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ABSTRACT
The process of aging is associated with numerous changes in all bodily systems that ultimately manifest in a decline in peak physiologic function. Preservation of functional ability in advanced age is predicated on maintenance of the 4 components of fitness-cardiorespiratory endurance, muscular strength and endurance, flexibility, and body composition-each of which show changes with aging that adversely impact functional ability. A requisite awareness and understanding of the effects of aging on the components of fitness and understanding of the role of exercise as intervention is of paramount importance. This review presents underlying changes and adaptations within each component of fitness and the effects on overall physiologic capacity from the more overt changes underlying declining aerobic capacity, pulmonary function, and flexibility, to the more latent changes such as demineralization of bone leading to changes in body composition and the contraction-specific decline in the force generating capacity of skeletal muscle. Because exercise and physical activity have been shown to attenuate or delay many of the agerelated changes in the components of fitness, recommendations and guidelines for exercise prescription are offered in the context of the these changes.
INTRODUCTION
In the 30-year period from 1965-1995, the United States has witnessed an evolution in the structure of the age classes evidenced by an 82% increase in those over the age of 65 years. Representing 13% of the population in 1995, current estimates are that by the year 2005, those over the age of 65 will account for 20% of the population in the United States. Additional evidence of the increased population of older adults is noted in those over the age of 85 years, considered the 'old old,' which is the fastest growing segment of the population.1
The process of aging in humans is characterized by a multitude of changes in all bodily systems that ultimately result in a decreased capacity to function.2 Although the incidence of pathology and co-morbidity is greater in older populations than in younger, the process of aging itself is nonpathological and presents in a variety of changes manifesting in reduced functional capacity.3 While variability exists in defining an older population, many of the physiologic changes due to aging are observable by the middle of the sixth decade.
While greater variability exists...