The Influence of Motor Unit Number and Muscle Activation on Early Phase Rate of Torque Development in Younger and Older Men
Mitchel A. Magrini, Ryan J. Colquhoun, Matt C. Ferrell, Sydnie R. Fleming, Jacob A. Mota, Jacob A. Siedlik, Nick M. Poidomani, Nathaniel D.M Jenkins and Jason M. DeFreitas
This study examined the influence of muscle activation and motor unit number estimation (MUNE) on early phase voluntary rate of torque development (RTD) in younger (YM) and older (OM) men. Thirty-two YM (n = 17; Age = 22 yrs) and OM (n = 15; Age = 74 yrs) volunteered to participate in this study. Early phase RTD (first 50 ms of a rapid isometric contraction; RTD
50
) and normalized surface electromyography (first 50 ms of muscle excitation; nEMG
50
) were recorded from the right quadricep muscle group. MUNE was examined from the right vastus lateralis. Multiple linear regression analyses revealed that nEMG
50
had a significant effect on RTD
50
independent of age group (p ≤ 0.001). nEMG
50
had a significant effect on RTD
50
in the OM group (p = 0.037). MUNE had no effect on RTD
50
independent of age. Older adults may depend more on muscle activation at contraction onset of early phase RTD compared to younger adults.
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Title
The Influence of Motor Unit Number and Muscle Activation on Early Phase Rate of Torque Development in Younger and Older Men