Fitness / HIIT

10 Most Common HIIT Mistakes, According to Trainers

HIIT may be your favorite workout, but make sure you’re doing it correctly.

By now, HIIT training is well-known as a fast way to build muscle, increase aerobic fitness, and burn fat. Most high-intensity interval training workouts are less than 30 minutes and alternate between maximum effort for a period of 20 to 30 seconds and shorter rest sets of lower intensity.

You can also customize HIIT for your body’s needs and apply it to running, strength training, or both.

Related: Check out Aaptiv’s sample HIIT workout here. >>

The only downside? There are a lot of ways to do HIIT wrong, which not only leads to injury and fatigue but also prevents you from accomplishing your goals. Here are ten common HIIT mistakes trainers see all the time, plus how you can fix them.

You’re skipping your warmup or cooldown.

Dr. Susan Fu, director of rehabilitation services at Providence Saint John’s Health Center, says a proper warm-up and cooldown are key because everyone has different injuries, needs, and aches and pains. Stretching prepares your body for high-intensity exercise. It may minimize muscle soreness or aid in post-workout recovery.

HIIT Pilates instructor and wellness coach Melanie Kotcher adds, “HIIT involves intense cardio movements like jumping, which can be rough on your joints. So it’s important to remember to stretch to avoid potential injury.”

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You’re not eating beforehand.

“HIIT is the one workout that is really hard to do without some carbs to pull from,” notes Aaptiv trainer Jessica Muenster. “Steady cardio burns fat and can be done when you wake and without eating. But try to go to that HIIT workout on an empty tummy. You’ll not only have noticeably decreased performance but also likely feel sick and off-balance as your body scrambles for energy for the higher-intensity pieces but has nothing to grab.”

The solution is simple: Eat before your workout.

Your intervals are too long.

Personal trainer Stephanie Lincoln warns against any HIIT interval that lasts longer than 30 seconds or so. She recommends staying within the 15- to 30-second range. During HIIT, the objective is to go as hard and as fast as you can during work intervals. You’ve got a small window of time to do so before hitting fatigue or failure.

“HIIT training is short bursts of effort, which are very tough, followed by rest periods,” explains Rob Jackson, a personal trainer at London-based Minimal FIT. “Just like you can’t maintain a sprint for many kilometers, you can’t maintain HIIT workouts for hours on end. If you try to do HIIT for an hour, you are most likely going to go easy in parts of it, which defeats the purpose.”

Our HIIT interval workouts are designed by the best fitness trainers around. Click to listen to our sample workouts.

Your form is wrong.

“This is one of the most frequent HIIT mistakes I see,” Lincoln says. “HIIT is pretty intense and takes a big burst of energy and effort. So, people completely forget about keeping proper form in their focus on doing the hard work. I would rather people do fewer reps and do them perfectly to form than have crappy form and do more. Bad form can put too much strain on the joints, work the wrong targeted muscle groups, and make you susceptible to injury.”

If a HIIT workout feels too challenging, then modify. Andrea Levine, fitness instructor and wellness coach in New York City, says many people assume HIIT means taking the hardest variation available of an exercise, but that’s not true. Rather than opting for poor form and more intensity, she suggests picking the version of a movement you can perform most effectively. As long as your heart rate is up, you’re still getting a great workout.

“A lot of exercises look more fun to do but may be more complex in the movement pattern than you realize,” Dr. Fu agrees. “Good form and technique should never be sacrificed for a high volume of work.”

You’re resting too long between sets or circuits.

“It’s important to make sure that you are staying strict with small breaks to bring your heart rate down in between exercises,” says Aaptiv trainer Meghan Takacs. “You want to be able to work hard during the work periods and have a small recovery during the recovery periods. This type of training style allows you to burn more calories post-workout. Whereas 60 minutes of steady-pace cardio allows you to only burn during that time. The minute you step off the treadmill, that’s when the calories stop burning. There is no post-calorie burn.”

Your intensity isn’t high enough.

“HIIT is meant to be really intense and hard, hence the name,” says Meghan Kennihan, personal trainer and running coach in Illinois. “Unfortunately, many people, especially beginners, are not able to exercise at that intensity. If you are not in shape enough to work out at a high intensity, start with your general fitness and build yourself up to HIIT. If you are ready for HIIT, realize that pushing outside your comfort zone is not something that comes naturally. Follow the most important rule of HIIT: Do not hold back on the effort until it is your rest period.”

Lincoln thinks most people are used to pacing themselves for longer workouts. But with HIIT, you need to do the exact opposite. Your workout is already super-short, and you won’t be at the gym for an hour. So if you push yourself hard, you can be done in about ten to 20 minutes. Remember, high intensity doesn’t equal high impact, says personal trainer Jill McKay. For those with physical limitations or joint pain, HIIT workouts can be done with resistance bands, while walking or swimming, or on an elliptical, as long as you bring up your heart rate and then recover before repeating.

“Hard work is a must to reap HIIT’s benefits,” says Rob Shoecraft, head trainer at Three Storm Fitness. “Use the talk test to grade your effort. If you can hold a conversation after the workout, you didn’t work hard enough. If you can’t get through the “Pledge of Allegiance” without taking a break between conjunctions, you probably did it right.”

You’re wearing the wrong shoes.

“Wearing training shoes—aka those cute Nikes you’d never run in—is horrible,” Muenster says. “HIIT typically includes a lot of jumping, which needs supported feet to support your knees, hips, etc. If you are training in shoes without stability and cushion built in, you will be prone to injuries and doing yourself a disservice. I always wear my running shoes rather than my training shoes when I do HIIT. I know my feet need just as much support for the impact of all the jumping moves.”

You’re skipping rest breaks.

“The interwebs and social media are littered with HIIT workouts that have unsafe and just plain poor ratios of work to rest,” McKay advises. “Ideally, you want to work for a period (perhaps 30 seconds to one minute) and then rest for double (so one minute or two minutes, respectively). That would be an appropriate 1:2 ratio. For those looking to build muscle endurance or cardio endurance, a 1:3- or 1:4-minute ratio may also be appropriate. Rest is important. It’s how we get a quality workout.”

Muenster says many people hear “high intensity” and forget about the interval part, which is crucial for your body to get into a fat-burning zone. True rest time also allows you to regroup and catch your breath for the next exercise, Dr. Fu says. So don’t resist active recovery time in between muscle groups. It is just as vital as the actual work itself.

“HIIT is designed to be a hard session, therefore it places lots of stress on the body,” Kennihan says. “You must take time to recover between workouts. Overtraining and under-recovering can lead to burnout, both mentally and physically. HIIT workouts are always about quality, not quantity!”

You’re overdoing it with heavy weights.

Dr. David Greuner of NYC Surgical Associates says it may be tempting to use equipment as a way to build muscle faster. But in reality, you don’t need racks of dumbbells for a successful HIIT workout. Bodyweight, sprints, or anything that gets your heart rate up is more than sufficient. Using too many weights can defeat the purpose of HIIT.

Shoecraft adds, “People use too much weight. The goal of performing high-intensity intervals isn’t to increase absolute strength, nor is it to show everyone how strong you are. People who fail to realize this always get hurt. If your HIIT exercise selection includes a loaded variation (i.e., where you use weights), choose a weight where you can complete 15-25 reps before failure. When in doubt, start light. You can always go faster and bump up the load next time.”

You’re doing HIIT too much.

“The misconception that more is better often leads to burnout or injury,” McKay says. “Consistency is important, but you only need to do HIIT workouts three to five days a week. Walking, stretching, getting good sleep, and eating well are all important, too. I see people who pay for a gym program that offers seven-days-a-week classes, so they feel [the need] to get their money’s worth and take classes at least six days a week. Your body needs rest to recover. That’s how muscles grow, by repairing. Listen to your body, and don’t overdo it.”

High-intensity workouts should only be performed two to three times per week, according to both Shoecraft and Levine, to make space for adequate recovery and long-term results. Additionally, Levine discourages people from doing HIIT every day. “If you properly push yourself in HIIT workouts at high intensity, then your body needs time to recover and replenish your muscles before they are worked again,” she says. “Repeated HIIT workouts without recovery time can lead to injury.”

You’re not doing workouts you enjoy.

Finally, if you’re tackling HIIT workouts as a beginner, make sure to get the OK from your doctor first. More than anything, Dr. Greuner says, have fun with it! “Don’t do any workouts that you’re going to give half-effort to because then you are just wasting your time,” he concludes. “If you’re not comfortable with it, it causes any pain, or [you] just simply don’t look forward to doing it, then avoid the workout. There are plenty of different options that you can use and still find the results you want.”

“As with any exercise, if you don’t enjoy it, you won’t stick with it,” McKay agrees. “Create a consistent routine of HIIT workouts to incorporate what you enjoy. Do you like to bike? Pedal fast from one telephone pole to another, and rest easy between the next two. Enjoy the rower? Pull harder during the TV commercials (about two minutes), and go easier (or decrease the ease) during the show (about eight minutes). HIIT doesn’t need to be complicated.”

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