Many triathletes who are pressed for time think they should train hard all the time to get the most from their limited workouts.
This is wrong and counter-productive.
Long distance triathletes should spend 60-75% of their entire training time at a Zone 2 pace to build aerobic capacity.
Dr. Iñigo San Millán, Ph.D., director of exercise physiology at Colorado University, explains some of the science behind why Zone 2 training is so essential. Much of it has to do with enhancing Type 1 muscle fibers, which increases your lactate clearance capacity and improves your fat-burning efficiency.