Skeletal Muscle Power and Functioning in Older Adults
Skeletal Muscle Power and Functioning in Older Adults
Muscle power declines earlier and more precipitously with advancing age compared with muscle strength. Peak muscle power also has emerged as an important predictor of functional limitations in older adults. Our current working hypothesis is focused on examining lower extremity muscle power as a more discriminant variable for understanding the relationships between impairments, functional limitations, and resultant disability with aging.
The prevention or postponement of mobility limitations for the aging population is of major public health importance. Mobility, the ability to move without assistance, is critical for maintaining independent functioning. Limitations in mobility, typically defined as difficulty in performing physical tasks, such as walking one-quarter mile, climbing a flight of stairs, or rising from a chair, are indicative of a marked decline in functional health. With persons aged 60 yr or older representing the fastest growing segment of the worldwide population, there will continue to be a corresponding increase in the prevalence of mobility limitations. Improved knowledge of the specific physiological mechanisms that mediate impairments in physical functioning will be crucial for developing effective therapeutic interventions for preserving mobility and independence among older people.
According to the disablement model, impairment refers to a loss or abnormality at the tissue, organ, and body system level. At an individual level, impairments can progress to functional limitations and to subsequent disability. Although a large number of studies have established the role of muscle strength (the ability to generate maximal muscle force) as a proximal determinant of functional limitations in older adults, skeletal muscle power (the product of the force and velocity of muscle contraction) has been shown to decline earlier and more rapidly than muscle strength with advancing age. The underlying physiological mechanisms that contribute to this reduction in muscle power output among older adults include a quantitative decline in muscle mass (sarcopenia), changes in muscle composition, muscle quality (reduced muscle strength per unit muscle mass), individual muscle fiber contractile properties, and alterations in neuromuscular function.
Our current working hypothesis is focused on examining lower extremity muscle power as a more critical variable in understanding the relationship between impairments, functional limitations, and resultant disability (Fig. 1). This review article will summarize studies from our research group that have identified peak muscle power as a more influential predictor of functional performance in older adults compared to muscle strength. We also will describe recent evidence from our work investigating the underlying physiological determinants of skeletal muscle power impairments among elders with overt mobility limitations. Finally, we will describe novel therapeutic interventions targeted at restoring muscle power in older
(Enlarge Image)
Figure 1.
Power driven pathway to age-associated disability. [Adapted from (35). Copyright © 1994 Elsevier. Used with permission.]
Abstract and Introduction
Abstract
Muscle power declines earlier and more precipitously with advancing age compared with muscle strength. Peak muscle power also has emerged as an important predictor of functional limitations in older adults. Our current working hypothesis is focused on examining lower extremity muscle power as a more discriminant variable for understanding the relationships between impairments, functional limitations, and resultant disability with aging.
Introduction
The prevention or postponement of mobility limitations for the aging population is of major public health importance. Mobility, the ability to move without assistance, is critical for maintaining independent functioning. Limitations in mobility, typically defined as difficulty in performing physical tasks, such as walking one-quarter mile, climbing a flight of stairs, or rising from a chair, are indicative of a marked decline in functional health. With persons aged 60 yr or older representing the fastest growing segment of the worldwide population, there will continue to be a corresponding increase in the prevalence of mobility limitations. Improved knowledge of the specific physiological mechanisms that mediate impairments in physical functioning will be crucial for developing effective therapeutic interventions for preserving mobility and independence among older people.
According to the disablement model, impairment refers to a loss or abnormality at the tissue, organ, and body system level. At an individual level, impairments can progress to functional limitations and to subsequent disability. Although a large number of studies have established the role of muscle strength (the ability to generate maximal muscle force) as a proximal determinant of functional limitations in older adults, skeletal muscle power (the product of the force and velocity of muscle contraction) has been shown to decline earlier and more rapidly than muscle strength with advancing age. The underlying physiological mechanisms that contribute to this reduction in muscle power output among older adults include a quantitative decline in muscle mass (sarcopenia), changes in muscle composition, muscle quality (reduced muscle strength per unit muscle mass), individual muscle fiber contractile properties, and alterations in neuromuscular function.
Our current working hypothesis is focused on examining lower extremity muscle power as a more critical variable in understanding the relationship between impairments, functional limitations, and resultant disability (Fig. 1). This review article will summarize studies from our research group that have identified peak muscle power as a more influential predictor of functional performance in older adults compared to muscle strength. We also will describe recent evidence from our work investigating the underlying physiological determinants of skeletal muscle power impairments among elders with overt mobility limitations. Finally, we will describe novel therapeutic interventions targeted at restoring muscle power in older
(Enlarge Image)
Figure 1.
Power driven pathway to age-associated disability. [Adapted from (35). Copyright © 1994 Elsevier. Used with permission.]
