MTB Fit - Back Pain

[ariw]

Just finished my first endurance MTB race on Sunday, I raced the 3-hour solo option. I did pretty well in terms of pace, although my last lap (4 laps, 7.3 mile/each) wasn't great, probably due to blood sugar issues. I had some serious back pain towards the end, which makes me think that I would have been doubtful to finish the 6-hour option, even if I had the miles in my legs. I want to work up to longer races, so I was hoping for some ideas here.

Bike is a Niner Jet 9 alu, Fox 120mm fork, 90mm stem. Suspension setup is pretty good, although I also want to spend some time playing with settings there. I have been mountain biking for about 20 years, and over time, my position has moved with the trend of a shorter stem, higher bars, less overall reach. In terms of control and my ability to tackle the terrain, the bike feels pretty great. However, this race made me wonder if moving my weight back is what left me in pain.

I am open to suggestions, I have had a Guru fit on the road bike, but nothing similar for mountain biking.

TIA,
-Ari

[jtakeda]

What kind of back pain?

It’s entirely possible that this is a nutrition/dehydration issue.

[jmal]

Are you used to the distance/time and terrain you were racing? Back pain doesn't necessarily mean there is a fit issue, especially on MTBs. You move around so much on a MTB that I personally find fit much less of a concern than on a road bike. Back pain is very common in endurance racing when your fitness is not matched well with the race. I also find hydration packs can cause low back pain, but clearly there are plenty of people that don't have an issue with them. Anyhow, my first guess is that you just pushed longer and harder than you are used to doing.

[charliedid]

What kind of back pain?

It’s entirely possible that this is a nutrition/dehydration issue.

^ This is my question too.

[John H.]

What tire pressure?

How does your mtb reach compare to your road reach? I get the shorter stem thing- But the reach should longer than reach to the tops on your road bike.

[jimcav]

but I got a new to me MTB after my ribs healed, and thought I set it up to the same contact as my other bike, but noticed low back pain on rides over an hour. I assumed it was just me getting back into riding shape after several weeks off, but it turned out I was a little off in the saddle height (different SAG and slight pre-load on the seatpost too). I lowered the saddle less than 1cm and all was well (If I remember correctly, I did /8 inch rode a few times, then another 1/8th inch).

[.RJ]

have you been spending enough time on your mtb over the winter?

if its all been on the road/trainer, there's your answer. i get the same way, 5-6 hours on the road no problem, but the first long MTB ride of the season will ruin me.

[ariw]

More info:

Most of my training is on the road, this is florida so weather not as much a concern. Managed to rack up several 3 hour plus road rides leading up to this, nowhere near as much mtb. Longest mtb ride this year was about 2 hrs 20 a few weeks ago, didn’t leave me feeling too bad, but effort level was obviously lower. Tires were at 28 psi, dry course usually means higher pressure, but I am thinking lower next time. I used a camel bak, but that doesn’t bother me, it’s pretty light. I do have spacers on one of my road shoes to make up for a small leg length differential that I don’t have on Mtb shoes.

I almost drained a 100 oz camelback, which is about right for me for that length of ride. Definitely need to modify my insulin pump settings, I had to eat more than I planned to for only a 3 hour race.

I tend to ride seated quite a bit, I have been on full suspension for so long now. I wonder if that is a contributing factor

Ari

[jmal]

More time on the MTB and lower tire pressure are in order. Road riding builds great fitness, but it is no substitute for acclimating to the rigors of rough terrain. I'm assuming that the trails there have lots of roots based on videos I've seen from the Ocala area. Lower pressure will help with this. Other than that, regular MTB rides, some at race pace, will help a lot.

[.RJ]

I tend to ride seated quite a bit, I have been on full suspension for so long now. I wonder if that is a contributing factor


Might be, it will put a lot of pressure on your core. I have the same bike, and doesnt reward out of the saddle efforts much.

I think just a combo of the distance/effort on the MTB compared to what you've been doing did you in. More stretching, core work, strength training, mtb riding.

[Marc40a]

have you been spending enough time on your mtb over the winter?

if its all been on the road/trainer, there's your answer. i get the same way, 5-6 hours on the road no problem, but the first long MTB ride of the season will ruin me.

Same here. Dying from this past Sunday.

Like the original poster, I was thinking it might be a fit issue as well, but I think you hit the nail on the head.

[Gummee]

Real old adage:

Lower back hurts, you're too long and/or too low

Upper back hurts, you're too high and/or too short

In the case of mtn biking, if you're wearing a camelbak for the first time in a while, that weight could add to the problem of all the pushing and pulling and moving about on the mtn bike.

IME if I'm doing lots of climbing (Hilly Billy Roubaix) that I'm not ready for, my lower back hurts because I'm pulling on the bars and not just spinning away. My lower back hurts for a few days, then goes away as I ride on the flats again.

HTH

M

[beamin]

This is general and not MTB specific. More just for anyone experiencing lower back issues related to biking (assuming it's not because of fitness or fit) who is reading this. Not saying this is what's going on with OP - just putting this out there for everybody who rides a bike as a friendly reminder.

At the risk of sounding like a gym coach: Your hamstrings and lower back are connected in ways such that you are entirely capable of hurting your back if you don't keep your hammies loose and limber as part of your biking routine.

Sit at a desk all day? Then you're worse off in this department.

Sweating a lot while you ride and not replenishing electrolytes? Another point off.

Google the doorway hamstring stretch. This is a foolproof way to stretch your hamstrings without potentially injuring your lower back more. Okay, getting off my soapbox.