FRIDAY, April 18 (HealthDay News) -- Exercise may help improve fatigue caused by cancer and its treatments, new research says.

"A lot of time, the medical response to patients is that they should expect to be fatigued, that it is a normal side effect. If patients are told that fatigue is just a side effect and to accept it, what they are not getting is any advice or support to help them cope," review lead author Fiona Camp, a lecturer at the University of the West of England in Bristol, said in a prepared statement.

Camp and her colleagues examined data on more than 2,000 cancer patients in 28 studies, which tested exercise programs that lasted from three weeks to eight months. The typical duration was 12 weeks. Walking and stationary bike riding were the most common types of exercise in the studies.

The researchers found that exercise is more effective at combating cancer-related fatigue than the usual care provided to patients.

"Exercise shouldn't be used in isolation but should definitely be included as one of the components in the package of interventions used during and after treatment," Camp said.

She said a clearer "exercise prescription" for cancer patients can be developed after experts learn more about what intensity, frequency, duration and kinds of exercise best suit cancer patients. Until then, available evidence shows that exercise therapists, physical therapists and exercise physiologists need to part of cancer patients' treatment teams, she added.

The review was published in the current issue of The Cochrane Library.

The first step in treating cancer-related fatigue is to check for any underlying medical conditions (such as anemia or an underactive thyroid) that can cause fatigue-like symptoms, said exercise researcher Karen Mustian, an assistant professor in the department of radiation oncology at the University of Rochester School of Medicine. She was not involved in the review.

"There will still be a fair amount of patients dealing with fatigue after we get other situations under control," Mustian said in a prepared statement.

"I think it's safe to say at this point that the sort of generalized guidelines of walking 30 minutes a day three to five times a week generally help patients. We can't say what specific doses are best. With the evidence currently out there, we can't say much beyond that," she said.

More information

The U.S. National Cancer Institute has more about cancer-related fatigue.