example of a CPA would be a lateral step to maintain balance after being pushed at shoulder level while walking. The aging process affects both APAs and CPAs due to sensory losses, Musculoskeletal changes Several age-related declines typically occur in the musculoskeletal system in older adults. This section will cover changes in muscle strength, flexibility, and posture. Muscle strength and age-related changes A decline in muscle strength, especially lower extremity strength, has been identified as a common risk factor for falls. Although muscle strength can be maintained or improved well into advanced age, it does experience age-related declines, with some older adults experiencing up to 40% reduction in lower extremity strength between the ages of 30 and 80 years. This decline starts around age 30 and accelerates after 50 years of age and is most evident in frail older adults and those with a history of falls (Keller & Engelhardt, 2014). The rate of decline in strength is variable among older adults. For example, an 80-year-old man typically has a 12% to 17% loss of knee flexor and extensor strength (Keller & Engelhardt, 2014). Loss of grip strength, in both men and women, also has been linked to fall risk in a few studies (Szulc, Feyt, & Chapurlat, 2016). Physiologic changes in the muscles of older adults include loss of Type I (slow twitch) and Type II (fast twitch) muscle fibers, a decrease in the number of functional motor units, and muscle fatigue, especially during concentric contractions. Loss of Type II fibers is typically greater than loss of Type I fibers. In addition to loss of strength, muscle endurance and muscle mass in the lower extremities are reduced with aging, more so than in the upper extremities. Lack of activity accelerates a greater loss of strength than of muscle mass (Keller & Engelhardt, 2014), although both muscle strength and mass (to a lesser degree) can be improved in older adults with resistance training. Although resistance training can improve muscle strength and power in older adults, “detraining” can result in swift reversal in strength gains. It is imperative that older adults make strength training a habit for the remainder of their lives to avoid changes in function and to decrease their risk for falls. Bone health In general, the major skeletal changes that occur with aging include calcium-related loss of bone mass and density, decreased circulating levels of vitamin D, and an overall decrease in bone strength (Lewis & Bottomley, 2008). Significant bone loss can lead to the pathologic condition of osteoporosis, where an imbalance occurs between breakdown of bone (osteoclast activity) and buildup of bone (osteoblast activity). This imbalance results in excessive calcium absorption from bone in order to meet the needs of various bodily systems. For women, a typical rate of bone loss per year due to aging is 1% starting at age 30 to 35, with loss starting for men at age 50 to 55 (Lewis & Bottomley, 2008). In some cases, severe osteoporosis may result in a pathologic fracture, resulting in a fall, versus the other way around. If a fall occurs, an osteoporotic bone is more likely to fracture than a healthy bone. Factors such as poor nutrition, inactivity, and smoking can accelerate the rate of bony loss, whereas age, sex, race, body type, and genetic makeup can predispose adults to development of osteoporosis. Assessing for these risk factors can help guide the clinician when developing safe and effective exercise programs aimed at strengthening lower extremity muscles and preventing falls. For example, an older adult with severe osteoporosis may not be able to tolerate single leg stance activities such as stair climbing (Lewis & Bottomley, 2008). Changes in flexibility and posture Older adults can experience several changes in flexibility that can influence fall risk. These changes can occur in the spine, in connective tissue, and in individual joints. In general, older adults can experience a loss of spinal flexibility, especially spinal extension, resulting in as much as a 50% reduction compared with young adults (Holland, Tanaka, Shigematsu, & Nakagaichi,
decreased muscle strength and power, impaired joint mobility, and changes in sensory integration (Shaffer & Harrison, 2007).
2002). Connective tissue loss in elastin and collagen, which increases joint and soft tissue stiffness, can lead to individual joint loss of range of motion (ROM), which happens primarily in extension ranges, and can be compounded by presence of disease, pain, surgery, or injury (Holland et al., 2002). It is also common for adults 55 to 85 years of age to experience declines in ankle joint flexibility of 50% in women and 35% in men (Holland et al., 2002). These changes in flexibility coupled with the typical age-related changes in strength can lead to a “geriatric posture” (Lewis & Bottomley, 2008). Geriatric posture results from declines in the neurologic and musculoskeletal systems, primarily in strength, flexibility, and sensory changes. The presence of a disease, such as Parkinson’s, which induces a more flexed posture, also can negatively affect posture (see Figure 1 for an example of changes in cervical posture). The typical geriatric standing posture includes the following: ● Increased forward head posture (FHP). ● Increased thoracic kyphosis and rounded shoulders. ● Increased overall hip flexion and knee flexion. ● Varying lordosis, but typically decreased. ● Overall decrease in height as spinal compression occurs. FHP and increased thoracic kyphosis are typically accompanied by internally rotated shoulders, changes in lumbar lordosis, and flexion in the hips and knees. These changes may be asymptomatic and pain free, with age-related, disease-related, and sex-related variation among older individuals. Geriatric posture can progress to a painful state, in more extreme cases, resulting in limited mobility and avoidance of functional positions, such as standing for longer periods of time or walking long distances. Postural changes can affect strength, ROM, vestibular function, visual field, balance, and ADLs (Lewis & Bottomley, 2008). Some studies more recently have linked FHP to increased fall risk and deficits in vestibular efficiency (de Groot et al., 2014; Lee, 2016; Yip, Chiu, & Poon 2008). Some researchers consider of the presence of FHP as a trigger for a fall risk assessment (Nemmers, Miller, & Hartman, 2009). Figure 1: Forward Head Posture
Note . From Western Schools, 2019.
Frailty and falls Frailty is considered a geriatric syndrome. A geriatric syndrome is a common health condition in older adults grouped by a pattern of symptoms and signs typically with multiple underlying causes, but that may not be known or that did not fit into discrete disease categories (Tinetti, Williams, & Gill, 2000). According to a 2013 consensus meeting on frailty, physical frailty is “a medical syndrome with multiple causes and contributors that is characterized by diminished strength, endurance, and reduced physiologic function that increases an individual’s vulnerability for developing increased dependency and/or death” (Morley et al., 2013). Many researchers have attempted to measure frailty using factors such as impairment in mobility, balance, muscle strength, cognition, nutrition, weight loss, depression, incontinence,
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