The top video is former 100m WR holder Asafa Powell. The second is marathon WR holder and distance legend Haile Gebrselassie. Especially focus on the last 1000m of the Geb’s 10k. Absolutely beautiful.
Now ask yourself, what’s the difference mechanically b/t the two? If you’re studying closely, you know this is a trick question. Mechanically, the answer is nothing. Both are deriving power from the hamstring, mid foot striking, landing on and letting their body pass over their COG (center of gravity). The ONLY difference is torque production from the hamstring. Asafa Powell is producing an exponential amount more torque from the hamstring AT A FASTER RATE than Geb. The result is greater foot speed and thus a harder foot strike.
So where do the hip flexors come into play? At the top of the pull, the hip flexors are driving the leg back down. It’s called the B-Skip drill in T&F and allows for a faster cadence. Notice the initial engagement of the hamstring and the return to the ground with the hip flexors allowing a rolling wheel image of the legs.
And so the “roadrunner wheel” image comes to mind. Hamstrings pulling up, hip flexors rotating back down. Absolute poetry in motion. When done properly, world records are broken…