This proposal is for the competitive renewal of RO1 AG018844, which is in its third year of funding and is submitted in response to PAS-03-122 """"""""Frailty in Old Age: Pathophysiology and Interventions"""""""". The focus of this research has been to examine the physiologic and functional effects of a muscle power training intervention in comparison to traditional progressive resistance training in a community-based group of elderly men and women with moderate mobility limitations. During the current project period, we have successfully demonstrated that peak lower extremity power is closely associated with functional limitations and self-reported disability in older community dwelling men and women. We propose to extend our previous findings by examining the physiological mechanisms that contribute to the age and gender-related declines in peak muscle power. To compliment our existing data on skeletal muscle fiber contractile properties, we will assess the neural contributions to the generation of muscle power with advancing age. We will test the hypothesis that skeletal muscle single fiber contractile properties (i.e. single fiber power, shortening velocity, specific force), neural factors (i.e. intermuscular coordination patterns, central activation ratios/and motor unit control properties) and lower extremity power will be reduced with advancing age and degree of risk for mobility disability, and these differences will be attenuated in women compared to men. Middle-aged healthy (40-55 yrs.), older healthy (70-85 yrs), and older (70-85 yrs) men and women at risk for mobility disability will be studied under controlled conditions (Study 1). In addition, in light of our recent observations that differences in lower extremity maximal velocity occur at relatively low external forces (eg: 40% 1 RM) and are most closely associated with gait velocity in older individuals, we propose conducting a randomized controlled trial of high velocity low resistance exercise training in individuals at risk for mobility disability to test the hypothesis that a short-term resistance training intervention performed against a low external force and at maximum voluntary velocity will induce significant reductions in mobility disability as evidenced by improvements in gait velocity during performance of a 400 M walk in older individuals at risk for mobility disability (SPPB score <_9, 70 - 85 yrs) (Study 2). The results of these studies will have important implications in understanding the proximal determinants of physical disability in the frail elderly and in designing intervention strategies targeted at improving mobility.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG018844-08
Application #
7626303
Study Section
Special Emphasis Panel (ZRG1-BDA-A (02))
Program Officer
Joseph, Lyndon
Project Start
2001-03-15
Project End
2012-05-31
Budget Start
2009-06-15
Budget End
2012-05-31
Support Year
8
Fiscal Year
2009
Total Cost
$440,126
Indirect Cost
Name
Tufts University
Department
Nutrition
Type
Organized Research Units
DUNS #
039318308
City
Boston
State
MA
Country
United States
Zip Code
02111
Trombetti, A; Reid, K F; Hars, M et al. (2016) Age-associated declines in muscle mass, strength, power, and physical performance: impact on fear of falling and quality of life. Osteoporos Int 27:463-71
Reid, Kieran F; Martin, Kimberly I; Doros, Gheorghe et al. (2015) Comparative effects of light or heavy resistance power training for improving lower extremity power and physical performance in mobility-limited older adults. J Gerontol A Biol Sci Med Sci 70:374-80
Fielding, Roger A (2015) A Summary of the Biological Basis of Frailty. Nestle Nutr Inst Workshop Ser 83:41-4
Clark, David J; Reid, Kieran F; Patten, Carolynn et al. (2014) Does quadriceps neuromuscular activation capability explain walking speed in older men and women? Exp Gerontol 55:49-53
Reid, Kieran F; Pasha, Evan; Doros, Gheorghe et al. (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. Eur J Appl Physiol 114:29-39
Clark, David J; Pojednic, Rachele M; Reid, Kieran F et al. (2013) Longitudinal decline of neuromuscular activation and power in healthy older adults. J Gerontol A Biol Sci Med Sci 68:1419-25
Pojednic, Rachele M; Clark, David J; Patten, Carolynn et al. (2012) The specific contributions of force and velocity to muscle power in older adults. Exp Gerontol 47:608-13
Reid, Kieran F; Doros, Gheorghe; Clark, David J et al. (2012) Muscle power failure in mobility-limited older adults: preserved single fiber function despite lower whole muscle size, quality and rate of neuromuscular activation. Eur J Appl Physiol 112:2289-301
Choi, Seung Jun; Lim, Jae-Young; Nibaldi, Eva G et al. (2012) Eccentric contraction-induced injury to type I, IIa, and IIa/IIx muscle fibers of elderly adults. Age (Dordr) 34:215-26
Reid, Kieran F; Fielding, Roger A (2012) Skeletal muscle power: a critical determinant of physical functioning in older adults. Exerc Sport Sci Rev 40:4-12

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