FROM my own practice and research, I know that yoga is generally a good thing. The bending, stretching and deep breathing can renew, calm, heal, strengthen, lift moods, lower the risk of heart disease, increase flexibility and balance, counter aging and improve sex. In short, the benefits are many and commonplace while the serious dangers tend to be few and comparatively rare.

Even so, last year, after my book on yoga came out, letters from injured guys prompted me to see if the practice, despite its benefits, was hurting one sex more than another. To my surprise, reports from hospital emergency rooms showed that, proportionally, men got injured more often than women and suffered damage that was far worse, including fractures, dislocations and shattered backs.

It made sense. Women are well known to be more flexible than men. Macho guys, yoga teachers told me, too often used their muscles to force themselves into challenging poses and got hurt. The overall numbers were relatively small but large enough to argue that men who did yoga should exercise caution.

Earlier this year, the picture of female superiority began to blur when a prominent yoga teacher in Hawaii wrote me about a poorly known threat to women.