The consequences of fracture are well-documented, but the most serious osteoporotic fracture is that of the hip. Hip fractures result in increased mortality by up to two years, increased morbidity, and long-term care costs.1

Identification of risk factors enables interventions to be provided to those at greatest risk of fracture. As well as factors such as age, gender and maternal history of fracture, there are other risk factors that are directly affected by activity levels.2 These include the risk of falls, and current activity status. Indeed, almost 90% of hip fractures result from the impact of a fall3 and physically active individuals have a 20-40% lower risk of sustaining hip fractures than sedentary individuals.4

The UK Chief Medical Officers' guidelines for physical activity and health in older people now include recommendations to perform two sessions of activities that improve strength and two sessions of activity that improve balance in addition to accumulating 150 minutes of moderate physical activity and avoiding long periods of sitting in any given week.5

Effects of activity on bone in older age

In order to achieve maximal benefit, regular physical activity or exercise must target vulnerable bone sites (specificity) and be progressive in intensity (overload).6,7 Additionally, activities must be of sufficient duration and sustained over time (overload). BMD will return to previous levels if exercise is stopped (reversibility).6,7 Exercise interventions are typically those that stress or mechanically load bones (when bones support the weight of the body or when movement is resisted, for example when using weights) and include aerobics, strength training, walking and Tai Chi.8

The most recent Cochrane review of evidence on exercise and bone health in post-menopausal women showed that the most effective type of exercise intervention on bone mineral density (BMD) for the neck of femur was non-weight bearing high force exercise such as progressive resistance strength training for the lower limbs and for BMD at the spine, combination exercise programmes.8 The authors also concluded that there was no effect on numbers of fractures (odds ratio (OR) 0.61; 95% CI 0.23 to 1.64) but that seven women out of 100 who exercised had a fracture compared to 11 women out of 100 who did not exercise.8

There is less evidence on the effects of exercise on fracture rates, owing to the difficulties in recruiting sufficiently large numbers of participants within homogeneous exercise programmes, to show a treatment effect.9

One study in postmenopausal women, did demonstrate a significant reduction in vertebral fracture rates, which was maintained over a 10 year follow-up period.10 This was achieved through progressively weighted prone back extension exercise, and demonstrated persistent beneficial effect long after exercise cessation.10

Intuitively, despite the lack of current available evidence, exercise is likely to reduce fracture rates, as it is the only intervention which can both reduce falls risk and improve BMD.11, 12 It is worth noting that although most research on exercise and bone health has been on females, studies have demonstrated similar effects in men,13 and therefore recommendations currently apply equally to men and women.

Effects of activity on falls in older age

During later years, the focus of exercise shifts from preserving bone mass, to preventing falls.14 Because most fractures in older people are preceded by a fall, an exercise programme designed to reduce falls must be the priority for those at increased risk of falls or with poor bone health. Sherrington highlighted the key role that exercise plays in reducing falls rates, when incorporating balance activities at the core of the programme.11

Balance training exercise that improves clinical balance outcomes in older people include gait, balance, co-ordination and functional tasks; strengthening exercise; 3D exercise, Tai Chi and multiple exercise types.15 In post-menopausal women, Tai Chi has been linked with a three- to fourfold slowing down in the rate of bone loss in both trabecular and cortical compartments of the distal tibia compared with a sedentary lifestyle,16 as well as reducing fall risk.17

Another six-month exercise programme consisted of standing on a single foot for one minute per leg three times per day and showed significantly increased hip total BMD in those aged 70 years or over.18 In older women with a history of frequent falls, a nine-month programme of strength and balance training (FaME) not only significantly reduced falls risk, but also showed improvements in BMD.19,20 The FaME programme and the Otago home exercise programme,21 are the most common rehabilitation programmes run by falls services across the UK.22 However, this is a challenging group to work with as fear of falling and consequent avoidance of activity is common.23

Exercise recommendations for those with impaired bone health

Individuals with a diagnosis of osteoporosis should be advised to avoid all high impact exercise, due to the risk of exposing the skeleton to excessive loads and increasing fracture risk, as well as activities that could increase risk of falls.24 An exercise programme should therefore be modified to incorporate low and medium impact exercises, as well as site-specific, progressive resistance exercise. Excessive spinal forward flexion, or loaded or uncontrolled spinal rotation should be avoided, due to the increased strain placed on the vertebral bodies, thereby increasing the likelihood of vertebral fracture.10,24 It is important to note that falls risk can be improved even in individuals with osteoporosis.25 Fitter individuals with osteopenia are able to incorporate some high impact exercise, but only as part of a mixed-impact exercise programme, with gradual introduction and build-up of exercise impact and intensity.24

Getting started

Prior to commencing an exercise programme, all individuals should consult their healthcare professional to confirm exercise suitability if unsure. Initially, simply increasing daily activity levels is recommended. This could be in the form of housework, walking, or gardening, although brisk walking is not recommended for fall-prone older people as it can increase the risk of falls and fractures.11, 26

The Department of Health guidelines may be unachievable for some frailer older people, so the message of moving more often, attempting moderate activity in bouts of 10 minutes or more, and appreciating that with the relative fitness in this population this may be a relatively slow walk, are important.5 The addition of activities that strengthen muscle and challenge balance are more difficult to convey to a group who may be fearful of falling, however, knowledge that activities such as repetitive chair rises (which warm the muscle and make it feel tight) are strengthening, and activities such as repetitive slow heel raises by the kitchen sink improve balance are motivating for this frailer older group. For specific exercise advice a physiotherapist or a specialist postural stability exercise instructor can offer an individualised assessment, which may include examination of posture, flexibility, balance and mobility, and tailoring an exercise programme accordingly. With any exercise, it should be gradually introduced, commencing with low intensity and low impact activities, and progressing as abilities allow.

Summary

Physical activity and exercise is an important part of a healthy lifestyle, which has numerous benefits including improving and maintaining bone health and reducing or managing the outcomes of falls. More research is needed into the effects of exercise on bone, in particular the effects on fracture rate. Exercise must be viewed as a lifelong commitment, starting with exercise to optimise bone structure in early years, preserving bone mass throughout adulthood, and then exercising to maintain bone health and prevent falls in later life.

Conflict of interest: none declared

Prof Skelton and Craig Ross ran a workshop at the British Geriatrics Society conference on falls and postural stability on 9 September in Bristol. For more information see: www.bgsevents.org

References

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