Lower Back Pain during a race

As a person currently having back problems, I'll suggest a few things that I have heard and been working on.

Like most people your core could probably use some work but it probably isn't the cause of your problems. But strengthening it could help any future issues, so add some in.

Did you have any back issues on the bike?  Depending on your flexibility your fit might be great for Olympic distance but not for HIM distance.  I have 2-3 positions I put my bars in depending on the length of the race. 

Another thing to look at with regards to flexibility is how tight are your hamstrings, glutes, calves, etc.  From talking to both Chiropractors and Sports massage people it's scary how many things in your body are connected.  Tightness in one area can lead another area to work a bit more, which then pulls on things like your lower back. 

I have horrible flexibility and muscle tightness, which I believe is the cause for my current problems and I'm working on stretching and a few strength routines to help even everything out.  My chiro even pointed out I had weakish glutes which could be causing diffent muscles to be firing when pedaling and then pulling on my lower back, so doing a bit of strength to try to work that out.

If you're truly concerned about it I would go see a Chiropractor or at least a Sports massage person to evaluate you.  Depending on your insurance Chiropractor could be covered, luckilly it is on mine. 

I recommend core work (front and back).  I consider the core everything between the belly button to the upper thighs front and back.

Core work includes flexibility work.  Yoga is excellent for core flexibility in the hips/glutes/hamstrings.  It's also a lot more fun to do than just plain stretching.  (I use the P90X Yoga workout.)

There's a good core strengthening workout here on BT... do a search.

Andi

Core work is often useful for triathlons, but it might or might not make a difference to your lower back issues. 

I was having frequent lower back difficulties until I got my bike re-fit by a more knowledgeable fitter (I had also lost a bunch of weight since my original fit). That made a huge difference to the back pain that I had been experiencing both on the bike and on the subsequent run. 

I know it's a pain the a$$, but core work & foam roller & stetching (tight hammies cause lower back issues too) make a HUGE difference for back issues.

I had problems as well.  I tried massage, ART, ultra sound & chiropracter.  All were a waste of money until I adapted the above.