Prof. Dain LaRoche works with Jean Haigh during a study on preventing falls by seniors. (Courtesy Dain LaRoche)

Taking up exercise helps elderly women gain muscle strength, but not the power they may need to prevent falls, a study suggests.

Falls occur in 40 per cent of people over 65 and are the top reason for injury-related visits to emergency rooms, the researchers said. Hip fractures are often linked to falls, and may result in loss of mobility.

"There's a gap between life expectancy and quality of life in older age," the study's lead author, Dain LaRoche, a professor of exercise science at the University of New Hampshire, said Friday. "We can improve that a lot with physical activity."

Inactive young and elderly women who participated in an eight-week training regime showed similar percentages of strength, but the older was group was far less effective at increasing power — which is more important than strength for recovering from loss of balance or walking ability, LaRoche said.

In the study appearing in the journal Medicine & Science in Sports & Exercise, the researchers reported that women aged 65 to 84 showed a 10 per cent increase in power compared with a 50 per cent increase among female participants aged 18 to 33.

"The major findings of the study suggest that while older women are capable of making similar gains in strength as young, they are less capable of making gains in muscle power [force divided by time]," the researchers concluded.

"This is especially troubling as muscle power is more closely related to fall risk and the ability to perform activities of daily living."

In the study, 25 young and 24 older women had their strength measured initially and then after they did six sets of resistance training, three times a week. The exercises were done on a machine that targeted knee extensor muscles that are critical for walking, climbing stairs or rising from a chair.

"It seems that the key to muscle power in the elderly is to maintain it over the lifespan rather than try to develop it later in life," LaRoche said.

The researchers speculated that seniors aren't able to boost their power since the fast twitch type of muscle fibres atrophy with age and inactivity. But resistance training did not seem to change muscle twitch measurements for knee extensors during the experiment, according to the study.

It's possible that other training protocols may be better for helping older women gain power, the researchers said. Other studies aiming to improve muscle power have used low-intensity hops or rapid weight lifting.

In 2006, about 17,000 hip surgeries were performed in people 65 or older, according to the Canadian Institute of Health Information.

Fall-prevention strategies can help reduce the risk, Greg Webster, a director of research at the institute, said when the report was released. Osteoporosis, low physical activity, taking many medications, and a senior's physical surroundings are all linked with the risk of fracturing a hip.