Happy Feet - spreading toes; only able to do it on one side!

[JesseW]

I just tried the Happy Feet workout (and found it valuable, unsurprisingly), but I was very surprised to find out that while I could spread out my toes on my left foot, on my right foot (which was feeling a bit sore on the sole, which may or may not have been related), I couldn't. I could very briefly get my little toe to spread a bit, for an instant, then it would snap back. After some more practice, it got a bit better, but I'm very curious which muscle is weaker on that side, and why it might be!

 

[Laura Rainbow Dragon]

Our feet are quite complex! Spreading the toes primarily requires activation of abductor muscles.

Abductor hallucis is responsible for abducting your big toe.
Abductor digiti minimi is responsible for abducting your baby toe.
The dorsal interossei (4 on each foot) abduct the lateral four toes.

I'm thinking there's likely some extensor involvement as well.

This site goes into wonderfully geeky detail on the subject.