Exercise as it relates to Disease/High impact exercise and its effects on osteoporosis

=High impact exercise and its effects on osteoporosis=

What is osteoporosis?
Osteoporosis affects millions of people worldwide, and is characterised by low bone mass and micro-architectural deterioration of bone tissue, leading to bone fragility and a consequent increase in risk of bone fracture, and can be considered as the pathological advancement of osteopenia. Osteoporosis is a difficult condition to diagnose, since it remains asymptomatic until skeletal fragility is well advanced, though dual X-ray absorptiometry (DXA) is the most commonly employed technique for bone mass determinations world-wide. Using DXA scan data and statistical analysis (T-scores), the World Health Organization has developed a diagnostic threshold for low bone mineral conditions. The T-score value indicates the number of standard deviations that an individuals DXA results are away from the young adult reference mean for their particular reference group. Common analysis sites are the hip, spine and forearm.
 * T-score of 1 to -1; Normal bone mass
 * T-score of -1 to -2.5; Low bone mass (osteopenia)
 * T-score of -2.5 or more; Osteoporosis
 * T-score of -2.5 or more with fragility fracture; Severe (established) osteoporosis

Risk Factors for Osteoporosis
The International Osteoporosis Foundation has grouped osteoporosis risk factors into two categories; fixed & modifiable. Having one, or several, of these risk factors can increase the likelihood of developing osteoporosis.

Prevalence in Australia
In 2007/08, it was estimated that osteoporosis affected 3.4% (692,000) of all Australians. This estimate has more than doubled since 1995 in Australia, from 1.5% to 3.1% of the total population. According to Osteoporosis Australia, over 1 million people in Australia suffer from osteoporosis at present., and this number appears to be increasing with an aging population. In 2004/05, the total direct health expenditure for osteoporosis in Australia was $304 million. Of this amount, $215 million was spent on pharmaceutical medicines, despite osteoporosis being a largely preventable disease.

What is High-Impact Exercise?
High impact exercise (HIE) is any action that applies a high or intense ground reaction force to the body. Types of HIEs may include jumping (and variations of), plyometrics, skipping, running and drop jumping. HIE is essentially any exercise that applies a high, rapid loading rate to a bone.

High-Impact Exercise and it's effect on Osteoporosis
HIE utilises Wolff's Law of bone remodeling to cause positive adaptations in bone tissue. Wolff's Law states that a will bone grow and remodel in response to the demands and stresses placed on it. Therefore, the high loading rate of HIE places stress on a specific bone, causing it to remodel and strengthen in response. HIE has been proven to increase bone mass at the femoral neck following HIE protocols. Odd-impact exercises, those with random loading directions, have caused similar positive bone adaptations, but are mechanically less-demanding on the body than HIE. Therefore, using HIE with odd-impacts and random loading directions may be best for improving bone strength, and slowing osteoporosis.

Limitations of High-Impact Exercise on Osteoporosis
Using HIE for bone adaptations may not be practical for some bones (eg. ribs). The benefits may be restricted to those bones that are readily loaded with high forces. These high loads may increase a persons susceptibility to fracture during impacts however, and therefore may not be practical for use in conditions with weak bones, or those susceptible to falls.

Recommendations for High-Impact Exercise and Osteoporosis

 * HIE should not be used in populations with a fracture history. The high loads placed on bones during HIE may cause a fracture.
 * Those with poor balance and coordination should not use HIE as it may increase the likelihood of a fall.
 * HIE should be used to maximise peak bone mass during childhood and adolescence.
 * HIE with odd-impacts are best for bone remodeling. Odd-impact activities include basketball, netball, plyometrics, dancing and gymnastics.
 * Other exercise types that involve high impact loads may be more beneficial as they include other benefits, such as muscle growth (resistance) and cardiovascular health (aerobic).
 * Prevention is the best method for reducing the likelihood of osteoporosis, and this can be done by minimising the effect of modifiable risk factors.

Further Reading/Information
Osteoporosis Australia

International Osteoporosis Foundation

FRAX - WHO Fracture Risk Assessment Tool for Australia

Health Insite - Osteoporosis