Strength training can help older people function better and reduce pain for those suffering from arthritis, according to a review of the medical literature.

But more information is needed on the safety of progressive resistance training for frail seniors or those recovering from illness, the reviewers conclude.

People typically get weaker as they get older, which can lead to disability and increase their risk of falling, Drs. Chiung-ju Liu of Indiana University in Indianapolis and Nancy K. Latham of Boston University point out in The Cochrane Library, a publication of the Cochrane Collaboration, an international organization that evaluates medical research.

Progressive resistance training, in which a person uses weights, elastic bands or exercise machines to strengthen their muscles by doing progressively tougher exercises, offers promise in helping people to maintain their strength as they age, Liu and Latham report.

However, the researchers say, more information is needed on how this kind of training effects people's functioning in the real world and whether it's safe for people with health problems or disability.

To investigate, they looked at 121 randomized controlled trials involving 6,700 people. In most studies, participants did high intensity exercises two or three times a week. All of the trials compared progressive strength training with no exercise, or with another type of exercise such as aerobic training.

Overall, the researchers found, progressive resistance training reduced weakness and improved people's ability to perform both basic and more complex tasks of daily living, including rising from a chair and climbing stairs.

Osteoarthritis patients who did progressive resistance training reported a reduction in pain. Osteoarthritis is the wear-and-tear form of arthritis in which the cartilage cushioning the joints gradually breaks down.

According to Liu and Latham, 53 of the studies didn't address the issue of adverse events at all, while 25 reported that there were no adverse events related to the training program and 43 reported some adverse events, typically pain in the joints or sore muscles.

While serious events were uncommon, "some caution is warranted with this intervention as in many studies adverse effects have been poorly monitored," Liu and Latham wrote.