The other key lesson of this study is that athletes generally get more out of time spent at low intensity than they get out of time spent at moderate intensity. The subjects in the polarized group had the greatest imbalance between low-intensity and moderate-intensity training, and again, they improved the most. This lesson in particular should hit

The overzealous distance runner will want to work hard during these training runs and complete them at a moderate intensity, which in turn means that they are not fresh when it comes to the hot sessions and can only complete them at a moderately high intensity4.

Recent research also shows that runners wishing to improve their speed should spend at least 80 per cent of their time at low intensity, so beneficial is it to heart, muscle, skeletal and neurological health.