Men should exercise to improve sex life

LA Times article "Men should exercise to improve sex life" (May 31st, 2010) notes a study that finds

Men who exercised had significantly higher scores on a sexual-function questionnaire compared with men who were sedentary, according to a study released Monday at the annual meeting of the American Urological Assn.

The article then makes the causal claim implied in its title. Of course, the relationship (that more exercise implies better sex life) may be inverted. Perhaps it is true that men who have greater utility from their sex life are willing to pay more to maintain that sex life. This will, among other things, cause these men to exercise more, improving their appearance to the opposite sex (and so increasing the amount of sex they have). In addition, it may be that more virile men have both better sex and are pre-disposed to exercise more. Fundamentally, the article gives us no reason to exclude either reverse-causality or a correlation caused by an unobserved third factor as responsible for the relationship reported between sex and exercise. Nonetheless, the article suggests in its title that people change their lives in way fundamentally rooted in a rejection of these possibilities.