"Fit in 6 Minutes a Week?"
When this was posted on the New York Times website...
...I got a lot of emails from athletes wanting to know if I thought it was something from which they could benefit. I guess there are a lot of people who have limited time to train. I certainly understand their dilemma. It's a common problem for those of us with jobs, families, and other responsibilities. (An athlete once jokingly told me that he was "sentenced to a 30-year mortgage and three kids.")
The above NY Times article describes a Japanese study in which the researchers had one group of rats swim for three hours on two occasions. Another group of rats was weighted down and put in the water to swim for 20 seconds, 14 times with 10 seconds of rest between "intervals." So one group of rats swam for six hours and the other for just short of five minutes. The article goes on to say that...
"Afterward, the researchers tested each rat’s muscle fibers and found that, as expected, the rats that had gone for the six-hour swim showed preliminary molecular changes that would increase endurance. But the second rodent group, which exercised for less than five minutes also showed the same molecular changes."
I've been unable to find this study so I'm not sure if these six-hour and five-minute bouts were repeated on subsequent days and, if so, for how many days. I also don't know what "molecular changes" are. So there is some mystery about what actually happened.
There's no doubt that intervals are the most powerful training tool available. The athletes I coach do them several times a week. This includes cyclists training for 45-minute crits up to Ironman triathletes preparing for 12-hour races. You can accomplish a lot in a short time with intervals. But the intervals for these two groups of athletes aren't the same. The crit riders are doing very short (12-30 seconds) sprints at maximal effort. The triathletes do long intervals (10-30 minutes) at a moderate intensity (zones 3-4 primarily). This is not to say that the crit racers never do long, lower intensity intervals and the Ironman athletes short, fast intervals. But the bulk of their interval training is similar to the intensity they will experience in a race.
This bings us to the principle of specificity. Basically this says that if you want to prepare your body (and mind) for a specific stressor (like an Ironman race) you need to do things in training that are similar to an Ironman race. But both groups of athletes in my example also do workouts that are dissimilar. For example, the crit riders also do long, steady rides, just not as long as the triathletes.
In the study notice that the scientists didn't give the rats the ultimate test: swim until they drown (I know this is cruel but it's been done by some researchers). I wonder which group would have lasted longer? We also don't know what all was tested for physiological adaptation. Did they measure VO2max? Aerobic capacity might well have been similar for the two groups of rats. But there are many elements of fitness that must change in order to produce a good physical performance.
I doubt if we will ever see someone win Ironman Hawaii after doing 6 minutes of intervals a week, as the article seems to imply is possible.
Should you do intervals? Without a doubt, yes. I have novices do them and they improve rapidly. I also have seasoned veterans do intervals and we always produce positive changes. And if you are short of time, by all means do intervals. One of the fastest ways to increase fitness is to do five, three-minute repeats on a hill at CP6 (your power or pace when at your VO2max) with three-minute recoveries. This session done twice a week will give you a high level of fitness in a few weeks. But there is not just one workout that leads to the highest performance in all events. There are many.