I get asked about HIIT training A LOT. ( Also known as High Intensity Interval Training.)
There seems to be a new study that shows up every month or so talking about how it can save you time plus keep you fit. Over the past two decades this type of training modality has become all the rage. It has been the subject of many studies ranging from reducing obesity to helping to stabilize blood sugars.
HIIT training is basically physical activity that has brief intermittent burst of very intense activity, followed by a period of rest or lower intensity exercise. HIIT can be performed using weights or as a cardiovascular workout.
An example of a strength training workout using HIIT Training may look like this:
Repeat all above for 1 minute at max effort and then rest for 1 minute.
Cardiovascular HIIT programs are what most of the health studies have focused on. They are short and intense. The goal is to get your heart rate into a 80-90% of max heart rate (MHR) during a given time. For example:
Ride a bike at 80-90% of MHR for 20 seconds followed by 10 seconds of rest repeated 8 times
OR a little less scientific…
Run up a hill at max effort, walk back down the hill. Repeat 10 times
There is nothing fancy or exactly inventive about HIIT training. It can literally be done anywhere. Your living room to your local park. The draw to it is the time saving factor. Since many of us are always running from one meeting to the next or rushing to pick up kids from school. This type of training can absolutely help to keep you in shape with as little as 10 minutes three times a week!
The draw of HIIT training and what many proponents of its say is that you can get the same health benefits as walking for 30 minutes keeping your heart at a lower steady state. For just a little amount of intense exercise and I mean very intense you can reach the same health benefits of a longer slower steady state type of exercise.
Many studies over the past 20 years have focused on the benefits of HIIT training.
One study in particular focused on HIIT training versus moderate intensity continuous training (MICT) altering body composition in post menopausal women (1). In this study each participant was divided into three groups. They had to perform their given activity 3 times a week for 12 weeks.
All of the women in this study lost weight plus fat mass over the 12 week time period. Not surprisingly the group that included resistance training increase their muscle mass.
The surprising part to me was the HIIT and HIIT + resistance training lost “signficant” abdominal/visceral fat. Not the MICT group. Similar findings were found in another study with young women. With three times a week of HIIT training they lost significant total body fat in addition to reduction in leg and abdominal fat. This study also found a decrease in insulin resistance. (2)
While these studies focused on women there are still plenty out there for both sexes.
Overall studies have shown HIIT can help with body fat reduction, insulin sensivity, Type 2 diabetes, and blood pressure.(3) In addition the conclusions on most studies support the fact that HIIT is just as beneficial as moderate intensity longer cardio sessions.
So yes HIIT training is worth all the hype. However as with all exercise and nutrition recommendations there a couple of asterisks.
The studies that have been performed so far are typically done in a very supervised setting and focus on the effects with obese individuals.
In a separate, Australian study they looked at HIIT in the real world. They wanted to see how individuals performed HIIT without being supervised. So they took 250 overweight people and let them choose between HIIT training and moderate intensity training. They were given a one time tutorial then told to do their chosen exercise three times a week for 12 months.
The results? No difference in health outcomes when comparing HIIT versus moderate training. No surprise there, however, “regular participation in unsupervised HIIT declined rapidly, those apparently adherent to regular HIIT demonstrated beneficial weight loss and visceral fat.” (4.)
The take away? Without someone keeping you accountable to doing your HIIT workout you probably won’t do it. In fact 60% of the HIIT group dropped out by the end of the year.
Besides HIIT being difficult there are other reasons it might not be good for a given person.
First, if you have an injury, high intensity movements may be contra-indicated. If you have a bulging disc or arthritic knees, for example, doing an all out effort may cause more damage than help. This may lead to you dropping out of exercise all together.
Second, your current stress level and sleep patterns. If you are highly stressed adding a stressful type workout on top of your current stress may lead you into getting sick or injured.
I also would not recommend it for those you who have problems sleeping. A lot of repair of the bodies systems occur during sleep and if you are only getting a couple of hours of sleep a night than you are not repairing and will do further damage.
So, my take away on HIIT? It's great for those that can commit consistently to it 3 times a week that are not currently injuried or incredibly stressed. If you are in this category, I would recommend going outside for a steady walk for 20 to 30 minutes instead.
In terms of cardiovascular training and, really exercise in general, ask yourself, "What type of physical activity do I enjoy doing? AND What will I do consistently?"
People who can answer these two questions are more likely to find paths to staying healthy and strong for the long term.
Find an activity that you love to do. Is it long hikes on the weekends with your spouse or biking to work? Or maybe it’s tennis or pickle ball (a new favorite for some of my clients.) Or maybe it’s HIIT training on your bike. Not knowing is ok too, just go try some things and see which ones you like, even those that you scratch off the list counted as exercise in the moment.
The point, is studies can show a particular exercise is beneficial but only IF you do it consistently. So, yes HIIT is a great way to get fit and healthy but make sure it is the best way for YOU to become fit and healthy!