One of the aims of interval running is to get the body used to running fast for a long (overall) period of time. Interval work allows you to do huge amounts of mileage at fast running pace--yet without wearing yourself out. Achieve the target speed, then emphasize improving endurance at that speed. Add about half a mile of reps each time you do a particular session. For instance, a nine session program might look like this. 12 times 300 meters at two mile pace 10 x 400 meters at 5k pace 8 x 600 meters at 5k pace 15 x 300 at two mile pace 10 x 400 ONE second per rep faster than 5k pace 10 x 600 at 5k pace either 18 x 300 at two mile pace; or, 15 but with a shorter recovery 10 x 400 at two mile pace (2 seconds a lap faster than 5k pace) 12 x 600 at 5k pace Note how each distance progresses in a different way. Only you and your body can set the limit on the number of reps. Each time you increase the speed of your reps, a greater proportion of the repetition is anaerobic. As you get stronger; as your muscles get used to the new speed; as your body learns to process more oxygen, (with a nudge from your steady runs), it becomes more aerobic. Over a series of interval sessions, the anaerobic training changes to aerobic training: You will be able to race faster. You can make a conscious effort to run every fourth rep a second or two faster to break up the session. You need to avoid running 400s or 200s week in, week out. Doing the same session will only make you good at running that session. The 200s and 300s do something for you which the 400s wonít. Donít miss out on their benefits. Progress will be phenomenal for several sessions, but be prepared for it to slow as you get close to your potential--the potential at your current level of training. Keep the speed of reps in a proper relationship to your race pace. Run the 300s at 3,000 meters (or two mile) pace; run 400s at 5,000 meters pace. Gradually increase the speed of 400s to run 3000 meter pace. Aim towards 6,000 meters worth in each interval session.
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