Hi Artist...stop wearing heels! , just kidding. First of all when you say heels how tall are the heels?

I have some medical background, I'm an occupational therapist, studied the muscles for my degree but....really a physical therapist area. However it sounds to me that you need to start stretching your gastrocnemis and soleus muscle. See when your wearing heels your stretching those muscle. If you don't wear heels on a daily basis then decided your going to wear heels one day, the gastrocnemis muscle along with the soleus are getting stretched out. Now the muscles don't like it if your not stretching them on a daily basis so, the muscles are going to give you a hard time and cramp up on you. When you pull your toes back up your shortening those muscles just enough to give them some relief which stops the cramping.

I have RSD in my left leg and every day I stretch both legs to avoid that cramping feeling you are describing.

Hope this makes some sense to you and that it has helped you.
Hugs, Jewells