Sprint to the finish line?
An occasional sprint does more than just get you there faster...
Did you ever think that you could gain all the benefits of working out long each day by just working out harder for less? This concept was behind the development of the 4-minute exercise gyms that sprouted up around the country in the past decade.
Now a new study confirms that the inventors of the short, intense workout machines may be on to a good thing, and here's why:
According to the latest research published in February 2009, doing 7.5 minutes of intense exercise each week is just as good as 30 minutes of moderate physical activity done every day when it comes to reducing your risk of developing type 2 diabetes (or insulin resistance if you have type 1), and maybe even more so.
Researchers located in the United Kingdom reported that that young, sedentary men who did 15 minutes of all-out sprinting on an exercise bike (broken down into 4 to 6 30-second sprints with four minutes of rest between) over two weeks substantially improved their ability to metabolize blood sugar after drinking 75 grams of glucose (that is, during an oral glucose tolerance test that is used to diagnose insulin resistance or diabetes).
From an exercise physiology point of view, I understand fully that the reason that intense exercise may be helpful is that it causes you to recruit more muscle fibers than moderate exercise and consequently use up more stored carbs (glycogen) in less time. It also helps you retain the muscle fibers you would lose over time if you don't recruit them--which is mostly the ones that you only recruit while sprinting or doing intense weight training. You likely won't get as fit doing this compared with endurance activities, but it's an interesting idea nonetheless.
Why any type of faster intervals may work just as well
For decades, the standby exercise prescription has been 30 minutes of moderate exercise (like brisk walking) most days of the week. This is problematic for two reasons: 1) most individuals are not making the time to meet this recommendation as it is; and 2) doing moderate exercise does not recruit the muscle fibers that you're most likely to lose as you age (the fastest twitch fibers). So, if all you ever do is moderate walking, you'll end up with substantially less muscle mass over time.
A viable alternative is to add any length of faster intervals into your moderate walking sessions. This includes walking even just 10 percent faster between two light poles every couple of blocks or doing a hill profile on a treadmill. By doing so, you'll recruit more of those faster fibers (and if you use them, you don't lose them), use up more stored carbs, and get physically fitter--even if you exercise for less than the recommended 30 minutes. Adding in intervals is easier to do than sprinting--and likely a lot safer for older and unfit individuals--and can be just as effective in the long run.
A word to the wise: Start out slowly if you haven't been doing anything intense and work up to that higher level slowly. And after reading all this, you still don't think you have time for less than 8 minutes of vigorous exercise a week, we need to talk...
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