The "100/0" Phase of 80/20 Endurance: You might be wondering: If this is an 80/20 Endurance plan, why are there no hard interval days? Because true beginners are not ready for the "20." Before your body can safely handle high-intensity speedwork, your bones, tendons, ligaments, and cardiovascular system need a massive foundation. For an absolute beginner, the safest and most effective ratio is 100/0 (100% easy aerobic effort, 0% high-intensity). This 12-week protocol uses the famous ...