Neuromuscular function and motor unit recruitment of the tibialis anterior in the fasted and fed state 

Future Physiology 2020 (Virutal) (2020) Proc Physiol Soc 46, PC0156

Poster Communications: Neuromuscular function and motor unit recruitment of the tibialis anterior in the fasted and fed state 

Siobhra Dooley1

1 School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Dublin, Ireland

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Introduction  Effective motor control is reliant upon successful communication and integration of the peripheral nervous system and skeletal muscle (1), with increases in muscle force reliant upon the recruitment of additional, progressively larger motor units (MU). The control and functioning of the tibialis anterior (TA) muscle is essential in performing activities of daily living (ADL), such as standing balance and walking. Although ingestion of carbohydrate is known to facilitate motor output, with effects believed to largely occur centrally (2),the effects of feeding on the peripheral motor system is poorly understood. Therefore, the aim of the study was to determine the effects of a standardised low-glycaemic index meal on neuromuscular control and MU recruitment strategies of the TA. Methods Eight young, healthy participants (3 males, 28±7 years) completed a series of neuromuscular assessments after an overnight fast (~12hrs) and subsequently after consumption of a standardised low-GI meal, normalised to body mass. Maximal voluntary contraction (MVC) of the dorsiflexors was recorded using an isometric dynamometer. To determine motor control, force steadiness was assessed via a isometric contraction held at 25% MVC for 15 seconds, with visual feedback. The same procedure was used to determine complex force tracking with an oscillating line around 25% MVC (±4%). Postural sway was assessed on a commercially available force plate (Footscan, 200 Hz, RScan International, Belgium) during 30-second single leg balance tasks (eyes open and closed). Intramuscular electromyography (iEMG) was used to measure  MU potential (MUP) area, which is indicative of MU size, during isometric contractions (3). All data was statistically compared using paired Student’s t-tests with a p-value of <0.05 considered significant. Results Dorsiflexion MVC did not differ greatly between the post-absorptive and postprandial conditions (p=0.48, 202.25±104.75 vs. 189.25±94.75). Neither force steadiness (p=0.97, 5.98±3.06 vs. 5.97±4.29) nor complex force tracking (p=0.24, 45.06±13.68 vs. 41.01±11.44) in the TA were changed following feeding. There was no notable change in standing balance either with eyes open (p=0.46) or eyes closed (p=0.35). The mean MUP area in TA showed a 30% decrease (p=0.01) following feeding. Conclusion The results of this study demonstrate that in young, healthy individuals feeding of a mixed macronutrient meal has no significant effect on a number of functional neuromuscular parameters, suggesting that performance of this postural muscle is not influenced by feeding status. The TA is known for its ability to resist fatigue and its fibre type composition may partly explain its ability to resist performance decrements in the fasted state. The significant decrease in MUP area upon feeding may be explained by reduced perceived effort in the fed state reflecting positively in centrally mediated motor commands (4) and  resulting in recruitment of smaller MUs.



Where applicable, experiments conform with Society ethical requirements.

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