Abstract
Changes in skeletal muscle electrical resistance during muscle contraction may be associated to two main factors. Changes at muscle morphology e.g. length, volume or cross-sectional area; and changes in its impeditivity, related to changes of biochemical and physiological processes during muscle activity. However, the mechanisms by both morphological or metabolic parameters and, more importantly, if they increase or decrease electrical impedance parameters is yet controversial. The present study aimed to investigate the behavior of the muscular electrical resistance of the gastrocnemius muscle of Wistar rats during muscle contraction at different levels of force. To address that, tetrapolar invasive needle electrodes were placed in the animal muscle for impedance measurement, while two other needles electrodes were placed on muscle ends to electrical stimulate the muscle and evoke contraction. The experimental protocol consisted of ten pulse trains with 1 s duration with 40 s rest using randomized frequencies. All the procedures were approved by the Institutional Ethics Committee for Research with Animals under the decision number 019/15. Results show a decrease on muscle resistance during contraction. It was observed a correlation of r = −0.76 between the intensity of muscle contraction and resistance changes. Our findings suggest that resistance decrease is expected for invasive measurements in healthy muscles. Also, indicates that different changes at resistance amplitudes can be linked with metabolic processes. However, morphological influences cannot be neglected.
Published Version
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