You may have heard me talk about how the lower kinetic chain is connected, how ankle rocker effects hip extension and how important hallux (great toe) extension is. 

What can we conclude from this study?

• toe spreading exercises are important for reducing navicular drop (and thus mid foot pronation, at least statically)
• In addition to increased abductor hallucis recruitment in ascending and descending stairs, when hip external rotation exercises were added along with toe spreading exercises folks had more recruitment of the vastus medialis (a closed chain external rotator of the leg and thigh)

Keep in mind:

• the exercises given were all non weight bearing and open chain for the external rotators. Imagine what might have happened if they were both closed chain AND weight bearing!
• They concentrated on the effects of toe spreading (AKA  lift/spread/reach) on the abductor hallucis. It also has far reaching effects on the dorsal interossei, long and short extensors of the toes.
• Here is an example of an exercise that would work those muscles.

Abstract: The purpose of the present study was to examine the effects of toe-spread (TS) exercises and hip external rotator strengthening exercises for pronated feet on lower extremity muscle activities during stair-walking. [Subjects and Methods] The participants were 20 healthy adults with no present or previous pain, no past history of surgery on the foot or the ankle, and no foot deformities. Ten subjects performed hip external rotator strengthening exercises and TS exercises and the remaining ten subjects performed only TS exercises five times per week for four weeks. [Results] Less change in navicular drop height occurred in the group that performed hip external rotator exercises than in the group that performed only TS exercises. The group that performed only TS exercises showed increased abductor hallucis muscle activity during both stair-climbing and -descending, and the group that performed hip external rotator exercises showed increased muscle activities of the vastus medialis and abductor hallucis during stair-climbing and increased muscle activity of only the abductor hallucis during stair-descending after exercise. [Conclusion] Stair-walking can be more effectively performed if the hip external rotator muscle is strengthened when TS exercises are performed for the pronated foot.

Goo YM, Kim DY, Kim TH. The effects of hip external rotator exercises and toe-spread exercises on lower extremity muscle activities during stair-walking in subjects with pronated foot. J Phys Ther Sci. 2016 Mar;28(3):816-9. doi: 10.1589/jpts.28.816. Epub 2016 Mar 31. link to  FREE FUL TEXT: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4842445/