By Belinda Goldsmith

BEIJING (Reuters) - U.S. swimmer Michael Phelps is not only the hottest competitor the pool in the first week of the Beijing Olympics but also the athlete causing the biggest buzz online.

An analysis of online discussions on blogs and message boards by market researcher Nielsen Online found Phelps, 23, was the most discussed of 50 high-profile athletes competing in Olympic swimming, basketball, gymnastics and beach volleyball.

Among these four sports, swimmers led in overall volume dominating 46 percent of the discussion between August 4 and Aug 10, followed by basketball players with 38 percent. Gymnastics took up 9 percent on online chat and beach volleyball 7 percent.

"It appears that swimming is benefiting from a number of interesting stories this year, including Michael Phelps' race for gold, Dara Torres' return to the games and Park Tae-Hwan's win to bring home South Korea's first-ever gold medal in swimming," said Nielsen Online spokesman Jon Gibs in a statement.

"As other events build momentum and the track and field competition begins, it will be interesting to follow the fan favorites online."

Phelps was the most discussed athlete followed by basketball players Yao Ming from China and Americans Kobe Bryant and LeBron James as the United States and China faced off in the preliminary round.

Torres, the oldest member of the U.S. swimming team at 41, was the fifth most talked about athlete followed by U.S. gymnast Shawn Johnson, French swimmer Laure Manaudou and U.S. beach volleyball player Kerri Walsh.

Rounding out the top 10 were U.S. swimmer Katie Hoff and U.S. volleyball player Misty May-Treanor.