The gastroc, does it cause ankle dorsiflexion and ankle plantarflexion ? Yup. What ?
You may think you know the answer, the gastrocs are ankle plantarflexors, because that is the easy one we all recognize. But I stew on things when unique cases come in and do not fit the "normal" models and it got me reviewing principles I need to always keep in mind.
Think about it, the gastroc cross the knee, so it causes knee flexion. And when the knee flexes, the proximal tibia is progressing forward in the sagittal plane. Now remember, the foot is on the ground, so the distal tibia is (relatively) fixated in relation to the upper tibia. So, as this proximal top tibial moves forward, because of gastroc contraction, the muscle is actually causing ankle dorsiflexion !
So, it is it important to know your normal gait cycle events ? Yes, Ivo and i harp on that all the time ! One has to know the normal cycles to know when abnormal gait cycles are presenting clues.
So, am I saying that the gastroc are helpers of ankle rocker and ankle dorsiflexion ? Yes, they can be. It is a timing thing. So, we have to again get out of our model of open chain events, and thinking that only the anterior compartment muscles are ankle dorsiflexors. We also have to remember that a bent knee heel raise is not the same as a straight leg (knee extension) heel raise. One can stimulate and assist in ankle dorsiflexion and the other cannot so much. So, in clients with loss of ankle dorsiflexion/ankle rocker should you be assessing the function of the gastroc at the proximal knee, for its effects of dorsiflexion at the ankle ? Yes. Go ahead and try it, bend knee and straight knee heel raises, they are different beasts. This gets more complicated, and i will go into that next week ! I have had some deeper epiphanies i wish to share.
Also, remember, single and biarticular muscles have varied and vast capabilities. Thus it is always vital to consider whole body movements where muscles have abilities to accelerate, decelerate, and control and stablize joints they span, and do not span, via dynamic coupling.