Furthermore, because muscle power is an important predictor of functional capacity, strategies to develop skeletal muscle power in this population must be included to prevent or postpone functional limitations and subsequent disability.4,17,52,171
Exercise to counteract iatrogenic disease
Finally, exercise may counteract undesirable side effects of standard medical care, a use of exercise that is just emerging in the literature. Such use of exercise would include resistance training for patients receiving corticosteroid treatment to counteract the associated proximal myopathy and osteopenia, substituting exercise for psychotropic medications to prevent falls,172 or neutralising the adverse effects of energy‐restricted diets in obesity or protein‐restricted diets in chronic renal failure,173 for example.
Osteopenia associated with corticosteroid usage appears to be eliminated by concurrent progressive resistance training, which should be recommended for all such patients. Although bisphosphonates have also been shown to be very effective for corticosteroid osteopenia, they do not address the coexisting steroid myopathy as resistance training does and are therefore an insufficient antidote for corticosteroid side effects. An excellent target group for such health promotion efforts would be older men with steroid‐dependent chronic lung disease, in whom pulmonary cachexia, malnutrition, tobacco use, steroid myopathy, and osteoporosis combine to produce profound wasting, osteoporotic fracture, and impaired exercise tolerance. Aerobic training will improve functional status in this clinical cohort but is insufficient to address musculoskeletal wasting.
Exercise and the prevention and treatment of disability
There are many ways in which physical activity may influence the development and expression of disability in old age. These theoretical relationships are now borne out in many epidemiological investigations and provide the rationale for both the experimental studies and exercise recommendations found in many recent reviews of this topic. For example, 1097 participants from the Established Populations for Epidemiological Studies of the Elderly (EPESE) study who were not disabled at baseline were analysed for factors related to disability‐free survival until death in old age. Physically active adults were more likely to survive to age 80 or beyond and had approximately half the risk of dying with disability compared with their sedentary peers. The most obvious conclusion from a review of the literature in this area is that there is a great deal of overlap between the identifiable risk factors for disability and the consequences or correlates of habitual inactivity. At the most basic level, shared demographic characteristics between those at risk of disability and those more likely to exhibit sedentary behaviour include advanced age, female gender, non‐Caucasian ethnicity, and lower educational level and income. Psychosocial features common to both cohorts include social isolation, low self‐esteem, low self‐efficacy, depressive symptoms, and anxiety. Lifestyle choices more prevalent in disabled and/or inactive adults include smoking and excess alcohol consumption. Body composition changes associated with both functional decline and inactivity include sarcopenia, obesity, visceral obesity, and osteopenia. Exercise capacity is typically reduced in both conditions in all domains, including aerobic capacity, muscle strength, endurance and power, flexibility, and balance. Gait instability and slowness and impaired lower extremity function and mobility characterise both disabled and inactive populations. Since most studies have not assessed the full complement of factors known to be associated with disability, and many have made observations at a single point in time, it is not possible to say with certainty how all of these complex relationships fit together, which relationships are causal, and which risk factors are independent of each other.
In addition to the associations above, chronic diseases associated with inactivity, such as obesity, osteoarthritis, cardiovascular disease, stroke, osteoporosis, type 2 diabetes, hypertension, and depression, are all risk factors for disability. In some cases, data linking inactivity to disability‐related diseases are available from cross‐sectional or prospective cohort studies and also experimental trials (e.g., diabetes, cardiovascular disease) and in other cases from epidemiological data alone (colon and breast cancer174). Disability is complex and not fully explained by deficits in physical capacity such as strength and balance, and other pathways may be operative, including sensory function, glycaemic control, psychological constructs, and other aspects of health status.
Recent prospective and experimental studies have strengthened the hypothesised causal relationship between sedentariness, functional limitations, and disability in older adults. Miller et al. reported results from 5151 participants in the Longitudinal Study of Aging175 and showed that physical activity was associated with a slower progression of functional limitations and, thereby, slower progression to ADL / instrumental activity of daily living (IADL) disability. In one of the largest reported randomised controlled trial of exercise and disability in frail elders to date,176 704 residents of nine different nursing homes were randomised into resistive, balance, and aerobic exercise; nursing rehabilitation; or control conditions. After 17 months, residents in both types of intervention homes had significantly less decline in ADL functioning than those in control homes.
A review of studies targeting disability in disease‐specific populations such as depression, cardiovascular disease, stroke, chronic lung disease, and arthritis is beyond the scope of this review, but there is evidence that exercise is beneficial in all of these conditions as a primary or ancillary treatment. The largest body of data exists for older adults with osteoarthritis of the knee, which is one of the commonest conditions related to disability in older adults.177 Weight‐bearing functional exercises, walking, and resistance training have been used in various combinations in these studies, and there is no clear indication of the superiority of one modality over another in the reduction of pain and disability from osteoarthritis. Notably, land‐based exercise is superior to stretching and aquatic exercise, despite the common perception that these less‐robust exercises are more efficacious or feasible in this cohort.177 It is likely that the disability reductions in arthritis are due to the impact of exercise on a variety of factors, including muscle strength, gait and balance, body weight, pain, comorbid disease expression, self‐efficacy, and depressive symptoms, among others, as there is no simple link between improvements in function or pain and fitness adaptations.177
Exercise for acute hospitalised older patients
The traditional model of care for acute hospitalised older patients depends on a series of circumstances beyond the disease process that caused the hospital admission and usually worsens the hospitalisation outcome.178‐180 Hospitalised older patients are often bedridden.181,182 resulting in reduced functional and physiological reserves. Consequences arise at multiple levels, including functional loss, cognitive impairment, increased length of hospital stay, sarcopenia secondary to immobilisation, falls, frailty, institutionalisation, and mortality.181,183,184 Although the typical patient profile has changed dramatically over the past century and is currently characterised by frailty, disability, multimorbidity, and polypharmacy in chronic patients, the hospital care model remains embedded in the previous century, which increases the risk of patients developing avoidable complications associated with hospitalisation. Exercise and early rehabilitation programmes are among the interventions through which functional decline is likely to be best prevented in older patients during hospitalisation.185‐187
Healthcare systems are still poorly adapted to the needs of elderly patients, and low in‐hospital mobility is directly associated with functional deterioration at discharge and, even more so, at follow‐up.188,189 In this context, physical exercise can play an essential role in preventing functional and cognitive decline during hospitalisation in the elderly.5,190 The benefits of exercise have been clinically, biologically, and even economically confirmed,179,190 making exercise a valuable addition to the therapeutic arsenal. Although only a few RCTs have examined the potential benefits of exercise training for acutely hospitalised elderly patients, the effects of in‐hospital exercise intervention on functional outcomes are promising.179,180,190‐192 Recently, Martínez‐Velilla et al.179