Aging is often characterized by a decline in multiple body systems, including loss of muscle strength and mass. Muscular strength peaks in individuals in the 2nd to 4\" decades oflife, and decreases thereafter. Muscle strength declines, on average, by 20-40% from the 3\'d to 7th decades oflifel. In addition, over 20% of individuals 60-70 years old experience a significant decrease in muscle mass, and that number increases to nearly 50% in individuals over 75 years of age\'. These changes in muscle function and quantity directly influence the decreased functional capacity, increased risk for falling, and increased mortality that occur with aging. The estimated cost of healthcare services that directly address consequences of decreased strength and functional capacity is comparable to that spent on services to address osteoporosis. In the US, the annual cost of decreased physical function and physical disability related to a decline in muscular strength and function is estimated to be $18 billion, whereas the annual cost associated with osteoporosis is estimated to be $16.3 billion 3. As with osteoporosis, the decrease in muscle strength and power and the resulting decrease in functional capacity with aging can largely be prevented or reversed. The muscle cells of older adults remain adaptable to training stimuli, in particular to resistance training, even into late adulthood ls. 16.25. Proper resistance training is thus an important aspect of preventative medicine in the elderly or late-middle adulthood population" 9. In developing treatment programs to increase strength and power in the elderly, and thus improve function in this population, it is important to understand the factors that contribute to the decrease in these measures with aging. The first is a decrease in total muscle mass3, s, Muscle strength is directly dependent on the cross-sectional area of the muscle, and thus a decrease in the size of a muscle decreases its force-generating capacity. The loss of total skeletal muscle mass and function with aging is termed sarcopenia. The second factor is decreased neural activation of motor units wi thin skeletal muscle3, s, Because power is a result of force generated over a finite time, reduced neural activation particularly influences muscular power in the elderly, The third and final factor is a change in the contractile property of muscular fibers that may result from excitation-contraction uncoupling, alteration of myofibrillar protein structure, or infiltration of adipocytes into•skeletal muscle 3. Resistance training programs have been shown to effectively ameliorate or reverse decreased muscle strength and sarcopenia in the elderly population" s, 6, 7, s, 9 • Resistance training can increase muscular strength and power by altering any of the factors mentioned above, but the type of program implemented will influence one factor more than another. According to the principle of training specificity, human skeletal muscle will adapt to meet the demands placed upon it. Specifically, a high-intensity or high-velocity program will preferentially recruit more motor units and improve powers. 13, whereas a high-volume, low-intensity program will increase muscular endurance13. When designing a program to improve strength and function in an elderly patient, it is important to consider that muscular power decreases more than static strength with aging4, and that this decrease has the most profound effect on physical function in the elderly population4. 29 . Several studies have demonstrated that it is not muscle mass per se that determines muscular function, but overall neuromuscular function 3,4, 6. It would follow that exercises emphasizing higher power output and demanding more neuromuscular recruitment are most effective at increasing functional strength and power. While numerous studies have shown the effectiveness of progressive resistance training in increasing muscle mass and strength in the elderly population, uncertainty remains regarding the efficacy of this intervention in increasing physical function9. Additionally, it remains to be established whether higher-intensity resistance training programs are safe for more physically limited elders, or those elderly patients with other medical complications 9. It is the purpose of this review to search the available literature and answer the following question: In an elderly population (>65 years old) with documented physical disability, is a high-intensity resistance training program more effective than traditional, low-intensity resistance training program at increasing muscular strength and function (specifically, reducing the number of falls experienced in this population, and improving overall mobility as measured by standard tests (TUG, 6 minute walk-test, etc.) in the elderly? Additionally, is a free-form mode of resistance training more effective than a fixed-form mode of training at improving the same parameters in the same population? Finally, can elderly individuals train safely using relatively high resistance?


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resistance training, elderly, optimize function, prevent falls

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