Fartlek training is a Swedish method of speed training, in which you run intervals at various speeds; indeed, "fartlek" translates as "speed play." The difference between fartleks and regular interval training is that instead of measuring the intervals by time or distance, you measure them by how you feel. A heart rate monitor can be a valuable tool in showing you the difference between your perceived exertion and how hard you are actually working, and it gives you a way to track your progress.
Your Heart Rate
Subtract your age from 220 if you're a man or 226 if you're a woman to determine your maximum heart rate, the Walking Site instructs. Your heart rate monitor will do this for you, but it's still good to know this number. You should warm up at between 50 and 60 percent of your maximum; endurance training is done in the aerobic zone between 70 and 80 percent; speed work is done in the anaerobic zone between 80 and 90 percent. Depending upon your goal, you want to spend different amounts of time in each zone. Many heart rate monitors allow you to set alarms that will alert you when you reach a certain zone, and some will even alert you when it's time to speed up or slow down according to a pre-programmed workout.
Aerobic Versus Anaerobic
The aerobic zone trains you for endurance runs, where your body is using oxygen to power your muscles. This is where you learn how to go from a 10-kilometer race to a marathon, covering more distance at a slower speed. Your anaerobic zone is where you begin to place too much demand on your muscles for the oxygen supply to keep up, so your body turns to stored energy for fuel. This is where speed gains occur, where you train your muscles to contract very quickly for a short period of time. The anaerobic zone is not sustainable for an entire run, the American Council on Exercise warns.
Turning Intervals Into Fartleks
There are as many different types of interval workouts as there are coaches, and many such workouts measure the intervals by time or distance for the sake of convenience. To turn these workouts into a true fartlek, run the prescribed number of intervals based on how you feel. For example, the Saltin fartlek requires you to run hard for three minutes then jog for one minute, performing this back-and-forth six times for a total of 24 minutes, the Brian Mac Sports Coach website explains. Instead, try running hard until you can do so no longer, then jogging until you recover sufficiently to go again. You can vary the intensity by running more slowly or walking to recover, but over time, your recovery period will shorten as your body adapts. Your heart rate monitor can help you recognize when you are fully recovered as well as when you are giving all-out effort.
Endurance Versus Speed
To increase your speed, you must work at a higher intensity, usually around 90 percent of your maximum heart rate. This level is unsustainable, so the hard intervals are shorter. To build endurance, you work at a lower intensity during the hard intervals --- usually about 70 percent --- but the hard intervals should last longer. For endurance runs, your goal is to gradually extend the duration of the hard interval and keep your heart rate at a constant level. For speed intervals, you want to keep the duration of the hard interval the same, but gradually increase the intensity. Programmable heart rate monitors can alert you when your heart rate changes during an endurance run, or when you reach a target heart rate during speed work.
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