César Ferreira Amorim

Muscle Activation During Four Pilates Core Stability Exercises in Quadruped Position

UNLABELLEDnQueiroz BC, Cagliari MF, Amorim CF, Sacco IC. Muscle activation during four Pilates core stability exercises in quadruped position.nnnOBJECTIVEnTo compare the activity of stabilizing trunk and hip muscles in 4 variations of Pilates stabilizing exercises in the quadruped position.nnnDESIGNnRepeated-measures descriptive study.nnnSETTINGnA biomechanics laboratory at a university school of medicine.nnnPARTICIPANTSnHealthy subjects (N=19; mean age +/- SD, 31+/-5y; mean weight +/- SD, 60+/-11kg; mean height +/- SD, 166+/-9cm) experienced in Pilates routines.nnnINTERVENTIONSnSurface electromyographic signals of iliocostalis, multifidus, gluteus maximus, rectus abdominis, and external and internal oblique muscles were recorded in 4 knee stretch exercises: retroverted pelvis with flexed trunk; anteverted pelvis with extended trunk; neutral pelvis with inclined trunk; and neutral pelvis with trunk parallel to the ground.nnnMAIN OUTCOME MEASURESnRoot mean square values of each muscle and exercise in both phases of hip extension and flexion, normalized by the maximal voluntary isometric contraction.nnnRESULTSnThe retroverted pelvis with flexed trunk position led to significantly increased external oblique and gluteus maximus muscle activation. The anteverted pelvis with trunk extension significantly increased multifidus muscle activity. The neutral pelvis position led to significantly lower activity of all muscles. Rectus abdominis muscle activation to maintain body posture was similar in all exercises and was not influenced by position of the pelvis and trunk.nnnCONCLUSIONSnVariations in the pelvic and trunk positions in the knee stretch exercises change the activation pattern of the multifidus, gluteus maximus, rectus abdominis, and oblique muscles. The lower level of activation of the rectus abdominis muscle suggests that pelvic stability is maintained in the 4 exercise positions.

Age-related differences in time-limit performance and force platform-based balance measures during one-leg stance

Poor posture control has been associated with an increased risk of falls and mobility disability among older adults. This study was conducted to assess the test-retest reliability and sensitivity to group differences regarding the time-limit (TLimit) of one-leg standing and selected balance parameters obtained with a force platform in older and young adults. A secondary purpose was to assess the relationship between TLimit and these balance parameters. Twenty-eight healthy older adults (age: 69±5years) and thirty young adults (age: 21±4years) participated in this study. Two one-leg stance tasks were performed: (1) three trials of 30s maximum and (2) one TLimit trial. The following balance parameters were computed: center of pressure area, RMS sway amplitude, and mean velocity and mean frequency in both the anterio-posterior and medio-lateral directions. All balance parameters obtained with the force platform as well as the TLimit variable were sensitive to differences in balance performance between older and young adults. The test-retest reliability of these measures was found to be acceptable (ICC: 0.40-0.85), with better ICC scores observed for mean velocity and mean frequency in the older group. Pearson correlations coefficients (r) between balance parameters and TLimit ranged from -0.16 to -0.54. These results add to the current literature that can be used in the development of measurement tools for evaluating balance in older and young adults.

Analysis of various conditions in order to measure electromyography of isometric contractions in water and on air

The aim of this study was to verify if there are differences in the amplitude of signals from surface electromyography (EMG) during maximal and submaximal voluntary isometric contraction (MVC and 50% MVC, respectively) under different conditions, in our case, water and air, with and without extra protection (water-resistant tape) on the electrode. The isometric force and muscle activation of the MVC and 50% MVC of the biceps brachial muscle of nine healthy trained men were measured simultaneously, performed in water and on air, with and without protection of the EMG electrode. The multivariate analysis of variance with a post hoc Tukey test was applied to detect significant differences between the levels of muscular force. For the amplitude values of the EMG signal, the Wilcoxon signed rank test was applied to compare all experimental conditions in order to detect a significance of p<0.05. The values of isometric force were not significantly different among conditions (MVC and 50% MVC). The results showed a significant difference among conditions in the water without extra protection compared to the conditions on air with and without extra protection and in water with extra protection. Reduced EMG amplitude was seen in water without extra protection from 37.04% to 55.81% regarding the other conditions. However, no significant difference was seen among conditions in water with extra protection in relation the conditions on air (with and without extra protection). This study suggest that it is necessary to use a water-resistant tape as an extra protection on the electrode when using EMG underwater, to avoid having a significant decrease in the EMG amplitude underwater and not to suffer interference from the water. There was no significant difference among the recordings of EMG with and without the use of protection on air; therefore, the protection does not influence the recording of EMG amplitude and isometric force on air.

Behavior analysis of electromyographic activity of the masseter muscle in sleep bruxers

The effects of occlusal splint on the electric activity of masseter were studied in 15 women who presented sleep bruxism using surface electromyography. Sleep bruxism was defined by its clinical characteristics. The signal acquisition was done during mandible occlusion without clenching and maximum voluntary contraction in two situations. The first was after a workday without using the occlusal splint; and the second, after a sleeping night using occlusal splints. Evaluating masseter muscles during mandible occlusion without clenching, it could be observed that lower values were noticed after splint wearing in both sides. The same results were verified in maximum voluntary contraction (MVC). These results confirmed that the use of occlusal splints reduced the electromyographic activity of the right and left masseters, showing its myorelaxing effect.

Eletromiografia de superfície da musculatura supra-hióidea durante a deglutição de idosos sem doenças neurológicas e idosos com Parkinson

PURPOSE: to investigate differences between electromyographic samples of right and left suprahyoid muscles during deglutition of thickened liquids and liquid consistencies by elderly people with Parkinson disease and elderly people without any neurological disease. METHODS: 30 subjects, from both genders, took part in this study. Fifteen were elderly without neurological disease whereas the others showed Parkinson disease. All of them were submitted to a clinical evaluation protocol and surface electromyography. RESULTS: significant amplitude difference was found between subjects (f=14.4 and p=0.000) and between sides (t=4,4 and p=0.0037). As for muscular contraction time, the differences were just significant between the consistencies (f=8.2 and p=0.005). CONCLUSION: the electromyographic amplitude was shorter for subjects with Parkinson disease and this amplitude was higher in both groups at the right side. The duration of the muscular contraction did not display significant difference between the subjects with Parkinson disease and elderly without neurological disease. This duration was shorter during the deglutition of liquid consistencies.

Misalignment of the knees: Does it affect human stance stability

INTRODUCTIONnData describing the relationships between postural alignment and stance stability are scarce and controversial.nnnOBJECTIVEnThe aim of this study was to evaluate the effects of sensory disturbances on knee alignment in upright stance and the effects of knee hyperextension on stance stability.nnnMETHODnKinetic and kinematic data of 23 healthy adult women were collected while quietly standing in four sensory conditions. Kinematic data: knee angle (dependent variables) variations were analyzed across sensory conditions. Kinetic data: as subjects with hyperextended knees showed a clear tendency to flex their knees as balance challenge increased, center of pressure (COP) parameters (dependent variables) were analyzed in each sensory condition among trial sub-groups: Aligned-Trials (knee angle<180°), Hyperextended-Trials (>180°) and Adjusted-Trials (>180° initially, turned <180° under challenging conditions).nnnRESULTSnDifferences were found in mean velocity of COP in two conditions showing that knee alignment can affect stance stability.nnnCONCLUSIONnKnee hyperextension is a transient condition changing under postural challenges. Knee hyperextension affected postural control as mean velocity was the highest in the hyperextended group in natural standing sensory condition and lowest with sensory disturbance.

Electromyographic preactivation pattern of the gluteus medius during weight-bearing functional tasks in women with and without anterior knee pain

BACKGROUNDnProximal factors have been proposed to influence the biomechanics of the patellofemoral joint. A delayed or diminished gluteus medius (GM) activation, before the foot contact on the ground during functional activities could lead to excessive femur adduction and internal rotation and be associated with anterior knee pain (AKP). There are few studies on this topic and the results were inconclusive, therefore, it is necessary to investigate the GM preactivation pattern during functional activities.nnnOBJECTIVEnTo compare the GM electromyographic (EMG) preactivation pattern during walking, descending stairs and in single leg jump task in women with and without AKP.nnnMETHODSnNine women clinically diagnosed with AKP and ten control subjects with no history of knee injury participated in this study. We evaluated GM EMG linear envelope before the foot contact on the ground during walking and GM onset time and EMG linear envelope during descending stairs as well as in a single leg vertical jump. Mann-Whitney U tests were used to determine the between-group differences in GM EMG preactivation pattern.nnnRESULTSnNo between-group differences were observed in GM linear envelope during walking (P=0.41), GM onset time and linear envelope during descending stairs (P=0.17 and P=0.15) and single leg jump (P=0.81 and P=0.33).nnnCONCLUSIONSnWomen with AKP did not demonstrated altered GM preactivation pattern during functional weight bearing activities. Our results did not support the hypothesis that poor GM preactivation pattern could be associated with AKP.

The use of surface electromyography for the study of auricular acupuncture

The advancement of knowledge in neurophysiology has demonstrated that acupuncture is a method of peripheral neural stimulation that promotes local and systemic reflexive responses. The purpose of this study was to determine if surface electromyography can be used as a tool to study the action of auricular acupuncture on striated skeletal muscle. The electromyographic amplitudes of the anterior, middle and posterior deltoid muscle and the upper trapezium muscle with 20%, 40% and 60% of maximal voluntary contraction of 15 healthy volunteers, were analyzed after the individuals were submitted to the auricular acupuncture treatment. The non-parametric Friedman test was used to compare Root Mean Square values estimated by using a 200 ms moving window. Significant results were further analyzed using the Wilcoxon signed rank test. In this exploratory study, the level of significance of each comparison was set to p<0.05. It was concluded in this study that a surface electromyography can be used as a tool to investigate possible alterations of electrical activity in muscles after auricular acupuncture. However there is still a lack of adequate methodology for its use in this type of study, being that the method used to record the electromyographic signal can also influence the results.