Long, slow endurance work does not cause leg soreness that prevents subsequent leg training, unlike high-intensity interval training (HIIT) which can lead to delayed recovery and inability to perform leg workouts.

“never are my legs so sore from that long slow endurance work, because it is long and slow, that I'm unable to train legs. Contrast that with a, say, high intensity interval training workout, which comes later in the week, and my legs might be sore. In fact, they might not even be recovered such that I'm able to do a real legwork, I want to say a real workout.”