Aerobic Exercise Training and Healthy Aging
Aerobic exercise is physical exercise that depends mainly on oxygen utilization to meet the metabolic demands of the body. Examples of aerobic exercise include walking, jogging or running, cycling, and swimming.
Maximal aerobic exercise capacity declines across the adult lifespan, accelerating at older ages. This age-associated decline in aerobic capacity is exacerbated by sedentary lifestyle, loss of muscle mass, and superimposed comorbidities common to older adults such as cardiac, pulmonary, and peripheral artery disease. Aerobic exercise training elicits significant improvement in peak oxygen consumption (VO2) in both healthy and diseased older adults and produces salutary effects on blood pressure, lipids, glucose tolerance, bone density, depression, cognition, and quality of life. However, increasing the low participation rates of older adults in both home-based and supervised aerobic exercise programs constitutes a major challenge to physicians and society.
Key Research Findings
Effects of aging on aerobic capacity: The most widely used measure of maximal functional capacity is peak VO2 measured on a treadmill or cycle ergometer. Although cross-sectional studies show declines in peak VO2 of 8–10% per age decade in healthy men and women (Talbot et al. 2000), longitudinal studies have shown peak VO2 declines of 20–25% per decade in healthy adults older than 70 years (Fleg et al. 2005; Jackson et al. 2009). Similar age-associated declines in peak VO2 are observed even among highly active individuals. Conversely, the mean peak VO2 in 2,331 largely middle-aged outpatients with chronic heart failure (CHF) was 14.5 ml/kg/min (O’Connor et al. 2009), approximating that of a healthy octogenarian. Given that a peak VO2 of ~18 ml/kg/min distinguished low versus high physical function (Morey et al. 1998) in community-dwelling adults 65–90 years old, the ability to maintain higher aerobic capacity is a major determinant of functional independence in older adults.
Trainability of Older Adults
Observational data: Numerous observational studies have demonstrated that endurance athletes, even those in their 60s and beyond, maintain a peak VO2 considerably higher than that of their less active age peers. For example, the peak VO2 in distance runners aged 60–80 years was 30–40% higher than non-trained but active age peers in the Baltimore Longitudinal Study of Aging (BLSA) (Fleg et al. 1994).
Training studies in healthy elders: A more robust and realistic assessment of the ability of older adults to increase their aerobic capacity derives from training studies of sedentary individuals. Over the past three decades, numerous studies have documented training induced increases of 10–25% in peak VO2 among adults in their 60s to 80s, increases similar to those in younger adults (Hagberg et al. 1989; Vaitkevicius et al. 2009). A meta-analysis of training studies in persons aged 60 and older found a mean increase in peak VO2 of 16% (Huang et al. 2005). In general, training of higher intensity and longer duration elicited greater improvement.
Aerobic training in elders with cardiovascular disease: Substantial data have shown that after a coronary event, patients older than 70 years old derive similar increases in functional capacity and improvements in risk factors from traditional cardiac rehabilitation programs as their younger counterparts (Ades et al. 1995). For example, Ades et al. (1995) noted a mean increase of 16% in peak VO2 among 60 patients aged 65 ± 5 years following 3 months of training after myocardial infarction (MI) or coronary revascularization. Accumulating evidence has shown similar training-induced benefits in older versus younger CHF patients. A trial of 200 CHF outpatients 60–89 years old demonstrated a 15% mean increase in 6-min walk distance, a surrogate for aerobic capacity, and improvements in quality of life (QOL) and exertional symptoms (Austin et al. 2005; Fleg 2017).
Non-cardiac Benefits of Exercise Training in Older Adults
Hypertension: In both younger and older persons with hypertension, regular aerobic exercise reduces blood pressure (BP). The reductions in BP from aerobic exercise are often similar to those induced by a single antihypertensive drug; mean BP reduction in a large meta-analysis averaged 3.8/2.6 mmHg (Whelton et al. 2002). Importantly, lower intensity exercise equivalent to brisk walking demonstrated similar BP reductions as more intensive training in older hypertensive adults.
Dyslipidemia: Abnormal blood lipids remain powerful risk factors for CV events in older adults. Aerobic exercise training has beneficial effects on abnormal lipid levels, irrespective of age. In a meta-analysis of aerobic exercise training trials in older adults, significant increases in high density lipoprotein (HDL) or “good” cholesterol and reduced total cholesterol/HDL cholesterol ratio were observed; improvements in blood lipids correlated with increases in peak VO2 (Kelley et al. 2005).
Glucose tolerance: Both age-associated increases in body fat and reduced physical activity contribute to the impaired insulin sensitivity and glucose tolerance in older adults, often resulting in type 2 diabetes. Thus, it is not surprising that both weight reduction and aerobic exercise training ameliorate these impairments. A 9-month aerobic exercise intervention in 71 older men increased peak VO2 by a mean of 17% and reduced insulin secretion on an oral glucose tolerance test (Katzel et al. 1995).
Bone density: Reduction in bone density with age occurs in both sexes but accelerates in women after menopause, increasing risk for osteoporotic-related fractures. Weight-bearing aerobic as well as resistance exercise increases bone density in older adults by increasing the loading force on bone, stimulating osteoblast activity. In a Cochrane review, walking improved bone mineral density at both the hip and spine by 1.3% and 0.9%, respectively, in postmenopausal women (Bonaiuti et al. 2002).
Depression: Psychological depression has an adverse impact on morbidity, mortality, and functional recovery from CV disease. Clinical depression is present in 10–15% of older adults, often the result of social isolation, low income, and declining general health. Regular aerobic exercise has been shown to reduce depressive symptoms and improve QOL after cardiac rehabilitation (CR) in older coronary patients (Lavie and Milani 1995).
Quality of life: Given the adverse impacted of illness and disability on QOL, improved physical function might be expected to cause parallel increases in QOL. In a trial of supervised aerobic exercise training followed by home exercise in adults with moderate-to-severe CHF, QOL improved significantly with training (Flynn et al. 2009).
Barriers to Aerobic Exercise Training in Older Adults
Despite the incontrovertible evidence that exercise training has major health benefits in older adults, several barriers to its widespread adoption in this population exist. The first barrier is the mindset among many elders that “exercise is only for young people.” The clinician confronted with this challenge should emphasize that exercise training can be as simple as a vigorous walking regimen 30 min daily.
Another major barrier to regular exercise in older adults is the multiple comorbidities from which they often suffer. Non-weight bearing exercise such as cycling and swimming are especially useful in patients with significant arthritis. Some comorbidities such as CHF, peripheral artery disease, or chronic obstructive lung disease may require training to begin at very low absolute exercise intensities. Nevertheless, marked relative improvements may be achieved in such severely debilitated individuals.
Further barriers to CR participation in the elderly include lack of transportation to the facility and the need to care for a dependent spouse. In these situations, home exercise training may be a useful substitute for supervised training.
Probably the greatest barrier to more widespread use of aerobic exercise training in the elderly is the failure of physicians to recommend it to their patients and to refer them to formal rehabilitation programs. Repeated studies have showed dismal referral rates of Medicare beneficiaries to supervised CR programs after a cardiac event, despite their reimbursement by Medicare. In a recent analysis, only 12.2% of ~600,000 such patients participated in CR; those who participated experienced 21–34% lower mortality over the next 5 years than non-users (Suaya et al. 2009). Greater education of practitioners regarding the benefits of CR in the elderly is clearly required as well as facilitation of the referral process (Grace et al. 2011).
Aging is accompanied by an accelerated loss of aerobic exercise capacity, best quantified by peak VO2. This decline in aerobic capacity is exacerbated by many comorbidities common to the elderly. However, numerous studies have demonstrated the beneficial effects of aerobic exercise training in older adults, both in healthy and diseased populations. Increasing the participation of older individuals in such training programs remains a major challenge.
The author has no relevant conflicts to disclose. The views in this manuscript are solely those of the author and do not necessarily reflect those of the National Heart, Lung, and Blood Institute the National Institutes of Health or the US Department of Health and Human Services.
- Bonaiuti D, Shea B, Iovine R, et al (2002) Cranney A. Exercise for preventing and treating osteoporosis in postmenopausal women. Cochrane Database Syst Rev 3Google Scholar