I have been using Optygen for almost a year now, and have had a very positive response to it. In the interest of full disclosure, I am sponsored by the manufacturer - so I can't comment on the price :0) other than to say that I would buy the product at retail if I had to...
I really hate to offer purely subjective/anecdotal data in response to a question like this, but I will say that the Optygen regimen has appeared to offer a benefit to me very much as advertised; notably my recovery from hard efforts, both in training and during a race is much improved. In training, I am able to train harder and longer before I exhibit symptoms of fatigue (on the immediate scale) or overtraining (on the macro-scale), and during a race, I appear able to more quickly recover from Z4 & 5 efforts than before the supplementation. I have pretty comprehensive training and HR logs from the last several years, and they definately support these conclusions.
I think there are a couple of things that really point to First Endurance (the manufacturer of Optygen) as a quality company: they guarantee the purity of the product (no false positives!) they guarantee all the ingredients are "legal," and they print references to clinical studies - right on the bottle - to support all the claims they make. How many other companies do these things?
As an aside, there are a LOT of pro cyclists using Optygen these days, both on the domestic scene and abroad (Rodriguez and Leipheimer, Navigators team...) and some notable Tri-folk are starting to use it (Larsen for one.) Generally, this doesn't mean a lot, given sponsorship and such, but almost all the domestic road pros that I know are using either Optygen or Athletes Octane (which is a very similar product) and most are paying for them. In a couple of years, my guess is that products like these will be a ubiquitous part of an athlete's supplement regimen.
[The "mushrooms" (Rhodiola) in Optygen actually have a pretty fair base of support in clinical trials - I was looking for the link to an abstract I read, but couldn't get it to work: I will post it if I can get it to go through.]
MH - 35+ and a cat 1 on the road, I need all the help I can get.
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