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5K Race

Runners' True Test

Published May 25, 1998, in The Post-Standard.

By Dr Kamal Jabbour, Contributing Writer

Every weekend, the race calendar contains one or more local 5K races. Charity events and fun runs feature 5K races. The distance of 5 kilometers, or 3.1 miles, is short enough to walk within an hour, yet long enough to give it some legitimacy as a distance event. As a result, the 5K road race has become an integral part of the American running scene.

A beginner's first race is almost always a 5K. Many seasoned runners stay away from 5K races, preferring the endurance of the longer distances. In doing so, they miss out on what may be the true fitness test of running.

Running relies on a mix of aerobic and anaerobic energy to achieve optimal performance. Short sprints rely almost entirely on anaerobic power, while marathons use pure aerobic energy. A runner's pace decreases as the distance of the race increases. As a result, long distance events are contested at a fraction of a runner's all out pace, and use only a portion of the runner's maximum aerobic capacity.

Maximum aerobic capacity VO2max is measured in milliliters of oxygen consumed per minute per kilogram of body weight. In his landmark book on sports physiology, Inside Running, Dr. David Costill reported that runners use close to 100 percent of their VO2max when running a 5K race, about 85 percent for a 10-mile race, but require only 70 to 80 percent of VO2max when running a marathon.

These results suggest that VO2max is the main predictor of 5K race performance. At longer distances, VO2max and efficiency combine to determine race performance. For example, a runner with a VO2max of 65 performing at 80 percent will beat a runner with a VO2max of 70 performing at 70 percent.

While VO2max remains a leading predictor of maximum performance, a distance runner's training must include components to increase VO2max, as well as increasing efficiency. In this context, efficiency refers to a runner's ability to operate for long periods of time near their VO2max. While mere mortals run marathons at about 75 percent of their VO2max, legends Bill Rodgers and Grete Waitz used to run the whole way at 90 percent of their VO2max.

The only accurate measurement of VO2max is performed on a treadmill with a breathing mask. The concentration of oxygen is measured in the runner's air intake and exhaust, leading to the computation of VO2max. However, since most athletes do not have access to such equipment, the 5K road race becomes a good substitute.

You can use the following formula to estimate your VO2max: VO2max=125-3.6*T, where T is your 5K race time in minutes. According to this formula, 15-minute, 20-minute and 25-minute 5K runners have VO2max of 71, 53 and 35 respectively.

Training with slow long distance runs will improve your marathon performance, but may not necessarily improve your 5K time. The reason is that long slow distance runs increase your efficiency in burning oxygen, but they do not increase the rate of your oxygen intake.

Since 5K races require only a few days of recovery, it may be a good idea for an athlete in training to race hard a 5K about once a month. Extraneous parameters being equal, such as stress, nutrition, hydration and rest before the race, a 5,000-meter time trial on the track may be the best test of current fitness, and a predictor of potential performance at longer distances.

Fortunately, the Central New York running calendar is packed with 5K races. A certified, flat course with few turns is a good substitute for an outdoor track, and yields good results. My favorite 5K run is on Onondaga Lake Park, starting at the Onondaga Yacht Club. There, the course is certified and closed to vehicles, the pavement is flat like a pancake, the mile markers are permanent, there is only one turn, after which the wind is to your back all the way to the finish.

Kamal Jabbour estimated his VO2max at 55 ml/min/kg. His RUNNING Column appears in The Post-Standard on Mondays. He maintains The Syracuse Running Page and receives email at jabbour@syr.edu.


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