Lately I have been feeling like my cardio routine has been getting a bit... predictable. I know it's best for our bodies to change things up so that we don't get too conditioned (and thus expend less energy) and HIIT (high intensity interval training) for the treadmill is just the thing to get me out of my rut. My usual treadmill experience involves a 2 minute warm up at 3.5 followed by a 33-38 minute run at a steady 7.5 pace with a 1.0% incline. This usually results in a ~500 calorie expenditure and anywhere between 4-5 miles. However today was my first day incorporating HIIT into my treadmill routine and boy was it tough!
The basic tenants of interval training on a treadmill is repeating a set of 2 minutes of moderate activity followed by 1 minute of extreme physical exertion at a very challenging pace. Basically you run like hell for a minute and then let your heart rate come down a bit with a 2 minute "cool down" of sorts before running like hell for another minute and so on and so forth. This high intensity action is not only shooting your heart rate up significantly but it is engaging your fast-twitch muscle fibers, which require more energy than your slow-twitch muscles fibers (which are what you are engaging during the long/steady runs) and thus burn many more calories. Another benefit to this HIIT on the treadmill is the afterburn (or calories that you burn after concluding the workout) are significantly higher than that of a more traditional steady pace run.
During my HIIT treadmill session I was engaging in a slow jog at 6.0 with my "fast/challenging" rate being 9.0 for one minute. It definitely wore me out and I do have to admit that at first I was a bit uneasy running that fast on a treadmill but quickly got used to it. I'm curious to see if my calorie burn will be as high if I lowered my "rest" rate to a 3.5. I must admit that I only did the HIIT for the first half of my workout and spent the second half running at my usual steady 7.5 pace with a 1.0% incline. But this definitely merits further exploration and I look forward to seeing if I can make any changes in my body using this treadmill method!