studies suggest that optimal adaptations continue to accrue with high‐intensity resistance and power training in older adults.70
Optimal exercise modality and intensity for bone health
The predominant exercise training factor that influences bony adaptation is the intensity and novelty of the load, rather than the number of repetitions, sets, or days per week or even the total duration of the programme. This observation is also true for animal models of mechanical loading, in which bone is most sensitive to short periods of loading characterised by unusual strain distribution, high strain magnitudes, and rapid rate of loading.
The relative efficacy of aerobic versus resistive exercise regimens for postmenopausal women may perhaps be best assessed via studies that have directly compared various intensities of these two exercise modalities in randomised subjects. Kohrt et al.71 found that both aerobic activities with high ground‐reaction forces (walking, jogging, stair climbing) and exercises with high joint‐reaction forces (weight‐lifting, rowing) significantly increased the BMD of the whole body, lumbar spine, and Ward’s triangle, whereas only the ground‐reaction group increased BMD at the femoral neck.71 The weight‐lifting group preserved femoral‐neck BMD relative to controls, as has been seen in other resistance training studies. However, lean mass and muscle strength increased only in the weight‐lifting group, leaving overall benefits of these two types of exercise for ultimate fall and fracture prevention still unresolved. Kerr et al.72 randomised 126 postmenopausal women to two years of high‐intensity weight‐lifting exercise, moderate‐intensity aerobic training (circuit training and stationary cycling), or sedentary control condition. Total hip and intertrochanteric BMD were improved only by strength training and were significantly different from aerobic training or control groups (+3.2% at two years). As most comparative studies other than those of Kohrt et al.71 and Kerr et al.72 have not sought to optimise both exercise modalities, it is still not possible to choose definitively one best modality for all bone sites. In general, the older the individual, the more favourable the resistance training appears, due to its broader benefits on muscle, bone, balance, and fall risk, relative to aerobic training. If aerobic training is used, however, activities that are weight‐bearing and higher impact have greater efficacy for bone health than non‐weight‐bearing or low‐impact aerobic activities.
It is important to consider not only the optimal modality of exercise but also the relative intensity, as the skeletal adaptation is critically linked to the intensity of the loading (whether due to increased amount of weight lifted during resistance training or higher ground‐reaction forces during aerobic/jumping activities). Interesting results have been reported by Cussler et al.73 in a randomised trial of 140 postmenopausal women participating in a multimodal exercise programme (high‐intensity resistance training and a weight‐bearing circuit of moderate‐impact activities including walking/jogging, skipping, hopping, and stair climbing/stepping with weighted vests). Bone density improvements at the femoral trochanter were significantly and linearly related to total weight lifted during the 12 months, and also total weight lifted in leg press, squat, and military press exercises, but not to the volume or quality of the non‐resistance training components of the programme. High‐intensity resistance training is also more beneficial than low‐intensity training for muscle strength gains and muscle hypertrophy, in addition to associated gait disorders, functional impairments, and disability, making it ideal as a multiple risk factor intervention strategy for injurious falls prevention in osteopenic women.
Exercise in the treatment of osteoporotic fracture
In older men and women who have already sustained an osteoporotic fracture, exercise is still extremely important to help recover function and prevent recurrent injurious falls. Progressive resistance training has been shown to be superior to standard physical therapy during the recovery from hip fracture in elderly patients.74 In addition, resistance training has been shown to be a potent treatment for depression in older adults75 and may thus substitute for antidepressant medications, which are known to increase the risk of falls and hip fracture.23 A combination of resistance training and balance training may offer the best approach to rehabilitation in this setting, as it optimally targets several of the remediable physiological risk factors for falls, fractures, and disability in this cohort.76 Additional studies are needed to define the effects of training in this clinical setting on bone density and strength itself and the optimal timing and duration of such interventions in the post‐fracture recovery period.
Role of exercise and physical activity in adipose tissue accretion and distribution
The rising epidemic of obesity is now recognised internationally in both younger and older cohorts and is projected, if it continues, to lead to significant changes in related diseases such as diabetes and also life expectancy. Prevention of excess adiposity is both protective and in some cases therapeutic for many common chronic diseases, offering significant risk reduction in the case of osteoarthritis; cardiovascular disease; gall bladder disease; type 2 diabetes; breast, colon, and endometrial cancer; hypertension; stroke; and vascular impotence, for example. Although generalised obesity is associated with excess mortality, cardiovascular disease, osteoarthritis, mobility impairment, and disability, it is predominantly excess visceral fat that is associated with the derangements of dyslipidaemia, elevated fibrinogen, hyperinsulinaemia, glucose intolerance or diabetes, vascular insulin resistance, hypertension, and cardiovascular disease known as metabolic syndrome or insulin resistance syndrome. Reductions in visceral fat have been shown to improve glucose tolerance and insulin sensitivity in those with and without diabetes, and changes in trunk fat correlate with improved glycaemic control in type 2 diabetes.77,78 Hence the potential for exercise to impact favourably on the accretion and distribution of adipose tissue, as reviewed below, has enormous significance in that it may reduce the burden of disease expressed in the ageing population.
Cross‐sectional studies of physical activity and fat mass
Numerous cross‐sectional analyses have confirmed an inverse relationship between physical activity and abdominal fat. Master athletes compared with age‐ and BMI‐matched controls have lower waist circumference, and physically active women have lower waist‐to‐hip ratios than inactive women. It has been determined that the higher the intensity of activity independent of energy expenditure, the lower are the abdominal fat estimates for men and women. In a study of monozygotic and dizygotic female twins, physical activity was the strongest predictor of central obesity after controlling for genetic and environmental factors, and this persisted for those with a genetic predisposition to obesity.
Experimental studies of the influence of physical activity on abdominal fat
In the last few years, there has been accumulating evidence from well‐designed studies supporting the benefit of physical activity in reducing total abdominal fat. There is no evidence that age limits abdominal fat loss secondary to exercise. Most studies have included middle‐aged to older populations who have a higher accumulation of abdominal and visceral fat than younger adults. They are more likely to demonstrate a greater magnitude of change than subjects with lower abdominal fat mass at baseline.79 Furthermore, the potential for physical activity to attenuate the gain in visceral fat is evident in the obese as early as childhood.
Decreases in both total adipose tissue accumulation and its abdominal (visceral) deposition are achievable by both aerobic and resistive training, with significant changes in total body fat usually only in conjunction with an energy‐restricted diet or very large volumes of exercise (7 hours per week). Preferential visceral fat mobilisation is often seen in response to exercise and dietary intervention, which means that small amounts of total body weight or fat mass (5%) may be associated with substantial changes in visceral fat (25% or more), with important metabolic implications for the prevention or treatment of insulin resistance syndrome.80
Exercise and diet in combination are the most effective non‐surgical treatment for obesity, and