TY - JOUR
T1 - Age-Associated Changes in Motor Unit Physiology
T2 - Observations From the Baltimore Longitudinal Study of Aging
AU - Ling, Shari M.
AU - Conwit, Robin A.
AU - Ferrucci, Luigi
AU - Metter, E. Jeffrey
N1 - Funding Information:
Supported by the Intramural Research Program of the National Institutes of Health, National Institute on Aging.
PY - 2009/7
Y1 - 2009/7
N2 - Ling SM, Conwit RA, Ferrucci L, Metter EJ. Age-associated changes in motor unit physiology: observations from the Baltimore Longitudinal Study of Aging. Objective: To examine motor unit characteristics (size and firing rate) associated with aging. Design: Cross-sectional, observational. Setting: Community. Participants: Baltimore Longitudinal Study of Aging participants (N=102), aged 22.2 to 94.1 years, were studied. Interventions: Not applicable. Main Outcome Measures: Surface-represented motor unit size and firing rate were collected from the vastus medialis during knee extension at 10%, 20%, 30%, and 50% of each subject's maximum isometric voluntary contraction (MVC). Results: MVC declined with older age (P<.0001). Adjusting for differences in MVC, both firing rate and motor unit size per newton force generated began to increase in the 6th decade of life. Motor unit size increased per newton force to a greater extent than firing rate. Those over the age of 75 years also activated significantly larger motor units per unit force (P=.04). Relative to force generated, the average firing rate began increasing at 57.8±3.4 years and between 50.2 and 56.4 years (±4y) for motor unit size. Conclusions: The size of motor units and firing rates used to achieve a given force changes with age, particularly after middle age. Whether these changes precede, follow, or occur concurrent to age-related modifications in muscle structure and contractile properties or sarcopenia is not known.
AB - Ling SM, Conwit RA, Ferrucci L, Metter EJ. Age-associated changes in motor unit physiology: observations from the Baltimore Longitudinal Study of Aging. Objective: To examine motor unit characteristics (size and firing rate) associated with aging. Design: Cross-sectional, observational. Setting: Community. Participants: Baltimore Longitudinal Study of Aging participants (N=102), aged 22.2 to 94.1 years, were studied. Interventions: Not applicable. Main Outcome Measures: Surface-represented motor unit size and firing rate were collected from the vastus medialis during knee extension at 10%, 20%, 30%, and 50% of each subject's maximum isometric voluntary contraction (MVC). Results: MVC declined with older age (P<.0001). Adjusting for differences in MVC, both firing rate and motor unit size per newton force generated began to increase in the 6th decade of life. Motor unit size increased per newton force to a greater extent than firing rate. Those over the age of 75 years also activated significantly larger motor units per unit force (P=.04). Relative to force generated, the average firing rate began increasing at 57.8±3.4 years and between 50.2 and 56.4 years (±4y) for motor unit size. Conclusions: The size of motor units and firing rates used to achieve a given force changes with age, particularly after middle age. Whether these changes precede, follow, or occur concurrent to age-related modifications in muscle structure and contractile properties or sarcopenia is not known.
KW - Aging
KW - Muscles
KW - Rehabilitation
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U2 - 10.1016/j.apmr.2008.09.565
DO - 10.1016/j.apmr.2008.09.565
M3 - Article
C2 - 19577038
AN - SCOPUS:67649395595
SN - 0003-9993
VL - 90
SP - 1237
EP - 1240
JO - Archives of physical medicine and rehabilitation
JF - Archives of physical medicine and rehabilitation
IS - 7
ER -