Poor coordination of the toes is a common deficit I see with many of the runners I work with. One drill that is often prescribed for runners when they are dealing with ankle and foot injuries is called "Toe Yoga". Jay Dicharry's book Anatomy for Runners was the first place I was exposed to it and many clinicians will use this with runners dealing with foot and ankle injuries (plantar fascitis, achilles tendinitis, posterior tibias tendinitis, etc.). It's a great drill and is something I often prescribe to both my performance clients and patients. The goal is to be able to perform great toe flexion and extension without compensating through the 2nd through 5th toes.
It's a great way to teach a runner to keep a good position of the foot and ankle as runners begin to progress towards more challenging single leg exercises.
However, It can be incredibly tough. People often struggle when they first try this exercise and can easily compensate by using excessive force throughout their IP joints. Here's an easy way to teach your foot how to perform the drill correctly. Simply raise the toes into extension you are looking to isolate and then hold that position. Try it out and let me know what you think!