// Strong bones, strong future

Taking care of bone health with clients of every age is one of the most valuable ways of increasing their quality of life in later years, says Megan Riddington.

Good bone health is often considered relevant only to older adults with their increased concerns about osteoporosis, falling and the potentially debilitating effects of breaking a bone. The fact is, bone health is important to people of all ages, and taking care of it is one of the most valuable ways of increasing quality of life in your older years. This often neglected element of health can be promoted by fitness professionals as yet another reason why exercise and healthy eating is good for you.

We can’t increase bone density in later life, only slow the rate of its decline. So it’s imperative that we encourage our clients who are in the first three decades of life to achieve peak bone mass through good lifestyle choices.
For clients over the age of 50, the focus should be on controlling the rate of decline through good nutrition and varying exercise routines that include resistance training and training that applies stress to bones. To help our older clients maintain quality of life, we need to do everything possible to prolong the onset of declining bone density.

Building strong bones in youth

Bones experience their greatest gains in mineral density around puberty (Kohrt 2004). After this time, until the age of around 30, bone mass may continue to be increased, though at a lesser rate. The primary determinants of bone density over which we have control are frequency, intensity, duration and type of physical activity, as well as calcium and vitamin D intake.

Bones must experience deformation to become stronger, not unlike the way in which muscles must experience stress in order to achieve gains. Bones are a dynamic organ, constantly remodelling and changing. The process of bone turnover, which takes three to four months, involves bone resorption (where cells called osteoclasts remove damaged cells), as well as bone formation which is carried out by osteoblasts. This remodels the architecture of the bone to form a stronger, denser structure after trauma (such as high impact exercise) has occurred. It is important these two processes occur at the same rate; when they don’t ‘uncoupling’ occurs and this can be damaging to bone health. When prescribing exercise to increase bone strength, it is necessary to apply activities of an intense nature to cause osteocyte deformation, as this stimulates remodelling. While ground reaction force is a good indicator of the intensity of an exercise, it is usually more practical to use other intensity markers such as heart rate or percentage of one repetition maximum (%1RM).
Adolescence offers the final chance to reach peak genetic potential for bone density, so the importance of physical activity is paramount, as is adequate nutrient intake.

Nutrition and vitamins

Along with physical activity, good bone health requires the adequate intake of both calcium and vitamin D. Vitamin D is important because it assists the absorption of calcium, and mineralisation of bones. The best source of vitamin D is ultraviolet light from the sun. You might think that this would not be a problem in a sunny country like Australia, but as the sample of recommendations for exposure to sunlight shows, in winter vitamin D deficiency can occur, as the recommended sun exposure is higher than most people realise. Vitamin D is also only found in very small doses in certain foods, so supplementation provides an effective means of increasing intake. The daily requirement of vitamin D is 400 to 600IU, though a higher dosage should be taken if stores are already depleted (Diamond 2005). Calcium is important for strengthening bones, and decreasing the risk of fractures, so children should aim to consume 1,000 to 1,300mg per day of calcium, and adults should aim for 1,000mg per day (Sanders 2009), which is usually achievable with three daily serves of dairy.

Bone mineral accrual in childhood and adolescence

The American College of Sports Medicine’s (ACSM) guidelines for bone mineral accrual in children and adolescents recommend that children participate in the following level of activity:

Mode: Impact activity, such as gymnastics, plyometrics and jumping, and moderate intensity resistance training. Participation in sports that involve running and jumping (soccer, basketball) is likely to be of benefit, but scientific evidence is lacking.

Intensity: High in terms of bone-loading forces. For safety reasons, resistance training should be <60%1RM.

Frequency: At least three days per week.

Duration: 10 to 20 minutes (two times per day or more may be more effective).

The elements of this recommendation (mode, intensity, frequency and duration) are important to ensure adequate stimulation is applied to the bone to cause optimal remodelling.

For more detailed exercise prescription for children and youth, www.strengthandconditioning.org has a position stand from the Australian Strength and Conditioning Association.

Controlling density decline after the age of 50

From the age of about 30, it seems that bone density is maintained until menopause in women, and until approximately 50 years in men. After this, a steady decrease of two to three per cent bone mass is seen in women for the first five years, and around one per cent per year thereafter. Men lose bone mass at around one per cent per year after the age of 50 (Korht 2004). It is important to note that physical activity reduces the rate of bone loss in men and premenopausal women, but no physical activity guidelines can prevent the menopause-related bone loss seen in women. Pharmacological treatments to prevent osteoporosis do exist for this population, and it is wise to refer clients to their doctor for more information regarding these options.

Preservation of bone health through adulthood

Resistance training in adults is beneficial to bone health because it applies stress to the bone at the origin and insertion sites of the muscles being trained, causing strengthening in these areas. Training causes localised strengthening, so loaded squats, for example, are beneficial as they cause strengthening of the bones at the origin and insertion points, while jump squats strengthen the deeper trabecular region of the femur. The following guidelines from the ACSM are designed to optimise preservation of bone health through adulthood:

Mode:
Weight bearing endurance activities (tennis, stair-climbing, jogging – at least intermittently during walking), activities that involve jumping (volleyball and basketball), and resistance exercise (weight lifting).

Intensity: Moderate to high, in terms of bone loading forces.

Frequency: Weight bearing endurance activities three to five times per week; resistance exercise two to three times per week.

Duration: 30 to 60 minutes per day of a combination of weight bearing endurance activities, activities that involve jumping, and resistance exercise that targets all major muscle groups.

There is no upper age limit for the adult guidelines, and you should encourage clients to persist in vigorous exercise as much as possible throughout life to deter increased rates of bone loss. When physical activity ceases, gains found in bone mass will return to sedentary levels. As clients become older, balance, leg strength and flexibility should also be incorporated into their training programs to decrease the risk of falling, a major cause of injury and mortality. Naturally, safety must be considered when prescribing exercise so as to minimise risks.

A lifelong consideration

In order to remain as functional as possible as the years progress, bone health should be considered throughout life, not just as older age appears on the horizon. Adequate vitamin D, calcium and impact exercise are vital for achieving this. As fitness professionals we must be aware of the implications of poor bone health, we must know how to identify areas for improvement in our client’s diet and exercise regime, and we must know when it is appropriate to refer our clients to a doctor or dietitian. While bone health may not be as visible as muscle gain, or weight loss, it is every bit as important.

  
 

Megan Riddington, BSc
Megan has completed a Bachelor of Exercise and Sport Science, majoring in physiology and sports nutrition at Deakin University. She has been working in the fitness industry since 2003, and is currently a personal trainer at Fitness First in Malvern East, Victoria. For more information, email meganriddington@hotmail.com.


NETWORK • SPRING 2010
• PP 30-32