Menstrual Cycle Associated Alteration of Vastus Lateralis Motor Unit Function.

Autor:	Piasecki, Jessica, Guo, Yuxiao, Jones, Eleanor J., Phillips, Bethan E., Stashuk, Daniel W., Atherton, Philip J., Piasecki, Mathew
Předmět:	QUADRICEPS muscle physiology NEUROMUSCULAR system physiology MOTOR unit KNEE joint STATISTICS EVOKED potentials (Electrophysiology) CELL culture HORMONES MUSCLE contraction PROGESTERONE NEUROPHYSIOLOGY ANALYSIS of variance CONFIDENCE intervals MENSTRUAL cycle LUTEAL phase REGRESSION analysis QUADRICEPS muscle DESCRIPTIVE statistics RESEARCH funding ELECTROMYOGRAPHY OVULATION DATA analysis DATA analysis software MOTOR neurons
Zdroj:	Sports Medicine - Open; 10/24/2023, Vol. 9 Issue 1, p1-14, 14p
Abstrakt:	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 < 0.05. Results: Knee extensor maximum voluntary contraction, jump power, force steadiness, and balance did not differ across the menstrual phases (all 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 < 0.001), with no difference in motor unit potentials analysed from 25% maximum voluntary contraction contractions. Motor unit potentials were more complex during ovulation and mid luteal phase (p < 0.03), with no change in neuromuscular junction transmission instability (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. Key Points: Intramuscular electromyography recordings of vastus lateralis motor units (MU) potentials showed a suppression of firing rate of low threshold MUs during the ovulation and mid-luteal phase, with minimal further MU differences identified across three phases of the cycle. Measures of knee extensor strength, force steadiness, lower limb power or balance did not differ across the menstrual cycle in healthy young eumenorrheic females. Despite differences in the firing rate of low threshold MU, there were no observable effects of the menstrual cycle on neuromuscular performance. [ABSTRACT FROM AUTHOR]
Databáze:	Complementary Index
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