Ask most endurance athletes what quality they’d like to develop in their sport, and many would say “I want to be stronger.” Ironic, then, because “stronger” means different things to different athletes. To one, it means durable: able to withstand continued stresses and discomforts. To another, it means powerful: able to generate greater force in less time. To still another, it means actually stronger: able to move a heavier weight (regardless of the speed of the movement)....