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Bike fit concerns re: knee & back pain ...(11 posts)

Bike fit concerns re: knee & back pain ...HouseMoney
Nov 4, 2003 9:21 AM
... and I'll conclude with a crankarm length question since I'm in the market for a new crankset.

After being "fitted" by two different shops (post-purchase tweaking), I've discovered that although I have a long inseam (88cm±) for my height (6' tall), my femur is short. I have long arms. I ride a 58cm bike, with a 73.5° seat tube angle. In order to get KOPS (using a plumbline) the saddle was moved as far forward as the rails would allow. When I bought the bike last year, I went with a 110mm stem, although the shop said as I progressed in my riding, I'd probably want to go longer. I also had a layback post originally.

For the first fitting, the guy measured everything, on my bike & me, including flexibility & leg angles. He's the one who moved my saddle forward (also went from a layback post to a straight post). I used to get lower back pains once I hit about 30 miles, but that stopped after this initial fitting.

For the 2nd fitting, the guy (different shop) measured my inseam & sternum notch, eyeballed my leg angles, and used a plumbline to measure saddle position. He said my saddle was too far forward, set it in the middle of the rails, which put me a little behind KOPS. Because he moved the saddle back, he also lowered it slightly. He then increased my reach by dropping my stem (flipped a spacer from below to above stem). Since I was told when I first bought the bike that I'd end up with a longer reach eventually, this made sense. He said any back pain should be alleviated by strengthening my core muscles, and not by setting up for a more upright riding position as the first guy did (saddle forward, etc.).

I did a 26 mile ride Saturday and all was fine. Yesterday I did a grueling 46 mile ride (many climbs) and my back started up again, and I felt discomfort (tightness) behind my left knee with about 2-3 miles to go.

So ... what do I do? Move the saddle all the way forward again? Raise the stem? Continue to work on strengthening my core? Stop worrying and ride more? None/all of the above?

As for my next crankarm, I now have a 175mm. Although my height, inseam, bike size "may" indicate I should ride a 175, does my short femur mean I should go shorter? If so, how short?
re: Bike fit concerns re: knee & back pain ...andy02
Nov 4, 2003 9:49 AM
Check both leg lenghts, hamstring/quad strength (one stronger then the other cause knee and back pain), work on core strenght.

This helped me but you have to figure it out for yourself.
re: Bike fit concerns re: knee & back pain ...divve
Nov 4, 2003 9:55 AM
I think it's better to ride more before making additional changes which might or might not suit you. The stuff you describe sounds a lot like "beginner" pains and should decrease over time. As you get more comfortable you'll also have a better understanding of what you actually should adjust or change. Only adjust something now if it causes a pain you really can't take.

Also, instead of suddenly almost doubling your ride distance, it's better to ride more frequently with less miles and gradually increase distance over time.
back pain may be more climbing than you're used to ...dzrider
Nov 4, 2003 12:22 PM
I get some in the spring when I do my first longer rides.
I notice the pain mostly when climbing, so it may be just the results of a longer, hillier ride than you usually do.

I don't know how far it is from the middle to the back of the rails, but it sounds to me like a big adjustment. You also didn't say why you wanted another fitting. I'd stay with this new position for a few more weeks. If the pain goes away, great. If not I'd go back towards where you started. If you were pain free before the change, go all the way back.
Core work good, but keep in mind..hrv
Nov 4, 2003 1:05 PM
if you are already having back problems you might end up doing the wrong exercises. I went to a doc/pt and had people in the know give me some tailored exercises to help with my back pain. Your pain could be caused by a structural problem (messed up curvature, one way or the other, etc.) that could be really screwed up by forcing it into positions it doesn't want to be in!

Yeah, why did you get the 2nd fitting again? New bike? Developed back pain again? Felt loss of power? Like the prev. poster said, go back to the original setting, or something in between, and try that 'grueling' ride. See how your back does. You might have to do the bike tweaking on your own, a millimeter here and there, after marking the base parameters.

By the way, I just started doing some basic Pilates tapes and it's unbelievable! Way more focused and effective than just doing crunches.

good luck,
Yea, what he said . . . and STRECHDrone 5200
Nov 4, 2003 3:34 PM
At about 1600 miles this year I had a problem with lower back pain and went to the doc/pt. Two months of core strengthing exercise and streches, especially hamstring stretches, was the cure. The pt gave me some very basic exercises and streches that have made a huge difference. The most important thing for me has been the hamstring streching.
re: Bike fit concerns re: knee & back pain ...crankset
Nov 4, 2003 2:48 PM
It seems to me that you were already used to the first position they fitted you in. Then the second guy comes along and makes some pretty big changes. And of course, after a hard ride, you start getting back and knee pains.

You have two options: Either go back to your original position and slowly move into the new position; for example, instead of moving the seat back like he did, just move it 3mm per week until it ends up where the second guy set it up.

Your second option is leave everything like it is but keeping in mind that your body is in a completely new position and it needs time to get used to it. So instead of going out and riding hard, you will have to start easy and progressively start riding longer and harder. This option is the most difficult of the two because, at least for me, sometimes you get caught up in the ride, go too hard and end up in pain.

Of the two, I would go with the first option which won't change your riding intensity because of the small, incremental changes you will do. That way your body can adapt without going into shock, aka pain.
Could my femur be *so* short ...HouseMoney
Nov 4, 2003 3:25 PM
that considering my seat tube angle (73.5°, which seems fairly standard) and assuming my saddle height is correct for my inseam length (88cm), that I would need to have the saddle ALL the way forward? Since neither shop changed the saddle height much except for a slight adjustment to compensate for moving the saddle fore/aft, I'm guessing the saddle is at or near its "correct" height.

That's why I went for a "2nd fit opinion", since I found it hard to believe that my body is that whacked! If so, I guess for my next bike I'll need either a stock bike w/ a really steep seat tube angle or custom.
Nov 4, 2003 5:03 PM
I had a frame that was too long for me (top tube, stem,etc.). It wasn't helped by shortening the stem, adjusting the seat, etc as I still had back problems, especially with a lot of climbing. Next bike had shorter top tube, etc. However, I also went on intense exercise to stretch and to build abs (cycling doesn't do much for abs). Improved stretching in legs and built up abs.... no more back problems.
So she said "How short is it?"Kerry Irons
Nov 4, 2003 5:39 PM
The normal ratio of femur to tibia length is 1.11 in men, 1.14 in women. Coppi was 1.18, Merckx 1.16, and Hinault 1.2. It is difficult for you to measure yourself, or even to have a friend do it because you don't know exactly where to take the measurements to insure comparability with these figures. There can be quite a bit of variation, and there are certainly differences in both saddles and seat posts. Yes, it is possible that your best position is to have the saddle all the way forward. It is also possible that your pain is just a response to a too-rapid change in your position.
Some links to confuse you even more.hrv
Nov 4, 2003 7:14 PM
Found these when I was looking up stuff on bike fit: