It’s an oft debated subject among distance runners: volume or intensity? Of course, the answer is both, but how much? Wouldn’t it be nice if someone had done a study, or two? Well, in fact someone has. Stephen Seiler and Espen Tønnessen surveyed the literature over the years, and they’ve come to the conclusion that “there is reasonable evidence that an ~80:20 ratio of low to high intensity training (HIT) gives excellent long-term results among endurance athletes training daily.” Full article here.