AF,

Boy, it sure sounds like a Bonk. How hard are you riding the early miles? Is it possible you're starting out too hard?

Pete's right on. Depending on your pre-ride eating and energy level, a banana and breakfast bar may not be enough to eat during the ride. During longer rides I start eating at 1 hr., and every 1/2 hour thereafter, each time consuming something like a banana or breakfast bar. You don't want to overwhelm your digestive system, since it will contend with your legs for the available blood supply, but you sure don't want to go hungry, either.

If you're riding every day, are you recovering sufficiently? How do your legs feel early in the ride... heavy and tired, or do you have to exercise some restraint to pace yourself for 50+ miles? If it's the former, maybe taking a day off, or an easier day prior to the long ride is in order.

Headaches can have all sorts of different causes... neck strain is one, as is low blood sugar. Is the pain in an area that would lead you to believe it is muscle strain? Add my vote to Aerobat and Hunters, the shoulder/upper back pain may require some bike setup adjustment. Either way, lots of cyclists carry ibuprofen or Aleve (sorry, don't know the generic name). Both are excellent anti-inflammatories and reduce muscle aches and pains. (Aleve is more likely to cause stomach trouble, they advise taking it with a full glass of water).

Finally, another source of potassium... if you use salt, Morton makes a product called Lite Salt that's part potassium chloride, instead of pure sodium chloride. It's a good and inexpensive way to add a little more potassium to the diet.