Brokeback: Why does it go numb when I ride?

June 22, 2006 1:23 PM

When I ride my bike for extended periods of time (30 minutes or more) the left side of my lower back goes numb. When I dismount, I regain feeling within 5 seconds and there is never any associated pain. Is this bad?

Back when I was riding competitively I still had the same problem, but my handlebars were quite a bit lower for aerodynamics (plus I always figured that discomfort was just a natural part of racing).

Since I quit racing, I talked to a trainer who suggested that I shell out the cash to have my bike erognomically fit. I did that and my bike is quite a bit more comfortable (though not terribly aerodynamic) but the numbness still happens.

What is causing this? And will this affect anything in the long run? I know that you are not doctors and that I should see one, but have any Mefites had experience dealing with similar numbness? Why is it unilateral?

posted by |n$eCur3 to health & fitness (17 comments total)

You sound like you're pretty familiar with biking issues, but the first thing I thought of was your seat - does your seat have a groove down the middle, bisecting it into left and right halfes? There's a fairly important bundle of nerves between your legs and a cheap seat or one that doesn't have groove in it can compress the nerves, which can lead to a number of problems.
posted by lekvar at 1:55 PM on June 22, 2006

Yeah I think you are compressing a nerve. You don't want to do a lot of that as you can damage that nerve and lose muscle control, even cause intense pain. A good Physical Therapist or Sports Medecine specialist could advise you on the specifics.
posted by scarabic at 1:59 PM on June 22, 2006

Yes, this is bad. Or it could be in the future. (BTW, IANAD :) Lekvar and scarabic are giving you good advice. Numbness is a signal that something's not right. It's not bad yet, because you regain feeling right away. But compression of a nerve can, indeed, damage it for good (speaking from experience.) There could be something else not right about your spine that is causing the compression, so that is another reason to check it out.
posted by shifafa at 2:17 PM on June 22, 2006

Well, I don't have a cheap seat, but one that is without a groove... I had always thought that those were gimmicky. Maybe I will give it a chance. Since the consensus so far is that this has potential to be more serious than I had imagined, I'm going to play it safe and see a doctor. If only I had better medical coverage...
posted by |n$eCur3 at 2:35 PM on June 22, 2006

Bicycling and Pain.
posted by popcassady at 3:57 PM on June 22, 2006

Can you be more specific about the region of numbness?
posted by docpops at 4:03 PM on June 22, 2006

Yes, the region of numbness is about the size of my hand. Vertically, it starts at my left butt cheek, only slightly below the hip, continuing upwards. The region is bound, horizontally by my spine and side. Does this help docpops?
posted by |n$eCur3 at 5:32 PM on June 22, 2006

IANAD, but I've seen a lot of them for my back problems, and I am a cyclist.

Nerve compression is a probable cause, but it isn't necessarily due to the saddle. Ignoring the gonads, saddle issues generally aggravate the sciatic nerve which runs down the leg.

For lower back numbness, it sounds more like a nerve originating from the mid/lower spine. It might be compressed between vertebrae with you hunching over. Or muscle spasm is compressing the nerve directly, or starving the nerve of bloodflow. And the assymmetry of your condition may be due to mild scoliosis, sacro-iliac joint dysfunction, assymetric inflexibility or muscle imbalance.

In short, it could be anything. And unfortunately it's hard for doctors to determine the exact cause for mild symptoms like yours because the symptoms are difficult to reproduce on demand, because doctors have more urgent cases to attend to, and because back issues are complicated in general. Believe me, I've been dealing with similar problems for a few years now.

Anyway, do see sports doctor or a physiotherapist. And strengthen your core and improve your lower limb flexibility -- often that fixes many other problems.
posted by randomstriker at 5:44 PM on June 22, 2006

Hope this helps.
posted by |n$eCur3 at 5:55 PM on June 22, 2006

Yes, that helps in that it rules out the saddle as the cause. Most likely something to do with you being hunched over.

Again I am not a doctor, but a long-time cyclist dealing with my own back issues.
posted by randomstriker at 6:45 PM on June 22, 2006

Well, this is the cutaneous distribution of the dorsal ramus of the left L1 spinal spinal nerve.

The question that comes to my mind is whether the compression is external to the spinal column or not.

Here are a couple ideas:

If the L1 disc is herniating when you flex your back over in a cycling crouch (which is entirely possible; flexion stresses the intervertebral discs), that's something you want to know, because you want to rule out spinal column instability and also prevent it from getting any worse.

If you have a hereditary tethered cord, the whole thing could be put right with a minor operation.

And if it's just the nerve getting pinched somewhere outside the spinal column, between two layers of muscle, then it's a nothing-to-worry about situation.

An MRI and possibly an EMG study could sort this out definitively; those are expensive if you don't have good insurance.

I'm not your doctor and I can't advise you as to what you should do, except that I think you should ask your doctor for advice.
posted by ikkyu2 at 9:19 PM on June 22, 2006

Ikkyu2 will/can/should weigh in here to correct me, but given your illustration, my guess is that your posture while riding is leading to a degree of forward flexion of your lumbar spine and causing a minor degree of neural impingent at L2 or L3 on the left. More likely still is that it's simply a minor sensory branch that's being irritated by lumbar muscle tissue. It doesn't take much to impair light sensory fibers but far more to knock off motor fibers. I'll put forth the usual disclaimers regarding the importance of checking with your doctor on this for a full exam, etc.
posted by docpops at 9:20 PM on June 22, 2006

Well, that was interesting. Next time I'll use the preview.
posted by docpops at 9:21 PM on June 22, 2006

Wow, ask metafilter never ceases to amaze me. Thanks, I am armed with great questions to ask my doctor when I make an appointment.
posted by |n$eCur3 at 9:34 PM on June 22, 2006

Apparently it's a matter of 60 seconds that separates the specialist from the learned referring physician :)
posted by ikkyu2 at 11:32 PM on June 22, 2006

I have the same issue, but the pain has stuck around for a year. The orthopaedist did not see anything structurally wrong, but physical therapy and a chiropractor have not helped it. I was cycling a lot last summer and I think that's what caused it.
posted by Frank Grimes at 2:16 PM on June 25, 2006

Frank Grimes, there is no pain, just numbness for me.
posted by |n$eCur3 at 6:54 PM on June 28, 2006