Homebrew01

How to help someone else solve sore lower back ??
My 15 year old son just started riding a road bike. He's about 5' 11" , riding 1 of my bikes (old 56 cm Cannondale) which I think is a good size for him. It appears to be a decent fit with reach & seat height, but I see his lower back curved, and looks like it should be flatter.

I suggested he think about posture, the same way that you can slouch in a chair with a curved back, or make yourself sit more upright with a straighter back. It may also just take a bit of time to adapt to a road bike. I raised the stem an inch, from my fairly aggressive setup.
A bit tricky trying to help someone else with fit, and guess how they feel.

f4rrest

What kind of soreness? If it's just muscle fatigue, then work up to the position and time with rest days included.

Curved back on an aggressive position you've had years to adapt to seems too much for a young rider. I put the bars up and higher for my sons. But they'd rather play baseball and basketball.

Campag4life

Common for newbs.
There is a drill I use to help others and occasionally use myself to teach proper posture. Proper posture starts with how one must sit on a saddle to get aero. It starts with the pelvis. Intuitively male's don't like to rotate their pelvis forward because it puts pressure on our balls. An acquired taste.

The drill goes:
Hands on hoods
feet at 3 and 9 o'clock on pedals.
Butt out of the saddle
Back more or less horizontal with butt sticking out rearward
Lower butt onto saddle.

What you discover about this drill is many things:
1. He likely never sat on the saddle like this before with a forward rotated pelvis
2. It may or may not be comfortable depending on choice of saddle.
3. His back and even neck should be more relaxed because the lumbar region is about the same posture as walking down the street...that is the goal.

So good back posture starts with rotating the pelvis on the saddle. Most people like to sit on a saddle like they are at a baseball game. This position doesn't work on a roadbike with the aggressive position you mention.
HTH
PS: a by-product of a more rotated pelvis btw is moving a riders CG rearward which also takes more pressure off the hands. As the pelvis is rotated forward the rear end shifts rearward which moves the rider's weight back unless a rider deliberately rotates his pelvis on the front of the saddle when hammering (on the rivet) closer to a TT position which is easier to get more aero.

Standalone 

Saddle changes may also make it more comfortable for his sit bones.

dtrain

Tight hamstrings pull on one's back all day long. Stretching and foam rolling those (plus the IT bands) make a big difference for my back and knees.

calamarichris

56cm sounds pretty small for a 5'11" rider. Consider seeing a pro-fitter if you foresee him getting seriously into cycling. I felt like a complete tool paying Nate Loyal in Santa Monica $150 for 2.5 hours of measuring, looking at me pedal on the bike, shifting my saddle, shifting my cleats, and I walked out with only a little business card with my measurements recorded on it.
But two weeks later, I cancelled my appointment with the knee surgeon, and two months after that, I was regularly riding hilly centuries in sub-5 hours.

Money spent on fit is not wasted. Wish someone had told me that back when I was in my 20's, when I was wasting money on sew-ups and the latest Oakley BS.

+1 on the stretching. Stretching & yoga have also been hugely beneficial for me.

2manybikes

To get a little warmed up before stretching, I stretch on the bike after riding a few miles, while coasting. It saves me time on a long ride day too.

mlamb01

I got a new bike back in December, and had the shop professionally fit it to me. From the beginning, I thought I was abit stretched out, and needed a shorter stem. They encouraged me to put some miles on, and then re-evaluate. Well, it was fine up until mid summer, when I was riding more and started getting lower back pain about 45 minutes into a ride. Ironically, after about 3 hours of riding, it would start to subside. I did some research, and saw that having too much of a reach can cause lower back pain. I moved the saddle forward 5mm, and it seems to have fixed my lower back pain.

I debated putting a shorter 90 mm stem on, but with the 100 mm stem that I have on there now, my thighs almost hit the bars when out of the saddle. Plus I don't want to sacrifice any stability.

Try moving the seat forward 5mm, but remember that will effectively shorten the seat height, so you will want to raise that by a mm or two.

cicatrize

I was suffering from some nasty back pain early in the year from riding. A lot of people think that raising the stem or lowering the seat is good for your back, but it had the opposite effect for me. I pushed my seat back and lowered the angle of my handlebars, and I get very minimal pain now. I suspect it has to do with your back stretching out to a more optimal position for riding and placing less stress on it.

therhodeo

Not really.

dtrain

+1. I'm 5'11" a ride 56cms.

ColaJacket

DO NOT move the saddle forward for a reach problem. The saddle should be adjusted for your legs to the pedals. If there is a reach problem, get a different stem.

GH

mlamb01

I had my first professional fit done in March 2011. I never moved anything, and rode that bike until December 2014. After hard rides, I would get a numbness in my left hip that would hang around for a day or two, it was something that I would only notice when getting up after being seated for awhile. Just felt like my hip was slightly asleep. Got a new bike in December 2014, got it fitted by a different pro at a different shop. I said just try and match my old bike. They said my saddle was nose up too much. I did not realize it at the time, but because the nose was up too much, I was not tilting my pelvis forward like I should have been, causing my hip issue. That problem is gone now...

Bottom line - Don't be afraid to tweak your pro fit abit, its just a starting place. Take good measurements beforehand so you can put it back the way it was before if you do not like the change. Make changes in MM, not CM.

ravenmore

+2 or +3 or whatever we're up to. I used to race and ride 20+ hours a week and over the years I learned a 56cm works best for me (I'm actually right at 6'). I went to Performance recently to buy a bike and found my current bike which I liked straight away in a 56. The sales person said no you should be in a 58. I told him no that a 58 is too big based on my experience. I then got on the bike to show him and he admitted I was right.

Also, back pain can be from being too upright. It's totally counter intuitive. I had it on said new bike while I was dialing in the fit. It went away for me when I lowered the bars a lot and raised the saddle a hair. Lowering the bars also helped with numbness in the hands as I was putting pressure on my palms in the wrong place.

Not saying this is the answer for your son but it might be worth remembering as something to try.

FLvector

Part of this is likely getting used to a new position for an extended period of time. Is your son very athletic and work out frequently? I've found that strengthening the core helps to keep back problems to a minimum. Also, make sure the saddle height and stem length are correct to give him the proper reach allowing him to flatten out some. Nice to hear your son is riding. You'll probably have trouble keeping up with him soon.

puddinlegs

^^^ this ^^^ And a lot of spinning until 5-600 base miles are in. Core strength and flexibility. Both take work.

Homebrew01

Thanks for all the great replies !

afterburn

It definitely depends on your proportions, but that certainly sounds right to me. I am 6'2" and I supposedly between a 58 and 60. But I can tell you every 60 I've ever ridden has been too long for me in reach (I can make the seat work no problem). And I've never ridden a 58 that put me too high, or hunched me up. I have a 34.5" bike inseam and 35" arm, so I am fairly evenly proportioned. Long legs or long torso can throw this off, but it really has to be fairly extreme.

bbattle

I would also suggest stretching and more core exercises.

For a flatter back, I'd go with a longer stem and/or a higher declination angle on the stem. Both would stretch him out and reduce the "hump". But at age 15, he's got a lot of rubber in his bones so might not be worth worrying about.

gc3

I prescribe medicinal marijuana for all minor aches and pains....

Outback Cayucan

Yoga!

MagicHour

+17 - 5'11" + change and anything bigger than a 56 for most brands will almost always be too long (and tall) for me.
Having said that, there are probably some tweaks that can be made to his bike fit-like saddle ht, setback and stem length.
That and stretching, working on flexibility and spending more time in the saddle should hopefully help him get more comfortable.

Homebrew01

Here's a link to another thread, including a picture
https://www.bikeforums.net/fitting-yo...ower-back.html