How Running Makes You Less Fit

Published December 22, 2010 08:51AM

Chances are you are slower over very short distance than your couch potato twin.

In exercise science laboratories, the Wingate test is often used to assess various dimensions of fitness. It’s a simple, unpleasant test consisting in 30 seconds of all-out pedaling at a fixed resistance level on a stationary bike. Power output is recorded in five-second intervals throughout the protocol.

As you might imagine, Wingate test subjects almost always achieve their peak power output in the first five seconds of the test. After that, power begins to decline as the subject fatigues. The power output level in the first five seconds of a Wingate test is therefore a good assessment of maximum power output capacity in the legs. Trained strength and power athletes typically put up the best numbers in this part of the test.

The average power output for the full 30-second span of the test is a decent measure of a person’s anaerobic capacity—that is, a person’s capacity to sustain very high levels of work output. Anaerobic capacity is largely a function of anaerobic glycolytic metabolism, which is the use of carbohydrate to fuel muscle contractions without the aid of oxygen. As you might expect, athletes who engage in a lot of anaerobic efforts in their training and competition tend to put up the best numbers in this aspect of the Wingate test. Think hockey players and boxers.

The Wingate test can also be used in a somewhat oblique way to assess aerobic capacity. As I mentioned above, in the typical Wingate test, peak power is attained in the first five seconds of the test and then power declines through the remainder of the test. However, there is a high degree of inter-individual variation in the rate of power loss. Trained endurance athletes tend to lose significantly less power than other types of subjects. That’s because a Wingate test is not a purely anaerobic challenge. Endurance athletes are able to call on their well-developed aerobic systems to help out their failing anaerobic systems as the test wears on.

Here’s an interesting fact: On average, trained endurance athletes record lower peak power outputs in a Wingate test than completely untrained, sedentary couch potatoes. Put another way, if you performed a Wingate test in a state of peak 10K race fitness, then stopped running cold turkey for eight weeks, and then did another Wingate test, you would more than likely record a better peak power number in the second test.

But is that a good thing or a bad thing? The answer is complicated. It certainly is not necessarily a bad thing. In a study performed a number of years ago, researchers took measurements of various characteristics of the muscle fibers of collegiate cross country runners over the course of a season. They found that the maximum force production capacity of individual muscle fibers decreased. But the cross-sectional area of individual fibers decreased even more. In other words, the muscle fibers basically shrunk. In fact, they shrunk enough so that the ratio of maximum force production to cross-sectional area of the muscle fibers actually increased. Loosely put, the runners got weaker, but they also got smaller, such that their “strength-to-size” ratio improved. And oh, by the way, so did their running performance.

Endurance training works like this: It curtails an athlete’s top-end speed, but it increases the percentage of top-end speed that he or she can sustain over race distances even more.

Does endurance training necessarily curtail top-end speed, though? I don’t think this question is quite answerable as framed, but I can say this: Plenty of research has shown that endurance performance improves when athletes make some training efforts to preserve their top-end speed.

These efforts must not go too far, however. A long time ago I read an article about how endurance athletes train all wrong, which was written by a well-known expert on…weightlifting. He argued that endurance athletes should try not merely to preserve but to increase their maximum speed. His logic went like this: If your 10K speed is 50 percent of your maximum speed, and your maximum speed is 18 mph, then you can run a 10K at 9 mph (or in 41:20). But if you increase your maximum speed to 20 mph, then 50 percent of your maximum speed becomes 10 mph. Now you can run a 10K in 37:12.

Except it doesn’t work like that. The problem with this weightlifting expert’s argument is that the training required to increase your maximum sprint speed will reduce—sharply, in most cases—the percentage of maximum speed that can be sustained over long durations. So the runner who begins with a maximum speed of 18 mph and the ability to sustain 50 percent of that speed over 10K, and who then increases his or her maximum speed to 20 mph, is now able to sustain only 40 percent of his or her maximum speed over 10K and goes from a 41:20 10K runner to a 46:30 10K runner.

I think there’s a happy medium. Distance runners stand to perform best in races if they do more sprint training than distance runners typically do but not so much that speed gains come at the expense of endurance gains. Besides, you don’t really want to lose a Wingate test to a couch potato, do you?