Muscular men really do get the girls more often than their less brawny brothers - at least in the short term, research suggests.

The well-muscled are twice as likely to have more sex partners, flings and affairs than those with less toned and chiseled physiques. But in the end, the research suggests, women tend to choose the less buff for long-lasting love.

Women choose musclemen for brief liaisons, but the less burly appear more desirable for long-term relationships because women believe they're more faithful and romantic. The brawny were seen as more domineering and volatile.

"If a man is interested in long-term relationships, maybe he shouldn't spend so much time at the gym," says Martie Haselton, an associate professor at the University of California-Los Angeles and co-author of the research. The study will be published in Personality and Social Psychology Bulletin in August.

Haselton and David Frederick, a UCLA graduate student in psychology, conducted six studies from 2002 to 2006 in which they analyzed responses about muscularity and sexual partners from a total of 788 college students - 509 women and 279 heterosexual men.

Some of the UCLA studies used photographs of men ranging from slender to brawny and asked heterosexual men to report on the muscular features of their own body type and their sexual relationships. Men who were more muscular than average had twice the number of sex partners, flings and affairs with women who had a boyfriend as those of average or below average muscularity.

The research also compared the men's responses with women's tallies of their sexual encounters and the muscularity of their short- and long-term partners. Sixty-one percent reported that their short-term partners were more muscular than their long-term partners.

Steven Gangestad, a psychology professor at the University of New Mexico in Albuquerque who was not involved in the UCLA study, says the research may well be the first to correlate muscularity with sexual prowess.

"Certainly, the study confirms what I believe are people's suspicions: that men who are more fit and more muscular are indeed seen as more attractive."