Are you one of the many who take the supplement Resveratrol for the antioxidant and anti-aging potential?
A new piece of research appearing in the Journal of Physiology might interest you.
The research was conducted with subjects 65 years of age. That might not apply to you age-or-gender-wise, but the results are thought-provoking no matter what your age or gender.
Could be especially important if you find your endurance seems to be not improving, or is falling off a little.
Basically the research showed what it says in the headline: "Resveratrol blunts the positive effects of exercise training on cardiovascular health in aged men." The quick abstract is here.