Studies of players during competitions have found that their heart and respiration rates become elevated. Top players say they exercise regularly to keep in shape because they feel they cannot play their best otherwise. And there is anecdotal evidence to support them.

Five years ago, Vladimir Kramnik, a Russian grandmaster who was then world champion, began to falter in tournaments. Doctors diagnosed rheumatoid arthritis, and he began receiving treatments and stopped playing for six months. Once the arthritis was brought under control, Kramnik returned to competition, and his results improved.

In 2006, chess was included in the 15th Asian Games, an Olympic-style event that also includes basketball, boxing and wrestling competitions.

The 16th Asian Games began last weekend in Guangzhou, China, and chess is again in the lineup. There are several competitions. The first was a rapid chess event, in which players had 25 minutes at the start of each game and had 10 seconds added after each move.

Among the men in the rapid competition, Rustam Kasimdzhanov of Uzbekistan took the gold by edging out Le Quang Liem of Vietnam on a tie-breaker. The women’s division was won easily by Hou Yifan of China, who finished a full point ahead of Zhao Xue, also of China.

In Round 7, Hou beat Zhu Chen, who was born in China but lives in and plays for Qatar. The game was rich with tension.

It would have been a mistake for Zhu to play 9 Qc6 because her queen would have been trapped after 9 … Bd7 10 Qb7 Rb8 11 Qa6 Bb5 12 Qa7 Qc8 13 a3 Ra8.

After 25 … h4, Zhu could not take Hou’s rook by playing 26 Rd8 because after 26 … hg3 27 fg3 Bg3 28 Kh1 Bh2 29 Qc2 Qh4 30 Qg6 fg6 31 Kg2 Qg3 32 Kh1 Qh3, White would have been lost.

Zhu blundered with 30 Qc3, but Hou missed the win. She should have played 30 … hg3 31 fg3 Rh2 32 Qc7 Qh5; if she had, White would have soon been mated.

Hou blundered with 32 … Qh5; 32 … f5 would have been better. But Zhu overlooked 33 Re5, when after 33 … Qf3 34 Rf5 Qe4 35 Qe4 de4 36 Rf7, White would have had a big advantage.

Instead, Zhu erred with 33 Rb1. This time, Hou did not miss her chance.

Once Hou forced the queens off the board, there was no way for Zhu to save the game, and she soon gave up.