Is it true that the treadmill is not the best thing to use when doing an HIIT (interval training) workout?

Answer #1:
Doing interval training workouts on the treadmill is fine if you’re using longer intervals since it takes most treadmills a fair amount of time to reach the desired speed. I would suggest using the treadmill for running workouts that involve intervals of at least 30 seconds. Using faster and thus shorter intervals of 10 or 15 seconds could be more difficult because it will take the treadmill that long to reach the intended speed.

Answer #2:
To do interval training outside is fairly simple yet not as accurate when it comes to calculating running speed. My best advice is to use a track if you can. That way you’ll know exactly how much distance you cover in a given amount of time and thus can calculate your speed or pace.

For example, you can set up a simple interval where you run 100 m in 12 seconds and then recover for 300 m in under 1 minute. You could then repeat this protocol for 10-15 minutes.

Personally, I prefer doing interval runs outdoors because you can usually reach greater running speeds in only a few seconds (instead of waiting for the treadmill to change speeds). One method of doing these interval runs outdoors (if you don’t have access to a track) is to arbitrarily assign landmarks as your start and stop locations.

For instance, if you’re running on a sidewalk you could accelerate to full speed between streetlights or street corners and then jog for recovery for twice that distance (ie. 2 street corners). The same can be done in a park using big trees or other landmarks that you choose to use.