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(2021)
摘要
Purpose To examine the effects of 10 weeks of endurance cycling training on mechanomyographic amplitude (MMG RMS )–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). Methods 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 (POST ABS ). MMG was recorded from the VL and b terms were calculated from the natural log-transformed MMG RMS –torque relationships for each subject. mCSA was determined with ultrasonography. Results 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 POST ABS (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 POST ABS ( p = 0.020, r = 0.471). Conclusion The decrease in MVC and increase in MMG RMS ( 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. MMG RMS –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 MMG RMS and muscle size.
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关键词
Endurance training, Log-transform model, Mechanomyography, Motor unit activation strategies, Vastus lateralis
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