TY - JOUR
T1 - Age-related differences in rates of torque development and rise in EMG are eliminated by normalization
AU - Jenkins, Nathaniel D.M.
AU - Buckner, Samuel L.
AU - Cochrane, Kristen C.
AU - Bergstrom, Haley C.
AU - Palmer, Ty B.
AU - Johnson, Glen O.
AU - Schmidt, Richard J.
AU - Housh, Terry J.
AU - Cramer, Joel T.
PY - 2014/9
Y1 - 2014/9
N2 - The purpose of this study was to compare the voluntary and evoked, absolute and normalized leg extension rates of torque development (RTD) and rates of rise in electromyography (RER) during commonly reported time intervals in young and old men. Fourteen young men (21.9±3.2years) and 16 older men (72.3±7.3years) completed three evoked and three voluntary isometric leg extension muscle actions to quantify absolute voluntary (peak, 30, 50, 100, and 200ms) and evoked (peak, 30, 50, and 100ms) RTD and RER. All RTD values were normalized (nRTD) to peak torque, while RER values were normalized (nRER) to peak-to-peak M-wave amplitude (MPP). Absolute voluntary RTDs and RERs were 58-122% and 70-76% greater (p≤0.05) for the young men, respectively. However, there were no age-related differences (p>0.05) for voluntary nRTDs, absolute and normalized evoked RTDs, or voluntary nRER. MPP and evoked RER and nRER were greater (p≤0.05) for the young men. In addition, voluntary RTD was more reliable in the young than the older men. Normalizing RTD to peak torque and RER to M-wave amplitude eliminated the age-related differences and suggested that the age-related declines in RTD and RER were a result of reduced muscle strength and M-wave amplitude, respectively. Therefore, our findings questioned the value of RTD and RER measurements in the various time intervals for explaining sarcopenia and suggested that maximal strength and M-wave amplitude may be sufficient.
AB - The purpose of this study was to compare the voluntary and evoked, absolute and normalized leg extension rates of torque development (RTD) and rates of rise in electromyography (RER) during commonly reported time intervals in young and old men. Fourteen young men (21.9±3.2years) and 16 older men (72.3±7.3years) completed three evoked and three voluntary isometric leg extension muscle actions to quantify absolute voluntary (peak, 30, 50, 100, and 200ms) and evoked (peak, 30, 50, and 100ms) RTD and RER. All RTD values were normalized (nRTD) to peak torque, while RER values were normalized (nRER) to peak-to-peak M-wave amplitude (MPP). Absolute voluntary RTDs and RERs were 58-122% and 70-76% greater (p≤0.05) for the young men, respectively. However, there were no age-related differences (p>0.05) for voluntary nRTDs, absolute and normalized evoked RTDs, or voluntary nRER. MPP and evoked RER and nRER were greater (p≤0.05) for the young men. In addition, voluntary RTD was more reliable in the young than the older men. Normalizing RTD to peak torque and RER to M-wave amplitude eliminated the age-related differences and suggested that the age-related declines in RTD and RER were a result of reduced muscle strength and M-wave amplitude, respectively. Therefore, our findings questioned the value of RTD and RER measurements in the various time intervals for explaining sarcopenia and suggested that maximal strength and M-wave amplitude may be sufficient.
KW - Aging
KW - Dynapenia
KW - M-wave
KW - Neuromuscular function
KW - Quadriceps
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UR - http://www.scopus.com/inward/citedby.url?scp=84900562430&partnerID=8YFLogxK
U2 - 10.1016/j.exger.2014.04.015
DO - 10.1016/j.exger.2014.04.015
M3 - Article
C2 - 24806786
AN - SCOPUS:84900562430
SN - 0531-5565
VL - 57
SP - 18
EP - 28
JO - Experimental Gerontology
JF - Experimental Gerontology
ER -