Authors
Abstract
Aim: The aim of the current study was to investigate the neural control of muscle contraction at different levels of muscle contractions. In this study, we hypothesized that motor unit discharge rate act as mechanism to shift low - level muscle force to a higher level. Methods: Surface and fine wire intramuscular EMG signals were concurrently recorded from the distal location of the vastus laterlies muscles (%15 distances between superior iliac spin and lateral boarder of the patella) during 5-second contractions at % 4, %16 and %32 of maximal voluntary contraction. Motor unit discharge rate were extracted from intramuscular EMG signals based on cross correlation method, at the beginning of each contraction, and surface EMG signals were used to compute mean power frequency and EMG amplitude during 5-second contractions. Results: One -way ANOVA revealed that high-level muscle contraction resulted in greater motor unit discharge rate than low-level muscle contraction (P <0.05). Moreover high-level muscle contraction generated larger EMG amplitude and means power frequency than did the low-level contractions. Conclusion: As hypothesized, change in muscle contraction levels can be controlled by motor discharge rate.
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