That's only one point of several in the article, but I agree that it is one of the most questionable:
"She and a group of scientists assembled 3,075 seniors in their seventies and asked them to traverse a 400-meter course, walking as fast as they could. [...] For every minute longer it took someone to complete the 400-meter walk, he had a 29 percent higher chance of mortality and a 52 percent greater chance of being disabled. People who walk faster live longer -- and enjoy better health in their later years."
The article doesn't explore the alternate explanation that healthier seniors are able to walk faster. (...although, to its credit, it does raise the possibility that people who like to walk are more likely to move to New York.)
"She and a group of scientists assembled 3,075 seniors in their seventies and asked them to traverse a 400-meter course, walking as fast as they could. [...] For every minute longer it took someone to complete the 400-meter walk, he had a 29 percent higher chance of mortality and a 52 percent greater chance of being disabled. People who walk faster live longer -- and enjoy better health in their later years."
The article doesn't explore the alternate explanation that healthier seniors are able to walk faster. (...although, to its credit, it does raise the possibility that people who like to walk are more likely to move to New York.)