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Beware The Moderate-Intensity Rut

Proponents of polarized training warn against too much time in the middle gear.

The not-too-hot, not-too-cold approach may have worked for Goldilocks, but it's actually counterproductive for fitness efforts. The average recreational athlete, according to Stephen Seiler, an American exercise physiologist based in Norway, spends 45 to 75 percent of his or her total training time at moderate intensity. But new research indicates that athletes of all ability levels get better results when they 'polarize' their training, doing lots of low-intensity exercise, a modest amount of high-intensity interval work, and little or no exercise at moderate intensity.

For a recent study on polarized training, a large number of cyclists, runners, triathletes, and cross-country skiers were required to balance the intensity of their training in four different ways for nine weeks. At the end of that period, the polarized group, whose members did more than two-thirds of their training at low intensity and most of the rest at high intensity, showed significantly greater improvements in aerobic capacity and performance compared to the other groups.

These results confirm the findings of previous studies, including a 2014 study in which recreational runners who did 78 percent of their running at low intensity and 22 percent at high intensity improved their 10K race times by 7 percent, whereas runners who did about half of their training at moderate intensity (as most endurance athletes do) improved by only 3.5 percent.

Why is polarized training so much more effective than the way most endurance athletes train? According to Seiler, low-intensity exercise enables athletes to move more efficiently in their physiological “low gears.” High intensity increases the capacity to push really hard in the top gears. “Too much training in the middle intensity range flattens this response,” Seiler says. “The athlete’s physiological transmission gets stuck in the middle gears.”

Breaking out of the moderate-intensity rut and taking advantage of polarized training is easy. There are just two steps:

Step 1: Learn the difference between low, moderate, and high intensity. At low intensity, you can speak comfortably in full sentences. At moderate intensity, you can speak a few words at a time comfortably. At high intensity you can’t speak comfortably at all.

Step 2: Plan and execute your training so that roughly 80 percent of your total training time is spent at low intensity and most of the remaining 20 percent is done at high intensity.

Note that, in high-intensity interval workouts, the whole interval block, including low-intensity recovery periods, should be counted as time spent at high intensity, because your heart rate will remain within the high-intensity range throughout it.

Here’s a one-week example: