Once the domain of elite athletes, interval training has become a powerful tool for the average exerciser. And it's not complicated -- it just means that you alternate bursts of intense activities with intervals of lighter activities.

What is it? Interval training has been the basis of athletic training for years. Originally called "fartlek" (the English translation is "speed play"), it involves alternating short, fast bursts of intensive exercise with slow, easy activity. These work-rest intervals were first measured by how the body feels rather than a set time, making this interval style less structured.

Over the years since the development of this form of training, interval programs have become highly sophisticated methods of structured training for athletic performance. Interval training can be designed specifically for an athlete's sport, event and individual training needs.

Who'd like it? You don't need to be a world-class athlete to benefit from interval training -- it's well-suited for fitness enthusiasts with general health and fitness goals.

The key benefit is that it enables you to work out at a higher intensity for a longer period of time by alternating high-intensity work with low-intensity intervals. This kicks your body's physiology into high gear.

By working out at higher intensities -- even for short periods of time -- you'll burn more calories and increase your aerobic capacity, working both the aerobic and anaerobic energy systems. This ultimately trains the body to be able to handle more work at any given intensity. Basically, exercise and sport performance feels easier.

The sweat factor Interval training can be extremely intense or moderately intense, depending on the interval program structure. The standard "speed play" training works well for most people and is easy to do.

For example, while walking, add intensity by walking or jogging at a faster pace until your heart rate elevates to a level higher than you are used to training at. Follow this by continuing to walk at your regular pace, lowering the heart rate to a comfortable level. Once you feel recovered, repeat the harder interval. This would be done for a set number of repetitions or total exercise time.

For elite athletes, the intensity of interval training is very high and needs to be monitored by a trainer.

The klutz factor Intervals can be structured or unstructured, so the complexity and difficulty of the intervals will vary.

For elite athletes, the appropriate intensity and duration of the intervals is determined by the results of anaerobic threshold testing that includes measuring the blood-lactate of an athlete during intense exercise.

Most people don't need to go that far, though -- just don't push yourself so hard during the intense intervals that you risk injury or klutz-inducing levels of fatigue.

What do you need? You don't need any specific equipment for interval training. Take the activity you are currently doing and add bursts of higher intensity exercise into your routine.

For timed intervals, you will want to invest in a sports watch or stop watch.

Where do you find it? If you are working toward a specific fitness goal, you may want to take a more scientific approach. Attend a group fitness class or consult a personal trainer or athletic coach to help you design an interval program specific to your needs and goals.

What are the costs? Nothing if you add it to your current exercise routine.

Bottom line Add a little interval training to your program and you will be surprised at the results.

Interval training will boost calorie expenditure and increase performance, so whether your goal is to lose weight or increase your sports performance, interval training is for you.

The other benefit of interval training is that it can decrease the boredom factor by adding a little play to your workout routine.

Helen Vanderburg is a trainer, corporate wellness speaker and owner of Heavens Fitness in Calgary.