I've had periods of drowsiness on long rides and I can almost always track it to one of the usual suspects:
- low blood sugar/glycogen
- not taking an off bike break often enough
The cure 99% of the time is stop and get off the bike, walk and stretch while eating a granola bar and downing 12 oz or so of water or diluted sport drink. Usually ready to go in 2-3 minutes and feeling awake after another 5-10 min of riding. I noticed that the last poster mentioned sodium a couple of times. While electrolytes are important, sodium is just one of four important electrolytes (the others being potassium, calcium, and magnesium) that must be kept in balance. There is no need to load up on electrolytes. Yes, you lose a small amount in sweat but if you are well nourished to start with and you consume normal foods like fig newtons, oatmeal raisin cookies or granola bars during your ride, you are very, very unlikely to develop hyponatremia (dangerously low sodium) during even an extended strenuous ride. Your body does an excellent job of maintaining electrolyte balance except under extreme circumstances. There is no need to seek out foods "loaded with sodium". Far more important to watch are hydration and carbs. Dehydration is prevented by drinking water, not by consuming excessive amounts of sodium.
If anyone really wants to check this, have your blood drawn before and after a 100-mile ride. Even if you drank only sufficient amounts of water and ate a few handfuls of fig newtons, your serum potassium and sodium levels won't have changed very much and will most likely be well within the normal range, even if you were sweating like a draft horse through the entire ride.
Last edited by Myosmith; 05-28-12 at 09:05 PM.