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18.02.2021 | Original Article

Endurance training alters motor unit activation strategies for the vastus lateralis, yet sex-related differences and relationships with muscle size remain

European Journal of Applied Physiology
Stephanie A. Sontag, Michael A. Trevino, Trent J. Herda, Adam J. Sterczala, Jonathan D. Miller, Mandy E. Parra, Hannah L. Dimmick, Jake Deckert
Wichtige Hinweise
Communicated by Toshio moritani.

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To examine the effects of 10 weeks of endurance cycling training on mechanomyographic amplitude (MMGRMS)–torque relationships and muscle cross-sectional area (mCSA) of the vastus lateralis (VL) for 10 sedentary males (Age ± SD; 20.2 ± 1.9 years) and 14 sedentary females (21.9 ± 5.3 years).


Participants performed maximal voluntary contractions (MVCs) and an isometric ramp up muscle action to 70% MVC of the knee extensors before (PRE) and after training at the same absolute pre-treatment submaximal torque (POSTABS). MMG was recorded from the VL and b terms were calculated from the natural log-transformed MMGRMS–torque relationships for each subject. mCSA was determined with ultrasonography.


Cycling decreased MVCs from pre- (168.10 ± 58.49 Nm) to post-training (160.78 ± 58.39 Nm; p = 0.005) without changes in mCSA. The b terms were greater for POSTABS (0.623 ± 0.204) than PRE (0.540 ± 0.226; p = 0.012) and for males (0.717 ± 0.171) than females (0.484 ± 0.168; p = 0.003). mCSA was correlated with the b terms for PRE (p < 0.001, r = 0.674) and POSTABS (p = 0.020, r = 0.471).


The decrease in MVC and increase in MMGRMS (b terms) post-training suggests increased motor unit (MU) recruitment to match pre-training torques. The greater acceleration in the b terms by males may reflect sex-related differences in fiber-type area. MMGRMS–torque relationships during a high-intensity contraction provided insight on MU activation strategies following endurance training and between sexes. Furthermore, the findings suggest a relationship between MMGRMS and muscle size.

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