June 12 (HealthDay News) -- A session of moderate aerobic exercise can help reduce anxiety and improve the quality of sleep for insomnia patients, according to a Brazilian study. Heavy aerobic or moderate strength exercises don't have the same effect.

Researchers at the Federal University of Sao Paulo divided 28 women and eight men with primary chronic insomnia into three exercise groups -- moderate aerobic, heavy aerobic, and moderate strength -- and one control group.

After the exercise session, those who did moderate aerobic exercise showed reductions in sleep onset latency (54 percent) and wake time (36 percent) and increases in total sleep time (21 percent) and sleep efficiency (18 percent). They also showed a 7 percent decrease in anxiety.

"These findings indicate that there is a way to diminish the symptoms of insomnia without using medication," study author Giselle S. Passos said in a prepared statement.

"This is the first study to look at the importance of using physical exercise to treat insomnia and may contribute to increased quality of life in people with one of the most important kind of sleep disorders around the world," Passos said.

The findings were presented Wednesday at the annual meeting of the Associated Professional Sleep Societies, in Baltimore.

SOURCE: American Academy of Sleep Medicine, news release, June 11, 2008