Increasing awareness of the benefits of exercise and longer lifespans is leading to more older patients seeking care for musculoskeletal injuries. Older individuals are more prone to overuse injuries and are slower to heal. Despite that, most researchers and clinicians agree that the benefits of exercise far outweigh the risks. The volume of research on aging is increasingly showing that there are physical, cognitive and psychosocial benefits to remaining physically active as we age.1
While age-related changes are unavoidable, research is suggesting that many of the declines previously associated with aging may actually be due more to a sedentary lifestyle that many older individuals adopt.2 Some researchers estimate that exercise can offset the decline by up to 50 percent.3-5 In addition, many older individuals also have chronic diseases such as hypertension, diabetes or obesity. Regular exercise has long been a recommended part of management for these conditions.
The known benefits of exercise bode well for our older patients and provide an opportunity to speak to them about remaining active or increasing their activity as they age. Montoye and colleagues found that college athletes who stop participating in sports have a rapid weight gain beginning at the age of 45.6 Conversely, even patients who have previously been sedentary can significantly decrease their risk of serious illness and risk of disability by starting a fitness program later in life.
The aging process starts earlier than many of our patients would suspect. Studies show some physiological and physical changes begin as early the third decade of life. This decline progresses in a relatively linear fashion until approximately age 60 to 70 when there is a steeper and more progressive drop-off.7 These age-related changes are inevitable of course but people can make them worse by inactivity.5
Understanding the physical and physiological changes of aging is important so we can tailor our patient education in order to promote physical fitness and help decrease the risk of injury.
Cardiac, vascular and pulmonary function decline at a rate of approximately 10 percent per decade after the age of 25.8 Decreased maximal heart rate and myocardial contraction combined with increased peripheral vascular resistance, diminished lung capacity and alveolar gas exchange are just some of the changes that combine to decrease the delivery of oxygen to muscles and other tissues. It is extremely important that all patients have a pre-activity exam/screening by a physician because underlying cardiac disease increases the risk of myocardial infarction and sudden cardiac death. For this reason, even fit patients should also have regular follow-up exams with their physicians to monitor for changes that might alter their risk factors.9
Neurologic changes manifest as a loss of nerve tissue including cerebral cortex and spinal cord axons, and the dysfunction of peripheral nerves.4 These losses affect not only cognition but coordination, fine motor skills, proprioception and balance as well. Dorfman found a 30 to 50 percent reduction in ankle proprioception and vibration sense in aged adults and noted that absent ankle reflexes are a common age-related finding even in the absence of pathology.10 Depression and some medications can also have negative effects on neuromuscular coordination.11
Impaired balance and concern about falling are two of the most often cited reasons for decreased activity in older individuals.12 Most acute injuries in older people are related to falls or slips.13,14 Research shows that training balance and lower extremity strength simultaneously is an important strategy in maintaining physical function and decreasing the risk of falls.15,16
Age-related decline in muscle function in theory has the greatest impact on functional muscle capacity.11 There is a 20 to 40 percent decrease in strength between the ages of 20 and 70.17,18 Sarcopenia describes the process of muscle deterioration, which includes a reduced number and size of muscle cells, and a decreased density of mitochondria. Sarcopenia results in decreased muscle power and endurance. Wolfson and colleagues showed strength and balance improvements in older adults with a lab-based training program.15 The older adults in the study then transitioned to a tai chi program and were able to maintain the gains but to a lesser degree. The preservation of muscle power into late life can greatly decrease the risk of disability and enhance functional independence.19
Aging itself is not a risk factor for tendon injuries but changes to the cellular matrix of tendons occur with age.20 Increased collagen, decreased collagen turnover, increased cross-linking and changes in elastin and water content all lead to altered tendon stiffness. Diabetes can accelerate the changes in aging tendon.21 Research has shown physical activity to increase the cross-sectional area of tendons while enhancing collagen turnover and remodeling.22 Individuals who continue to exercise and incorporate flexibility and eccentric strength training slow the decline in flexibility one would otherwise see with aging.11
Common changes to the bone of older individuals include: decreased bone mineral density, thinner cortex adipose tissue deposits in marrow and decreased osteoblast activity. These affect women earlier and more significantly than men.3 In fact, women start losing bone mineral density in their 30s and lose it twice as fast as men.23 Physical exercise, including resistance, aerobic and endurance training, all help maintain and improve bone health.24
Cartilage relies on joint loading and the fluid dynamics of synovial fluid for nutrition and removal of metabolic waste. Chondrocytes and extracellular matrix proteins experience little cell turnover so they may be less resistant to aging than other tissues. In addition, the increased oxidative stress and decreased growth factors present in aging cartilage may contribute to the development of osteoarthritis.25 Decreased joint loading, similar to what occurs with even short-term immobilization, results in disuse atrophy and the diminished metabolic activity of cartilage.26
Osteoarthritis is the most common source of musculoskeletal pain and disability in the older population.9 Softening, fissuring and fibrillation of the weightbearing surfaces occur with repetitive joint loading and microtrauma to mechanically compromised articular cartilage.23 Activities that subject the joints to high levels of impact and torsional loading may increase the risk of injury and cartilage degeneration.27,28 Individuals with early osteoarthritis can benefit from regular exercise but one should advise them to select activities that maintain joint motion and build strength with minimal loading of the affected joints.28 For example, runners who develop knee osteoarthritis may transition to cycling or elliptical exercise machines to minimize knee joint loading.
Other age-related changes that are relevant to active individuals may be more insidious. Older athletes may unknowingly have difficulty with fluid balance. The thirst mechanism is less sensitive with age, renal function decreases and sweat response is impaired.29,30 These changes can contribute to overhydration, dehydration and electrolyte imbalance. These imbalances may subsequently result in the decreased ability to thermoregulate and/or regulate cardiopulmonary function, and negatively affect performance as well.31
The incidence of overuse injuries is higher and the incidence of acute injuries is lower in older athletes.32,33 Finnish researchers found that of the injuries sustained in athletes aged 70 to 81 during a 10-year period, 75 percent were to the lower extremity.34 The knee and foot/ankle were the most common sites at 20 percent and 19 percent respectively.
While it appears that older athletes are more likely to get injured, researchers on aging are nonetheless unanimous in advocating for exercise and sports activities over sedentary lifestyles. In one study, one year of endurance training improved patients’ maximum oxygen uptake to the level of sedentary people 10 to 20 years younger and also improved muscle function and decreased body fat.35
However, the literature review by Hawkins and coworkers suggests that it is important to combine endurance training with resistance training to reap the maximum benefits of exercise.36 Chen and colleagues pointed out that “anti-aging” agents such as growth hormone, antioxidants and androgens can be costly, come with significant risks or unknown long-term risks, and have not proven to be superior to exercise.22
The United States Public Health Service declared that exercise is one of the five priority areas to prevent premature morbidity and mortality. The National Council on Aging recommends that “older adults engage in moderate physical activity for at least 30 minutes five days a week and muscle-strengthening activities on two or more days a week that work all major muscle groups.”37 However, statistics show that less than one-third of Americans 65 years of age and older meet this level.36
As medical professionals, we owe it to our patients to not only treat their current conditions but educate them on the benefits of maintaining or starting a fitness program so they may enjoy a better quality of life as they age.
Dr. Langer is in private practice at Twin Cities Orthopedics in Minneapolis. He is an Adjunct Clinical Professor at the University of Minnesota Medical School and a board member of the American Academy of Podiatric Sports Medicine.
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