Thanks for helping try to figure this out...

The head ache isn't severe, it's more of a marker of the whole feeling, if you will. It starts out as a little tightness, and gradually grows. I could ride with that feeling, but it feels like my ability to pay attention & respond to what's happening around me isn't as sharp either. And my feelings dive. (It's similar to pms, in that my feelings just seem to come out of nowhere & don't correspond to what's really happening.) I feel almost like my brain is sort of shutting down, even though the legs will keep right on pedaling.

I really thought it was blood sugar, so I've been reading up around here & online about fueling for endurance, and trying to pay attention to what I'm eating & when. On Saturday, we did a 4.25 hour ride, and here's what I ate:

Giant bowl of old-fashioned oatmeal w/nuts & raisins for breakfast.

On the ride, spaced fairly evenly:

1 hard-boiled egg
1 banana
1 slice pesto/mushroom pizza (fantastic!!!) minus part of the cheese
1 Clif bar
4 Accelerade brand gels (the 4:1 carb/protein ones, as I was trying to see if this would help)

I'm small & this seems like plenty for 4 hours of flat riding.

I drink 1-1.5 bottles of water/hour, and if I don't have electrolytes via drinks or gel, I take an electrolyte capsule every hour.

I started training in February, and have been building my long rides following a progressive training plan since then. (started from 1 hr sat/ 1 hr sun; built to 5 hr sat/ 4 hr sun.) Even though it's been progressive, it is a big increase in volume over the course of 6 months.

Could it be that I'm riding at just a little too high of an intensity? I was pretty conscientious about wearing a HR monitor and keeping the longer rides at low intensity when I started out. Then I started to feel more confident in my judgment of intensity, and just went by feel & got out of the habit of using the monitor. But lately, I think I've been feeling strong, and wanting to work harder. Which feels good, but maybe I'm going beyond what I can sustain for the long rides... My training plan calls for low HR zones on the long rides even still.

Hmmmmmm.............