I recently have noticed that while resting my claf muscles both twitch fairly regularly. It is not painful, but looks very strange. Addtionally, I have a lot of tightness in my calves, and think it could be related.
I did recently start more intense training in preparation for an upcoming 10k/half maratho in about a months time.
Im 33/male and run about 75 miles/wk. I run about 33:30 10k, and 1:14 for the HM....if any of that info. helps. Also never noticed this is n the past before.