I listened to a great interview with Podiatrist Emily Splichal on propulsion. She classifies propulsion with three key steps. Step one is supination of the forefoot through concentric contraction of the tibialis posterior. 2nd, dorsiflexion of the big toe. 3rd, windlass mechanism by activation of the plantar fascia.
I will try to sum up the first step as best as I can. Tibialis Posterior (TP) is the key supinator of the foot. Understanding the anatomy lets one understand the importance of it. It has expansive connections not only into the navicular, but it fans into every bone of the foot except the 5th metatarsal.
Concentrically TP is supinating, eccentrically it is decelerating pronation. It dissipates ground reaction forces and prepares the foot for push off.
3 things control the optimal function of the TP. Ankle mobility, foot strength and hip strength. If the ankle doesn't have enough mobility, one will tend to overpronate and it will change the lever arm of the TP. Must train the TP eccentrically, concentrically and isometrically. Cal Dietz, triphasic training comes to mind. Hip strength will profoundly influence foot strength, they work together. If we want stronger TP the hip external rotators must get stronger.
She gives an example of squeezing a small ball between the heels and doing a calf raise. This will strengthen the TP as well as influencing the hip external rotators.
If you are interested in the other parts of the interview you can go to Movement Lectures. I have found this to be a valuable learning resource.