regarding exercise for frail individuals with cognitive impairment
The novel cognitive frailty construct was first defined some years ago and is characterised by the presence of both physical frailty and potentially reversible cognitive impairment in the absence of dementia.126 The role of physical exercise interventions on cognitive function in older adults has been previously studied112,127; however, the large variability in measured cognitive outcomes and methodological aspects of studies makes it difficult to draw conclusions about the effects of physical exercise on cognition in older adults. A recent randomised controlled trial (RCT) examined the effects of four months of low‐intensity high‐speed resistance training (i.e., muscle power training) in older adults with MCI and found that the intervention improved cognitive function and physical performance.128 Similarly, it has been shown that four weeks of high‐speed resistance training combined with walking and balance exercises improved gait ability, balance, and muscle strength and reduced the incidence of falls in frail patients with dementia after long‐term physical restraint during nursing care.4 In agreement with other studies, there is a strong link between cognition and muscle strength, and physical frailty is associated with worse cognitive performance in multiple domains such as verbal memory, processing speed, and working memory in older people.126,129 Therefore, an individualised multicomponent exercise training with special emphasis on high‐speed resistance training may be a cornerstone for frail individuals with cognitive impairment to improve their physical and cognitive function simultaneously.5
Effects of exercise interventions on mobility and frailty syndromes
Beginning in 1990,130 with the first report of high‐intensity resistance training in nonagenarians, it has been shown that exercise interventions inclusive of robust resistance training increase muscle strength in frail older individuals.17,131‐133 As expected, most of the studies reported improved strength using resistance training programmes132,133 or multicomponent exercise interventions, including resistance training.17,131 Nevertheless, some studies did not find significant changes in muscle strength in this population, which may be related to the use of home‐based exercise interventions,134 few weight‐bearing exercises,135 or very low workloads106 that may not have provided sufficient stimuli for inducing strength gains. The use of scales of perceived exertion rather than strength testing to guide progression of loads during resistance training in frail older people is another factor that may limit the stimulus and consequently reduce the magnitude of adaptations.136
Exercise interventions also reduce the incidence of falls in older adults with physical frailty.17,133,135,137 Most studies have used multicomponent exercise programmes including the combination of resistance training, balance and/or gait retraining,17,135 and (less commonly) only resistance exercises133 or an alternative exercise intervention such as Tai Chi.137
Several trials have also investigated the effects of exercise interventions on gait ability in frail older people, with conflicting results. Whereas some studies showed improvements in gait ability after the physical training period,17,132,138,139 others found no improvement.17 Interestingly, the bulk of studies that demonstrated enhancements in gait ability utilised multicomponent exercise programmes,4,17,138‐140 while others used only resistance exercises133 or a combination of aerobic training and yoga.141
Based on the evidence that multicomponent exercise interventions are more effective in improving most, if not all, of the frailty syndrome hallmarks (i.e., poor balance, reduced muscle strength, poor gait ability, and increased incidence of falls), it is recommendable that this type of intervention, which includes resistance training, gait retraining, and balance exercises, among others (i.e., occupational therapy) be prescribed to prevent frailty syndrome in the elderly, as well as in people with pre‐frailty.5,6,136,142 Recently, the Vivifrail Project, an EU‐funded project that is part of the Erasmus+ programme, focuses on providing training and design material to promote and prescribe such physical exercise in older adults143‐145 (www.vivifrail.com).
In addition, because of the strong associations between functional capacity test performance and muscle power output or rate of force development in the healthy elderly,6,92,95 explosive resistance training has emerged as an essential intervention to improve functional capacity in older adults, including those who are frail.5,6 Indeed, in a 12‐week multicomponent exercise programme including explosive resistance training applied in institutionalised frail nonagenarians, improvements were observed in muscle cross‐sectional area, muscle fat‐infiltration, maximal strength, muscle power output, balance, gait, and sit‐to‐stand ability, along with a reduction in the incidence of falls.4,17 Therefore, explosive resistance training should always be considered in exercise interventions to improve frail older individuals' functional capacity.
One potential adverse event related to muscle power training is injury to tendons/cartilage, particularly of the rotator cuff and knee, where degenerative tears are commonplace,104 or exacerbation of abdominal/inguinal hernias.146 Interestingly, a systematic review of the effects of resistance training in frail older adults reported only one case of shoulder pain related to resistance training intervention out of 20 studies and 2544 subjects.147 Notwithstanding, to prevent injuries that could interrupt the exercise programme and its benefits, screening for such problems is critical, care must be taken in the workload and volume progression, and heavy and repetitive workloads, as well as unfavourable positioning (such as an overhead or military press in rotator cuff disease), should be avoided.
Disease prevention through exercise
Both healthy and chronically ill older adults are candidates for preventive strategies that will lessen the burden of comorbidity, disability, and premature death caused by incident disease. Physical activity patterns may be influenced by ageing and genotype, and physical activity, in turn, may influence physiological capacity, psychological health, dietary intake, and other adverse behaviours or risk factors for chronic disease. All of these are potential pathways by which exercise could ultimately influence the prevalence of chronic disease in a population. Other than genetic factors and environmental insults (pollution, asbestos, heavy metals, infectious agents, etc.), most of the significant contributors to the development or severity of chronic diseases are in some way related to habitual levels of physical activity. Examples include cardiovascular disease, stroke, type 2 diabetes,148 obesity, hypertension, osteoarthritis, depression,110 and osteoporosis, among others.1,7
Although appropriate levels of physical activity may optimise risk factor profiles, the presence of risk factors may lead to reduced physical activity and thus heightened risk of disease. For example, inactivity may lead to loss of muscle mass, followed by muscle weakness and further restriction in activity levels, subsequently contributing to the development of osteopenia and gait abnormalities and, finally, hip fracture.
Although observational studies can never completely separate the effects of physical activity from genotype or other unmeasured characteristics of individuals who self‐select an active lifestyle, the best studies attempt to control for demographic differences and other known risk factors for the incident disease and eliminate early or occult disease at baseline if possible prior to analysis. Thus, for example, exercise reduces the risk of cardiovascular disease by ~50%, even after controlling for such risk factors as smoking, obesity, hypertension, and dyslipidaemia. Longitudinal cohort studies have generally confirmed the cross‐sectional data linking exercise to reduced disease risk. Of particular interest are studies in which middle‐aged sedentary adults with low fitness levels have become fit at follow‐up and have markedly reduced cardiovascular mortality compared with those remaining unfit or inactive. These findings suggest that preventive exercise prescriptions
