There have always been competing training philosophies in the sport of distance running. At the most general level of classification, there are two training schools: the high-mileage school and the high-intensity school. Representatives of the high-mileage school believe runners should do most of their training at an easy pace--but lots of it. Representatives of the high-intensity school believe that it's better to run less but run hard.
While most competitive runners continue to favor the high-mileage approach, exercise scientists have lately found more merit in the high-intensity school. This belief is based on short-term studies in which the addition of high-intensity workouts to the training schedule of volunteers seems to improve their performance. I believe these studies need to be taken with a grain of salt, however, because they do not closely represent the real-world training environment of competitive runners.
It's very difficult to conduct truly valid scientific studies on the general effectiveness of specific training practices. The reason is that it's hard to adequately control the training of large groups of runners over extended periods of time. Some of the best studies on the effects of specific training practices in runners have been conducted by a team of researchers at the University of Madrid, Spain. And it so happens that a recent study by this team provides support for the philosophy that distance runners should do most of their training at an easy pace.
The team divided 10 high-level male runners into two groups. At the beginning of the study period, all 10 runners completed a 10.4-km time trial and their times were recorded. Over the next five months, the runners in the two groups trained identically except for one key difference. The members of one group did two threshold runs per week, while the members of the other group did just one. Their total training mileage, speed training schedules and strength training regimens were the same. The only difference was that the members of one group did more threshold running and less easy running than the members of the second group.
At the end of the study period, all 10 runners repeated the 10.4-km time trial. The members of the "threshold" group improved their time by 2:01, on average, while those in the "easy" group improved by 2:37. Statistical analyses revealed that such a large discrepancy was extremely unlikely to occur by chance. Therefore the researchers concluded that a training program in which 81 percent of running is easy, 10.5 percent is done at threshold pace, and 8.5 percent is done at speeds exceeding race pace is more effective than an equal-mileage program in which only 67 percent of running is easy, 24.5 percent is at threshold pace, and 8.5 is fast.
These results are very troubling for those who deem threshold training to be the holy grail of training for distance running. But it's important not to draw too extreme a conclusion from this study. The runners in the "easy" group trained pretty hard, and those in the "threshold" group arguably trained foolishly hard, even by the standards of most representatives of the high-intensity school. Take a closer look at those numbers in the "threshold" training regimen: 24.5 percent of their weekly miles were run at threshold pace (plus another 8.5 at speed pace). I've never known of any runner who did such a high percentage of his or her training at such a high intensity level. Here's an example of a week of training that fits this breakdown: