Sports Medicine - Open (Oct 2023)

Menstrual Cycle Associated Alteration of Vastus Lateralis Motor Unit Function

  • Jessica Piasecki,
  • Yuxiao Guo,
  • Eleanor J. Jones,
  • Bethan E. Phillips,
  • Daniel W. Stashuk,
  • Philip J. Atherton,
  • Mathew Piasecki

DOI
https://doi.org/10.1186/s40798-023-00639-8
Journal volume & issue
Vol. 9, no. 1
pp. 1 – 14

Abstract

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Abstract Background Estrogen and progesterone are the primary female sex hormones and have net excitatory and inhibitory effects, respectively, on neuronal function. Fluctuating concentrations across the menstrual cycle has led to several lines of research in relation to neuromuscular function and performance; however evidence from animal and cell culture models has yet to be demonstrated in human motor units coupled with quantification of circulating hormones. Intramuscular electromyography was used to record motor unit potentials and corresponding motor unit potential trains from the vastus lateralis of nine eumenorrheic females during the early follicular, ovulation and mid luteal phases of the menstrual cycle, alongside assessments of neuromuscular performance. Multi-level regression models were applied to explore effects of time and of contraction level. Statistical significance was accepted as p 0.4). Firing rate of low threshold motor units (10% maximum voluntary contraction) was lower during the ovulation and mid luteal phases (β = − 0.82 Hz, p 0.3). Conclusions Assessments of neuromuscular performance did not differ across the menstrual cycle. The suppression of low threshold motor unit firing rate during periods of increased progesterone may suggest a potential inhibitory effect and an alteration of recruitment strategy; however this had no discernible effect on performance. These findings highlight contraction level-dependent modulation of vastus lateralis motor unit function over the eumenorrheic cycle, occurring independently of measures of performance.

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