Running too upright with your upper body posture may disrupt the kinetic chain of events on your leg swing and foot strike mechanics in ways that may increase rotational forces and torsional loads on the knee-joint as compared with leaning forward. Read more here about why leaning forward, especially when landing with a forefoot strike, is a more functionally useful direction to orient your upper body posture when running that can have pronounced improvements in runner’s knee prevention!
BSc Neurobiology; MSc Biomechanics candidate, ultra minimalist runner & founder of RunForefoot. I was a heel striker, always injured. I was inspired by the great Tirunesh Dibaba to try forefoot running. Now, I'm injury free. This is why I launched Run Forefoot, to advocate the health & performance benefits of forefoot running and to raise awareness on the dangers of heel striking, because the world needs to know.