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. 2012 Jun;112(6):2289-301.
doi: 10.1007/s00421-011-2200-0. Epub 2011 Oct 18.

Muscle power failure in mobility-limited older adults: preserved single fiber function despite lower whole muscle size, quality and rate of neuromuscular activation

Kieran F Reid  1 , Gheorghe Doros, David J Clark, Carolynn Patten, Robert J Carabello, Gregory J Cloutier, Edward M Phillips, Lisa S Krivickas, Walter R Frontera, Roger A Fielding
Affiliations

Muscle power failure in mobility-limited older adults: preserved single fiber function despite lower whole muscle size, quality and rate of neuromuscular activation

Kieran F Reid et al. Eur J Appl Physiol. 2012 Jun.

Abstract

This study investigated the physiological and gender determinants of the age-related loss of muscle power in 31 healthy middle-aged adults (aged 40-55 years), 28 healthy older adults (70-85 years) and 34 mobility-limited older adults (70-85 years). We hypothesized that leg extensor muscle power would be significantly lower in mobility-limited elders relative to both healthy groups and sought to characterize the physiological mechanisms associated with the reduction of muscle power with aging. Computed tomography was utilized to assess mid-thigh body composition and calculate specific muscle power and strength. Surface electromyography was used to assess rate of neuromuscular activation and muscle biopsies were taken to evaluate single muscle fiber contractile properties. Peak muscle power, strength, muscle cross-sectional area, specific muscle power and rate of neuromuscular activation were significantly lower among mobility-limited elders compared to both healthy groups (P ≤ 0.05). Mobility-limited older participants had greater deposits of intermuscular adipose tissue (P < 0.001). Single fiber contractile properties of type I and type IIA muscle fibers were preserved in mobility-limited elders relative to both healthy groups. Male gender was associated with greater decrements in peak and specific muscle power among mobility-limited participants. Impairments in the rate of neuromuscular activation and concomitant reductions in muscle quality are important physiological mechanisms contributing to muscle power deficits and mobility limitations. The dissociation between age-related changes at the whole muscle and single fiber level suggest that, even among older adults with overt mobility problems, contractile properties of surviving muscle fibers are preserved in an attempt to maintain overall muscle function.

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Conflict of interest statement

Conflict of interest None.

Figures

Fig. 1
Fig. 1
Specific peak power. Values are mean ± SD (*significant overall group differences, †significant group × gender interaction)
Fig. 2
Fig. 2
Specific 1RM strength. Values are mean ± SD (*significant overall gender difference)
Fig. 3
Fig. 3
Rate of vastus lateralis muscle activation. Values are mean ± SD (*significant overall group differences, †significant overall gender difference)
See this image and copyright information in PMC

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