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Interval training: a good way to cross train

Interval training is simply alternating bursts of intense activity with intervals of lighter activity.

Interval training works both the aerobic and the anaerobic system. During the high intensity effort the anaerobic system uses the energy stored in the muscles (glycogen) for short bursts of activity. Anaerobic metabolism works without oxygen. The by-product is lactic acid, which is related to the burning sensation felt in the muscles during high intensity efforts. During the high intensity interval, lactic acid builds and the athlete enters oxygen debt. During the recovery phase the heart and lungs work together to 'pay back' this oxygen debt and break down the lactic acid. It is in this phase that the aerobic system is in control, using oxygen to convert stored carbohydrates into energy.

This repetitive form of training leads to the adaptation response. The body begins to build new capillaries, and is better able to take in and deliver oxygen to the working muscles. Muscles develop a higher tolerance to the build-up of lactate, and the heart muscle is strengthened. These changes result in improved performance particularly within the cardiovascular system.
Interval training also helps prevent the injuries often associated with repetitive endurance exercise, and they allow you to increase your training intensity without overtraining or burn-out. In this way, adding intervals to your workout routine is a good way to cross train.

Circuit training is a common method of interval training.

The benefits of Interval Training:

  • You'll burn more calories. The more vigorously you exercise, the more calories you'll burn even if you increase intensity for just a few minutes at a time.

  • You'll improve your aerobic capacity. As your cardiovascular fitness improves, you'll be able to exercise longer or with more intensity. Imagine finishing your 60-minute walk in 45 minutes or the additional calories you'll burn by keeping up the pace for the full 60 minutes.

  • You'll keep boredom at bay. Turning up your intensity in short intervals can add variety to your exercise routine.

  • You don't need special equipment. You can simply modify your current routine.

Rules for Interval Training

  • Undertake a period of Continuous running before starting Interval running.

  • Consider the various elements of the session and ensure that they are within the scope of the person in question.

  • The length of the work interval, longer gives a better effect.

  • The pace should be comfortable raising the individual's heart rate to the required % of MHR

  • The number of repetitions should reflect the condition and age of the individual.

  • The rest interval should enable the person to jog and bring the heart rate down to near 100-110 bpm

  • Improvements can be made by altering any of the variables, however the coach should only change one variable at a time.

  • All changes should be gradual in nature and take place over a period of time

  • Ensure the surface to be run on is flat and even. It is usual to do interval training on a track although it can be done on good quality grass playing fields. Roads are not a suitable surface because of the pounding effect.


Precautions for Safe Interval Training

  • Always warm up before starting intervals

  • Assess current condition and set training goals that are within your ability

  • Start slowly. (for example: walk 2 minutes/ run 2 minutes) In general, longer intervals provide better results

  • Keep a steady, but challenging pace throughout the interval

  • Build the number of repetitions over time

  • Bring your heart rate down to 100-110 bpm during the rest interval

  • To improve, increase intensity or duration, but not both at the same time

  • Make any changes slowly over a period of time

  • Train on a smooth, flat surface to ensure even effort

  • You can also use circuit training as a form of interval training

Variables used in an interval training program:

  • Intensity (speed) of work interval

  • Duration (distance or time) of work interval

  • Duration of rest or recovery interval

  • Number of repetitions of each interval


Interval training isn't appropriate for everyone. If you have a chronic health condition or haven't been exercising regularly, consult your doctor before trying any type of interval training.

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