While we’re on the subject of injury, definitely don’t play hooky on your warmup, either. Whether you’ll be doing cardio- or strength-based HIIT, your warmup should include mobility moves, like hip-opening stretches and thoracic spine rotations, as well as slower-tempo reps of the exercise you intend to use for HIIT, such as squats.
“The more intense the workout, the more important the warm-up is,” Tamir says. “It’s kind of like prepping your nervous system as well. If your body is not ready for that work, the outcome could be injury, or your performance can suffer.”
Scheduling a long HIIT session is also a mistake because you’re not going to be able to sustain near-max intensity for a 45-minute class, Tamir says. Instead, a true HIIT workout would look something like this: eight all-out, 20-second sprints, with one minute of rest between each. That means your entire workout (not counting warmup and cool-down) would span just over 10 minutes.
Finally, there’s nothing that says you need to do traditional HIIT if you just want some demanding interval training. In fact, according to Tamir, the modified HIIT we often see in classes—and that he uses for some of his group sessions—is probably more accessible to the average exerciser, and thus the better choice.
Whether you’re doing true HIIT or modified interval training, don’t underestimate the importance of recovery: Prioritizing frequent, intense workouts while neglecting rest days can not only lead to diminishing returns on performance, but also leave you open to injury, fatigue, or burnout, as SELF recently reported. Limit HIIT to one or two workouts a week, and make sure you’re balancing it with plenty of easy workouts—as well as at least one straight recovery day.
Regardless of the HIIT (or HIIT-adjacent) workout you decide on, always consult a healthcare provider like your primary care physician before starting this type of demanding exercise, especially if you have a preexisting health condition (such as heart disease, diabetes, or high blood pressure), according to experts. And start slow and take precautions once you do dive in. Concerning symptoms like lightheadedness, confusion, and atypical changes in blood pressure or heart rate are cause to stop right away and seek medical attention.
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