Chronic training status affects muscle excitation of the vastus lateralis during repeated contractions

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Issue Date
2023-01-02Author
Jeon, Sunggun
Sontag, Stephanie A.
Herda, Trent J.
Trevino, Michael A.
Publisher
Elsevier
Type
Article
Article Version
Scholarly/refereed, publisher version
Rights
© 2023 Chengdu Sport University. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license.
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This study examined electromyographic amplitude (EMGRMS)-force relationships during repeated submaximal knee extensor muscle actions among chronic aerobically-(AT), resistance-trained (RT), and sedentary (SED) individuals. Fifteen adults (5/group) attempted 20 isometric trapezoidal muscle actions at 50% of maximal strength. Surface electromyography (EMG) was recorded from vastus lateralis (VL) during the muscle actions. For the first and last successfully completed contractions, linear regression models were fit to the log-transformed EMGRMS-force relationships during the linearly increasing and decreasing segments, and the b terms (slope) and a terms (antilog of y-intercept) were calculated. EMGRMS was averaged during steady force. Only the AT completed all 20 muscle actions. During the first contraction, the b terms for RT (1.301 ± 0.197) were greater than AT (0.910 ± 0.123; p = 0.008) and SED (0.912 ± 0.162; p = 0.008) during the linearly increasing segment, and in comparison to the linearly decreasing segment (1.018 ± 0.139; p = 0.014), respectively. For the last contraction, the b terms for RT were greater than AT during the linearly increasing (RT = 1.373 ± 0.353; AT = 0.883 ± 0.129; p = 0.018) and decreasing (RT = 1.526 ± 0.328; AT = 0.970 ± 0.223; p = 0.010) segments. In addition, the b terms for SED increased from the linearly increasing (0.968 ± 0.144) to decreasing segment (1.268 ± 0.126; p = 0.015). There were no training, segment, or contraction differences for the a terms. EMGRMS during steady force increased from the first- ([64.08 ± 51.68] μV) to last-contraction ([86.73 ± 49.55] μV; p = 0.001) collapsed across training statuses. The b terms differentiated the rate of change for EMGRMS with increments in force among training groups, indicating greater muscle excitation to the motoneuron pool was necessary for the RT than AT during the linearly increasing and decreasing segments of a repetitive task.
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Citation
Jeon, S., Sontag, S. A., Herda, T. J., & Trevino, M. A. (2023). Chronic training status affects muscle excitation of the vastus lateralis during repeated contractions. Sports medicine and health science, 5(1), 42–49. https://doi.org/10.1016/j.smhs.2022.12.005
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