NEW YORK: For women undergoing chemo for breast cancer, an exercise program doesn't do much to improve their quality of life -- but it can boost their self-esteem, physical fitness, and chemotherapy completion rates.

"Breast cancer chemotherapy may cause unfavourable changes in physical functioning, body composition, psychosocial functioning, and quality of life," Dr Kerry S. Courneya, of the University of Alberta in Edmonton, Canada, and colleagues write in the Journal of Clinical Oncology.

The researchers examined the possible beneficial effects of aerobic and resistance exercise on these changes in a study involving 242 breast cancer patients beginning chemotherapy.

The women were randomly assigned to usual care, supervised resistance exercise, or supervised aerobic exercise for the duration of their chemotherapy.

The average length of the exercise intervention was 17 weeks, and 70 per cent of the participants stuck with it.

Compared to usual care, aerobic exercise was significantly better in improving patients' self-esteem, aerobic fitness, and percent body fat.

Resistance exercise was also superior to usual care for improving self-esteem, lower and upper body strength, lean body mass, and chemotherapy completion rates.

However, neither type of exercise significantly improved any cancer-related quality-of-life measures such as fatigue, depression, or anxiety.

Nonetheless, the authors suggest that cancer doctors consider recommending an aerobic or resistance exercise program to women being treated for breast cancer.