Pool exercise may build strength, reduce falls

Women who did a high-intensity aquatic workout for six months increased their strength and suffered fewer falls, in a new study that suggests bone- and muscle-building resistance can be achieved with the right kinds of water exercises.

"What we did was to test the model for muscle training in the gyms and put it inside the pools," said lead author Linda Moreira, a researcher at the Universidade Federal de São Paulo.

The study should encourage postmenopausal women at risk for osteoporotic bone-thinning that pool-based exercise can increase muscle and bone strength, according to Moreira's team.

Aquatic aerobics became popular in the 1990s as a way for older people to exercise without straining their joints or being injured in falls.

However, aquatic exercise fell out of favor, experts said, because of concerns that the bone and muscle-building benefits of resisting gravity in standard exercises were diminished when someone is buoyant in water.

To test a water workout Moreira's group designed to increase resistance and build strength, they recruited just over 100 inactive women in their 50s and 60s.

All the women took 1,000 international units of vitamin D3 and 500 milligrams of calcium daily - both vitamins known to help build bone and muscle - during the six-month study.

Half the women were also assigned to an aquatic exercise program, which Moreira's group created to combat osteoporosis by preventing falls, and named HydrOS.

Instead of the more typical high-repetition, low-impact aqua-aerobics, the HydrOS interval training included bursts of intense activity between 10 to 30 seconds at up to 90 percent of maximum heart rate. The water created the resistance that weights would provide on land, Moreira said.

Seven months later, the number of falls among aquatic exercisers had dropped 86 percent, and the number of women who suffered falls dropped 44 percent. In the sedentary group, the number of falls remained unchanged, according to results published in the journal Menopause.

The researchers also found that flexibility plus hand, back, hip and knee strength increased in the aquatic exercisers. The women in the sedentary group showed mild increases in balance and strength as well, but the researchers attributed those improvements to the calcium and vitamin D supplements.

As people age, they lose muscles used for quick movements that stimulate bone health. But, according to Moreira, typical aquatic aerobics work muscles used for slower day-to-day movement.

"Physical instructors were training the wrong muscle type," she said.

About a quarter of the study participants had osteoporosis, half were at the beginning stage of the bone disease and the remaining quarter had normal bones.