Hacker News Reader

Comment by WalterSear | Hacker News Reader

>Also, "pushing off with your heel" is not a thing. It's impossible to finish the liftoff from the heel while running.

So what is going on in this picture?

https://i.makeagif.com/media/3-05-2014/hQcYHP.gif

I see the maximum force being applied just as the heel leaves the ground. Maybe the maxima is >just< slightly after, but the heel is still involved.

View on HN

The ball of the foot is doing the pushing at that point, and the ball of the foot finishes the liftoff. Try and take a few steps where the ball leaves the ground before the heel, you'll see.

The ball of my foot may be the last thing to leave the ground, but when I run barefoot style, I'm pushing off with my heel.

Your heel doesn't have leverage to lift your body off of the ground. If your heel is leaving the ground it's either your knee lifting it or your toes pushing it. In the gif you linked, and in proper running form, you push with the balls of your feet. Your ankle / heel system is solely a fulcrum that doubles as a dampening spring.

"pushing" isn't the only way to apply force. from the gif the ball of the feet start and end the "pushing", but this is unrelated to how much lifting you do with the heel

It looks to me like you're ignoring inertia, the force is highest right when you switch between catching yourself and pushing off

You can't draw any useful conclusions from that. It is only depicting vertical force. Pushing up, not pushing off.

Pushing off refers to forwards, longitudinal force. Walking and running are commonly modeled by inverted pendulums, and the best time to increase the energy of the pendulum is at the extreme of the range of motion. The middle of the swing is the worst time to add energy to the system.

Or think of it physiologically. If you are adding energy mid-stride, the gluteus maximus is responsible for producing all forwards force. (Which might be a fair assessment, humans's are unusually large for mammals.) Adding energy at the end of the stride allow the gastrocnemius to provide thrust as well.

yes, i they were focusing on the vertical force because it is the more likely to cause injuries and , when jogging, most of the total force.

i think everybody agrees that the forward sprint is in the end of the step, from the ball of the foot

Looks like over-supination in that picture? The heel is definitely not pushing off, the forefoot is last to touch the ground.

Reply on news.ycombinator.com