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Neuromuscular function of the plantar flexors and predictors of peak power in middle-aged and older males

Olmos, Alex A. et al.

Experimental gerontology. Volume 125: (2019, October 1st)

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  • Title:
    Neuromuscular function of the plantar flexors and predictors of peak power in middle-aged and older males
  • Author: Olmos, Alex A.;
    Stratton, Matthew T.;
    Ha, Phuong L.;
    VanDusseldorp, Trisha A.;
    Bailly, Alyssa R.;
    Feito, Yuri;
    Mangine, Gerald T.;
    Poisal, Micah J.;
    Jones, Joshua A.;
    Dalton, Benjamin E.;
    Smith, Tyler M.;
    Hester, Garrett M.
  • Found In: Experimental gerontology. Volume 125: (2019, October 1st)
  • Journal Title: Experimental gerontology
  • Subjects: Aging--Dynapenia--Muscle quality--Skeletal muscle--Neural--Rate of torque development; Dewey: 612.67
  • Rights: Licensed
  • Abstract: Abstract Little evidence exists regarding the contribution of torque and velocity to the age-related decrease in peak power (PP) for the plantar flexors (PFs). A comprehensive assessment of PF neuromuscular function is necessary to elucidate age-related changes, especially between middle-aged and older adults, in order to identify early, age-related decrements. Thus, the purpose of this study was to examine neuromuscular function of the PFs in middle-aged and older males, and identify predictors of PP. Twenty-eight healthy, middle-aged (n = 13; 45.1 ± 2.7 yrs) and older (n = 15; 65.3 ± 3.2 yrs) males performed concentric isotonic PF contractions ranging in intensity from 20% to 70% isometric strength using a dynamometer. PP in addition to velocity and torque at the moment in time PP occurred, as well as the rate of velocity, torque (RTD), and power (RPD) development were recorded. The rate of electromyography rise (RER) was derived from the linear slope of the normalized electromyography signal. Isometric and concentric dynamic strength were assessed, as well as cross-sectional area and muscle quality (i.e., echo intensity) of the PFs via panoramic ultrasonography. The relationship between serum c-terminal agrin levels and select variables was examined to explore the potential role of neuromuscular junction deterioration. Appendicular lean mass and physical activity level were similar between groups (p > 0.05), and only PP (p = 0.046; d  = 0.79), RPD (p = 0.026; d  = 0.90), RTD (p = 0.022; d  = 0.91), and RER (p = 0.010; d  = 1.04) were lower in older males. When groups were collapsed, RTD was the only significant predictor of PP, while c-terminal agrin levels were not associated with any variables. Our findings indicate that PP and time-dependent parameters of muscle activation and contractile function of the PFs are dramatically diminished in older adults compared to middle-aged adults. PP is produced at the same velocity and relative intensity in middle-aged and older males, and RTD is most influential for PP. The inability of the PFs to be rapidly activated appeared to be influential for the age-related impairment in PP and time-dependent contractile parameters. Highlights Plantar flexor strength and muscle size were similar in middle-aged and older males. Plantar flexor peak power was lower in older males versus middle-aged males. Rapid neuromuscular function and activation were diminished in older males. Rate of torque development was the sole predictor of plantar flexor peak power. C-terminal agrin fragment levels were not correlated with neuromuscular function.
  • Identifier: System Number: ETOCvdc_100086901611.0x000001; Journal ISSN: 0531-5565; 10.1016/j.exger.2019.110677
  • Publication Date: 2019
  • Physical Description: Electronic
  • Shelfmark(s): 3839.340000
  • UIN: ETOCvdc_100086901611.0x000001

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