I am curious if any available dietary supplements could be advantageous for me in my endurance competition. My racing is cross country motorcycle events. These races last from 3-4 hours [80 or more miles]. The riders in the best shape finish at the front vs. closed course motocross which lasts 15-30 minutes, where clearing all the big jumps is more important.

Anyway, I have trained hard this winter to build my cardio base. I have used intense cross country skiing 4-5 times per week, stuck with a 50/30/20 diet and lost 25 lbs. getting in shape. I have also lifted some to minimize muscle loss.

So can anyone suggest any supplements that may be helpful for me in search of greater endurance fitness?

I use a combination of Perpetuem, endurolytes, and hammer gel. You can read all about them and order these products at the following link.
http://www.e-caps.com/index.cfm

The hammer gel and endurolytes capsules are the easiest to use but for longer training Perpetuem works quite well.

Hope this helps.

I might recommend a product called "Optygen" from First Endurance.
Its a formulation of adaptogenic herbs that work to increase your VO2 Max - i.e. effeciecy of oxygen use.
I have used it in the past and it seems to help.

check this out... http://www.runnersworld.com/home/0,1300,1-53-87-6026,FF.html?site=RunnersWorld

food for long and short events.