High-Intensity Interval Training alternates demanding work with recovery periods. A 40-second work / 20-second rest ratio is a common starting template, and it is hard to track reliably with a phone stopwatch. A dedicated interval timer handles the switching so you can focus on controlled movement and good form.
A clear way to use it
- Warm up for 5 minutes before starting your first work interval.
- Select your exercise (squats, sprints, burpees) and start the timer at the same moment you begin.
- Use an effort level you can sustain with good form during each 40-second work interval, then recover during the 20-second rest.
- Repeat for 8 to 12 rounds depending on your fitness level, then cool down.
Adjust when needed
- Start with fewer rounds and build up — quality of effort beats quantity of rounds.
- Choose exercises that are safe to perform quickly with good form.
- Keep the timer within earshot or on a phone stand; the sound cues each transition.
Useful questions
How long should a HIIT session last?
A complete session is typically 15 to 25 minutes including warm-up and cool-down. The intervals themselves usually total 8 to 12 rounds, or about 8 to 10 minutes of total work time.
Is 40/20 HIIT suitable for beginners?
It may be too demanding for some beginners. Reduce the work interval, increase rest, choose low-impact movements, and ask a qualified professional for guidance if you have a medical condition or are returning after inactivity.