Lateralna dominantnost, promenljivost mišićne sile i aktivacija motornih jedinica kod unilateralnih i bilateralnih sportova

Abstract

Aim: The aim of this study was to determine the differences in muscle force control and motor unit activation between dominant and non-dominant lower extremity within and between groups of unilateral and bilateral sports, as well as to determine differences in muscle force control and motor unit activation depending on the characteristics of unilateral and bilateral sports. Methods: Thirty six young adults performed low to moderate isometric contractions (2.5, 5, 10, 20, 30, 40, 50 and 60% of maximal voluntary contraction, MVC), dominant and non-dominant lower limb, at three different ankle angles (75°, 90°: anatomical position and 105°), which corresponds to the short, medium and long length of the anterior part of the tibialis muscle. At the same time, the discharge characteristics of several motor units in tibialis anterior were recorded. Results: There are no statistically significant differences in muscle control and motor units activation between the dominant and non-dominant extremities in the unilateral group of athletes. In a bilateral group of athletes, there is no statistically significant difference in muscle force control between the extremities, but there is in a variable that defines the activation of motor units. The mean value of the motor unit discharge was discharged at lower values in the non-dominant leg compared to the dominant one, except at the force level of 30% MVC. In muscle force control, there is a statistically significant difference between the unilateral and bilateral group of athletes, where the bilateral group of athletes exhibits greater force variability of 2.5%, while the unilateral group of athletes exhibits greater force variability of 60% and greater effective force at all levels of power in relation to the bilateral group. In the activation of motor 7 units, the bilateral group of athletes shows higher values of relative and absolute amplitude of variability of the interspike interval of the motor unit in both extremities at all levels of force and at all muscle lengths compered to unilateral, while the average value of motor unit discharge in the dominant leg was volatile at force levels of 2.5 to 30% MVC. Finally, runners exhibit greater absolute variability of force and mean discharge rate of motor units in both extremities compared to cyclists, while volleyball players exhibit greater relative and absolute variability of force in both extremities compared to weightlifters and rowers, as well as higher values of mean discharge rate of motor units in the dominant leg. Conclusion: There is no difference in the control of muscle force between the lower extremities in healthy athletes. There is a tendency that the training process may influence the different effects of neural control of the CNS between the extremities in sports with excessive use of one side of the body. Finally, the results showed that the requirements of sport specificity affect the change in muscle force control and CNS neurocontrol. Additional research is needed to confirm these results and expand knowledge about the impact of the training process on muscle force control and motor unit behavior in other sports.