Since sunday – I did a nice even paced 50 miler on the road – the muscle on the inside of my thigh above the left knee periodically pulses/spasms.

The movement can be felt quite clearly and also seen through my trousers when seated.

WTF is causing it?

worms…

ah bugger

http://en.wikipedia.org/wiki/Fasciculation ??

FWIW I get these twitches all the time, in my legs/arms/eyelids. I haven't died yet so I'm not overly worried! 🙂

or maybe it's one of them aliens? 😯 it's about to hatch and burst out of your leg?

T'interweb doctor strikes again!!

"A fasciculation [f?.?s?k.ju.?le?.??n] (or "muscle twitch") is a small, local, involuntary muscle contraction (twitching) visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers. Fasciculations have a variety of causes, the majority of which are benign, but can also be due to disease of the motor neurons."

Wonder if my insurance will cover it?

stretching exercises can help.