Today in the United States, older adults are the fastest growing segment of the population. By definition, older adults are all individuals 65 years and older, as well as adults 50 to 64 years old who have clinically significant functional limitations and/or a chronic condition (1). Growing older technically begins at birth. However, in fitness and health, we tend to operationalize “growing older” by either the time in life when we pass our peak function or when noticeable declines in functional ability begin to arise. The declines noted with advancing age are both structural and functional, even in the absence of any disease states. These declines result in reduced functional capacity and reduced strength, as well as alterations in muscle mass and function (1–3). Therefore, the cumulative effects of age-related decline can lead to older adults with decreased ability to engage in common activities of daily living and/or prevent individuals from living independently (1,2). Increasing age also is often associated with increased risk of several chronic diseases such as cardiovascular disease, arthritis, and type 2 diabetes, resulting in an increased burden on the U.S. health care system (1–4). In fact, older adults generate the highest expenditure of medical care costs in our country, with the Medical Expenditure Panel Survey reporting a mean expenditure of approximately $11,500 per person in 2017 for adults 65 years and older (1–5). Furthermore, the aging process is complex and involves primary and secondary processes along with certain genetic factors. Primary processes and genetic factors may be hard to overcome; however, clear evidence supports physical activity (PA) as a great mediator of the secondary aging effects, typically leading to increased quality of life and increased longevity.
AGING AND PA
Participation in regular PA leads to numerous favorable physiological responses that contribute to both healthy aging and the slowing of functional decline (1,2). We know that older adults who perform regular exercise have a more favorable body composition profile, greater relative muscle mass and strength, and higher bone mineral density, all of which lead to a reduction in chronic disease risk and incidence of falls (1–3). In addition, inactive older adults who begin a PA program, almost regardless of age, can see important functional gains in muscle strength, balance, cardiovascular fitness, and overall functional ability (2,3).
For optimal health in older adults, ACSM’s Older Adult Exercise Prescription Guidelines suggest both moderate and vigorous aerobic and strength exercises along with both flexibility and balance training (6). In more recent years, researchers and clinicians have recognized that regular exercise and PA also have several psychological and cognitive benefits for older adults. Both higher physical fitness and higher PA levels are associated with a decreased risk for clinical depression and anxiety in older adults (1,2). In addition, regular exercise training has been linked to improvements in cognitive performance on executive control tasks, whereas an acute bout of exercise has shown short-term improvements in memory, attention, and reaction time (1). Therefore, psychological well-being is regularly included in the discussion when addressing exercise prescription for all populations, including older adults.
However, the PA guidelines of today were not always in place. In fact, there was a time when only low-intensity PA was recommended for older adults, with vigorous PA being discouraged after the age of 60 years (7). Thankfully, this is no longer the case, and a look at the history of exercise in older adults and the evolution of PA guidelines can help develop an appreciation for where we are today, while also providing a point of reference for future advances in exercise and PA for older adults.
EVOLUTION OF EXERCISE PRESCRIPTION FOR OLDER ADULTS
Beginning of the Road:
For many centuries, being physically active was known to be beneficial for all people, including older adults. In the ancient Greek and Roman cultures, which extended through about 450 AD, exercise was recognized as an important component of health and was promoted in the older population (8). Over the next 1500 years or so, the world was evolving rapidly, and PA guidelines for anyone, much less older adults, were not at the forefront of health concerns. However, it was the early 20th century when there was a rekindled interest in PA for older adults. In 1914, Ignatz L. Nascher, M.D., the father of geriatrics, wrote, Geriatrics: The Diseases of Old Age and Their Treatment. In this classic text, Nascher acknowledged the need for PA in his older patients; however, it was with caution. Nascher advocated that the best form of exercise for older adults was walking slowly up an incline with frequent breaks, and he discouraged any vigorous PA (8). It was not until the 1960s, as the field of exercise science gained greater interest in the United States, that the promotion of PA in older adults became more widespread, with physicians beginning to recommend more than just casual walking (7,8).
Middle of the Road:
It was the late 1990s when ACSM first published its position stand addressing the evidence supporting exercise prescription for healthy aging and chronic disease prevention in older adults (2). These expert recommendations included the need to engage in both aerobic and strength training on a regular basis. Aerobic training was recommended to be of light to moderate intensity, which was more than Nascher suggested, but still not where we are today. In addition, neither frequency nor duration of exercise was addressed (2). Furthermore, it was recommended that older adults take part in strength training to help reduce sarcopenia and muscle weakness, not necessarily to gain strength, and similar to aerobic exercise, no specific recommendations were outlined (2).
Balance and flexibility training also were included in this first position stand, yet at the time, there was a lack of evidence to fully support either with specific recommendations (2).
In the late 2000s, Nelson et al. (3) published PA recommendations for older adults with the help of experts at the American Heart Association (AHA) and ACSM (2). Several key differences arose in these recommendations as compared with the previously outlined ACSM position stand:
- Aerobic exercise training should be performed at least at moderate intensity for optimal health benefits.
- The frequency, intensity, time, and type (FITT) principle was used to outline the recommendations for both aerobic and strength training.
- Recommendations for flexibility training to be performed on ≥2 days/week for at least 10 minutes per session.
- Balance exercises were recommended for frequent fallers.
In 2009, ACSM published its second position stand addressing PA and exercise prescription in older adults. Unlike the initial position stand, this one outlined evidence to support the use of exercise and PA not only for the prevention of chronic disease but also for the treatment of chronic diseases (1). The position stand also expanded on the association between cognitive function and PA in older adults, indicating a potential inverse relationship between frequency of PA and risk of dementia or cognitive decline (1,4,9). The available evidence at that time also supported that exercise training and PA were associated with a decreased risk of clinical depression and anxiety in older adults (1).
In the past decade, the basic recommendations for exercise prescription in older adults have stayed relatively constant (1–4,6,9,10). The primary noticeable shift has been toward an encouragement for the inclusion of high-intensity interval training (HIIT) to meet aerobic exercise recommendations, as mounting evidence supports HIIT in many different forms for older adults (11,12). When a combination of aerobic and resistance training is incorporated into a HIIT regimen, typically called multimodal HIIT, it also can improve muscle strength and power (13). In fact, HIIT may even be more effective than moderate-intensity, continuous aerobic exercise in improving clinical outcomes and decreasing body fat percentage in older adults (11). Furthermore, HIIT can decrease the time spent in exercise, which may make it more appealing to many older adults.
In addition to HIIT for aerobic and strength gains, the general idea of vigorous exercise in older adults is now more accepted than ever. Of course, as with any population or individual, screening for untoward events should always take place before starting an exercise program or before increasing exercise intensity (6). However, once cleared for exercise, intensity should be a matter of choice for each individual, unlike the early 1900s when Nascher caution anything beyond a casual walk. Looking to the future, there will certainly be continuous support for older adults to regularly exercise, and it is just as likely that the list of known benefits associated with regular exercise will continue to expand, even for those who do not take up exercise until their 70s, 80s, or 90s. Along with the evidence of PA mitigating cognitive decline, the future holds promise that exercise, particularly vigorous exercise, may be able to improve cognitive function in those who are already suffering early decline (1,14–16). This is just one of the exciting areas that may emerge in the next 10 years as the science behind exercise and PA in older adults continues to expand.
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