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whereas there was a dose‐response relationship between training intensity and muscle strength and endurance changes favouring high‐intensity training.¹⁰² Therefore, using heavy loads during explosive resistance training may be the most effective strategy to achieve simultaneous improvements in muscle strength, power, and endurance in older adults. In addition, power training at low loads (during which velocity is much faster) poses a risk of meniscus or tendon injuries if undiagnosed degenerative changes are present, as is common in older adults.^103,104

      Several studies have used standard free weights and weight machines for power training,^17,96,105 but some studies used pneumatic resistance machines designed specifically for this type of resistance training,^106,107 resulting in similar neuromuscular and functional improvements.¹⁰⁸ As it is not possible to overcome resistance with momentum on such machines (as can be done by ‘swinging’ a free weight), they offer a theoretical and practical advantage. In the absence of such machines for power training, plyometric training (e.g., jumping up onto platforms/boxes) has traditionally been used in children and athletes for this purpose. However, arthritis and balance impairment preclude plyometrics in many frailer adults most in need of such muscle power improvements. As an alternative, the use of body weight as resistance (e.g., rising quickly from a chair) may be substituted as an initial strategy. It could start with slower execution and another person’s assistance but progress until the person can perform it alone and as fast as possible. This strategy may be easily performed in hospital rooms, at home, or in aged care residences. However, once body weight is no longer a sufficient overload of the capacity of lower extremity muscles, additional resistance provided by machines or free weights is needed to ensure progression.

Promotion of psychological well‐being

      Psychological well‐being is vital to optimal ageing and is dependent on a host of factors, including genetic traits, social support systems, personality types, and the presence of positive and negative psychological constructs such as happiness, optimism, morale, depression, anxiety, self‐esteem, self‐efficacy, and vigour. Participating in physical activity has been shown to be associated with more positive psychological attributes and a lower prevalence and incidence of depressive symptoms in cross‐sectional and prospective epidemiological studies and experimental trials.^75,109 It is notable that effects are most significant in those with comorbid illness, such as cardiovascular or pulmonary disease or major depression,^109,110 attesting to the clinical relevance of this exercise adaptation.

The experimental evidence for exercise as an isolated intervention for treating clinical depression in both younger and older cohorts is robust and consistent. Both aerobic and resistance training exercise produce clinically meaningful improvements in depression in such patients, with response rates ranging from 25 to 88%. In the studies that have addressed exercise modality, resistance training was found to be equivalent to aerobic training in young adults with depression and yoga as effective as aerobic exercise. Blumenthal et al.¹¹⁰ directly compared high‐intensity aerobic exercise with antidepressant medications in older adults with major depression and found the two approaches to be equipotent, with no added benefit of combined exercise and medication. Singh et al.⁷⁵ compared high‐ and low‐intensity progressive resistance training to GP referral and care in older adults with major depression and found that a clinical response (50% reduction in Hamilton Rating Scale for depression) was achieved in 61% with high‐intensity training, significantly different than the 29% with low‐intensity training and 21% with the GP care control group who responded similarly to placebo rates.⁷⁵ Similarly, low‐intensity aerobic training in older adults with depression has been shown to be similar in efficacy to social contact controls, reducing depression scores by only 30%. Thus, the literature on exercise and depression suggests that it is effective in young and old, it is approximately as effective as antidepressants in clinical cohorts, both aerobic and resistance modalities appear equally beneficial, and optimal responses are seen with higher intensities of training.

Exercise and cognitive function

      There is a growing body of observational data and experimental evidence that physical activity can significantly influence a wide range of cognitive functions.^111,112 The earliest lines of evidence were provided by cross‐sectional studies of athletes or physically active individuals versus sedentary controls, with active or fit individuals demonstrating superior performance in tests of reaction time, motor control, and visual‐spatial tasks. Changes in executive‐control processes and brain structures and functions most closely related to these processes are disproportionately affected by ageing and exercise in some studies.^113,114 This has led to speculation that age‐related cognitive dysfunction might be partially mediated by suboptimal and diminishing participation in physical activity across the lifespan. Virtually all of these studies have focused on cardiorespiratory fitness (maximal oxygen consumption) or aerobic exercise as the putative protective factor. However, ~50% of the variance in maximal oxygen consumption in children and adults is thought to be mediated by genetic factors rather than physical activity patterns,¹¹⁴ raising the possibility that shared predisposition to low fitness, vascular risk factors, and cognitive decline may explain these associations, rather than adaptation to an active lifestyle. In addition, changes in maximal oxygen consumption with ageing are explained as much by losses of muscle mass (sarcopenia) as they are by losses of cardiovascular reserve, suggesting that non‐aerobic activities could be just as important as aerobic activities for the prevention of cognitive decline.

      More recently, well‐designed prospective cohort studies that have controlled for many known risk factors for cognitive dysfunction have in large part supported cross‐sectional associations between physical activity patterns and risk of dementia.^112,115 For example, in the Honolulu–Asia Ageing Study,¹¹⁶ 2257 physically capable, cognitively intact men < 71–93 were followed for 7 years for incident dementia. Walking significantly reduced the risk of dementia in a dose‐dependent fashion, with a 1.8‐fold increased risk for those who walked less than 0.25 miles per day compared with >2 miles per day, controlling for other possible risk factors.

      Acute exposure to even one bout of aerobic exercise may improve cognitive test performance and reduce depressive symptoms and anxiety. It is not known how long such acute bout effects persist, whether weightlifting exercise has similar acute effects on cognition, or what proportion, if any, of chronic exercise effects are explained by cumulative acute bout effects. Animal data demonstrate that voluntary wheel running (not stressful forced swimming) is a powerful means to enhance neural plasticity and function, improve learning and memory, and increase the availability of brain‐derived neurotrophic factor (BDNF), the formation of new neurons and synaptic transmission in the hippocampus. Exercise also protects against the neurotoxicity of ageing, stress, cortisol, or oestrogen withdrawal in these animal models and potentiates the beneficial effect of oestrogen and antidepressants on hippocampal volume and metabolism.

      A recent meta‐analysis found that physical exercise protected against physical decline with an effect size of 0.62.¹¹⁷ Exercise also slows decline in people with Alzheimer’s disease.¹¹⁸ Aman and Thomas¹¹⁹ found that supervised exercise reduced agitation in nursing home residents. Importantly, it is clear that not all exercise is alike and that low‐intensity, minimally progressive, mostly unsupervised regimens such as employed in the recent DAPA (Dementia and Physical Activity) trial¹²⁰ may provide no cognitive benefit at all. As these types of regimens do not address other common comorbidities such as falls, frailty, depression, sarcopenia, osteoporosis, cardiometabolic disease, etc., there would appear to be little rationale for their use in aged care settings or cohorts with established dementia.

Potential mechanisms by which exercise could improve cognitive function include changes in fitness, increased cerebral blood flow, reduction in depression, increase in presence or activity of neurotrophic factors (BDNF, insulin‐like growth factor‐1 [IGF‐1]), downregulation of neurotoxic factors (C‐reactive protein, cortisol, interleukin‐6 [IL‐6]), and other inflammatory cytokines and prevention or better control of chronic disease (e.g., stroke, diabetes, cardiovascular disease). Considering the non‐robust

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