MUD Mired in time...

Momentum compression

swing

^Transition^

^slow both: hip flexion & knee extension

Brief psoas here.

Stiff AFO toe plate or heel planted + stiff equinus kills psoas’s thigh nudge. No energy to drive eccentric mechanism. Walker becomes a stepper.

The psoas briefly inserts the needed energy at the real swing beginning. Everything else is deflection. Think pool cue as psoas. Balls bouncing off cushions deflect but add no new energy. The more things that impede the supple swing of the double pendulum the vastly more energy the psoas has to supply. Establishing suppleness to swing phase can quiet the seemingly overactive hip flexors. When he stance leg harp line H_A approaches vertical the dampening of the opposite swing leg provides a boost to the stance to reach the top of its trajectory. Incomplete swing arc robs the opposite leg of the energy boost it needs to get to the top. Deflecting momentum is eccentric. If energy is lost due to whatever is awry, then concentric muscle (the primitive obvious this-does-that muscle approach) takes over at a much higher energy cost. When we walk UP steep stairs we have no momentum to run the process and so we become concentric. The medial rotation crouch is not THE problem. It is a stair climbing movement that works when eccentric inertial mechanisms are dampened. Get that? As the swing leg extends at the knee, the full swing is TERMINATED (by hamstrings limiting extension) and thus diverting the momentum to the pelvis which pulls the other leg over its hill approaching verticality. This is a VITAL target of corrective surgery. Terminal knee extension needs a link to transfer momentum and at the right time – and not too early. The ‘fast/slow’ knee extension exam is looking at this.