This study suggests that it takes a vigorous workout to move the oxygen consumption markers indicative of a beneficial workout. The slow paced 5k single group walks in the resveratrol study may not cut it. Problem for studies like this is safety. They're probably reluctant to let the older out of shape subjects they want to test perform anywhere near their limits out of concern they may drop dead on them.
http://www.ncbi.nlm....les/PMC3667025/