A little exercise can go a long way in preventing osteoporosis, a crippling bone disease that affects 200 million people worldwide.

Medical experts say that exercising for at least one hour a day three times a week can keep the bones strong and prevent fractures of the hip and spine in women. The best part is that you don't have to spend a bundle or run a marathon to experience the benefits of exercise. You can stay in shape and prevent osteoporosis right in the comfort of your own home or neighborhood.

Osteoporosis or porous bones is a disease that affects primarily white and Asian women. After menopause, the ovaries stop producing the female hormone estrogen that affects the calcium content of bones. As the bones lose calcium, they become thin and brittle. Although men may also suffer from osteoporosis as they age, women are more vulnerable because they have less bone mass.

This silent disease may progress for years without any symptoms, leaving its victims susceptible to fractures of the hip, wrist and spine. Worldwide, osteoporosis causes over 1.6 million hip fractures every year. About 20 percent of these women die within a year from complications.

"One of the most crucial strategies for preventing osteoporosis is to start a lifelong exercise program. The reason is that the skeleton is responsive to mechanical load, the amount of force you use against your bones. The more mechanical load you apply, the more your bones increase in mass. The best way to 'load up' is to engage in activities, such as weight-bearing exercises, that use the body's own weight as a force against gravity. These types of exercise stimulate bone-cell production," according to the editors of "The Women's Book of Home Remedies" published by Consumer Guide.

To improve bone strength and stimulate bone growth, exercises such as walking, cycling, tennis, aerobics or jogging are best. But before you start any exercise program, consult your doctor or a qualified physical therapist. In general, your routine should include aerobic exercise, stretching and strengthening workouts.