Typically upon waking up, I get strange muscle action in my lower legs. It seems to be more on the sides of my calves than the calf itself. I don't know if it is muscle extension or muscle flexion, but it is not exactly like a cramp. It's causes me to walk stiff-legged for several moments after getting out of bed.

What is this and what is it called? I've had it for years, but last night it went on for hours without me even getting out of bed. Now, my lower legs are sore and, of course, I'm exhausted.

Thanks.