Sprinting for Gold
Sprint runners will tell you that most of them have the same goal with each run or training session: get faster. For Olympic runners, the difference between silver and gold can be measured by hundredths, if not thousandths, of seconds. One way a runner can increase his overall speed is by interval training.
Running in sprints involves a distinctively different style and skill set than distance running. Sprinters must rely almost completely on anaerobic energy, where the body is burning the oxygen already in the body as opposed to taking in oxygen constantly through paced breathing as distance runners do. While sprinting for 10 seconds, a competitive runner doesn't have time to purposefully inhale and exhale because it uses too much energy that must be devoted to speed.
This anaerobic energy is stored inside the muscles. Once your body finishes an anaerobic metabolic period, it releases lactic acid that can cause cramping. Your body comes to a stop; your heart and lungs start to replenish the oxygen and energy spent during the anaerobic period.
How Interval Training Helps
Interval training actually trains your body to extend the anaerobic capacity so that you can sprint faster and longer. Interval training involves a highly intense workout followed by short periods of recovery followed by another intense workout. One example involves changing speeds while running laps. During an interval lap, the runner starts off with a slow jog for a quarter of a lap. He then builds up to a fast jog for another quarter of a lap and then an all-out sprint for half a lap. After the sprint, the runner fast jogs for another quarter lap and then slow jogs for half a lap and start the cycle again for at least 1 mile.
During interval laps, the periods of intensity utilize anaerobic metabolism that builds up lactic acid. During the slower speeds, your heart and lungs help dissipate the lactic acid by pumping in oxygen-rich blood to those leg muscles. Once the muscles are full of oxygen, they can handle another anaerobic period before returning to aerobic metabolism. As these different cycles happen, your leg muscles are slowly building stronger capillaries, able to handle more and more before reaching the point of fatigue. As a result, instead of slowing down towards the end, a sprinter can maintain high speeds for longer periods.