, et al. The effects of high intensity interval training vs steady state training on aerobic and anaerobic capacity. Journal of Sports Science and Medicine. 2015;14(4):747-755.
- Metcalfe RS, Babraj JA, Fawkner SG, Vollaard NBJ. Towards the minimal amount of exercise for improving metabolic health: beneficial effects of reduced-exertion high-intensity interval training. European Journal of Applied Physiology. 2012;112(7):2767-2775.
