Center of pressure (COP) position and ground reaction force impulse in humans walking with different limb postures.

A) COP movement during bipedal walking. Fraction from touchdown (TD) is the mean time as a fraction of stance phase when the COP passes anterior to the metatarsal heads (error bars are SEMs). B) Late stance impulses during bipedal walking. Values are mean for the ground reaction force impulse after the COP passes anterior to the metatarsal heads (error bars are SEMs). Normal is extended limb walking, BKBH 1 is walking with a slightly flexed knee and hip, BKBH 2 is walking with a deeply flexed knee and hip.