The lymphatic system has active and passive parts, which are both affected with aging. The active part is from lymphatic muscle contractions— specifically, activity from lymphatic vessels—and muscle contractions knead the lymphatic valves of the lymphangions (Filelfi et al., 2021). The passive part is extrinsic contractions from all other forces that influence lymphatic flow such as the force of gravity, muscle contractions, artery pulsations, and respiratory activity (Filelfi et al., 2021). Aging has been associated with alterations in muscle strength and function, and can be associated with all organ systems. The lymphatic system is interwoven through all systems. It is responsible for sensing damage to body tissues, containing damage, and clearing damaged cells (Davan-Wetton et al., 2021). If the lymphatic system is compromised, tissue repair is slowed or halted; homeostasis cannot be achieved through necrotized cell clearance; and cell apoptosis and failed resolution can be seen through chronic inflammation, which is referred to as lymphedema (Filelfi et al., 2021). Participation in moderate exercise improves senescence, reduces edema, and improves adapted immunity even in people who were previously sedentary (Papp et al., 2021). and size reduce approximately 1% to 1.5% per year, and this is more noticeable in the lower limbs in both men and women (Frontera, 2017). Muscle size Muscle size is another factor to be considered in the aging body, as muscle atrophy occurs with aging, and there are some correlations between muscle strength and muscle size. Though it may seem intuitive that the loss of muscle mass leads to an equal loss of strength, it is now known that the loss of muscle strength actually exceeds the loss of muscle mass. Reduced strength is only partially due to reduced muscle mass (Frontera, 2017), though muscle atrophy is an important determinant of muscle dysfunction in older adults. “Skeletal muscle comprises approximately 40% of the human body weight and contains between 50% and 70% of all proteins in the human body” (Frontera, 2017, p. 707). Sarcopenia is age-related loss of skeletal muscle mass, strength, and function. Muscle atrophy is the loss of muscle tissue. Muscle quality Assessment of the loss of both muscle strength and power at rates that are greater than that seen in the loss of muscle mass has been termed muscle quality (Barbat-Artigas et al., 2012; Russ et al., 2012). Muscle quality is the muscle’s ability to produce strength or power relative to the muscle size (Russ et al., 2012). If the loss of strength and power exceeds the loss of muscle mass, then muscle quality has decreased. Muscle quality may be lost by as much as 2.5% per year in healthy individuals (Goodpaster et al., 2006). This is more than double the loss of lean muscle mass. These findings indicate that neurological changes and/ or some change in the intrinsic force-generating capacity of the muscle is/are responsible for the decrease in muscle quality. Tendons and ligaments Tendons make movement possible by leveraging bones to muscle force. Aging affects tendon structure and function, and tendon injuries become more frequent in locations such as the rotator cuff, the patellar tendon, and the Achilles tendon (Frontera, 2017). Ligaments provide joint support and stability, and go through changes similar to those the tendons experience. For example, ligaments change in cellular density, collagen and elastic fibers decrease, and cross-links between collagen fibers in the articulated cartilage change (Frontera, 2017). Not only does the connective tissue surrounding a joint change, but the amount and quality of synovial fluid within a joint also decreases. Decreased quality and amount of synovial fluid make movement more difficult by increasing the friction within the joint. The combination of changes in connective tissue and the synovial fluid results in impaired and slower joint
for example, how doing yoga can reduce anxiety (AOTA, 2017; Ballantyne et al., 2019; White et al., 2020). There is evidence that mindfulness therapies work, that physical domains and how they function can be addressed through CHAIHs. The above described CHAIHs are all missed opportunities for therapy practitioners to help patients who have GVHD, cancer, type 2 diabetes, human immunodeficiency virus (HIV), and other disorders with neuropathic pain, sclerodermic changes, and autoimmune issues (Mohammed et al., 2019; Rosenthal et al., 2019; White et al., 2020). Interventions and changes within the interstitial system also impact the endocrine and musculoskeletal systems. The interstitial system changes with age, as described earlier, with beneficial and detrimental cellular senescence; most research has looked at the affected lymphatic system. Older adults have up to a 70% reduction of circulating lymphocytes as compared to young adults (Filelfi et al., 2021). Apoptosis (cell death), which occurs as a normal and controlled part of an organism's growth and development, increases with age in all body systems, including the interstitial system (Davan-Wetton et al., 2021). Cells lose the power to divide and grow. Musculoskeletal system changes As with the other body systems, aging brings about numerous significant changes in the musculoskeletal system, which includes skeletal muscle, tendons, ligaments, bone, and articular cartilage. While changes in all body systems may impair mobility and function in older adults, decline in musculoskeletal system function may be especially harmful. Most components of the musculoskeletal system show significant losses of structural and functional properties, with aging affecting joint changes such as pain and stiffness (Frontera, 2017). Joint pain and stiffness lead to decreased range of motion, standing, and movement tolerance. These changes affect a person’s ability to perform many activities of daily living (ADL) as well as participate in many tasks that require functional mobility (Frontera, 2017). However, many musculoskeletal changes can be ameliorated with appropriate exercise training and a physically active lifestyle (Frontera, 2017). Many ADL can also be adapted if an individual has orthopedic limits due to pain or joint deterioration, or if they need to follow postsurgical orthopedic restrictions. According to Frontera, in his discussion of physiological changes to the musculoskeletal system with aging, “The main challenge associated with advanced age is the relationship between significant alterations in many physiologic functions, the development of multiple impairments, the decline of overall functional capacity, the associated morbidity and mortality, and the resulting loss of independence that most older adults fear and death” (2017, p. 706). If these impairments are left unaddressed, they can lead to life-threatening complications such as falls and bone fractures associated with muscular weakness, thus further increasing mortality. Muscles Age affects all four domains of skeletal muscle’s capacity to generate force power and movement. These domains are structure and architecture, fiber type distribution, excitation– contraction coupling, and energy release. The number of muscle fibers (and therefore muscle mass) is reduced with age, there is in increase in muscle type I fibers (slow twitch) and a decrease in type II fibers (fast twitch), muscle proteins undergo biochemical changes, and there is reduced oxidative capacity as well as impaired excitation–contraction coupling due to the uncoupling and fragmentation of cellular elements (Frontera, 2017). Muscle strength Muscle strength is a strong predictor of mobility limitation, slow gait speed, increased fall risk, risk of hospitalization recidivism, and high mortality (Frontera, 2017). Aging is associated with a significant reduction in muscle strength. One factor that contributes to muscle strength loss is a reduction in the ability to activate motor units (Frontera, 2017). Lean muscle mass strength
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