Sprinting an entire 5K race is probably not possible, but a sprinter can be trained to run a 5K with little difficulty. As one of the shortest distance races, 5Ks don't require six months of tough training. Emphasizing your long-distance muscle fibers while maintaining some of your sprinting muscle fibers is an effective way to prep for a 5K race. Intervals, tempo runs and walk breaks can help you transition from sprinter to long distance runner.
Fast-Twitch and Slow-Twitch Muscle Fibers
Skeletal muscles are comprised of fast- and slow-twitch fibers. Fast-twitch fibers are used for sudden or high-intensity movements, like jumping or sprinting. These fibers don't use oxygen to make energy, and fatigue quickly. Slow-twitch fibers contain more blood vessels, and have a large supply of oxygen to make fuel. You use these fibers when running over distances at moderate and low intensity. Most muscles have a mix of each type, depending on how you typically use them. If you are a sprinter, you likely train your muscles to utilize fast-twitch fibers more often. As a result, you need to emphasize the slower muscle fibers to complete a 5K distance.
To encourage slow-twitch muscle growth without sacrificing too much speed, you can combine distance running with middle distance workouts, such as running 400-meter intervals. Hal Higdon, author of "Marathon: The Ultimate Training Guide," suggests intermediate-level runners schedule a day of 400-meter interval training into their week. In a seven-day week, try running three miles on two weekdays, at a low to moderate pace. Put a 400-meter workout on the day between your three-mile runs. Higdon suggests starting with five 400-meter sprints the first week. Add another three-mile run on Saturday, and try a five-mile run on Sunday. Give yourself two days off during the week to rest.
Tempo runs are another way to build up your long-distance muscles while maintaining fast-twitch fibers. During a tempo run, you mix up your pace. For instance, you can jog for five minutes, pick up the pace for 200 meters, jog again and then sprint for 100 yards. Higdon recommends aiming for time rather than distance. Add a 35-minute tempo run into your workout schedule, replacing the 400-meter sprint workout every other week. You can increase the tempo run's time as you progress.
Taking walk breaks during training, and even during the race, is recommended by Jeff Galloway, author of "Run Injury Free." Alternating running and walking from the onset of your training increases your recovery without losing endurance gains. Walking helps your muscles remain in an aerobic state, meaning they have sufficient oxygen for fuel. Sprinting uses anaerobic, or without oxygen, processes to create energy, and is less efficient. Staying in an aerobic state reduces muscle fatigue and prevents lactic acid buildup, allowing you to run more easily over longer distances.