From Amazon:

A breakthrough program for triathletes — beginner, intermediate, and advanced — showing how to balance training intensity to maximize performance — from a fitness expert and elite coach.

Cutting-edge research has proven that triathletes and other endurance athletes experience their greatest performance when they do 80 percent of their training at low intensity and the remaining 20 percent at moderate to high intensity. But the vast majority of recreational triathletes are caught in the so-called “moderate-intensity rut,” spending almost half of their time training too hard–harder than the pros. Training harder isn’t smarter; it actually results in low-grade chronic fatigue that prevents recreational athletes from getting the best results.

In 80/20 Triathlon, Matt Fitzgerald and David Warden lay out the real-world and scientific evidence, offering concrete tips and strategies, along with complete training plans for every distance–Sprint, Olympic, Half-Ironman, and Ironman–to help athletes implement the 80/20 rule of intensity balance. Benefits include reduced fatigue and injury risk, improved fitness, increased motivation, and better race results.