We all know many racers in Cats 1 2 3 4 and even 5 take supplements to increase performance. Among the leading legal supplements what are the best for endurance races? The market is full of powders telling us that they increase O2 utilization and such but most are just sugar and crap. Optygen is the leading seller but i have no real solid info on it. Its legal and "Safe". Does anyone know what works well to help increase performance without cheating?