Exercise as it relates to Disease/The role aerobic exercise can play as a treatment for osteoporosis

Background to Osteoporosis

Osteoporosis is a disease of the musculoskeletal system characterized by a low bone mineral density which leads to fragility of the bone structure. The people most commonly effected by osteoporosis are women and the elderly, this puts post menopausal women at a significant risk. As we age it is possible for our bone mineral density to decrease by as much as 1%-2% per year. Because bone density is reduced in osteoporosis sufferers they are at a greater risk of suffering fractures than those who have healthy bones. It is common for osteoporosis to only be diagnosed after a fracture occurs, by which time the disease is usually reasonably advanced and further fractures are likely. As the populations of countries age and the elderly make up a greater proportion of them the costs of osteoporosis is expected to increase. The rate of osteoporotic fractures has already increased fourfold since 1990.

Diagnosis of Osteoporosis

Dual energy X-ray absorptiometry(DEXA) is the gold standard test for measuring bone mineral density (BMD) and is the one that's most commonly used. A bone mineral density 2.5 standard deviations below that of a young healthy adult would generally diagnose someone as suffering from osteoporosis, the presence of a fracture would imply severe osteoporosis. Osteoporosis is very closely linked with fractures and the prevalence of people with a bone mineral density 2.5 standard deviations below a normal score is very similar to the prevalence of people who suffer from hip fractures. It can be difficult to diagnose because bone mineral density can be analyzed at various locations in the body and different results can be found at different locations. The most common places to do a bone mineral density scan are the femoral head, lumbar spine and the wrist as they are places where fractures are most likely to occur.

Diagnosis	BMD (STDEV below average)
Healthy	< 1
Osteopenia	1 - 2.5
Osteoporosis	> 2.5
Severe Osteoporosis	> 2.5 + presence of fracture

Significance

The reason osteoporosis has become a significant issue is the negative effects that it can have on an individual, and the way that this can influence that persons quality of life. These negative effects can be either physical or psychological. The main physical effect osteoporosis has is the reduction of bone mineral density that occurs and the increased likelihood of fractures. These fractures can then impact someone not only physically but also psychologically as a fear of suffering further fractures can result in anxiety and depression.

Treatment

The main treatment used to reduce fractures are lifestyle changes, such as exercise, and use of medication.

Medication

Biophosphonates are the most common type of medication used to treat osteoporosis and they work by reducing the amount of bone tissue that is reabsorbed from the bone. When used correctly, biophosphonates can reduce the incidence of certain fractures by up to 50% but like many long term treatments the compliance with the treatment can be as low as 50% of patients. This low adherence rate means that solely using medication may not be the best treatment.

The Role of Exercise

By increasing the load placed on the bones through exercise the bone mineral density can be maintained or even increase over time, as opposed the normal decrease that comes as a result of aging. Resistance exercise has been shown to have the greatest impact on improving bone health because it creates the greatest loading on the bones, although aerobic exercise still has an important role to play in bone health. When using aerobic exercise as a treatment for osteoporosis the type and intensity of the exercise is very important, both for its intended effects on bone mineral density, and when thinking about injury prevention. Resistance exercise stimulates bones by increasing the weight they must hold, aerobic exercise must be weight bearing as well if it's to provide a similar stimulatory effect on bone growth. Exercises such as swimming and cycling will not improve bone mass because they aren't weight bearing. More vigorous, high intensity exercise will be more effective at improving bone mineral density because of the greater stress placed on the bones. Aerobic exercise can have many benefits other than just an increase in bone mineral density such as improving other aspects of a patients health like aerobic capacity, muscular strength and a reduction in body fat.

Aerobic Exercise Recommendations

It is recommended that patients exercise for sessions of 30 – 60 minutes at least 3 times per week. The exercises need to be weight bearing, or of a reasonable intensity to provide enough stress on the bones to stimulate growth. In osteoporotic patients care must be taken when prescribing an exercise regime as their bones are more fragile and prone to fractures. High impact exercises such as plyometrics or exercises that carry a risk of falls should be avoided.

Examples of Inappropriate Exercises

• Plyometrics
• High impact aerobics

Examples of Ineffective Exercises

• Cycling
• Swimming

Examples of Effective Exercises

• Running
• Walking above anaerobic threshold
• Step climbing

Further reading

• Osteoporosis Australia [1]