Muscular activation patterns during active prone hip extension exercises.

BACKGROUND: Changes in activation patterns of hip extensors and pelvic stabilizing muscles are recognized as factors that cause low back disorders and these disturbances could have an impact on the physiological loading and alter the direction and magnitude of joint reaction forces. OBJECTIVE: To investigate activation patterns of the gluteus maximus, semitendinosus and erector spinae muscles with healthy young individuals during four different modalities of therapeutic exercise. METHODS: Thirty-one volunteers were selected: (16 men and 15 women), age (24.5+/-3.47years), body mass of 66.89+/-11.89kg and a height of 1.70+/-0.09m). They performed four modalities of therapeutic exercise while the electromyographic activity of the investigated muscles was recorded to determine muscle pattern activation for each exercise. RESULTS: Repeated measure ANOVA revealed that muscle activation patterns were similar for the four analyzed exercises, starting with the semitendinosus, followed by the erector spinae, and then, the gluteus maximus. The gluteus maximus was the last activated muscle during hip extension associated with knee flexion (p<0.0001), knee extension (p<0.0001), and with lateral rotation and knee flexion (p<0.05). CONCLUSION: Findings of the present study suggested that despite individual variability, the muscle firing order was similar for the four therapeutic exercises.

Relationships between muscular torque and gait speed in chronic hemiparetic subjects.

PURPOSE: To identify which paretic and non-paretic muscular groups of the lower limbs were the best predictors of gait speed in chronic hemiparetic subjects. METHOD: Twelve hemiparetic subjects with ages ranging from 65 to 75 years (70.67 +/- 3.31 years) were included in this cross-sectional study. All participants had time since onset of stroke of at least six months and the ability to walk independently. Main outcome measures included self-selected gait speed and maximum isometric torques of both the paretic and non-paretic lower limbs. Pearson's correlation coefficients and stepwise regression analysis were employed to investigate the level of associations between the outcome variables. RESULTS: Mean gait speed was 0.65 +/- 0.33 ms(-1). There were significant differences (p < 0.01) in torques values between paretic and non-paretic lower limbs for all assessed muscular groups. Stepwise regression analysis revealed that the most important independent variable for predicting gait speed was the isometric torque of paretic knee flexors ([image omitted] ). No significant associations were found between any torque values of the non-paretic side and gait speed. CONCLUSIONS: The paretic knee flexors were shown to play an important role in predicting gait speed after stroke, but no influences were found for the muscular groups of the non-paretic side. Therefore, findings of the present study suggest that paretic knee flexors torque should be addressed in rehabilitation programmes aiming to improve gait speed after stroke.

Scapular muscular activity with shoulder impingement syndrome during lowering of the arms.

OBJECTIVE: To compare isolated electromyographic (EMG) activity of the serratus anterior, upper, middle, and lower trapezius, as well as the coactivation of the upper and middle trapezius/serratus anterior in subjects with and without shoulder impingement syndrome (IS), during lowering of the arms. DESIGN: Cross-sectional study. SETTING: University laboratory. PARTICIPANTS: Twenty young adults, 10 with unilateral IS degree I or II (mean age 28.6 +/- 5.89 years) and 10 without any complaints or history of previous shoulder lesions (mean age 29.0 +/- 5.35 years), matched by gender, age, and levels of physical activity. MAIN OUTCOME MEASUREMENTS: Isolated EMG activity of the serratus anterior, upper, middle, and lower trapezius, as well as the coactivation of the upper trapezius and middle trapezius/serratus anterior. The EMG activity was quantified by root mean square calculations and normalized by maximal voluntary isometric contractions. RESULTS: Significant differences between groups were found only for the coactivation of the middle trapezius/serratus anterior (F = 6.81; P = 0.02). No significant differences were found between sides (F = 0.05; P = 0.83) nor for interactions between sides and groups (F = 3.85; P = 0.07). CONCLUSIONS: These findings pointed out the importance of evaluating the lowering of the arms in individuals with IS and suggested that measures of coactivation, besides reflecting the real purpose of the muscular actions during functional activities, are more sensitive to detect changes between groups. The evaluation of the coactivation of the middle trapezius/serratus anterior should be included in clinical assessment of individuals with IS and investigations on the etiology and progression of IS.