In an e-mail many years ago, a runner shared her running history and training regiment with me.

She explained that she had had no great love of athletics growing up and that the only reason she started running in her mid-30s was to lose weight. But by the time she had progressed to running two miles four or five times a week and her unwanted girth was gone, something else had grown: her enjoyment of running and the desire to do more.

She entered a local 5k race and loved everything about it except the amount of time it had taken her to finish. While she knew she'd never win a race, she didn't want to finish with the stragglers again either.

So she built up to running four or five miles a day five or six times a week a month before she entered another 5k. She was convinced the extra training would produce a faster time, especially when she found the course to be flatter than the first.

She was crushed, therefore, when she crossed the line only three seconds faster than before. She had been expecting more like a two-minute improvement.

The request at the end of the e-mail: She wanted me to tell her where she went wrong.

It was obvious. She had wanted to go faster, yet her training had developed something else: the ability to go longer at the same speed.

I suggested fewer total miles for a while, but for quarter- and half-mile segments of her training runs to actually be faster than the pace she wanted to sustain for an entire 5k race. I concluded my response with an aphorism about training I had read more than once: "To go faster, you must go faster."

Maybe the matter-of-factness of the saying offended her, for she never contacted me again.

But the saying has scientific merit. A study published in May by the Journal of Applied Physiology and currently available as an abstract online not only supports the saying but also uncovers less apparent health benefits to exercising less but harder.

University of Copenhagen researchers Professor Jens Bangsbo and graduate student Thomas Petursson Gunnarsson had what they described as 10 "a moderately trained runners" cut their training time in half. In the remaining training time, however, they followed the 10-20-30 training concept, a method of training developed by the Department of Exercise and Sport Sciences at the university that subjectively increases intensity but decreases total running time.

The 10-20-30 training concept, as explained by Medical News Today, consists of about a half mile warm-up that leads to 5 back-to-back 1-minute blocks where the runner constantly changes speeds. The first 30 seconds are performed at a low intensity; the next 20 seconds, a moderate one; the final 10 seconds, 90 percent of maximal effort.

After one such block, the runner rests for 2 minutes. He or she then performs the same pattern two or three more times before a brief cool-down.

After seven weeks of these workouts, the 10 were timed in a 1500-meter run. Even though this distance is relatively short, about 100 yards shy of a mile, when compared to a pretest, the average improvement by the runners was 21 seconds. When the test distance increased to 5k (about 3.1 miles), the improvement increased to 48 seconds.

Along with the decreases in running time came an increase in maximal oxygen uptake, usually referred to as VO2-max and considered a key indicator of fitness, by 4 percent even though overall running volume for the seven weeks was down 54 percent.

A bigger surprise to the study were the decreases in blood pressure and cholesterol in the blood that the 10 subjects who followed the 10-20-30 training concept decreases that were not experienced by a control group of 8 who continued the typical longer and slower running regiment.

But the biggest surprise of the study were the results of emotional health questionnaires administered to all 18 subjects before and after the seven-week study. The 10 who followed the 10-20-30 training concept reported a reduction in emotional stress after the lighter training load, but the control group did not, placing in question the supposed "runner's high" that results from LSD, long, slow distance running.

While the University of Copenhagen study focused on running, the 10-20-30 concept should work for other forms of aerobic exercise, especially walking, stationary bicycle riding, and workouts on stair steppers and elliptical trainers.

If you'd like to try it but don't feel you're quite ready for the degree of intensity that the 10-20-30 concept requires, adjust your effort accordingly.

Most who have been doing typical, steady-state workouts of 30 minutes or more should probably be able to handle 10 seconds of near maximal effort if it comes after 50 seconds of half of your normal steady-state intensity. After a week or two of that, you should be able to handle the pattern used in the aforementioned experiment.