Exercise is beneficial for cardiovascular health, for building muscle strength, and for losing weight and maintaining proper weight. Exercise also has benefits for the skeletal system, such as building bone density and decreasing the risk of osteoarthritis and osteoporosis. Exercise has some disadvantages for the skeletal system, however, mainly associated with too much or too strenuous activity.

Fractures

Competitive runners in particular are more likely to experience stress fractures, according to a study published in the October 2006 issue of "Topics in Magnetic Resonance Imaging." A stress fracture is a partial or complete bone break resulting from repeated application of stress, even though the stress is less than that required to fracture the bone in one application. Stress fractures account for up to 20 percent of all injuries seen at sports medicine clinics. Of all athletes, track-and-field athletes have the highest incidence of stress fractures. These fractures are also referred to as fatigue fractures, as noted by a study published in the August 1962 issue of "California Medicine." That study found the incidence of fatigue fractures to be highest in middle-distance runners who train intensively. The authors recommended part of the training be done on grass rather than on hard surfaces.

Possible Injury with Osteoporosis

Although exercise can help prevent osteoporosis, people who already have this condition should be cautious about exercising. They are more susceptible to spinal injuries or other fractures. The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) advises consulting with a doctor about safe activities. These individuals may need to avoid exercises involving flexing, bending or twisting the spine. High-impact exercise such as jogging also is a disadvantage for people with osteoporosis as it can lead to a fracture.

Disadvantages for Young Women

Too much exercise can have adverse effects on the skeletal systems of young women due to its effects on hormones, according to the American Medical Women's Association (AMWA). Low estrogen production results in delayed onset of menstruation, which has negative effects on bone growth. These girls have a higher incidence of scoliosis, stress fractures and lower-than-normal bone mineral density (osteopenia). This low bone mineral density may be irreversible.

Back Pain

Excessive exercise can cause trauma to the skeletal muscles, leading to back pain. An example is weight lifting with too much weight, or weight lifting out of proper position. Lower back strain can result from exercising too strenuously for one's fitness level, more common in weekend warriors who are sedentary during the work week. The individual may experience muscles aches, shooting pains, and limited flexibility or range of motion, as noted by the National Institute of Neurological Disorders and Stroke (NINDS).