A runner my son occasionally trains with has been extolling the virtues of a supplement he uses called Optygen. I googled the info below from one of their websites and it sounds fine. Bottom Line--does it work and are there any negative side effects?
Optygen is unlike any other endurance product available. Optygen is a legal, safe and stimulant-free formula designed specifically to optimize performance for endurance athletes. This revolutionary formula is based on human clinical trials and the latest scientific research on increasing endurance.
The adaptogens in Optygen have been studied extensively for their ability to:
Increase VO2Max
Increase the body's ability to adapt to high levels of physical stress
Increase anaerobic threshold
Reduce lactic acid