“There’s very good evidence” that high-intensity interval training provides “many of the fitness benefits of prolonged endurance training but in much less time,” says Chris Jordan, the director of exercise physiology at the Human Performance Institute in Orlando, Fla., and co-author of the new article.
Work by scientists at McMaster University in Hamilton, Ontario, and other institutions shows, for instance, that even a few minutes of training at an intensity approaching your maximum capacity produces molecular changes within muscles comparable to those of several hours of running or bike riding.
Interval training, though, requires intervals; the extremely intense activity must be intermingled with brief periods of recovery. In the program outlined by Mr. Jordan and his colleagues, this recovery is provided in part by a 10-second rest between exercises. But even more, he says, it’s accomplished by alternating an exercise that emphasizes the large muscles in the upper body with those in the lower body. During the intermezzo, the unexercised muscles have a moment to, metaphorically, catch their breath, which makes the order of the exercises important.
The exercises should be performed in rapid succession, allowing 30 seconds for each, while, throughout, the intensity hovers at about an 8 on a effort and discomfort scale of 1 to 10, Mr. Jordan says. Those seven minutes should be, in a word, difficult but bearable. The upside is, after seven minutes, you’re done.
Based on what I've learnt I've been trying out my own 'Twenty Plus' campaign; 20 seconds of intense activity when I can (running up stairs, cycling like crazy for short bursts on my bike), a minimum of 20 minutes of walking every day, and no more than 20 minutes of sitting at my computer or in front of the television without getting up and moving around.