Skip to main content
ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #306567
Title: Longitudinal decline of lower extremity muscle power in healthy and mobility-limited older adults: influence of muscle mass, strength, composition, neuromuscular activation and single fiber contractile properties

Author
item REID, KIERAN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item PASHA, EVAN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item DOROS, GHEORGHE - Boston University
item CLARK, DAVID - Malcom Randall Va Medical Center
item PATTEN, CAROLYNN - University Of Florida
item PHILLIPS, EDWARD - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item FRONTERA, WALTER - Vanderbilt University
item FIELDING, ROGER - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: European Journal of Applied Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2013
Publication Date: 1/1/2014
Citation: Reid, K.F., Pasha, E., Doros, G., Clark, D.J., Patten, C., Phillips, E.M., Frontera, W.R., Fielding, R.A. 2014. Longitudinal decline of lower extremity muscle power in healthy and mobility-limited older adults: influence of muscle mass, strength, composition, neuromuscular activation and single fiber contractile properties. European Journal of Applied Physiology. 114:29-39. DOI:10.1007/s00421-013-2728-2.

Interpretive Summary: The power generating capability of the muscles in the lower limbs is an important factor contributing to the maintenance of physical independence and mobility among older adults. However, there is limited understanding of the major underlying physiological determinants of muscle power loss with advancing age among older persons. Improved knowledge of these mechanisms could provide important information for developing appropriate intervention and management strategies that may prevent or delay age-related disability for older populations. For the first time, this study investigated the longitudinal physiological determinants of lower extremity muscle power loss among two distinct cohorts of healthy older and mobility-limited older adults. We demonstrated that, after three years of follow-up, the overall loss of muscle power was similar between the healthy and mobility-limited groups. However, within each group, muscle power declines were associated with divergent changes in muscle size, strength and neuromuscular function. In addition, in response to the declines in overall muscle power, we demonstrate that substantial compensatory adaptations occur within the contractile properties of surviving single muscle fibers in both healthy and mobility-limited groups. Finally, we show novel evidence that there is progressive infiltration of adipose tissue into skeletal muscle tissue, and this appears to be associated with impairments in the ability of skeletal muscle to contract and, subsequently, generate muscle power.

Technical Abstract: This longitudinal study examined the major physiological mechanisms that determine the age related loss of lower extremity muscle power in two distinct groups of older humans. We hypothesized that after ~3 years of follow-up, mobility-limited older adults (mean age: 77.2 +/- 4, n = 22, 12 females) would have significantly greater reductions in leg extensor muscle power compared to healthy older adults (74.1+/-4, n = 26, 12 females). Mid-thigh muscle size and composition were assessed using computed tomography. Neuromuscular activation was quantified using surface electromyography and vastus lateralis single muscle fibers were studied to evaluate intrinsic muscle contractile properties. At follow-up, the overall magnitude of muscle power loss was similar between groups: mobility-limited: -8.5 % vs. healthy older: -8.8 %, P > 0.8. Mobility-limited elders had significant reductions in muscle size (-3.8 %, P < 0.01) and strength (-5.9 %, P < 0.02), however, these parameters were preserved in healthy older (P is greater than or equal to 0.7). Neuromuscular activation declined significantly within healthy older, but not in mobility-limited participants. Within both groups, the cross-sectional areas of type I and IIA muscle fibers were preserved while substantial increases in single fiber peak force (>30 %), peak power (>200 %) and unloaded shortening velocity (>50 %) were elicited at follow-up. Different physiological mechanisms contribute to the loss of lower extremity muscle power in healthy.