It made me think about the physiology involved with running, why it is good for us, and what it does to the hormone and energy use patterns in our bodies. In addition to the immediate effects of burning energy while running and releasing hormones like endorphins that make us feel good, running also changes our metabolism, and the amount of energy we burn after the run while repairing all of the muscles and replacing the lost energy stores in the muscles may be much greater than the energy burned during the run itself. In other words, the repair phase is where most of the calories and metabolic improvements are noticed.
There is another type of exercise that is also extremely effective at stimulating this post-exercise hormonal and metabolic benefit, called High Intensity Training. The idea is that instead of running at say 75% capacity for 40 minutes, you sprint at full capacity for 30 seconds or so, followed by a short rest period of 90 seconds or so, and then repeat the pattern up to 8 times. Anyone who did high school sports will remember this as the basic idea behind "wind sprints."
Apparently, pushing your body into the anaerobic zone for short periods of time stimulates your body to burn fat and release growth hormone, and the metabolic benefits from this type of exercise will be much greater than the energy burned during the exercise. Remember how easy it was to stay lean and energetic when you were 18? That was the growth hormone. Getting the hormones to do the work for you is much easier than trying to work your way there one calorie at a time. So in some ways, HIT is a way of cooperating with how your body functions instead of working against it, and a way of working smarter rather than harder.
Now, this type of exercise won't necessarily release the endorphins that more endurance style running does, and it is a bit of a beating in the sense that you are really working hard, so it is not relaxing and zen like endurance running is. But -- if you are pressed for time, you can get through 8 repetitions of these cycles in about 15 minutes, and this will have the same metabolic and hormonal benefit to your body as a 45 minute run. I do these on a rowing machine, so you don't really need a lot of space.
The basic idea is sprint or row as fast as you possibly can for 30 seconds. At the end of this time you should be breathing hard, feeling like you can hardly go any further, and should have broken out in a light sheen of sweat. Gently row or walk for 90 seconds, then start the cycle over with another 30 seconds of hard sprint.
In the beginning, you likely won't be able to do more than 4 or 5 cycles. Don't push it. As your muscles start to store more energy and your anaerobic capacity increases, you will be able to increase the number of cycles until you reach 8. Up to 3 times per week is a good number of times to do this exercise.
Here's some links to studies with quotes underneath from the articles:
One of the most remarkable findings from our recent studies was the dramatic improvement in exercise performance during tasks that rely mainly on aerobic energy metabolism, despite the very low training volume. In our initial study, subjects doubled the length of time that exercise could be maintained at a fixed submaximal workload from approximately 26 to 51 min during cycling at 80% of pretraining V˙ O2peak V after only 6 HIT sessions over 2 wk.
The Scientific Basis for High-Intensity Interval Training
In summary, HIT in sedentary and recreationally active individuals improves endurance performance to a greater extent than does continuous submaximal training alone.
Exercise I (aerobic) consisted of continuous cycling at 100 W for 20 min. Exercise II (anaerobic) was intermittent cycling for one minute at 285 W followed by two minutes of rest, this cycle being repeated seven times.
GH levels were higher in anaerobic exercise (II) than in aerobic (I) at the end of the exercise (20 min) (2.65 +/- 0.95 micrograms X 1(-1) vs 0.8 +/- 0.4 micrograms X 1(-1); P less than 0.10) and into the recovery period (30 min) (7.25 +/- 6.20 micrograms X 1(-1) vs 2.5 +/- 2.9 micrograms X 1(-1); P less than 0.05, respectively)
High-Intensity Intermittent Exercise and Fat Loss
Research examining the effects of HIIE has produced preliminary evidence to suggest that HIIE can result in modest reductions in subcutaneous and abdominal body fat in young normal weight and slightly overweight males and females. Studies using overweight male and female type 2 diabetic individuals have shown greater reductions in subcutaneous and abdominal fat. The mechanisms underlying the fat reduction induced by HIIE, however, are undetermined but may include HIIE-induced fat oxidation during and after exercise and suppressed appetite.
No exercise type is perfect, all are tools that should be used in combination, but when you need to most bang for your buck, this is a good tool to use!
