80/20 training plans get results. Multiple studies reveal runners, triathletes, and other endurance athletes improve the most when they consistently do 80 percent of their training at low intensity and the other 20 percent at moderate to high intensity. Virtually all professional endurance athletes obey this “80/20 Rule,” yet the typical recreational endurance athlete spends only 50-70 percent of his or her total training time at low intensity. This so-called “moderate-intensity rut” is by far the most common and costly training mistake that endurance athletes make. The solution? An 80/20 training plan that ensures the optimal intensity balance.