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My mom bought a brand-new Fuji road bike a few years ago - but because she only used it a couple times, she's now given it to me (female, 31). She's a few inches taller, so I adjusted the seat level to accommodate. I can now ride it fine - except for one thing. When I coast, the leg that I put my weight on trembles uncontrollably and that thigh burns. I'm not overexerting myself, this happens pretty much immediately.

It's been awhile since I rode a bike but this never happened before. I do weigh more now (182 lbs compared to 170 lbs) - is that all this is? Or could it be a fit issue that would be solved with adjustments? I'm hoping it's the latter. This isn't just unpleasant, it also makes me feel less in control on the bike.

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    How's your general fitness level? Have you ridden a bike much in the last few years? Muscles that haven't had a lot of use tend to act strange at first. Could be you're pushing hard and the body is complaining.
    – Criggie ♦
    Oct 1 at 1:50
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    @Criggie I haven’t ridden much since my last bike was stolen around 4.5 years ago. Aside from walking, my main form of exercise the last few years is kayaking around 6 miles several times a week - which obviously doesn’t do much for my legs. Still, this happens basically as soon as I start biking. I didn’t think I was THAT out of shape...
    – Alison
    Oct 2 at 19:53
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    @JimmyJames Yes, I can easily stand on one leg in any other situation.
    – Alison
    Oct 2 at 20:02
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    @Alison some foot retention systems pretty much fix your foot position on the pedal. This is great when it works, but if it's set badly, can cause problems. That's not an issue if you're using flat pedals. It may be you're used to longer cranks - though I feel that more as a greater up-down movement, rather than more forward-backward. Or it may be you're used to a greater saddle setback so your feet are always further forward
    – Chris H
    Oct 2 at 20:19
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    @RobbieGoodwin I'm not sure how else to put it... My entire leg shakes without pause and the front of my quads hurts. It isn't a sharp pain but rather a burning sensation - unpleasant, but honestly the shaking bothers me more. People here have suggested I try standing on one leg with the knee bent to see if it's a fitness issue; I can do that easily.
    – Alison
    Oct 2 at 22:26

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I don't see how the slight weight increase should matter. The fact that your extended leg is the one with the issue(I am assuming you get this in both legs depending on what leg is at 6 o clock) suggests that you might still have the seat way too high. You might not notice when pedaling because you rapidly alternate sides and your back might be compensating subconsciously.

What happens if you coast with the weight on the seat and the cranks in 9 and 3 positions so that no leg is fully extended? If this is unproblematic then it suggests that your seat post is in fact too high.

Your knee should have quite a bend at the bottom of the pedal stroke so the knee is never fully extended. Some target an angle of approximately 140 degrees. A quick check: sit on the bike (support yourself against a wall/friend), and put one pedal in the bottom/most extended position. Your corresponding heel should be able to rest on that pedal comfortably. If you have to strech/bend your back to reach the pedal, the seat post is probably too high.

I suggest doing the coasting at 9+3 and/or do the heel-test. If one/both suggest the seat post is to high, lower it so that you pass the heel-test and go even 2-3 cm lower. You can increase it later incrementally as needed.

If this doesn't resolve the issue, then one could speculate on other reasons.

EDIT: (you could try to stand on one leg with a slightly bent knee (off the bike) and see if you experience the same issue ("immediate" burning thigh and trembling) just to check if it is an overall fitness issue that others have suggested as a possible cause. If so, put less weight on one leg when coasting and build up your strength over time. EDIT2: Consider seeing a health care professional if your issues are not resolved, progressing or seem suspicious to you)

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    The overall advice is good, but that 140° figure, while not wrong, represents more bend than many people aim for.
    – Chris H
    Oct 1 at 11:36
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    Might be true, but I think the heel test will give less of a bend than 140 and then one will get a sense of the range that is "acceptable". Also starting a bit low and slowly increase the height is in my opinion preferable to starting too high and creep lower.
    – WornChain
    Oct 1 at 12:37
  • This is incredibly helpful, thank you!! I don't have a problem standing on one leg w/ a slightly bent knee in any other situation. So yeah - I'm hoping this is a fit issue that is easily fixable. I really appreciate how specific your advice is.
    – Alison
    Oct 2 at 20:13
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To me it sounds like the biggest reason is that you haven't been riding in a while and are going way too hard now. If that is the reason, doing some short and easy rides should help.

If the bike was originally bought to fit a taller person, there is the chance that it can't be adjusted to fit you. But that would mean that the handlebars are too far away and it would give back and shoulder pain first.

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Rather than the additional weight I suspect that the problem is that your muscles lost a bit of tone due to a long period of little activity. After few months of regular use the problem should go away.

You may try a simple exercise when you are at home. Put one foot one or two feet forward then kneel down few times. Then swap the position of the feet and repeat the exercise. If the problem is the muscles tone probably you will need to do the exercise near something stable that you can grab with your hand (or hands) to hold to keep your balance and/or support yourself.

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    @Ted Hohl By grabbing something with the hand I did not mean to lean heaviy on it. The exercise should still exercise the thighs, not the arms. Holding with one hand the edge of a heavy table or a perch should be enough.
    – userFromEU2
    Oct 2 at 10:02
  • Thank you, I will definitely add that to my routine!
    – Alison
    Oct 2 at 19:44
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    Concur - walking uses different muscles even from running, let alone riding. I have "back of thigh" muscle pain when changing from upright bikes back to my recumbent after winter, and that's only about 4 months off it.
    – Criggie ♦
    Oct 2 at 23:21
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    @userFromEU2, fair enough. When doing the maneuver/exercise you suggest, some may just need steadying, others with less strength, balance issues, or joint degradation/injury may need more than steadying. They may need to supplement the movement with some upper body support to move through the range of motion without undue strain and/or injury. If someone does need that additional support initially, but with repetition over time builds up strength to need less support (or none at all), they can modify it within how the answer is worded. Just trying to make the answer more universal. Good answer
    – Ted Hohl
    Oct 3 at 1:34
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    @Criggie it only takes a few weeks off for me to lose running condition - my pace doesn't suffer, but my legs are painfully stiff for a couple of days.
    – Chris H
    Oct 3 at 6:19
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You should have your weight on your seat while coasting, not your leg. I would think it's your technique and perhaps a too low seat than anything else. I can't imagine a reason to have much weight being taken by either leg when you're not even pedaling.

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    This is not absolute. There are many situations where one wants to coast on their legs, perhaps completely standing. No such trembling should happen.
    – Vladimir F Героям слава
    Oct 1 at 8:55
  • @VladimirFГероямслава how often and under what circumstances do you coast on one leg?
    – Kilisi
    Oct 1 at 8:58
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    That is certainly much less common, but also happens. For example when slowing down before swinging my right leg to over the seat to dismount. But coasting when standing on both legs is very common. Anyway, I think here it is a clear case of a seat too high, not any technique.
    – Vladimir F Героям слава
    Oct 1 at 9:01
  • @VladimirFГероямслава I disagree, I coast sometimes standing up and stretch my arms and back, but not on one leg. I doubt a beginner is doing fancy dismounts.
    – Kilisi
    Oct 1 at 9:03
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    Coasting on the outside leg when cornering is an obvious example. Yes, even on a road bike if cornering hard or on imperfect surfaces (i.e. most of the time). And less commonly in general, but perfectly normal among those of us who ride long distance, coasting down gentle slopes on one leg, then the other, is an additional relief/stretch position than standing on horizontal cranks, allowing you to ease different aches. Also on slightly (uncomfortably but not technically demanding) tough surfaces when your sit bones have been taking your weight for what feels like a long time
    – Chris H
    Oct 1 at 11:33
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A too-low saddle also can't be ruled out. This overworks the thighs, which would normally be felt when pedalling, but often results in quivering when you straighten them.

I'd also into the saddle position front to back. This isn't independent of the saddle height, but shifts which muscles work hardest. It also changes the load on your knees, which can sometimes be felt at the bottom of your quads.

The fact that it happens so soon makes me wonder not so much about your overall fitness as your flexibility. If you've been largely sedentary you'll be prone to tightness in those muscles. Even other cardiovascular exercise isn't necessarily much help. For example, I ride a lot but get very stiff lower legs after running, painfully so in my shins and prone to quivering calf muscles.

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  • Thanks so much for the response! Do you have any advice regarding adjusting the saddle position front to back if it was originally fit for someone who is taller? Also, thank you for the advice regarding flexibility. I should definitely work on that.
    – Alison
    Oct 2 at 20:24
  • Because everything is interrelated, it's probably worth looking into a full DIY bike fit. My own approach was too hit-and-miss to recommend, but there are guides online
    – Chris H
    Oct 3 at 6:17

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