[keenerd]

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.

[kiriakasis]

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