I'm new to this whole thing. I've been riding 25-30km at a time on my hybrid and I've noticed that after the last couple of rides, I have a dull pain at the top-front of my left thigh (not sure how to describe it - it's in the center front of my leg where the thigh joins the torso) when I lift my leg up. This stays for a couple days. Last ride, I stayed home for a couple of days, it went away, I went riding again and it came back.

Things I should probably mention:

I'm right-leg dominant, but I mount from the right and swing the left leg (bad leg) over the saddle. I'm also none too flexible.

The LBS picked the frame size for me. I'm 6'3, 260lbs, it's a 20" frame. They didn't fit it to me though.

I'm pretty sure my saddle height is good. I can't touch the ground with my feet while I'm on it, with my heels on the pedals my leg is straight at the bottom of the stroke. I've never noticed my hips rocking at all.

I've never messed with the saddle fore/aft or tilt.

I've been wearing these fairly thick-soled Saucony running shoes which are quite 'squishy' so maybe my feet can move around on the pedals too much and strain my knee?

I've also worn a pair of Nike Shox which have much thinner soles under the ball of the foot and never had the same problem - although I haven't ridden as far in those shoes (probably 18km max).

The bike is really heavy. The 14.5" version of the frame is listed as 34lbs, mine is the 20" so presumably slightly heavier - extra metal isn't weightless obviously. The rides I'm going on have a few hills in them, some of them quite long - maybe I'm straining my muscles going up, but then why only in one leg?


What do you think the most likely cause is? Obviously I'm not looking for a diagnosis over the internet, but I'm really new to this, so I'm looking for ideas of things I can tinker with to start pinning the problem down.

Thanks!