proper nutrition while exercising is best. Keep up the electrolytes, carbs, and proteins, and you'll notice a huge difference over just plain old water. There is a ton of crap that claims to increase your performance. If it was true, why wouldn't everyone use it? either it's unsafe or has unpleasant side effects, or it's a bunch of crap. Since the FDA will ban most supplements with serious negative side effects, guess which option i'm thinking. Optygen appears to be safe, and all the online reviews i can find about it are mixed. But as one said, there are no magic pills that increase your performance. Supposedly it's also pretty pricey. Personally, i wouldn't want to take something i don't take while exercising to help my endurance. That leads me to think that it might have a more dramatic impact on my body than the stuff i drink while i ride. I prefer a drink like Cytomax or endurox that is basically high-test gatorade with some extra stuff to help out endurance. Supposedly, a 4:1 carb to protein ratio helps boost endurance over a normal carb only drink. Also, these types of drinks with carbs and protein are good for recovery, which can help you train harder and make better gains. If anyone else has any insight on Optygen or this type of supplement, i would love to hear about it.