Search

There is currently little information on the positioning of reference electrode (RE). It is generally accepted that it must be positioned on electrically neutral tissues, such as tendons or bony prominences. The objective of this study is to analyze the characteristics of the electromyographic signal (EMG) for different positions of RE as well as at different levels of muscle contraction. Signals from the brachial biceps and triceps were recorded from 18 healthy women (BMI: 21.20 kg/m 2  ± 1.72; mean age: 21.94 ± 1.98 years old) during 100 and 50% maximum flexion voluntary isometric contractions, as well as at rest. For each situation, the RE was randomly positioned in 4 different locations: a) homolateral acromion; b) homolateral brachial biceps; c) styloid process of the contralateral ulna; and d) lateral malleolus of the contralateral ankle. For statistical analysis, Shapiro-Wilk and Kruskal-Wallis tests were used, followed by Dunn's post-hoc test, at a significance level of 5% (p < 0.05). RMS, normalized RMS, PSD, median frequency and levels of energy at 60 Hz, 120 Hz and 180 Hz were assessed for the different sites of RE. The results show that the positioning of the RE on the four experimental locations did not change important features of the electromyographic signals in the time and frequency domains, for the three levels of isometric contractions studied. Such findings compel us to re-think the current trend regarding the RE position followed by the great majority of the researches in areas such as physical therapy.

The present study investigated the influence of a regular Physical Therapy program with emphasis on proprioceptive stimulation, on the center pressure trajectory and muscle adjustments necessary to maintain balance on orthostatic position. After medical assessment, 29 subjects (63.06 +/- 2.84 years) were submitted to electromyographic and baropodometric evaluation and, subsequently, to a program of 12 weeks of physical therapy intervention focusing on proprioceptive stimulation. The oscillation of the pressure center (Pressure platform-MatScanTekscan) was evaluated concomitantly to electromyographic signal envelopment and median frequency assessment of anterior tibial and gastrocnemius muscles (signal conditioner module--MCS 1000-V2-LYNX ). The Wilcoxon test was used for comparison of means, with the significance level of 5%. The pressure center trajectory unipodal position with open eyes (UO) decreased significantly after physical therapy intervention. In this position, there was a reduction of the electromyographic signal envelopment and an increase on median frequency of the gastrocnemius muscle, while the anterior tibial muscle showed increased median frequency after intervention. For the unipodal position with closed eyes (UC), the anterior tibial muscle showed significant electromyographic signal envelopment decrease and increase of median frequency, which also increased for the gastrocnemius muscle. It is concluded that the physical therapy intervention promoted decrease of body oscillation, recruitment improvement and adjustment of the gastrocnemius and anterior tibial muscles, contributing to the postural balance improvement in orthostatic position on senior population.