General Considerations
Demographics
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It is widely accepted that the average life expectancy continues to increase; as it does, the proportion of older adults in the population also increases.
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In Western industrialized countries, the average life expectancy increased from 47 years in 1900 to 78 years in 2007.
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The number of individuals older than 85 years has increased by 232% from 1960 to 1990, along with a total population growth of 39% during the same period.
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By 2030, 20% of the United States’ (US) population will be older than 65 years.
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It is important to maintain a working knowledge of the anatomic and physiologic changes associated with normal aging and to be able to differentiate them from pathologic entities.
Physical Activity and Health Promotion
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Numerous athletes are able to maintain a high level of participation and performance into their middle age and well beyond.
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Cumulative recommendations from the American College of Sports Medicine (ACSM), the American Academy of Orthopaedic Surgeons (AAOS), and the American Heart Association (AHA) encourage older adults to maintain a physically active lifestyle with an emphasis on moderate-intensity aerobic and muscle-strengthening activities as well as activities that promote increased flexibility and balance for older adults who are at a risk of falls.
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Evidence over recent years has demonstrated that senior athletes are not only able to participate in more endurance activities and competitive sports but also able to compete longer than ever and outperform historical comparisons.
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This growth is demonstrated by the increasing number of athletes participating in the National Senior Games, marathons, and triathlon competitions.
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Participation in the National Senior Games, which is a biennial competition for men and women aged ≥50 years, has increased from 2500 competitors in 1987 to >12,000 athletes in 2007.
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Almost half of all US participants in marathons are aged over 40 years. One-fourth of marathon runners in their 60s are able to outperform half of the runners aged 20–54 years.
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The overall participation in triathlons has increased by almost 60% since 2008, and now, an estimated 850,000 adults aged over 40 years compete in triathlons in the US.
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Despite increased rates of participation, older adults remain the least active group in the US. Healthcare providers need to continue to counsel older adults regarding health benefits that coincide with an active lifestyle.
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Several changes associated with aging can be limited, prevented, or even reversed with sustained exercise.
Physiologic Changes Associated With Aging
General Considerations
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Aging is an individual process that is influenced by a multitude of factors, including genetics, ethnicity, culture, diet, illness, environmental exposure, occupation, and physical activity.
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Age-related structural and functional changes occur at the molecular level and result in a gradual decline in the physiologic performance of virtually every organ system.
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At the cellular level, multiple changes are observed:
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Decreased capacity for division and cellular repair
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Impaired exchange of nutrition, cellular waste, and oxygen
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Intracellular accumulation of lipids and pigments
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Lipofuscin—“aging pigment” breakdown product of erythrocytes that collects in multiple issues, particularly smooth muscles and myocardium
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Effects of Aging on Specific Physiologic Systems
Cardiovascular
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An age-associated decline in cardiac output may be attributed to reductions in maximal heart rate, myocardial contractility, and stroke volume; these changes can result in an age-related drop in myocardial oxygen consumption/utilization (mVO2).
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Regular cardiovascular exercise and endurance training have been shown to increase mVO2 in individuals aged up to 70 years.
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Fatty and fibrous tissue deposits may occur in the myocardium that can interrupt normal conduction pathways contributing to occurrence of arrhythmias.
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Cardiac valves may thicken and lose compliance, contributing to the formation of valvular regurgitation, clinically manifesting as a murmur.
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Vascular physiology is affected by age-related changes in vascular compliance, microcirculation, and baroreceptor function; these changes, combined with atherosclerosis, can produce an increased peripheral vascular resistance, resulting in increased cardiac effort to maintain cardiac output.
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Increased blood pressure and orthostatic hypotension are commonly observed as consequences of vascular changes.
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Decreased capillary density and impaired vascular proliferation have also been implicated in reducing the exercise capacity of aging individuals.
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Pulmonary
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Reduction in pulmonary microvasculature and alveoli number results in limitations in oxygen exchange and an increased sense of respiratory effort exerted during exercise.
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Decreased lung compliance results from weakness of respiratory and accessory muscles, decreased alveolar tissue elasticity, and stiffening of costovertebral and sternocostal cartilages.
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Overall, these changes contribute to a decrease in total lung capacity, vital lung capacity, inspiratory and expiratory air flows, and an increase in residual volume, respiratory frequency, and work of breathing.
Renal
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A progressive loss in the number of glomeruli along with increased vascular rigidity and atherosclerosis results in a decreased glomerular filtration rate with aging. Coexisting renal disease and nephrotoxic medications can exacerbate this age-related decline.
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In addition, the ability of the kidneys to concentrate urine decreases with age, resulting in a greater relative water output; this can negatively affect a senior athlete’s ability to remain adequately hydrated.
Neurologic
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Progressive central nervous system deterioration has been shown to result in impaired hearing, short-term memory, balance, fine motor skills, and cognition. In addition, extrapyramidal dysfunction can result in impaired coordination and rapidity of motions and with a resultant increase in motor response time.
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Even in the absence of any known neurologic disease, peripheral nerve conduction velocities are known to decrease with age, affecting vibration and proprioception nerve fibers first.
Vision
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Progressive vision impairment is common with age. Typical changes include decreased visual acuity, accommodation, contrast sensitivity, peripheral vision, and ability to adapt to low-light situations.
Endocrinal
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As part of a normal consequence of aging, hormone levels gradually decline. Effects of this decline are noted in multiple organ systems:
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With age, basal metabolic rate decreases along with increased rates of metabolic syndrome, diabetes mellitus type 2, and obesity.
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Adrenal function is reduced, resulting in decreased aldosterone and reduced ability to regulate fluid/electrolyte balance as well as decreased stress response by cortisol.
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Moreover, decreased rates of trophic hormones such as testosterone and insulin-like growth factor are associated with a decrease in skeletal muscle mass with age.
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Musculoskeletal
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Senile sarcopenia is the age-related decrease in skeletal muscle mass. Between the ages of 50 and 80 years, an average person will lose one-third of his muscle mass. At the cellular level, decreased cell numbers and proliferative capacity of satellite cells leads to decreased muscle regeneration and response to injury. Extracellularly, dysfunction of actin–myosin cross-linking causes muscle units to become stiffer and more susceptible to injury, particularly muscular strains.
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The structure of both ligament and tendon changes with aging. Aging ligaments exhibit fewer fibroblasts and mechanoreceptors, which may contribute to decreased ultimate failure load and mechanical stiffness. On the other hand, aging tendons exhibit fewer fibroblasts and increased degenerative changes; this along with a less robust blood supply (watershed areas) helps to explain the epidemic of tendon injuries in senior athletes.
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Articular cartilage is particularly susceptible to injury and degeneration with aging ( Fig. 13.1 ). Few, if any, chondrocytes are produced after skeletal maturity. Production of extracellular matrix proteoglycans is more variable with time, rendering them less effective. Response to mechanical loading is impaired by decreasing cartilage water content and more rigid collagen fibrils, secondary to increased cross-linking, which increases the risk of fissuring or shear injury.
Figure 13.1
Early degenerative changes in articular cartilage with aging.
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With age, a progressive loss of bone mineral density results in compensatory widening of the diaphysis. Consequently, the susceptibility to fragility fractures and stress injuries increases.
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Men exhibit a 0.5%–0.75% annual loss of bone mass after the age of 40 years. In women, bone mass decreases much more rapidly, at a pace of 1.5%–2.0% before menopause and accelerating further after menopause to up to 3% per year.
Decline in Athletic Performance With Aging
General Considerations
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Successful care of aging athletes depends on understanding the differences between normal and pathologic aging.
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It is well recognized that sedentary older adults exhibit more significant changes in functional capacity and body composition than adults who remain physically active as they age.
Factors Affecting Performance
Decreased Muscle Strength
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Decrease in lean muscle mass (senile sarcopenia) is paralleled by an equal or greater decrease in strength and power. Senior athletes also experience an increase in muscle fatigability.
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Muscle power is lost at a greater rate than endurance capacity.
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Muscle cross-sectional area in men declines by 14.7% over a 12-year period, beginning at the age of 65 years.
Loss of Endurance Capacity
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Decreased maximal aerobic capacity (VO 2 max) is a primary contributor to decreased endurance capacity.
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VO 2 max is dependent on heart rate, cardiac output, and tissue oxygen uptake.
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Peak blood lactate concentration is an indirect measure of anaerobic glycolytic activity. Peak lactate concentrations following maximal activity have been shown to be lower in men aged >60 years.
Loss of Exercise Economy
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Decreased flexibility, joint motion, and coordination contribute to a decline in exercise economy.
Effects of Age and Gender on Athletic Performance
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A slow progressive decline in athletic performance is seen in most athletes, starting after 35–40 years of age. Aging athletes remain capable of high levels of physical performance into their 70s.
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Significant loss of function observed before the age of 70 years can likely be attributed to disuse, sedentary lifestyle behaviors, and genetic predisposition. Between 70 and 75 years of age, most athletes reach a tipping point, and athletic performance typically plunges.
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Analysis of running and sprinting records of master athletes in the Senior Olympics shows a <2% decline in performance per year among both men and women aged 50–75 years.
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Age-associated decline in performance is typically greater in women. Examples in peer-reviewed literature have shown these differences to be greatest in endurance running and sprint-type swimming events ( Fig. 13.2 ).
Figure 13.2
2001 Senior Olympic 100-m track percentage of performance change with age.
(From Wright VJ, Perricelli BC. Age-related rates of decline in performance among elite senior athletes. Am J Sports Med. 2008;36[3]:443-450.)
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Benefits of Exercise in Older Adults
General Considerations
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A continually growing body of evidence establishes the benefits of exercise in aging athletes. Recommendations from the American College of Sports Medicine advocate for a combined physical activity regimen for all adults including resistance, endurance, flexibility, and balance training ( Table 13.1 ).
TABLE 13.1
RECOMMENDED MINIMUM EXERCISE FOR SENIOR ATHLETES
Factor
Duration
Intensity (0–10) *
Comments
Endurance
150–300 min/week
5–8
At least 10- to 30-min episodes
Resistance
8–10 exercises of 8–12 repetitions
5–8
≥2 days/week
Flexibility
≥2 days/week
5–6
Sustained stretches, static/nonballistic movements
Balance
No specific recommendations
As tolerable
Progressively difficult postures, stressing postural
muscle groups (particularly for frequent fallers)
Adults who are unable to tolerate aforementioned recommendations should be encouraged to maintain the highest possible activity level and avoid a completely sedentary lifestyle.
From Chodzko-Zajko WJ, Proctor DN, Fiatarone Singh MA, et al. American College of Sports Medicine: American College of Sports Medicine position stand: exercise and physical activity for older adults. Med Sci Sports Exerc. 2009;41:1510-1530.
* On a scale of 0–10 for level of physical exertion, 5–6 for moderate intensity, and 7–8 for vigorous intensity.
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The prevalence of various diseases, including diabetes, cardiovascular disorders, mental disorders, and certain types of cancer, are lower in people who engage in consistent physical activity.
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The incidence of mortality and amount of functional disability is also lower in active aging populations.
Musculoskeletal Benefits of Exercise
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Impact exercise can help to counteract age-related changes in bone mineral density.
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Considerably increased bone mineral density has been observed in Senior Olympic runners aged >65 years compared with control subjects.
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Participation in resistance activities is the most effective method to offset sarcopenia.
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Resistance training in elderly adults has been shown to increase muscle strength and cross-sectional area, increase joint range of motion, and also improve dynamic balance.
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While structural alterations in tendon and ligament tissues are observed with aging, mechanical properties can be improved with regular physical activity.
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Physical activity has been shown to result in increased tensile strength, ultimate load, and mechanical stiffness of ligaments and preserve the size and mechanical properties of tendons.
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A decrease in age-related cartilage volume loss has been demonstrated with exercise.
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Senior athletes participating in moderate- to high-intensity activities that load the knee and strengthen knee extensors exhibit decreased patellar and tibial cartilage volume loss.
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Systemic Benefits of Exercise
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Participation in sustained, moderately intense, aerobic activity has cardioprotective benefits ( Fig. 13.3 ).
Figure 13.3
Effects of exercise on cardiovascular physiology.
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Stroke volume, which is a major determinant of cardiac output, can decline with age. Sustained exercise can reduce this decline by 50%.
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Additional cardiovascular benefits include increased vascular compliance, lower blood pressure, and decreased formation of atherosclerotic plaques.
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VO 2 max is frequently increased with moderately intense aerobic activity, which is beneficial for other organ systems: improved pulmonary gas exchange, renal function (resulting from better blood flow), and lactate threshold.
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Maintenance of flexibility with regular stretching activities has been demonstrated to decrease the risk of musculotendinous strains in senior athletes.
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Balance training can decrease the rate of falls in older adults at a higher risk of fall injuries.
Preparticipation Medical Evaluation (PPE)
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In general, exercise does not provoke cardiovascular events in healthy individuals with a normal cardiovascular system. Individuals with atherosclerosis or decreased cardiac performance are at an increased risk of an acute myocardial event with moderate- to high-intensity physical activity; moreover, this risk is compounded in individuals with a previous sedentary lifestyle who abruptly begin intensive training regimens.
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The risk of sudden cardiac arrest or myocardial infarction is very low in healthy individuals who perform moderate-intensity activities. The ACSM cautions that vigorous exercise confers an acute increased risk of sudden cardiac death and/or myocardial infarction in individuals with either diagnosed or occult cardiovascular disease.
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Cardiac assessment is not required before initiating moderate-intensity exercise programs in a majority of senior athletes. Older adults with >2 risk factors are considered to be at a moderate risk of adverse responses to exercise and are advised to undergo medical examination and exercise testing before initiating high-intensity/vigorous exercise ( Table 13.2 ).
TABLE 13.2Related posts:
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