Heel strike running is bad because multiple lines of research over the last few decades have proved the many verifiable aspects of heel strike running that are primarily responsible for nearly all running injuries vs forefoot running.
Heel Strike Running Bad for Knees Even at Slow Speeds
Even at slower running speeds, heel striking was found to increase cumulative loads and average loading rates beyond pain and injury predisposing levels on the knee-joint as compared with forefoot running, which was found to be most clinically effective at reducing net impacts to the knee.
