“Reduced intensity” HIT: the Flutter of exercise
Anyone remember this Twitter spoof video from back in 2009, when Twitter was just catching on? It’s all about “Flutter,” which “takes microblogging to the next level” by restricting the length of each message to 26 characters instead of 140 characters. Nanoblogging, they call it.
I couldn’t help thinking of this when I read this new study in the European Journal of Applied Physiology about “reduced-exertion high-intensity interval training” (REHIT). Over the last few years, high-intensity interval training (HIT) has gotten a lot of attention as a time-efficient way of getting many of the health benefits of aerobic exercise. There are various protocols — the classic is four to six 30-second sprints with 4:00 easy jogging or cycling to recover between each one; another common one is alternating bouts of 1:00 hard with 1:00 easy. These workouts seem to be highly effective at improving traits like insulin sensitivity. But there’s a catch, according to the authors of the new study:
However, whilst these observations [about HIT] are interesting from a human physiological perspective, their translation into physical activity recommendations for the general population is uncertain for two reasons. First, the relatively high exertion associated with ‘classic’ HIT sessions requires strong motivation and may be perceived as too strenuous for many sedentary individuals. Second, although a typical HIT session requires only 2–3 min of actual sprint exercise, when considered as a feasible exercise session including a warm-up, recovery intervals and cool-down, the total time commitment is more than 20 min [gasp!], reducing the time efficiency. Thus, there is scope for further research to determine whether the current HIT protocol can be modified to reduce the levels of exertion and time-commitment while maintaining the associated health benefits.
In other words, the “140 character” version of exercise is still too damn long, so we need to shorten it to 26 characters!
So here’s the protocol they used. The subjects (29 sedentary young men and women) did three workouts a week for six weeks. Each of these workouts was exactly 10 minutes long, and consisted almost exclusively of “low intensity” cycling, at 60 W. This is very easy. During each 10-minute workout, the subjects incorporated two 10- to 20-second hard sprints. That’s it. Lo and behold, the men in the REHIT group increased their insulin sensitivity by 28%. Strangely, the women didn’t improve — it’s not clear why there was a gender difference. It may be that the very short sprints are most useful for men, who tend to be more powerful and thus are able to burn through more glycogen in a short time.
Anyway, there you have it: REHIT, the Flutter of exercise. I have to admit, part of me finds this a little funny. Soon we’ll be doing studies to show that, if you’re really and truly unfit, just blinking your eyes will allow you to make “measurable gains” in fitness parameters. On the other hand, the barriers to getting people to exercise really are tough to beat. I’m always encouraging my parents to do a little HIT rather than just stick to low-intensity activity — and they do, but they’re rarely motivated to spend more than 10 minutes in total. So it’s encouraging — and useful — to know that even a very minimal bout of high intensity will help. In the end, though, the message is pretty much what we already knew: every little bit helps — but more is better.