ggg wrote:
he is off shell. Marathoners don't lift their knees like sprinters and don't land on their balls of their feet.
Too simplistic an explanation.
Running fast has economies and ideals. Forget about different body types for a minute.
Running at your fastest is a single support phase, walking is a double support phase. Sprinting involves hitting the ground and driving backwards, without propping.
When you coach sprinters you get them to build a rhythm of keeping their feet under them and increasing speed by putting more pressure on the ground, and more on the drive, coming onto your toes, raising their hips. But staying in control. That means the action stays pretty much the same, but your stride lengthens and your speed increases. You don't reach out the front to lengthen your stride.
All running is about power and efficiency. Yes marathon runners have less knee lift than 100 m runners. But so do 400 m runners. Marathon running is about consistent technique that minimises fatigue while maximizing the mechanics.
Sprinting is really just running faster. Salazar gets it. The best mechanics are with the sprinters as they have the least tolerance for error, going 25 mph+. Look at Bolt. He is mechanically fantastic.