Evaluación cefalométrica y electromiográfica de niños y niñas con incompetencia labial y anomalías dentomaxilares

Objetivo: Describir las características craneofaciales, dentoalveolares, de tejido blando, vía aérea y el patrón de actividad muscular determinadas a través de los estudios cefalométricos y electromiográficos de individuos incompetentes labiales y con presencia de anomalías dentomaxilares de 7 a 12 años de edad. Materiales y método: Cuarenta y seis participantes con incompetencia labial fueron sometidos a una toma de radiografía lateral de perfil para el análisis cefalométrico. Para el estudio electromiográfico se consideró el patrón de actividad de los músculos Orbicular superior de los labios, orbicular inferior de los labios y temporal anterior en funciones: reposo, fonoarticulación, deglución, máximo apriete labial. Resultados: Se observó clase II esqueletal y molar, retrusión mandibular, biprotrusión incisal, biprotrusión labial, disminución de vía aérea superior. La mayor actividad muscular fue observada en máximo apriete labial. Conclusión: Los niños y niñas con incompetencia labial y anomalías dentomaxilares presentan alteraciones en las características craneofaciales, dentoalveolares, de tejido blando, vía aérea y actividad muscular determinadas a través de los estudios cefalométricos y electromiográficos.

Objective: To describe craniofacial, dentoalveolar, soft issue and airway features, and the muscular activity, determined through a cephalometric and electromyographic study in individuals with lip incompetence and dentomaxillary anomalies aged 7 to 12 years. Methods: Forty-six participants with lip incompetence underwent lateral profile radiography for cephalometric analysis. For the electromyographic study, the activity of the superior orbicularis oris, inferior orbicularis oris and anterior temporalis muscles was considered in the following functions: rest, speaking, swallowing, and reciprocal compression of the lips. Results: Skeletal and molar class II, mandibular retrusion, labial biprotrusion, incisal biprotrusion, and upper airway dysfunction were found. The highest muscular activity was observed in reciprocal compression of the lips. Conclusion: Children with lip incompetence and dentomaxillary anomalies have alterations in the craniofacial, dentoalveolar, soft issue, and airway features, and in the muscular activity , determined through a cephalometric and electromyographic study.

Effects of expiratory effort on force variability in isometric knee extension / 体力科学

The aim of the present study was to determine the effects of expiratory effort on the magnitude and low-frequency components of force variability during submaximal isometric knee extension (IKE). Eight subjects performed 5-s IKE of the dominant leg at the intensity of 10% of maximal voluntary contraction (10% MVC). During the IKE, the subjects performed one of three forced expirations (FEs) of different effort levels. The three effort levels of FE were 0% effort (normal breathing, FE0), 50% effort (FE50) and 100% effort (FE100). In the expiratory phase of each IKE, the amplitude of the force variability was quantified by the coefficient of variation (FCV), and the low-frequency components of the force variability were evaluated by calculating the peak power values of the filtered force signal (F) and rectified EMG signal with high-pass filtering (rEMGH) of the vastus lateralis muscle. The cross-correlation between F and rEMGH was also calculated. FCV was significantly higher in FE100 than in FE0 and FE50 (p < 0.01). The peak power values of F and rEMGH was significantly higher in FE100 than in FE0 (p < 0.05). Cross-correlation between F and rEMGH with the latter preceding the former was observed in each FE condition. These results suggest that FE with maximal effort (FE100) increased not only the absolute amount of force variation but also low-frequency oscillatory components of force and EMG and that low-frequency oscillations of motor unit firing may be responsible for the increase in force variation induced by FE.

EMG characteristics of lower extremities during movement of white crane spreads its wings in Tai Chi Quan / 医用生物力学

Objective To analyze how the athletes control postural balance through observing their joint angular motion change，center of pressure (COP) change and EMG activities of lower extremities for both athletes and beginners when performing the movement of white crane spreads its wings in Tai Chi Quan. Methods Twenty subjects were divided into 2 groups as 10 athletes and 10 beginners of Tai Chi Quan in each. When performing the movement of white crane spreads its wings, their EMG activities of 10 skeletal muscles, two-dimensional angular motion of 3 large joints in bilateral lower extremities, and COP displacements in lateral and anterior-posterior directions were recorded. Each performing trial took 8 seconds and repeated 5 times. All data were statistically processed for EMG, motion and balance analysis, and the EMG data were normalized to compare the differences between the athletes and beginners of Tai Chi Quan. Results The EMG activities of tibialis anterior(Ta), biceps femur(bF), gluteus medium(Gm) in support leg of athletes were significantly greater than those of the ipsilateral muscles in support leg of beginners, and the same was the EMG activities of gastrocnemius (G) and rectus femur（rF) in virtual leg of athletes compared with the beginners. The maximal average angular motion of 3 large joints and the coxa -joint motion of support leg in athletes were both significantly greater than that in beginners, but the anterior-posterior COP displacement in athletes was significantly smaller than that in beginners. Conclusions When performing the movement of white crane spreads its wings in Tai Chi Quan, athletes could oppose the COP change by enhancing muscle activities to maintain the postural balance, while beginners couldn’t make such active muscle activities against the uncontrolled anterior-posterior COP displacement. This may preliminarily explain the reason why Tai Chi Quan exercise can improve the muscle strength in lower extremities and enhance the ability of postural control.

Effect of passive motion of from lower extremity on muscle fatigue when the back under head-down tilting / 医用生物力学

Objective To study the effect of passive motion from lower extremity on electromyography (EMG) activity of major muscles when the back under head down tilting state. Methods Thirty healthy subjects were selected. The EMGs of erector spinal and trapezius muscles were recorded and analyzed when human body was under head-down tilting at angel of 0°, 10°, 20° and 27° in static mode, respectively, in sway mode (along the axis of Z with frequencies of 120 and 140/min， respectively) and in vibration mode (along the axis of Y with frequency of 680/min) with the help of multifunctional test bed. Results In the static mode, the median frequency (MF) decreased with the increase of head-down titling angle; in the sway mode, the MF at each of 4 head-down tilting angles was smaller than that in the static mode. When the frequency was 120/min, the MF decreased with head-down tilting angle increasing, but when the frequency reached 140/min, the variation of MF became irregular. In the vibration mode, the MF increased with the increase of head-down tilting angle and was larger than that in the static mode. Conclusions In the static mode, the muscle fatigue increased with the head down tilting angle increasing; in the vibration mode, smaller head-down tilting angle should be selected to achieve better treatment effect; but in the sway mode, larger head-down tilting angle would be better, and the sway frequency should be set lower than 120/min to avoid potential damage due to excessive muscle fatigue.

Movement of trunk and surface electromyography under symmetric loading and unloading with static posture / 医用生物力学

Objective To observe the electromyography (EMG) activities and kinematic characteristics of the back, abdomen and hip muscles under the static symmetric loading and unloading with the flexion and extension posture. Methods Six healthy male subjects stood on a specially designed testing platform, doing flexion/extension under symmetric loading and unloading, respectively. Each trial lasted 4 seconds and was repeated 3 times. The EMG activities of 10 muscles(rectus abdominis，obliquus externus abdominis，erector spinae，multifidus，gluteus Medius), the 3D angular movement, the plantar COP (center of pressure) were recorded during the trial.The normalized EMG, trunk angle and COP displacement were calculated, and statistical analyses of all data were made. Results Muscle activities of the back were greater (10.47~16.94) with flexion both under loading and unloading. Muscle activities of the abdomen were greater with extension under unloading, and those of the back (3.70~17.95) and hip (6.64~11.52) were increasing under loading, with muscle activities of the abdomen decreasing (10.66~4.18). The flashing trunk numbers was increased with the increase of loading, especially 1.55-time increase in the trunk angle. The COP displacement in anterior posterior direction was shifted greater than that in lateral direction, and this shift was more during flexion (14.60) than that during extension (7.65).Conclusions Extension increases the activities of back muscles, especially for multifidus, and it also increases the torso angular displacement and flashing trunk numbers, especially under loading.

Effect of Forearm Position on the Supination and Pronation Strengths and EMG Activities of Related Muscles

OBJECTIVE: This study was designed to investigate the effect of forearm position on the maximal isometric voluntary supination and pronation strengths and EMG activities in the related muscles. METHOD: The maximal isometric supination and pronation strengths were measured in 14 normal male subjects using Work simulator at 4 different forearm rotation position. EMG activities were simultaneously measured in supinator and biceps brachii during supination and pronator quadratus and pronator teres during pronation. RESULTS: The maximal isometric supination strength and EMG activities of biceps brachii and supinator were significantly higher as the forearm was more pronated (p<0.05). The maximal isometric pronation strength and EMG activities of pronator teres were significantly higher as the forearm was more supinated (p<0.05). The maximal isometric supination and pronation strengths were higher in the dominant side than those of the nondominant side (p<0.05) and EMG activities of pronator teres and supinator were higher in the dominant side than in the nondominant side (p<0.05). CONCLUSION: The supination and pronation strengths and EMG activities of related muscles were influenced by the forearm rotation position. Therefore the forearm position should be considered in evaluation of upper limb strength and function, and rehabilitation of upper extremity for improving strength and minimizing the overuse of supination and pronation.

Characteristics of underwater walking using water flow machine / 体力科学

Six young males walked in a swimming pool, swimming flume and land treadmill at 0.4, 0.6 and 0.8 m·⋅<SUP>-1</SUP>. At 0.6 and 0.8 m⋅s<SUP>-1</SUP>, VO<SUB>2</SUB>and HR values were significantly lower for the swimming flume walking than for the swimming pool waking. At rest and 0.4 m⋅s<SUP>-1</SUP>, there were no significant VO<SUB>2</SUB>differences between swimming flume walking and land treadmill walking ; while significantly lower HR values were found for swimming flume walking. There was no significant difference in the VO<SUB>2</SUB>-HR relationship between land treadmill waking and swimming pool waking. On the other hand, a significant downward sift in the regression line was observed in swimming flume waking compared to land treadmill walking. The differences between the two types of underwater walking exercise may produce a different effect concerning the muscle pump on leg muscles. Soleus, and especially lateral gastrocnemius muscles, showed lower electromyogram activity at push-off phase during swimming flume walking compard with swimming pool walking. This activity may contribute to the lower VO<SUB>2</SUB>and HR values during swimming flume walking. It is apparent that the swimming flume walking has different physiological and kinematic characteristics such leg muscles EMG activity walking or swimming pool walking.

Electrodiagnostic Evaluation of Myofascial Trigger Point

Since the myofascial trigger point(MFTrP) has been described fifty years ago, its underlying pathophysiology has been remained unclear. The diagnosis also depends on the characteristic pain, tenderness and physical findin gs, which is yery subjective. In recent years, some physicians investigated the objective findings of MFTrP, using the pressure algometer and thermography. We investigated the electromyographic findings of MFTrP to evaluate the clinical usefulness of local twitch response(LTR) and sympathetic skin response (SSR), and to evaluate the electrophysiologic characteristics of MFTrP. 21 patients, diagnosed as myofascial trigger point syndrome on upper trapezius and so on, were evaluated for the triggering pain with visual analog scale(VAS), pressure threshold(THpr) using pressure algometer(Dolorimeter), LTP with concentric needle electrode and SSR on the palm. There was a significant negative correlation between VAS and THpr, but no significant correlation with electromyographic findings of LTR. Thus LTR could support the existence of MFTrP electrodiagnostically, but, could not explain the clinically correlated severity of MFTrP. There were only 3 patients showing abnormal SSR, who were all complaining the sympathetic sympathetic symptoms on the affected arm with reffered pain. Even though referred pain to arm and hand existed. SSR was normal because suggested autonomic dysfunction of MFTrP is localized mechanism. Among the 13 patients underwent the trigger point block, 8 patients who showed no residual LTR immediate after MFTrP block, had a great symptomatic improvement of MFTrP in a week, but 5 patients who showed the residual LTR did not, Regardless of complaint of pain and soreness immediate after block, loss of LTR would be predicted as a good treatment result. In some cases, spontaneous EMG activity exist within the 3-4mm sized focus of MFTrP. although the taut band of MFTrP is 3-4cm length and depth. But this focus of MFTrP is a electrophysiologic changes within a muscle, not a structural changes seen by ultrasonography.

CHARACTERISTICS OF THE FUNCTION OF BACK MUSCLES FOR POOR BACK-LIFT STRENGTH SUBJECTS / 体力科学

There have been an apparent trend in the decline of back-lift strength of young people during recent years. The purpose of this study was to investigate the cause-effect relationship of such a trend using young peoples and university students. In order to examine the characteristics of activities in the lumber back muscles during various physical activities, the surface electromyography (EMG) was obtained from the trapezius, latissimus dorsi, and elector spinae muscles for individuals with poor back-lift strength (5 male children and 4 university male students) and individuals with relatively strong back-lift strength (5 male children and 2 male university students) . The children with poor back-lift strength had significantly less EMG activities in both the trapezius and elector spinae muscles during the measurement of back-lift strength using a dynamometer than the strong back-lift strength children. The former children also had a less EMG activities in elector spinae muscle and a greater EMG activities in trapezius muscle during cycling the bicycle elgometer. Such a trend became more distinct when the load was increased. The university students with poor back-lift strength had a less EMG activity in the elector spinae muscle during the measurement of back-lift strength than those with strong back-lift strength. During running, there was not a distinct difference in the EMG activities of the muscles in the back between the poor and strong strength students. However, as the running speed increased, a greater EMG activity in the trapezius muscle or the latissimus dorsi muscle were observed for the poor back-lift strength students than the stronger back-lift strength students.<BR>These results indicated that the individuals with poor back-lift strength relied more on the upper portion of the back muscle group than the lower portion of the back muscle group during both static and dynamic activities, suggesting that the trend in the decline of back-lift strength of children and students was due to a lack of opportunity to use the lower back muscles in the daily physical activities.