Interval training, the geeky term for alternating bursts of intense effort with more moderate effort while exercising, has been all the rage in recent years. Now comes a more extreme version of interval training that sports physiologists call high intensity interval training, or HIIT (of course). It consists of very short–30 second –efforts at very intense–maximum- effort. Can anything so short and so hard really do any good? Writing in the New York Times, Gretchen Reynolds reports that researchers at McMaster University in Hamilton, Ontario found that six weeks of HIIT has pretty much the same benefit in the leg muscles of young men as multiple, hour-long sessions per week of steady cycling, even though the HIIT workouts involved about 90 percent less exercise time. Impressed, the researchers tested a workout that is a little longer and a little easier: a one minute workout at about 90 percent maximum heart rate (your age, subtracted from 220), followed by one minute of recovery. Reynolds reports that the researchers found that several weeks of doing 10 repetitions of the exercise resulted in significant gains in fitness and health. Read more in the New York Times.