Anaerobic capacity has been found to be the second greatest predictor of 5K performance after aerobic capacity.
Running is considered an aerobic sport, and rightly so. No factor is more important to running performance than the capacity to withdraw oxygen from the environment, deliver it to the working muscles, and use it to liberate energy from glucose, fat, and other fuels. An increase in this capacity is one of the most salient effects of training, and those athletes who are fortunate enough to have been born with a naturally high aerobic capacity are invariably the best distance runners.
Aerobic capacity is not everything in running, however. Other factors matter as well. These factors include raw speed, anaerobic work capacity, and running economy. A runner who has a little less aerobic capacity and a little more of these other factors can still do great things. And every runner can benefit from training to increase his or her speed, anaerobic capacity, and running economy alongside his or her aerobic capacity.
Speed and anaerobic capacity are related. Speed is, obviously, measured as the maximum speed a runner can attain in a very short sprint. Short sprints are fueled entirely by anaerobic metabolism in the working muscles. If you were to hold your breath while running a 50-meter sprint, your performance wouldn’t suffer, because your muscles don’t need any oxygen to fuel a maximal effort lasting only a few seconds.
Anaerobic capacity is defined as the amount of extra work you are able to perform in running beyond your aerobic capacity. When you sustain a fast but submaximal speed long enough, your body will reach a point at which it is consuming oxygen at the highest rate it possibly can. Yet you can still speed up a little from that point and continue running for a little while before you’re forced to quit in exhaustion. What allows you to do so is the capacity of your muscles to fuel extra work anaerobically, without the aid of addition oxygen. When you perform work in running that goes beyond your maximal rate of oxygen consumption, your body accumulates what is known as an oxygen deficit. Oxygen deficits can be calculated when a running test is performed in an exercise laboratory setting. It is simply the difference between the amount of oxygen you actually consume in such a test and the amount of oxygen your body would have to consume to do the amount of work performed in the test entirely aerobically. The largest oxygen deficit you can accumulate in such a test is a measurement of your anaerobic capacity.
Researchers at Georgia State University sought to determine how much raw speed and anaerobic capacity contributed to 5K performance in collegiate female cross-country runners compared to aerobic capacity. Thirteen runners participated in the study. Each of them ran a set of 50m sprints to determine her maximum speed, completed tests of aerobic and anaerobic capacity, and ran a 5K time trial on the track. Measurements of running economy and ventilatory threshold (which is basically the speed at which a runner begins breathing hard) were also taken.
Interestingly, anaerobic capacity was found to be the second greatest predictor of 5K performance after aerobic capacity. Individual differences in anaerobic capacity explained 31 percent of the individual differences in 5K times. Aerobic capacity and ventilatory threshold combined explained another 50 percent of 5K performance.
The authors of this study, which was published in the International Journal of Sports Physiology and Performance, concluded, “These results suggest that among trained female runners that are relatively matched, anaerobic energy production can effectively discriminate the [5K race pace] and explain a significant amount of the variation seen in 5-km race performance.”
What does this mean for you? It means that you should not neglect anaerobic development in your training, as many runners do. To increase your aerobic capacity you need to do workouts that take your body to the point where it is consuming as much oxygen as possible and then force it to do additional work beyond that point. It’s not fun, but it’s very effective and a little goes a long way.
The most effective type of workout to build anaerobic capacity is a set of intermediate-distance intervals. For example, go to the track, warm up, and run eight times 800 meters (two laps) hard with 200m jogging recoveries between intervals. The idea is to run the intervals just a hair slower than the fastest pace you could sustain through the end of the last interval without bonking.
Feel free to curse me for suggesting this workout while you’re doing it.
About The Author:
Matt Fitzgerald is the author of Iron War: Dave Scott, Mark Allen & The Greatest Race Ever Run (VeloPress 2011) and a Coach and Training Intelligence Specialist for PEAR Sports. Find out more at mattfizgerald.org.