CHICAGO (Reuters) - Exercise and yoga may improve the quality of life of women with early breast cancer, US and Canadian researchers said on Tuesday.

Women with breast cancer who did aerobic and weight training exercises had better self esteem, and the weight lifters were more likely to complete their chemotherapy, the study of 242 women in Canada found.

And a group of mostly black and Hispanic women with early breast cancer reported improvements in quality of life after taking a gentle yoga class each week for 12 weeks.

Both studies, published in the Journal of Clinical Oncology, suggest lifestyle changes such as exercise and yoga may help women with the emotional and physical challenges of breast cancer.

In the biggest study of its kind, researchers at the University of Alberta studied women undergoing chemotherapy in 2003 through 2005.

They were divided into three groups — an exercise group, a weight training group and those getting usual care in which patients are routinely told to take it easy.

Women in both exercise groups reported improved self-esteem, physical fitness and body composition.

And women in the weight-training group had the best chemotherapy completion rate of the three groups, with 78 percent completing the recommended chemotherapy, compared with 74.4 percent in the aerobic group and 65.9 percent in the usual care group.

"Breast cancer patients going onto chemotherapy can benefit from exercise programs, both weight training and aerobic," Kerry Courneya of the University of Alberta said in a telephone interview.

"And they don't need to worry that it will interfere with chemotherapy. If anything, our study shows it may actually help."

Low white blood cell counts are a frequent side effect of chemotherapy and and can often interfere with treatment.

Courneya said other studies have shown that weight training helps boost white blood cell counts. He suspects this may be helping the weight lifters stay on their chemotherapy regime.

Meanwhile, a group of breast cancer patients in New York found that a gentle weekly yoga class helped them to feel calmer and less emotionally depleted than those who did not take the class.

Researchers at the Albert Einstein College of Medicine studied 84 women breast cancer patients who took a weekly yoga class and 44 who did not.

Forty-two percent of the women were black and 31 percent were Hispanic. Women not in chemotherapy got the most benefit.

"I think the yoga class helped them with a sense of community," said study author Alyson Moadel, who noted that breast cancer can often lead to a sense of isolation.

"It helps them relax and slow down and stops the racing thoughts," she said.