**Of course, if you are starting a new exercise routine for the first time always consult with your physician to make sure you're in good health. :)
What is HIIT? It's a type of exercise with alternating bursts of short, intense anaerobic (sprinting) exercise where you get close to your maximum heart rate; coupled with low-intensity recovery periods. Your heart rate is the number of beats per minute; you can figure it out by subtracting your age from 220. A typical HIIT workout would involve a warm up, then a routine that alternates between 1 minute of a sprint (roughly 90% to 100% of the maximum heart rate), then one minute of a low to moderate intensity recovery. There are usually 6-10 bursts of sprints (depending on how hard you push yourself & heart), making the total workout lasting only about 20 minutes.
What are the researched benefits? Most studies I found were tested using a stationary bicycle, mainly because that is one of the easiest ways to measure how fast/hard a person is working. The results showed positive results in many aspects. Besides being a shorter form of exercise, there is this thing called an "after-burn" that happens on a metabolic level. During HIIT, muscles are pushed harder & after an intense workout they need to be repaired. It takes more energy to repair/rebuild muscle tissue, therefore burning more calories. Studies also showed an increase in resting metabolic rate (RMR) related to the afterburn for 24 hours after a workout. This increase in RMR is higher than what would normally be seen with longer aerobic exercise. HIIT was also shown to benefit endurance and heart health. Since the heart is pushed harder during sprinting (anaerobic) sessions than it would be during regular aerobic sessions; it helps make the heart muscle stronger. A stronger heart helps the body go farther than it would normally, thus increasing endurance. Personally, I noticed that it was easier for me to run a couple days ago and I didn't get quite as winded while trekking up the steep hills around my neighborhood. I guess it makes a little more sense to me when I think of how HIIT is strengthening my heart. This form of exercise has also been shown to burn fat more effectively than traditional aerobic workouts; which could be contributed to the after-burn effect mentioned earlier. A few other studies showed improvements in insulin sensitivity in healthy overweight people. Because the stress of the workouts are a bit more demanding on the heart, there have not been many studies on severely obese populations with more complicated metabolic conditions. Right now, scientists are modifying the HIIT routine to hopefully be able to adapt & translate it to that population.
So what do I think about it? For those of us who are pressed for time (well, that would probably all of us) I would recommend incorporating this type of workout to your routine. Am I going to do only this? No way. I consider running to be my personal therapy and hope to continue it as long as my limbs allow me to... But I do love the workouts as well as the cardiovascular and metabolic benefits of HIIT. I am a firm believer that it is important to balance cardiovascular training, muscle strengthening, and flexibility into workout routines.
If you want more information on this type of exercise or any others, check out the ACSM website. It will take you to helpful articles and research on exercise.
