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Too much HIIT can be bad for you.

So what is up with the HIIT workout trend? First off, if you aren’t familiar with HIIT, it is a type of interval training exercise, which stands for “High-Intensity-Interval-Training.” It incorporates several rounds of exercises that alternate between minutes of high intensity movements that are meant to significantly increase your heart rate at least 80 percent of your maximum heart rate, followed by short periods of lower intensity movements. Sounds like a total fat burner, right? Yes, however, too much of high interval training can have a negative effect on your fitness gains and mitochondrial function (provides energy for muscle functions) causing it to deteriorate.

The right amount of HIIT causes cells to make more proteins for their energy-producing mitochondria and their protein-building ribosomes, effectively stopping aging at the cellular level. Then again, incorporating too much HIIT into your weekly workouts has been known to lead to a disturbance in blood sugar and your fitness goals can actually begin to go backwards. Also know that high-intensity exercise is not suitable for everyone. Here’s what you need to know.

How Much HIIT is OK?

Too much of anything is bad for you, that’s a fact. The same goes for HIIT; so if you are wondering if it’s OK to add HIIT to your weekly workouts, the answer is yes you can, in moderation, of course. Typically, a HIIT workout lasts about 10 - 30 minutes in duration. Despite how short the workout is, it can produce health benefits similar to twice as much moderate-intensity exercise, that is if you allow at least 24 - 48 hours of rest time between, doing it only two - three days a week. “Rest” days can consist of strength training, cardio and stretching. When you don’t allow rest time in between high intensity workouts, you increase your risk of injury and actually overtrain your muscles.

Is HIIT for Me? You should already have a basic level of fitness to take part in HIIT training due to its intensity and impact on your joints. Without the proper introduction and training, HIIT can:

  • Make you dizzy.

  • Make your muscles sore.

  • Higher your risk for injury.

  • Cause less stable blood sugar levels.

  • Cause fatigue and increased inflammation.

Also, if you are looking for greater muscle gain, there is research that shows active people have actually shown lower muscle mass after joining in on too many hours of HIIT programs. Pure weight training is still the main form of exercise to include in your routine if you want to see an increase in muscle mass. However, smaller amounts of high intensity intervals can support a small amount of muscle growth.

If you are not very active, you may see some muscle gain after jumping into HIIT class, but not as much as you would engage in just weight training.

Before you swear off HIIT completely, know this: it is good to pursue any exercise in moderation allowing plenty of time to recover in between.

Benefits of HIIT

Now that we know too much HIIT isn’t good for you, the right amount of HIIT does have some benefits. If you are new to HIIT, take it slow and start small (do a 10 minute, less intense workout before jumping right into a 30 minute intense sweat session). Benefits include:

  • Improved oxygen consumption

  • Helps you lose fat

  • Increases metabolic rate

  • Reduces your heart rate and blood pressure

  • Improves aerobic and anaerobic performance

  • Burns more or the same amount of calories in a shorter amount of time

If you are interested in incorporating HIIT into your routine, Trainers Spot has personal trainers who can work the right workout into your routine based on your fitness level. Trainers Spot also has fantastic workout classes, workshops and more! Find a trainer, sign up for a class, workshop and find more information at

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