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10482014_644081579013549_8253591493431708665_o‘I’ve been using Optygen from First Endurance for at least 5 or 6 years for bike racing. I looked at the ingredients and thought that it might work well for my mountain guiding at very high elevations. I guided 3 groups up Kilimanjaro last summer and the Optygen worked great until the last trip up and I ran out. Without Optygen I felt a significant difference in coping with the 19,000′ elevation. I always knew that it worked well for bike racing and now I know that it provides a great benefit when trekking at high elevations. Just FYI. The stuff works!’- Ed Chauner