Vastus Medialis Activity Research Articles

Functional electrostimulation therapy for vastus medialis decreases the varus thrust during gait.

[Purpose] This study aimed to investigate whether modification of vastus medialis activity can delay the varus thrust. [Participants and Methods] Ten participants (Kellgren-Laurence grades I: n=2, II: n=6, and III: n=2) diagnosed with knee osteoarthritis were enrolled. The intervention involved free walking on a 10-m walkway at any speed after donning a functional electrical stimulation set to contract the vastus medialis before heel contact. Using a Vicon Nexus ground reaction force meter and a wireless electromyograph DELSYS, varus thrust, maximal knee extension angle, maximal knee adduction moment, and vastus medialis onset time were assessed both before and after intervention. [Results] A significant difference in varus thrust was detected from before to after the intervention (2.7 ± 1.1° vs. 2.2 ± 1.3°). Both the vastus medialis activation time (-0.06 ± 0.09 vs. -0.21 ± 0.1) and the knee-joint extension angle (8.7 ± 5.1° vs. 5.5 ± 5.9°) decreased following intervention, whereas the knee adduction moment significantly increased (0.50 ± 0.20° vs 0.56 ± 0.18°). [Conclusion] Wearing the functional electrical stimulation set caused the vastus medialis to act earlier in response to heel strike, thereby improving the knee-joint extension angle and suppressing varus thrust.

The Role of Biofeedback in Patellofemoral Pain Conservative Treatment: A Systematic Review.

This paper aims to investigate the effectiveness and the outcomes of the association between different types of biofeedback techniques and therapeutic exercises in the conservative treatment of patellar femoral pain (PFP). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines have been used and followed the Cochrane Handbook for Systematic Reviews of Interventions. Between April and June 2023, the following electronic databases were searched: PubMed, ScienceDirect, BIOMED Central, Cochrane Library, and PEDro. Only randomized controlled trials (RCTs) were selected. Following the search, 414 records were found, and after using strict inclusion and exclusion criteria, 12 RCTs were retrieved to include in this systematic review, assessing 513 patients. The association between biofeedback and therapeutic exercise may be beneficial for pain, function (AKPS), extensor muscle strength, reduction of the dynamic knee valgus and vastus medialis (VM) and vastus lateralis (VL) (EMG) optimization. All these results were valued in the short term. Regarding the intervention type, it was possible to correlate the EMG biofeedback with the benefits of the knee extensor strength and the EMG activity of VM and VL. Conversely, using mirror, verbal, and somesthetic (hands and band) feedback seems to be linked to the reduction of the knee dynamic valgus.

Functional electrostimulation therapy for vastus medialis decreases the varus thrust during gait.

[Purpose] This study aimed to investigate whether modification of vastus medialis activity can delay the varus thrust. [Participants and Methods] Ten participants (Kellgren-Laurence grades I: n=2, II: n=6, and III: n=2) diagnosed with knee osteoarthritis were enrolled. The intervention involved free walking on a 10-m walkway at any speed after donning a functional electrical stimulation set to contract the vastus medialis before heel contact. Using a Vicon Nexus ground reaction force meter and a wireless electromyograph DELSYS, varus thrust, maximal knee extension angle, maximal knee adduction moment, and vastus medialis onset time were assessed both before and after intervention. [Results] A significant difference in varus thrust was detected from before to after the intervention (2.7 ± 1.1° vs. 2.2 ± 1.3°). Both the vastus medialis activation time (-0.06 ± 0.09 vs. -0.21 ± 0.1) and the knee-joint extension angle (8.7 ± 5.1° vs. 5.5 ± 5.9°) decreased following intervention, whereas the knee adduction moment significantly increased (0.50 ± 0.20° vs 0.56 ± 0.18°). [Conclusion] Wearing the functional electrical stimulation set caused the vastus medialis to act earlier in response to heel strike, thereby improving the knee-joint extension angle and suppressing varus thrust.

Characteristics of walking techniques with different pelvic height and pelvic rotation: effect on muscle activation and energy consumption.

Purpose: Previous studies have proven that modifications in the natural walking technique alter muscle activation and energy consumption. This research aimed to determine the differences in muscle activation, energy consumption, kinematic characteristics, perceived muscular exertion and perceived cardio-respiratory fatigue between natural and modified walking techniques with altered pelvic height and rotation. Methods: Nine physically active, non-injured males walked on a treadmill. Modified walking techniques assumed maintenance of constant pelvic height and application of maximal pelvic rotation. Walking speed was subtransit - 0.4 km/h less than the transit. Sampled variables were: average normalized maximal activation during contact and swing phase relativized to maximal voluntary activation, average submaximal oxygen consumption relativized to body mass and subtransit speed, average step length and frequency, rating of perceived muscular exertion and perceived cardio-respiratory fatigue. Muscle activation, energy consumption and kinematic characteristics were assessed throughout each walking session. Perceived muscular exertion and perceived cardio-respiratory fatigue were evaluated post-session. Electromyographic activity was assessed for rectus femoris, gluteus maximus, vastus medialis, biceps femoris, tibialis anterior and gastrocnemius lateralis. Results: The most significant changes in muscle activation were observed during the contact phase. A decrease in pelvic height increased muscle activation of rectus femoris, vastus medialis and gastrocnemius lateralis. An increase in pelvic rotation increased muscle activation of all monitored muscles except for gluteus maximus. Both modifications increased energy consumption, perceived muscular exertion and perceived cardio-respiratory fatigue, and altered kinematic characteristics. Conclusions: Modifications in pelvic height and rotation at the same walking speed alter muscle activation, energy consumption, kinematic characteristics, perceived exertion and fatigue.

Impact of Starting Knee Flexion Angle on Muscle Activity and Performance during Plyometrics without Jumping.

Most of the existing research has focused on jump plyometrics, where landing reaction forces must be dissipated among lower limb articulations. In contrast, the investigation of resisted plyometrics without jumping, devoid of such landing forces, remains relatively limited. This study aimed to (i) investigate the impact of resisted plyometrics without jumping at two knee flexion angles (60 and 90 degrees) on vastus muscle activity relative to limb dominance and (ii) assess strength, power, and work during the concentric-eccentric phases of these exercises. Thirty-one healthy participants underwent quantification of lower limb muscle amplitude, strength, power, and work during resisted plyometrics without jumping from both 60° and 90° knee flexion positions. After anthropometric evaluations, participants used a dynamometer with a load equal to 80% of body weight while wireless surface electromyography electrodes recorded data. Statistical analyses utilized paired t-tests or nonparametric equivalents and set significance at p ≤ 0.05. Results showed significantly higher muscle activity in the vastus medialis (VM) (dominant: 47.4%, p = 0.0008, rs = 0.90; nondominant: 54.8%, p = 0.047, rs = 0.88) and vastus lateralis (VL) (dominant: 46.9%, p = 0.0004, rs = 0.86; nondominant: 48.1%, p = 0.021, rs = 0.67) muscles when exercises started at 90° knee flexion, regardless of limb dominance. Substantial intermuscle differences occurred at both 60° (50.4%, p = 0.003, rs = 0.56) and 90° (54.8%, p = 0.005, rs = 0.62) knee flexion, favoring VM in the nondominant leg. Concentric and eccentric strength, power, and work metrics significantly increased when initiating exercises from a 90° position. In conclusion, commencing resisted plyometrics without jumping at a 90° knee flexion position increases VM and VL muscle activity, regardless of limb dominance. Furthermore, it enhances strength, power, and work, emphasizing the importance of knee flexion position customization for optimizing muscle engagement and functional performance.

Neuromuscular Responses and Perceptions of Health Status and Pain-Related Constructs in End-Stage Knee Osteoarthritis During Resistance Training With Blood Flow Restriction.

Ogrezeanu, DC, López-Bueno, L, Sanchís-Sánchez, E, Carrasco, JJ, Cuenca-Martínez, F, Suso-Martí, L, López-Bueno, R, Cruz-Montecinos, C, Martinez-Valdes, E, Casaña, J, and Calatayud, J. Neuromuscular responses and perceptions of health status and pain-related constructs in end-stage knee osteoarthritis during resistance training with blood flow restriction. J Strength Cond Res 38(4): 762-772, 2024-We aimed to evaluate the neuromuscular responses and their relationship with health status, kinesiophobia, pain catastrophizing, and chronic pain self-efficacy in patients with end-stage knee osteoarthritis during acute resistance training with different levels of blood flow restriction (BFR). Seventeen patients with end-stage knee osteoarthritis participated in 3 experimental sessions separated by 3 days, performing 4 sets of knee extensions with low load and 3 levels of concurrent BFR performed in a random order: control (no BFR), BFR at 40% arterial occlusion pressure (AOP), and BFR at 80% AOP. Normalized root-mean-square (nRMS), nRMS spatial distribution (centroid displacement, modified entropy, and coefficient of variation), and normalized median frequency (nFmed) were calculated from the vastus medialis (VM) and lateralis (VL) using high-density surface electromyography. Subjects were asked to report adverse effects after the sessions. In the VM, nRMS was higher with 80% AOP than with 40% AOP ( p = 0.008) and control ( p < 0.001), whereas there were no differences between conditions in the VL. Normalized root-mean-square also showed an association with pain catastrophizing, chronic pain self-efficacy, and health status (VM: -0.50, 0.49, -0.42; VL: -0.39, 0.27, -0.33). Spatial distribution varied between conditions but mostly in the VL. Overall, nFmed did not vary, with only a slight increase in the VL with 40% AOP, between set 3 and 4. BFR during knee extensions at 80% AOP increases VM activity and VL amplitude distribution more than 40% AOP and control. Importantly, muscle activity increases are modulated by pain catastrophizing, chronic pain self-efficacy, and health status in these patients, and kinesiophobia seems to especially modulate entropy.

Lower Extremity Mechanics and Pathomechanics of People with Patellofemoral Syndrome: A Review

Introduction: The purpose of this study was to review the research conducted on biomechanical and pathomechanical variables of the limbs of people with patellofemoral syndrome and also to summarize and present information in a useful framework from past researches. Methods: The present study was systematic review. Keywords included: mechanics, pathomechanics of the lower limb, kinetics, kinematics, center of pressure and Electromyographic activity of lower limbs, patellofemoral syndrome on the sites of Google Scholar, Science Direct, Web of science, PubMed and Magiranwas searched One hundred nine articles were obtained by using the keywords of the study, and according to the intended purpose and removing duplicate articles, 48 articles were obtained, and according to the desired purpose, in the three parts of the patellofemoral joint, Plantar pressure variables and surrounding patellofemoral muscles were classified and analyzed in terms of mechanics, damage, forces on the joint, electrical activity of muscles and equipment used in the research in the form of tables and text. Results: Displacement of the center of pressure in people with patellofemoral syndrome during using orthotics with corrective exercises was reduced. The main cause of pain in patellofemoral syndrome was the delay in the activity of vastus medialis and vastus lateralis muscles relative to each other, which caused the abnormal displacement of the patella to the side and as a result increased the pressure on the patellofemoral joint and eventually caused pain. Closed kinetic chain exercises and biofeedback strengthened the mentioned muscles. Conclusion: Knowledge of the function of patellofemoral joint elements and orthoses and corrective exercises can help the mechanics and pathomechanics of people with patellofemoral syndrome.

Muscle activation while running on the ground compared to artificial turf in males with pronated and supinated feet

BackgroundRunning on different surfaces, including natural and artificial surfaces, requires different gait mechanics, especially in individuals with foot deformity. Research questionHow muscle activity change during running on the ground and artificial turf in males with pronated and supinated feet? MethodsIn this quasi-experimental study, we assessed a cohort of young male subjects, classified as healthy (n = 10), and with pronated (n = 10) or supinated (n = 10) feet. An electromyographic system was used to record lower limb muscle activity while running on the ground and artificial turf at constant speed (3.2 m/s). ResultsResults demonstrated significant main effects of the "surface" factor for vastus medialis activity during the loading phase (p = 0.040, η2 =0.147). Paired comparison revealed significantly greater vastus medialis activity while running on artificial grass with respect to the ground. A significant effect of the “group” factor was found for medial gastrocnemius during loading phase (p = 0.020, η2 =0.250). Paired-wise comparison revealed significantly lower medial gastrocnemius activity in the pronated and supinated feet groups than in the healthy group. SignificanceThe healthy group may possess better neuromuscular control, allowing them to effectively coordinate the activation of the medial gastrocnemius with other muscles involved in running. Based on these findings, running on artificial turf is useful when the runner would like to strengthen vastus medialis muscle. The runner should carefully choose the running surface according to his/her state and training session goal.

Effects of whole-body vibration training in static and dynamic semi-squat patterns on the lower limb muscle activity

The decline in physical function and the deterioration of the neuromusculoskeletal system in older people can easily lead to reduced muscle strength and slower mobility in the joints of the lower limbs, increasing the incidence of chronic diseases such as muscle wasting disorders, osteoporosis, debilitation and fall and fracture. It may also affect the quality of life and functional independence of older people, and in serious cases, even directly threaten their health. This study was conducted to determine the differences in lower limb muscle activation characteristics between static semi-squat (SSS) and dynamic semi-squat (DSS) training in middle-aged and old women at different frequencies and amplitudes and to explore a personalized whole-body vibration (WBV) training instruction program suitable for them. Fifteen healthy middle-aged and old women (60.8 ± 4.18 years old) were recruited for SSS and DSS WBV training. Their muscle activity of the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and gastrocnemius (GS) were calculated using the BTS FreeEMG300 wireless surface electromyography (EMG), which participants were completed that the two different contraction patterns of squats on WBV training. The knee flexion was maintained at 45° while the subjects were performing the SSS training, while during the DSS training, the knee flexion fluctuates between 10° and 45°. The SSS exercise requires the subject to remain stationary in the squatting position and the DSS to be performed at a rhythm of 4 s/repetition, with 2 s of squatting, 1 s of standing up, and 1 s intervals. The vibration frequencies and amplitudes were changed to the WBV training intensity, and the vibration frequencies were set to 0 Hz, 30 Hz and 40 Hz, and the amplitudes were set to 0 mm, 2 mm and 4 mm. Each subject is randomised to participate in WBV training with 5 combinations of frequency and amplitude in both static and dynamic semi-squat patterns. These were 0 Hz 0 mm, 30 Hz 2 mm, 30 Hz 4 mm, 40 Hz 2 mm, 40 Hz 4 mm for the static and dynamic demi-squat patterns of WBV training. A two-way repeated measures ANOVA was applied to compare the changes in surface EMG of the lower limb muscles in different modes of SSS and DSS with WBV training. (1) Our results showed significantly interaction effects in the frequency × amplitude of root mean square (EMGrms) in GS (P < 0.05), while no significant differences were observed in the interaction effects of SSS/DSS patterns, frequencies and amplitude of RF, VM, VL and BF (P > 0.05). (2) Comparisons between groups showed that the EMGrms of the RF were significantly higher for the DSS than the SSS (P < 0.05). Additionally, the EMGrms of VL and BF at 30 Hz and 40 Hz were greater than 0 Hz (P < 0.05). Also, The EMGrms at 4 mm for the VM, VL and BF were significantly higher than 0 mm, the EMGrms at 4 mm for the VM and VL were significantly higher than 2 mm (P < 0.05), and the EMGrms at 2 mm of VL and BF were significantly higher than 0 mm (P < 0.05). (3) The results showed that WBV stimulation significantly increased the EMGrms of the GS in the SSS compared with the vibration free semi-squat alone (P < 0.05). However, there were no significant differences between WBV training protocols for SSS patterns with different frequencies and amplitudes (frequencies and amplitudes not were 0 Hz and 0 mm) (P > 0.05). Comparison of EMGrms for WBV training of the GS in DSS patterns showed that 40 Hz/4 mm was significantly higher than 0 Hz/0 mm (P < 0.05), but there was no significant difference between the remaining vibration conditions (P > 0.05). WBV training for DSS can significantly improve the activation of the RF compared to SSS pattern. Compared with no vibration, WBV could significantly improv the activity of the lower limb muscles. Additionally, an increase in amplitude from 2 to 4 mm could significantly improve VM and VL activation, while no significant improvement on lower limb muscle activation was observed for increasing vibration frequency from 30 to 40 Hz.

Effects of Transverse Friction Massage on the Electromechanical Delay Components and Fractal Dimension of Surface Electromyography in Quadriceps Muscles

The purpose of this study was to assess the effects of transverse friction massage (TFM) on the electromechanical delay components and complexity of the surface electromechanical activity in the rectus femoris (RF) and vastus medialis (VM) muscles and to identify possible mechanisms behind TFM-induced alterations in the dynamics of RF and VM activity. Seven female and five male healthy subjects participated in this study. The subjects generated five maximal voluntary isometric contractions (MVICs) consecutively before and after TFM. Meanwhile, electromyography (EMG), mechanomyography (MMG), and force were recorded. The onset times of the recorded signals were detected offline by setting the threshold to three times the SD of the baseline. The delays between EMG and MMG (Δt(EMG–MMG)), MMG and force (Δt(MMG–Force)), and EMG and force (Δt(EMG–Force)) were computed from the detected onsets. The fractal dimension (FD) of the EMG time series was computed using the correlation dimension method. TFM increased Δt(MMG–Force) and Δt(EMG–Force) significantly in the RF but decreased Δt(EMG–MMG) and increased Δt(MMG–Force) in the VM. TFM decreased the FD in the RF and increased it in the VM. The results imply that TFM decreased the stiffness of both the RF and VM and decreased the duration of the electrochemical processes in the VM. It is proposed that the decrease in EMG complexity in the RF may be associated with the decreased stiffness of the RF, and the increase in EMG complexity in the VM may be associated with the decreased electrochemical processes in this muscle. It is also suggested that the opposite changes in EMG complexity in the RF and VM can be used as a discriminating parameter to search for the effects of an intervention in the quadriceps muscles. The present study also demonstrates how to discriminate the nonlinear dynamics of a complex muscle system from a noisy time series.

Effect of Aerobic Training on the Relationship Between Loading Rate and Quadriceps Muscle Activities in Men With Diabetic Neuropathy: A Clinical Trial

Background and Aims The increase in loading rate is associated with lower limb injuries such as tibial stress fracture. Quadriceps muscle activities absorb ground reaction force (GRF) shocks by eccentric activation. This study aims to evaluate the effect of aerobic training on the relationship between loading rate and quadriceps muscle activities in men with diabetic neuropathy (DN). Methods In this double-blinded, randomized, controlled clinical trial, participants were 40 men with DN who were selected by a convenience sampling method and randomly divided into two groups of training (n=20, age: 54.9±7.3, body mass index: 28.4±5.4) and control (n=20; age: 54.1±7.3, body mass index: 28.5±5.1). The GRF data was recorded using a force plate system during walking. The electrical activity of selected lower limb muscles was recorded using electromyography method. The training group performed aerobic training for 12 weeks (three sessions per week). Results The results showed an increase in the negative relationship between vertical loading rate and vastus lateralis activities after training (P=0.028). The activities of vastus medialis and rectus femoris muscles showed no significant relationship with loading rate after training (P&gt;0.05). Conclusion Aerobic training can improve the relationship between vastus lateralis muscle activity and vertical loading rate in men with DN.

Subject specific optimal control of powered knee exoskeleton to assist human lifting tasks under controlled environment

AbstractWearable robots, sometimes known as exoskeletons, are incredible devices for improving human strength, reducing fatigue, and restoring impaired mobility. The control of powered exoskeletons, on the other hand, is still a challenge. This necessitates the development of a technique to simulate exoskeleton–wearer interaction. This study uses a two-dimensional human skeletal model with a powered knee exoskeleton to predict the optimal lifting motion and assistive torque. For lifting motion prediction, an inverse dynamics optimization formulation is utilized. In addition, the electromechanical dynamics of the exoskeleton DC motor are modeled in the lifting optimization formulation. The design variables are human joint angle profiles and exoskeleton motor current profiles. The human joint torque square is minimized subject to physical and lifting task constraints. Then, the lifting optimization problem is solved by the gradient-based sparse nonlinear optimizer (SNOPT). Furthermore, the optimal exoskeleton torque is implemented through a two-phase control strategy to provide optimal assistance in lifting. Experimental validations of the optimal control with 6 Nm and 16 Nm maximum assistive torque are presented. Both 6 Nm and 16 Nm maximum optimal assistance of the exoskeletons reduce the mean values of vastus lateralis, biceps femoris, and latissimus dorsi muscle activations compared to the lifting without the exoskeleton. However, the mean value of the vastus medialis activation is increased by a small amount for the exoskeleton case, although its peak value is reduced. Finally, the experimental results demonstrate that the proposed lifting optimization formulation and control strategy are promising for powered knee exoskeleton for lifting tasks.

The effect of lumbopelvic manipulation on electromyography parameters of gluteus medius and vastus medialis in patients with patellofemoral pain syndrome: A double-blind, placebo-controlled trial

BackgroundPatellofemoral Pain Syndrome is the most common cause of anterior knee pain, especially in active young people. This study aimed to evaluate the effect of lumbopelvic manipulation on electromyography parameters of gluteus medius and vastus medialis in patients with patellofemoral pain syndrome. MethodsIn this double-blind placebo-controlled randomized clinical trial study, 26 patients with a diagnosis of patellofemoral pain syndrome were randomly divided into two groups. The first group received Lumbopelvic manipulation and the second group was a control group that received placebo manipulation. Electromyography activity of vastus medialis and gluteus medius muscles were evaluated as primary outcomes during the single-leg squat; pain intensity during rest and functional tasks (step up, step down, single leg squat) were assessed by numerical pain rating scale. Functional status was evaluated by step-down test and the score of the Kujala patellofemoral questionnaire, as secondary outcomes. All evaluations were performed before and after the intervention, except pain intensity at rest and the Kujala patellofemoral questionnaire that were assessed before the intervention and one week after. ResultIn both groups, no significant difference was observed before and after the intervention in terms of average amplitude and the onset of gluteus medius and vastus medialis. However, in the lumbopelvic manipulation group, pain intensity during rest and functional tests significantly decreased compared to the control group. Functional status significantly improved in the lumbopelvic manipulation group, with no significant difference between group comparisons. ConclusionLumbopelvic manipulation caused a reduction in pain intensity and improvement of functional status in the rehabilitation of patients with patellofemoral Pain Syndrome. However, it seems that this method could not change the EMG activity of muscles in these patients. Implications for practice•The results of present study can help physiotherapists to understand the possible underlying pathomechanics of patellofemoral pain syndrome and more effective treatment of these group of patients.

Intentionally Light-Loss Carbon-Optic Fiber (COF) Twisted Sensor for Calf Strength Sensing via Monitoring Vastus Medialis

Flexible sensing exhibits application scenarios in the measurement of muscle deformation and wearable robots. Muscle deformation during exercise is multi-directional, therefore one of the essential challenges is capturing muscle deformation in multiple directions. In this study, we proposed a wearable sensor of twisted carbon fiber and optical fiber (Polymethyl Methacrylate, PMMA) embedded in the fabric, and by converting the light intensity loss to voltage loss, the sensor has the capability to detect muscle activation during movement. The sensor mainly consists of an LED, a photodiode to provide and convert light to a voltage signal, a twisted carbon-optic fiber structure to ensure bending without elongation during deformation under force, and an amplification filter circuit to modulate the signal. A commercial tension sensor was used to verify the relationship between the activation of the vastus medialis and force during calf flexion and extension. Three subjects were employed to complete the experiment, and a correlation coefficient of 0.99 was obtained as well as an experimental average correlation coefficient with a standard deviation of around 0.01. Although influences of the manual manufacturing process are apparent, as well as individual reasons of different subjects, the experimental results suggested that the presented COF sensor can be effectively applied in finding the relationship between vastus medialis activation with tension in calf flexion and extension. We also indicate that the sensor is not sensitive to differences between the right and left legs. This work paves a new way for the design of sensing systems <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e.g</i> . prostheses and exoskeletons.

Effects of a Rehabilitation Exercise Program Using Electro Muscle Stimulation following Anterior Cruciate Ligament Reconstruction on the Circumference, Activity, and Function of the Quadriceps Muscle

The current study compared the effects of exercise program and a rehabilitation exercise program (REP) with electro muscle stimulation (EMS) on participants who had anterior cruciate ligament (ACL) reconstruction. The control group (CONG, n = 12) and the electro muscle stimulation group (EMSG, n = 12) were equally assigned among the 24 patients who underwent ACL reconstruction. For 12 weeks, CONG executed the REP, and EMSG executed of added EMS into the REP. Every participant in the rehabilitative exercise program completed two 60 min sessions each week for a total of 12 weeks. Both a pre- and post-evaluation were completed before and after the workout session. IKDC (International Knee Documentation Committee) score, Lysholm score, thigh circumference, muscular activity, and isokinetic muscle function were the variables examined. The EMSG exposed a significant increase (p &lt; 0.05) in Lysholm score, muscle circumference, muscle activity of vastus medialis (VM), rectus femoris (RM), and vastus lateralis (VL), and isokinetic function (peak torque, total work). However, CONG only showed a significant increase in IKDC score (p &lt; 0.05). This study proved that the REP employing EMS following ACL reconstruction enhanced muscular activation during muscle contraction when compared to REP, and it showed that using EMS in rehabilitation exercise is an effective rehabilitation strategy.

Inhibition of knee joint sensory afferents alters covariation across strides between quadriceps muscles during locomotion.

Sport-related injuries to articular structures often alter the sensory information conveyed by joint structures to the nervous system. However, the role of joint sensory afferents in motor control is still unclear. Here, we evaluate the role of knee joint sensory afferents in the control of quadriceps muscles, hypothesizing that such sensory information modulates control strategies that limit patellofemoreal joint loading. We compared locomotor kinematics and muscle activity before and after inhibition of knee sensory afferents by injection of lidocaine into the knee capsule of rats. We evaluated whether this inhibition reduced the strength of correlation between the activity of vastus medialis (VM) and vastus lateralis (VL) both across strides and within each stride, coordination patterns that limit net mediolateral patellofemoral forces. We also evaluated whether this inhibition altered correlations among the other quadriceps muscle activity, the time-profiles of individual EMG envelopes, or movement kinematics. Neither the EMG envelopes nor limb kinematics was affected by the inhibition of knee sensory afferents. This perturbation also did not affect the correlations between VM and VL, suggesting that the regulation of patellofemoral joint loading is mediated by different mechanisms. However, inhibition of knee sensory afferents caused a significant reduction in the correlation between vastus intermedius (VI) and both VM and VL across, but not within, strides. Knee joint sensory afferents may therefore modulate the coordination between the vasti muscles but only at coarse time scales. Injuries compromising joint afferents might result in altered muscle coordination, potentially leading to persistent internal joint stresses and strains.NEW & NOTEWORTHY Sensory afferents originating from knee joint receptors provide the nervous system with information about the internal state of the joint. In this study, we show that these sensory signals are used to modulate the covariations among the activity of a subset of vasti muscles across strides of locomotion. Sport-related injuries that damage joint receptors may therefore compromise these mechanisms of muscle coordination, potentially leading to persistent internal joint stresses and strains.

Can Data-Driven Supervised Machine Learning Approaches Applied to Infrared Thermal Imaging Data Estimate Muscular Activity and Fatigue?

Surface electromyography (sEMG) is the acquisition, from the skin, of the electrical signal produced by muscle activation. Usually, sEMG is measured through electrodes with electrolytic gel, which often causes skin irritation. Capacitive contactless electrodes have been developed to overcome this limitation. However, contactless EMG devices are still sensitive to motion artifacts and often not comfortable for long monitoring. In this study, a non-invasive contactless method to estimate parameters indicative of muscular activity and fatigue, as they are assessed by EMG, through infrared thermal imaging (IRI) and cross-validated machine learning (ML) approaches is described. Particularly, 10 healthy participants underwent five series of bodyweight squats until exhaustion interspersed by 1 min of rest. During exercising, the vastus medialis activity and its temperature were measured through sEMG and IRI, respectively. The EMG average rectified value (ARV) and the median frequency of the power spectral density (MDF) of each series were estimated through several ML approaches applied to IRI features, obtaining good estimation performances (r = 0.886, p &lt; 0.001 for ARV, and r = 0.661, p &lt; 0.001 for MDF). Although EMG and IRI measure physiological processes of a different nature and are not interchangeable, these results suggest a potential link between skin temperature and muscle activity and fatigue, fostering the employment of contactless methods to deliver metrics of muscular activity in a non-invasive and comfortable manner in sports and clinical applications.

Effect of change in patellofemoral joint contact area by the decrease in vastus medialis muscle activation on joint stress

Purpose Patellofemoral pain syndrome is a common orthopedic trauma among runners. It is unclear whether patellofemoral joint stress (PFJS) is the highest (or lowest) when the knee joint flexion angle and extension moment are in combination under the condition that vastus medialis (VM) activation decreases. This study aimed to investigate the effects of changes in the PFJ contact area by decreasing the activation of the VM muscle on PFJS. Methods A PFJ sagittal model was used to quantify PFJ reaction force and PFJS. The PFJ model and mathematical modelling procedure were used to quantify PFJS based on previous studies. The simulation ranges were set to knee joint flexion angles of 10–45 degrees and extension moments of 0–240 Nm. PFJS was calculated for the normal condition (NC) and decrease condition (DC) in VM activation. Results When the knee joint angle and knee joint moment were at the maximum, the PFJS showed the maximum value under both conditions (NC; 14.9 N/cm2, DC; 16.4 N/cm2). PFJS was found to be higher in DC than that in NC for all simulation ranges. Conclusions Decreased VM activation may be involved in the mechanism of patellofemoral pain syndrome. In addition, the results of this study provide evidence that clinicians can enhance VM to relieve pain in patients with patellofemoral pain syndrome.

Effect of Increasing Assistance From a Powered Prosthesis on Weight-Bearing Symmetry, Effort, and Speed During Stand-Up in Individuals With Above-Knee Amputation.

After above-knee amputation, the missing biological knee and ankle are commonly replaced with a passive prosthesis, which cannot provide net-positive energy to assist the user. During activities such as sit-to-stand, above-knee amputees must compensate for this lack of power using their upper body, intact limb, and residual limb, resulting in slower, less symmetric, and higher effort movements. Previous studies have shown that powered prostheses can improve symmetry and speed by providing positive assistive power. However, we still lack a systematic investigation of the effect of powered prosthesis assistance. Without this knowledge, researchers and clinicians have no framework for tuning powered prostheses to optimally assist users. Here we show that varying the assistive knee torque significantly affected weight-bearing symmetry, effort, and speed during the stand-up movement in eight above-knee amputees. Specifically, we observed improvements in the index of asymmetry of the vertical ground reaction force at the point approximating maximum vertical center of mass acceleration, the integral of the intact vastus medialis activation measured using electromyography, and the stand-up duration compared to the passive prosthesis. We saw significant improvements in all three metrics when subjects used the powered prosthesis compared to the passive prosthesis. We saw improvements in all three metrics with increasing assistive torque levels commanded by the powered prosthesis. We also observed increased weight-bearing asymmetry at the end of movement, and increased kinematic asymmetry with increasing assistance from the powered prosthesis. These results show that powered prostheses can improve functional mobility, potentially increasing quality of life for millions of people living with above-knee amputations.

Effects of Knee Extension Joint Angle on Quadriceps Femoris Muscle Activation and Exerted Torque in Maximal Voluntary Isometric Contraction.

Simple SummaryFor human movement to occur, the neural system needs to activate muscles. Muscles then pull the bones that rotate around the joints. As the joint angle for the movement initiation changes, the mechanical conditions for the muscle force production also change, as does the exerted torque (i.e., maximal endpoint force). However, it is unclear whether different joint angles produce different muscle activation in maximal voluntary isometric contraction. This study investigated the effects of knee joint angle on muscle activation, produced torque, and whether the knee angle affects the muscle activation–torque ratio. Participants were instructed to produce maximal isometric knee extension in joint angles of 80, 90, 100, 110, 120, and 130°, while their muscle activation and torque output were assessed. The results confirmed the dependence of torque on knee angle, while muscle activation remained unaffected. While the trend could be observed, significant effects did not occur in muscle activation–torque ratio for lateral and medial quadriceps heads. The investigated range of knee joint angles seems to provide optimal conditions for maximal muscle activation but not for the torque output, hence for the ligament loading and joint contact forces. Therefore, clinicians and sports coaches should carefully set the training goals and choose the knee joint angles accordingly.This study investigated the effects of knee joint angle on muscle activation, exerted torque, and whether the knee angle affects the muscle activation–torque ratio. Nine healthy adult male participants participated in the study. They performed maximal voluntary isometric contraction (MVIC) at six (80°, 90°, 100°, 110°, 120°, and 130°) different knee joint angles (i.e., angles between the thigh and shin bones). Their maximal torque was assessed utilizing an isokinetic chair, while their muscle activation (root mean square [RMS]) was assessed using an eight-channel single differential surface EMG sensor. For the purposes of the torque–knee angle relationship and muscle activation–knee angle relationship, the torque and RMS were normalized relative to the maximal value obtained by each participant. To evaluate the muscle activation–torque ratio in function of knee angle, RMS was normalized relative to the corresponding torque obtained at each knee angle. Repeated measure analysis of variance was used to investigate the effects of knee angle on muscle activation, torque, and muscle activation–torque ratio. There was a significant effect of knee joint angle on normalized torque (F = 27.521, p < 0.001), while the activation of vastus lateralis and vastus medialis remained unchanged. The changes in knee angle affected the muscle activation–torque ratio of vastus lateralis (Chi-square = 16.246, p = 0.006) but not the vastus medialis. These results suggest that knee joint angles from 80° to 130° provide a stable milieu for muscle electrification, while mechanical factor such as knee joint angle (i.e., lever arm length) affect the torque output when one needs to contract quadriceps maximally during the isometric contraction.