Muscle Strength Training Alters Muscle Activation of the Lower Extremity during Side-Step Cutting in Females

Abstract

The objective of this study was to examine the effects of muscle strength training on knee kinematics/kinetics and muscle activation patterns during anticipated side-step cutting. Three-dimensional knee kinematics/kinetics data and muscle activation of selected lower extremity muscles were measured while performing cutting before and after completing 10-week circuit strength training mixed typical resistance training and power training (intervention) or no training (control) from 25 female subjects. The muscle strength of quadriceps and hamstrings were measured before and after training using isokinetic dynamometer. No statistically significant differences were observed in quadriceps and hamstrings muscle strength, all kinematic/kinetic variables, and muscle activation for the control group. Both quadriceps (p?=?0.005) and hamstrings (p?=?0.030) muscle strength were increased after training. An increased biceps femoris (p?=?0.003) and H:Q ratio of activation (p?=?0.016), as well as decreased gastrocnemius muscle activation (p?=?0.012) during pre-activation phase in intervention group were found. No significant differences were found in knee kinematics and kinetics both at the time frame of the initial contact and the peak tibial anterior shear force after training. In conclusion, muscle strength training altered some muscle activations of lower extremity muscles, which might affect the risk of ACL injury, but it did not change the kinematic/kinetic parameters.     

Toddlers’ affective responses to sociomoral scenes: Insights from physiological measures

A growing literature suggests that preverbal infants are sensitive to sociomoral scenes and prefer prosocial agents over antisocial agents. It remains unclear, however, whether and how emotional processes are implicated in infants’ responses to prosocial/antisocial actions. Although a recent study found that infants and toddlers showed more positive facial expressions after viewing helping (vs. hindering) events, these findings were based on naïve coder ratings of facial activity; furthermore, effect sizes were small. The current studies examined 18- and 24-month-old toddlers’ real-time reactivity to helping and hindering interactions using three physiological measures of emotion-related processes. At 18 months, activity in facial musculature involved in smiling/frowning was explored via facial electromyography (EMG). At 24 months, stress (sweat) was explored via electrodermal activity (EDA). At both ages, arousal was explored via pupillometry. Behaviorally, infants showed no preferences for the helper over the hinderer across age groups. EMG analyses revealed that 18-month-olds showed higher corrugator activity (more frowning) during hindering (vs. helping) actions, followed by lower corrugator activity (less frowning) after hindering (vs. helping) actions finished. These findings suggest that antisocial actions elicited negativity, perhaps followed by brief disengagement. EDA analyses revealed no significant event-related differences. Pupillometry analyses revealed that both 18- and 24-month-olds’ pupils were smaller after viewing hindering (vs. helping), replicating recent evidence with 5-month-olds and suggesting that toddlers also show less arousal following hindering than following helping. Together, these results provide new evidence with respect to whether and how arousal/affective processes are involved when infants process sociomoral scenarios.     

Surface electromyography-based biofeedback and knee rehabilitation: A review of the literature

The number of total knee arthroplasties (TKA) performed yearly is rapidly increasing. Additionally, upwards of 50% of patients who receive TKA never achieve a full functional recovery. This suggests considerable room for improvement. This need for improvement expands beyond TKA as similar effects are noted across knee injuries. Electromyography-based biofeedback (EMGBF) involves the delivery of feedback based on the activity of targeted muscle. By providing feedback contingent on changes in muscle amplitude, EMGBF may be an effective tool for strengthening quadricep muscles. This review aims to evaluate the utility of sEMGBF during physical therapy for various knee injuries. All studies were evaluated for the effectiveness of sEMGBF at improving muscle strength, range of motion, and reducing pain. Most studies reviewed found that including sEMGBF in physical therapy produced greater clinical benefits for patients than exercise alone. Further research is necessary to determine the best practice for including EMGBF in physical therapy.     

Evaluation of Lower Limb Neuromuscular System Observability and Estimability of Muscle Activity

Abstract

In this work, we describe a method for estimating the muscle activity without drawing any assumptions regarding optimality principles in human motor control strategies; further, the method does not require any neural circuitry modeling which limits the neurophysiological terms and estimability of the method. We introduce the concept of system observability, which can reconstruct states from outputs and their derivatives based on system dynamics. Based on neuromuscular system observability, we estimate the muscle activity from joint torques and kinematics of multiple locomotive gaits, while considering the unknown neural inputs as system disturbances. Moreover, to quantify the robustness of the method, the degree of observability and parameter sensitivity are evaluated. Finally, the neurophysiological implications and generality of the method are addressed.     

Analysis and Discrimination of Surface Electromyographic Features for Parkinson’s Disease during Elbow Flexion Movements

Abstract

Parkinson’s disease (PD) is the second most common neurodegenerative disorder. Early intervention/treatment relies on early diagnosis of PD. There is increasing interest in methods based on electromyography measurements of PD patients because of its noninvasiveness. Thus, this study was to investigate electromyographic (EMG) characteristics of the upper limb between PD patients and healthy control subjects using EMG, and to distinguish PD patients from healthy control subjects according to the EMG information using a support vector machine (SVM) classifier. Sixteen right-handed PD patients and 25 right-handed healthy subjects participated in experiments involving elbow flexion movement. The frequency power, duration, skewness, recurrence rate, and correlation dimension of EMG signals and success rate for the right hand and the skewness of EMG signals for the left hand were found to be significantly different between the two groups. This information was subsequently used to distinguish PD patients from healthy control subjects using the SVM classifier to obtain a mean accuracy of 87.02%. Although the results may not be immediately available to use in clinical applications, the safety, simplicity and speed of the system still merits further consideration. Enhancing performance accuracy and examining PD patients in different stages of disease are anticipated in future investigations.