Comparison of muscle morphology, electromyographic activity and force production between prepubertal boys and girls
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The purpose of this research was to compare the maximal voluntary isometric force (MVIF), the electromyographic activity (EMG) and the muscle thickness between pre-pubertal boys and girls. The sample comprises 27children (12 boys and 15 girls) with 9.5W.52 years old. The M V F and the EMG signal were acquired when the subjects made a single exercise of arm curl and triceps press. To evaluate the MVIF was used a dynamometer (TSD121C from Biopac Systems Znc.). During the arm curl exercise, one surface electrode (TSD 150A from Biopac Systems Znc.) was attached in each biceps. During the triceps press, one surface electrode was attached to the vastus lateralis and other to the vastus medialis of the each triceps. Ground electrode was attached to the elbow. The EMG signals were amplified by a differential amplifier with 2MW, a gain of 1000 and a bandwidth between 15-450Hz. The EMG signals were full-wave rectified and smoothed, allowing to determinate the integral of the EMG signal (iEMG). The iEMG was relativized according to the duration of the contraction. The muscle thickness of the biceps and of the triceps of both arms were measured by B-mode ultrasonography, using real-time electronic scanner with 7.5MHz scanning head (Ecocamera Aloca SSD-500). For comparison of those variables between gender was used the ANOVA factorial and Scheffe as post-hoc test (p< 0.05). There was no significant differences on the MVIF between boys and girls doing the arm curl exercise F(1; 25)=4.128, p=0.0529] or the triceps press exercise F(1; 25)=0.003, p=0.9554]. In the same way, there were no significant differences according to gender on the thickness of the triceps of the left arm F(1; 25)= 0.075, p=0.7859] of the triceps of the right arm F(1;25)=0.925, p=0.3454] of the bicep sof the left arm F(1;25)=0.257, p=0.6166] and of the biceps of the right arm F(1; 25)= 0.016, p=0.8989]. The EMG parameters also didn't present significant differences according to gender for the vastus lateralis of both arms, for the vastus medialis of both arms and for the biceps of the right and of the left arm. Therefore, we might conclude that apparently there are no significant differences on the muscle morphology, electromyographic activity and force production between pre-pubertal boys and girls.
