Is High Intensity Interval Training (HIIT) a better way to exercise?
That is, of course, a leading question without a definite answer, and thus the question needs clarification. For starters, better for what? Weight loss? Fat burning? Muscle building? Explosive athletic performance? Feeling good? There are too many options to give one simple answer. Yet based on popular news and marketing, we are frequently lead to believe that we should all be doing HIIT all the time. However, the most important part in that equation is defining what are your specific goals? To help guide you, it may be best to start with defining what HIIT is and what it isn’t.
By definition, HIIT (also called Sprint Interval Straining or SIT) consists of short bursts of high intensity, maximal performance exercise lasting less than 2 minutes in duration (frequently less than 1 minute) with equal or longer rest periods. For generations HIIT has been used for sport and athletic performance. More recently, however, HIIT has has become popularized for the general exercising public with promises of better and more time efficient calorie burning, fat burning, weight loss and fun. Of course, the fun part is in the eye of the beholder, true for some and torture for others. You know who you are. But are the rest of these claims substantiated?
Looking at the following table, it becomes clear that HIIT is a better calorie burner than low intensity (3mph treadmill) exercise, but it is NOT better for burning calories than moderate (6mph treadmill) intensity cardio training. In fact, since HIIT can usually only be maintained for short periods of time and can’t be done for 60 minutes (usually 20 minutes max), the better choice for calorie burning is to do the longer, moderate exercise. (Of note, EPOC is Excess Post Exercise Oxygen Consumption, which has been linked to the improved metabolism from high intensity exercises that is not seen with moderate cardio exercise. However, while this is true, the absolute calorie yield is low at around 10% over 14 hours)
|HIIT||20minutes||175 kcal burned||EPOC approx. 20kcal/14 hours|
|Treadmill 3mph||20 min||96 kcal||Minimal EPOC|
|Treadmill 6mph||20min||195 kcal||Minimal EPOC|
|Treadmill 6mpgh||60min||585 kcal||Minimal EPOC|
So if burning fat or calories is your only goal, HIIT is not “better”. But it certainly is a better exercise for developing lean body mass and also improving athletic performance. Some other benefits that have been described are its ability to improve insulin sensitivity (very important for diabetics and pre-diabetics), and improving VO2 Max, as well as aerobic and anaerobic thresholds.
Interestingly, weight loss may not be one of the benefits HIIT. There was a recent article in the Wall Street Journal about the popularity of cross fit, a prime example of HIIT. But the article wasn’t about the exercises, the calorie burning, or the time efficiency. It was about how participants can’t fit into their jeans anymore! The high intensity exercise is excellent for building muscle, predominately on the legs and glutes. Thus, the need for new jeans. In fact, one crossfit member saw it as a business opportunity and started his own jeans company specifically cut for the “crossfit body type”. You may not lose weight, but you will gain muscle. Is that better? Again, it depends on your goals and what other types of exercise you are doing during the week.
If we view traditional exercise as 30-60 minutes on the elliptical or treadmill, you can quickly see how the interval style training (frequently done in a group setting with like mined people) can be a fresh change and introduce diversity. And that is where I see its best effect, to break up or add to a routine, and to force you to push your limits and rediscover what your body can accomplish. It may even build a community to help with motivation and enjoyment.
|Exercise||Calorie burn||Lean Body Mass||Performance||Fun|
|HIIT||Good||Very Good||Very Good||Depends|
|Moderate Cardio||Better||Minimal||Minimal||Less so|
So at this point you may be wondering, “What are the downsides to doing HIIT?” First of all, because of the high intensity, HIIT is not an exercise that should be done every day or even every other day. This type of high-intensity exercise can produce significant initial muscle breakdown and stress hormone release, thus requiring a longer recovery period. Therefore, HIIT should only be done once or twice per week in the general population (this recommendation is different for athletic performance training). Secondly, because of the increased intensity, HIIT can increase the potential injury risk for those who do not have an adequate base level of strength, mobility and stability or knowledge of exercise technique. Thirdly, the high-intensity may be difficult to maintain over an entire workout leading to poor form and inadequate results near the end of the workout.
These potential downsides make it very important to consult with health coach or experienced trainer prior to initiating HIIT training. The first goal of exercise should always be to do no harm, thus the need to ensure you are doing HIIT in a proper, and safe manner
In summary, HIIT is a very popular method of exercise that can be fun to do, can build lean body mass and improve athletic performance, and can provide much needed variety to a training program. HIIT can take you out of your comfort zone and challenge you to learn what you can accomplish. However, do not expect it to be a superior exercise for weight loss, fat burning and calorie burning, and be cautious of the potential risk of injury, as well as your body’s need to properly recover from a HIIT workout. When monitored by a trained professional, HIIT is a valuable addition to any training program.
At Boundless Health we specialize in designing a personalized health and fitness program that works for you and your specific goals. Is HIIT right for you? Contact us today so we can help you determine how HIIT fits into your program for a lifetime of health and fitness.
Bret Scher, MD, FACC
President, Boundless Health
NASM Certified personal trainer
TPI level 1 certified