oilman_15106

I have experienced lower thigh cramps for most of this year. I keep a riding log so here is what I have determined so far. The cramps start at 40 miles or so. Always when getting into a climb. I do like to stand when climbing but mix it up with spinning up a hill most of the time. I feel I stay hydrated and also have been on potassium and magnesium supplements(since starting these general cramping has been reduced).

The cramping is just above the knee at the bottom of the thighs usually on the inside. This Sunday on a 66 mile ride it was just discouraging. Tried to hang with 2 stronger riders but the cramps killed my hill climbing ability. Had to stop on two hills and return to the bottom. Spun around on the gears for a while until things settled down and then made it up the hills but still plenty of pain. Using a compact 50/34 front and 12/25 rear 9 speed most of the time.

The only thing I can come up with is my general riding position is straining the thigh group and when I get more gassed it translates into cramps? When not cramping, most hills are no problem.

All ideas appreciated.

BikeWNC

If your saddle is on the low side or forward (knee in front of the pedal spindle) it will put more emphasis on your VMO muscle. Try either raising your saddle or moving it back depending on what is better by a mm. Ride that for a week and reassess. Make very small changes and let them settle in before doing anything more.

Wildwood 

What cadence do you ride at on the flats? On the hills?
Well hydrated is good but are you eating something before mile 40?
How much has your weekly mileage increased over the last 3 months?
How many years have you been cycling?
Do you get any leg cramps from other activity?

Hermes

My sentiments exactly...plus what is your climbing position i.e. tops, hoods or drops and when you are on the hoods what is the angle of your back, generally speaking.

Pamestique 

It could be anything but most likely poor hydration. Do you take BP meds, like a diuretic? That can cause loss of electrolites (salt) and lead to cramping. Staying hydrated is a relative issue. After a 40 mile ride just how much fluid have you taken in? In summer heat it should be at least 70 - 100 fl ounces. That's 2 - 3 large bottles. There are some good supplements out there like Motor Tabs etc. Also is it possible you are over training, riding too much not allowing the legs and muscles to get some rest? That will also cause cramping.

And lastly, you know the old joke "Doc, it only hurts when I do this..." "Well don't do that anymore!" If standing causes the cramp, don't stand. Lower the gearing and spin up taking the rest and relief offered.

Also wildwood bought up an excellent point... are you eating? I learned after suffering heat exhaustion and being hospitalized that in order to retain fluids one must take in food. The food keeps the fluids in the system otherwise it sweats out. Every 20 - 30 miles you should be taken in some protein or carbs. Next time at 30 miles, try a Cliff or Balance bar, some nuts or dried fruit, fig bars, whatever, drink some electrolyte fluid and see if that doesn't help.

Terex

Are they really cramps, or are they getting over used based on your level of fitness? Are the "cramps" sudden and persistent (dehydration cramps) or do you feel on onset of fatigue, like the warning light flashing on your car in your vastus medialis?

BikeArkansas

I have the same problem, but mine is solved. It sounded like I was writing the story when reading what was happening to you. It turns out mine was due to shoes. The shoes caused an alignment problem for both knees, but especially my left side. This in turn caused the thigh muscle problems. Mine were almost always at 40 to 42 miles and on an incline or hill. Changed shoes and that pain has not come back. The LBS that sold me the shoes are partially involved with solving the mystery, but mostly it was solved with a lot of experimenting.

I also realize it could be some other problem for you, but it sounded so similar to mine. Good luck.

late

If you get a rear cassette with a 30T bailout gear, that should fix it.
I picked 30 because that 30 will work with almost any derailleur made.