What is your sitting position like are you leaning forward? pullback risers might, help not sure. Leg stretches help me avoid those upper thigh cramps before I ride. just a few and I am ok. Without them I get one going down the road. Maybe your knees are up too high when you ride?

 

What type of seat are you running on that bike. If it's the one in your sig pic it doesn't look stock. I have the same problem with the mustang touring seat I have it is to wide for my hips and forces me to ride bow legged and then bring my lower part of my legs in to hit the pegs. I was getting real bad hip pain and cramps. Went away when I went back to a narrower seat. Just my .02

Any one need a mustang solo seat?

 

sip ONE shot of good quality tequila before you ride (I dont care what time it is).....

 

Today, I took a set of heel rests off of another bike and put them on my FXST. I was expecting this to solve the leg cramp issued; it did not. What I did learn was that, as MCSarge and Rider1200 suggested, the problem is my seat. The seat came with the bike, but is not stock, and does not keep my butt in place. I keep sliding forward, so I am continuously leaning forward and using my legs to push me back in the seat. I found that if I allow my butt to slide forward, lean back, and hold the grips with my arms fully extended (kinda like Peter Fonda in Easy Rider), the pain in my legs goes away. So, I am now shopping for a replacement seat. Should I pick up a stock seat, or would an aftermarket seat be a better choice?

 

I'm running a stock seat on my FXSTC. It's a factory replacement for the original, but HD decided to add padding so it's fatter than the "stock" one but not any more comfortable.
I have a buddy running a mustang on his 2000 FXST and it has a nice step instead of the slope yours has. He loves it.

 

Two things: Temperature and age.

 

If you experienced this during other activities, you could have some sort of mineral deficiency or even be dehydrated. Given the fact this only happens during one specific activity, you have already answered your own question. It is directly related to your posture.

You may be pressing on a nerve, or constricting blood flow just by he way you are sitting. Perhaps finding a different seat or move your handle bars to see if it makes a difference, might help.

You'll just have to experiment a little to find the culprit that is causing this dilemma.

 

Sounds like your tampon string is pinching something...

JUST KIDDING

I had some weird hip pain when I first got my fatboy, like my legs were forced at an awkward angle that caused some joint pain. Put the stock seat back on and it went away. I'm 39, so I dont' know if I'm considered young or old, but I've never had this issue ever before.

 

You still haven't said how tall you are. If your 6'1" or taller you need forward controls as well as a new seat to keep your *** in place.

 

I am 6'0"