Assuming that you are in good physical condition and have built a reasonable aerobic base (you're comfortable at sustained running for 30 minutes or more on a regular basis), interval training can be your best choice for improving fitness, developing running economy, and getting faster.
You do not need to be a competitive athlete to make effective use of intervals in your training. Interval training can improve your running ability whether you run a 10-minute mile or a 20-minute 5K.
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Running an interval involves running at a faster pace than your usual aerobic pace. You know you are running aerobically if you are able to talk in complete sentences while you're running. A pace that requires more huffing and puffing, a step up from your aerobic pace, is run for a predetermined length of time, with a recovery jog interval, and repeated for a set number of repetitions.
These are intervals and they serve to improve the efficiency of the oxygen delivery system to your muscles. The result over time will be measurable improvements in speed, endurance, and efficiency.
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According to Jack Daniels, Ph.D., interval mileage should be capped at 8 percent of your total weekly mileage in any given quality workout. If you are running 25 miles a week, devoting a couple of miles to a quality workout with intervals a couple of times a week is reasonable and will produce results.
If you are new to interval training, try this workout twice a week in place of your regular run for four weeks. After four weeks you can increase the interval length to two minutes. Always remember to warm up and cool down adequately.
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Warm up for 10 minutes at an easy jog.
Run at interval pace (a step up from your usual pace) for one minute.
Jog for a two-minute recovery interval.
Repeat four times.
Cool down for five minutes and stretch.
If you are a more experienced runner with a higher mileage base, your intervals can be easily adjusted for your fitness level. Remembering the 8 percent cap on interval mileage, interval pace can be about your 5K pace, faster for shorter intervals, slower for longer intervals ranging from 30 seconds to five minutes. As a rule of thumb, your recovery interval should take about as much time as your working interval.
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