Pattern Of Electromyographic Activity Research Articles

Using textile sensors to assess electromyographic activation patterns during gait

Using textile sensors to assess electromyographic activation patterns during gait

Comparative Analysis of Neuromuscular Activation Patterns Associated with Force between Semi-Professional Female Soccer Players with Previous Anterior Cruciate Ligament Surgery and Healthy Players in Thigh Musculature Related to Valgus Collapse

This study investigates electromyography activation and force development differences in key lower limb muscles between female football players with previous anterior cruciate ligament injuries compared with healthy players. Twenty-two semi-professional players were divided into ACL-injured (n = 11) and non-injured groups (n = 11). Participants underwent maximal voluntary isometric contractions while electromyography activation, peak and average, and peak torque of force were measured. Results indicated significant differences in electromyography activation patterns between anterior cruciate ligament players and non-injured players, particularly in biceps femoris and gluteus maximus muscles. These differences were also evident when comparing between limbs within anterior cruciate ligament players. Interestingly, both groups exhibited similar peak torque of force during maximal contractions, suggesting a compensatory neuromuscular strategy that supports a return to sport based on kinetic and kinematic factors. However, these findings underscore persistent muscle integration imbalances potentially contributing to the high rate of anterior cruciate ligament reinjury. In conclusion, this study highlights the importance of evaluating electromyography activation alongside force development in understanding neuromuscular adaptations post anterior cruciate ligament injury. These insights emphasize the need for comprehensive rehabilitation strategies that address muscle imbalance to mitigate the risk of recurrent anterior cruciate ligament injuries in female football players.

Effects of Expertise on Muscle Activity during the Hang Power Clean and Hang Power Snatch Compared to Snatch and Clean Pulls - An Explorative Analysis.

The purpose was to compare the electromyographic (EMG) activity of the Hang Power Clean (HPC) and Hang Power Snatch (HPS) with the Hang Clean Pull (HCP) and Hang Snatch Pull (HSP). Additionally, the influence of weightlifting expertise (beginner, advanced and elite) on EMG activity was analyzed. Twenty-seven weightlifters (beginner: n = 11, age: 23.9 ± 3.2 years, bodyweight: 75.7 ± 10.5 kg; advanced: n = 10, age: 24.8 ± 4.5 years, bodyweight: 69.4 ± 13.9 kg; elite: n = 6, age: 25.5 ± 5.2 years, bodyweight: 75.5 ± 12.5 kg) participated in this study. Participants performed two repetitions of HPC, HPS, HCP, and HSP at 50%, 70%, and 90% 1RM, respectively. The EMG activity of vastus lateralis (VL), gluteus maximus (GM), erector spinae (ES), rectus abdominis (RA) and trapezius (TZ) was recorded and normalized to the maximum voluntary isometric contraction (MVIC) of each muscle. There were significant differences in RA and ES EMG activity at 70% and 90% 1RM during HPC compared to HCP in the beginner group (p < 0.05, Hedges g = 0.50-1.06). Significant greater ES activity was observed in the beginner, advanced, and elite groups (p < 0.05, g = 0.27-0.98) during the HPS when compared to the HSP at 50-90% 1RM. TZ muscle activity was significantly greater at 50% and 70% 1RM in the HCP compared to the HPC in the elite group (p < 0.05, g = 0.61-1.08), while the beginner group reached significance only at 50% 1RM favoring HPC (p < 0.05, g = 0.38). Moreover, the EMG activity of the TZ during the HSP and HPS was significantly different only at 50% 1RM in the elite group and favored HSP (p < 0.05, g = 0.27). No differences were observed between the levels of weightlifting expertise. Based upon the results of this study, the overall pattern of EMG activity of the predominant muscles involved in HPC/HPS and the corresponding weightlifting pulling derivatives, apart from the stabilizing muscle (RA and ES), is similar at higher intensities (>70% 1RM) and expertise does not influence muscle activity.

Long-Term Effects of Whole-Body Vibration on Hind Limb Muscles, Gait and Pain in Lame Dogs with Borderline-to-Severe Hip Dysplasia-A Pilot Study.

This pilot study aimed to evaluate the long-term effects of Whole-Body Vibration (WBV) on hind limb muscles, gait and pain in lame dogs with borderline-to-severe hip dysplasia. Ten lame client-owned dogs with borderline-to-severe hip dysplasia, aged from 1.5 to 9.0 years and weighing 14.5 to 53.0 kg, were enrolled. The WBV training program consisted of 15 min sessions three times weekly for 16 weeks. Muscles of the hind limbs were evaluated using measurements of thigh circumference, the cross-sectional thickness of selected hind limb muscles by ultrasound assessment, and vastus lateralis muscle activity determined by surface electromyography (EMG). Lameness and clinical signs of pain were assessed by visual lameness scoring, orthopedic examination and an owner-based questionnaire. Kinetic analysis was performed by using a pressure-sensitive walkway. Manual thigh circumference measurements of both hind limbs showed significant increases over the trial period with a greater degree of change observed after week 8. Ultrasound measurements of the left gluteal muscles and the quadriceps femoris muscles of both hind limbs showed significant increases in the cross-section thickness post WBV. Owner's perception of pain also showed a decrease in signs of pain at week 12 and week 16 compared to baseline. Based on graphs of the EMG activity patterns of the vastus lateralis muscle, 65% of the hind limbs had an improvement after 48 WBV sessions when compared to pre-session patterns. However, no significant differences were observed in visual lameness evaluation and kinetic analysis. Therefore, further studies will help to better clarify the role of WBV in canine rehabilitation protocols.

Effects of tendon elastic energy and electromyographic activity pattern on jumping height and pre-stretch augmentation during jumps with different pre-stretch intensity

ABSTRACT The present study aimed to investigate the effects of tendon elastic energy and electromyographic activity patterns (ratio of pre-landing to concentric: mEMG PLA/CON; ratio of eccentric to concentric; mEMG ECC/CON) on jump performance. Twenty-nine males performed five kinds of unilateral jumps using only ankle joint (no-countermovement jump: noCMJ; countermovement jump: CMJ; drop jumps at 10, 20 and 30 cm drop height: DJ10, DJ20 and DJ30). Jumping height, pre-stretch augmentation and electromyographic activity of the plantar flexor muscles were measured. The elastic energy of the Achilles tendon was measured during isometric contractions. Relative tendon elastic energy (to body mass) was highly correlated with jumping heights of CMJ, DJ10 and DJ20 but not with noCMJ and DJ30, whereas that was significantly correlated with pre-stretch augmentation in CMJ, but not with three DJs. The mEMG PLA/CON was significantly correlated with the pre-stretch augmentation of DJ20 and DJ30, but not with DJ10, whereas the mEMG ECC/CON was significantly correlated with the pre-stretch augmentation of DJ20 and DJ30, but not with CMJ and DJ10. These results suggested that jumping exercises with low pre-stretch intensity benefited from tendon elastic energy, but those with high pre-stretch intensity benefited from electromyographic activity patterns.

Determinants of joint stiffness and jumping height during drop jump.

The present study aimed to examine the effects of muscle-tendon mechanical properties and electromyographic activity on joint stiffness and jumping height and to explore the determinants of joint stiffness and jumping height. Twenty-nine males performed unilateral drop jumps at three drop heights (10, 20, and 30 cm) using only the ankle joint on the sledge apparatus. Ankle joint stiffness, jumping height, and electromyographic activity of the plantar flexor muscles were measured during drop jumps. Active muscle stiffness of the medial gastrocnemius muscle was calculated according to changes in the estimated muscle force and fascicle length during fast stretching at five different angular velocities (100, 200, 300, 500, and 600 deg s-1 ) after submaximal isometric contractions. Tendon stiffness and elastic energy were measured during ramp and ballistic contractions. Active muscle stiffness was significantly correlated with joint stiffness, except for a few conditions. Tendon stiffness measured during ramp and ballistic contractions was not significantly correlated with joint stiffness. The ratios of electromyographic activity before landing and during the eccentric phase to that during the concentric phase were significantly correlated with joint stiffness. In addition, jumping heights at 10 and 20 cm (except for 30 cm) drop heights were strongly associated with the tendon elastic energy, whereas no other measured variables showed significant correlations with jumping heights. These results suggested that (1) joint stiffness is determined by active muscle stiffness and electromyographic activity patterns during jumping, and (2) jumping height is determined by tendon elastic energy.

Effect of intervertebral disc degeneration on the stomatognathic system function in adults

ABSTRACT Objective To analyze the electromyographic activity (EMG) and thermographic patterns of the masseter and temporalis muscles and pressure of the orofacial tissues in individuals with intervertebral disc degeneration (IDD). Methods This study had two distinct groups: with IDD (n = 16) and controls (n = 16). EMG at rest, protrusion, right and left laterality, and maximum voluntary contraction were evaluated. Tongue, orbicularis oris, and buccinator muscles pressures were measured by Iowa Oral Performance Instrument. The thermographic patterns were analyzed using infrared thermography. Results Comparisons between groups showed significant differences regarding at rest [right (p = 0.05) and left (p = 0.05) masseter and right temporal (p = 0.05)], orofacial tissue pressure [tongue (p = 0.001), orbicularis oris (p = 0.01), and buccinator (p = 0.0001)], but no significant differences for the thermographic patterns. Conclusion IDD modifies the functionality of the craniomandibular complex, influencing the performance of the stomatognathic system.

Asymmetric and transient properties of reciprocal activity of antagonists during the paw-shake response in the cat.

Mutually inhibitory populations of neurons, half-center oscillators (HCOs), are commonly involved in the dynamics of the central pattern generators (CPGs) driving various rhythmic movements. Previously, we developed a multifunctional, multistable symmetric HCO model which produced slow locomotor-like and fast paw-shake-like activity patterns. Here, we describe asymmetric features of paw-shake responses in a symmetric HCO model and test these predictions experimentally. We considered bursting properties of the two model half-centers during transient paw-shake-like responses to short perturbations during locomotor-like activity. We found that when a current pulse was applied during the spiking phase of one half-center, let’s call it #1, the consecutive burst durations (BDs) of that half-center increased throughout the paw-shake response, while BDs of the other half-center, let’s call it #2, only changed slightly. In contrast, the consecutive interburst intervals (IBIs) of half-center #1 changed little, while IBIs of half-center #2 increased. We demonstrated that this asymmetry between the half-centers depends on the phase of the locomotor-like rhythm at which the perturbation was applied. We suggest that the fast transient response reflects functional asymmetries of slow processes that underly the locomotor-like pattern; e.g., asymmetric levels of inactivation across the two half-centers for a slowly inactivating inward current. We compared model results with those of in-vivo paw-shake responses evoked in locomoting cats and found similar asymmetries. Electromyographic (EMG) BDs of anterior hindlimb muscles with flexor-related activity increased in consecutive paw-shake cycles, while BD of posterior muscles with extensor-related activity did not change, and vice versa for IBIs of anterior flexors and posterior extensors. We conclude that EMG activity patterns during paw-shaking are consistent with the proposed mechanism producing transient paw-shake-like bursting patterns found in our multistable HCO model. We suggest that the described asymmetry of paw-shaking responses could implicate a multifunctional CPG controlling both locomotion and paw-shaking.

Are age-matched normative data mandatory for clinical decision making of axial deformities in children and adolescents?

This paper introduces a new approach for computing lower extremity muscle forces by incorporating equations that consider “bone structure” and “prevention of bending by load reduction” into existing optimization algorithms.Lower extremity muscle and joint forces, during normal gait, were calculated and compared using two different optimization approaches. We added constraint equations that prevent femoral bending loads to an existing approach that considers “minimal total muscular force”. Gait parameters such as kinematics, ground reaction forces, and surface electromyographic activation patterns were examined using standardized gait analysis. A subject-specific anatomic model of the lower extremities, obtained from magnetic resonance images of a healthy male, was used for the simulations. Finite element analysis was used to calculate femoral loads.The conventional method of calculating muscle forces leads to higher rates of femoral bending and structural stress than the new approach. Adding equations with structural subject-specific parameters in our new approach resulted in reduced femoral stress patterns.These findings show that our new approach improves the accuracy of femoral stress and strain simulations. Structural overloads caused by bending can be avoided during inverse calculation of muscle forces.

Gait patterns in ischemic and hemorrhagic post-stroke patients with delayed access to physiotherapy.

Objectives:(1) To assess the effects of a conventional, delayed physiotherapy protocol used by Ischemic Stroke (IS) and Hemorrhagic Stroke (HS) post-stroke patients, in their electromyographic activation patterns during hemiparetic gait; and (2) to study whether this protocol may improve the functional abilities in this population.Methods:This is an observational, descriptive, and analytical quasi-experimental trial. Forty patients with unilateral IS () and HS () stroke were recruited; the stroke involved the motor cortex or sub-cortical areas, and the patients were able to walk independently. Interventions with standard protocols of physiotherapy were carried out. Evaluations (clinical and gait assessment) were performed at the time of admission and at the end of the protocol. Outcome measures include Stroke Impact Scale, Timed Up and Go Test, and gait electromyographic evaluation.Results:Only IS patients (with an average of months delayed access to physiotherapy rehabilitation) had improvements in Timed Up and Go Test (change in seg ) and presented an anticipation of the onset in Upper leg muscles after the intervention. BF (), ST (), and RF (), started their recruitment (onset) earlier at the swing phase of the gait cycle, which is more similar to the normal pattern (grey shadow). IS and HS ( months since last stroke) patients presented higher electromyographic activation, after physiotherapy, of the posterior leg muscles (gastrocnemius, semitendinosus and biceps femoris) during stance phase ().Conclusion:IS patients had improvements after delayed conventional physiotherapy. For HS limited response to intervention was observed.

Electromyographic activation patterns during swallowing in older adults

Age-related weakness due to atrophy and fatty infiltration in oropharyngeal muscles may be related to dysphagia in older adults. However, little is known about changes in the oropharyngeal muscle activation pattern in older adults. This was a prospective and experimental study. Forty healthy participants (20 older [> 60 years] and 20 young [< 60 years] adults) were enrolled. Six channel surface electrodes were placed over the bilateral suprahyoid (SH), bilateral retrohyoid (RH), thyrohyoid (TH), and sternothyroid (StH) muscles. Electromyography signals were then recorded twice for each patient during swallowing of 2 cc of water, 5 cc of water, and 5 cc of a highly viscous fluid. Latency, duration, and peak amplitude were measured. The activation patterns were the same, in the order of SH, TH, and StH, in both groups. The muscle activation patterns were classified as type I and II; the type I pattern was characterized by a monophasic shape, and the type II comprised a pre-reflex phase and a main phase. The oropharyngeal muscles and SH muscles were found to develop a pre-reflex phase specifically with increasing volume and viscosity of the swallowed fluid. Type I showed a different response to the highly viscous fluid in the older group compared to that in the younger group. However, type II showed concordant changes in the groups. Therefore, healthy older people were found to compensate for swallowing with a pre-reflex phase of muscle activation in response to increased liquid volume and viscosity, to adjust for age-related muscle weakness.

The effect of electrical muscle stimulation on quadriceps muscle strength and activation patterns in healthy young adults

The aim of the present study was to clarify the effect of electrical muscle stimulation (EMS) on the spatial distribution pattern of electromyographic activity in healthy young adults using multi-channel surface electromyography (SEMG). A total of 32 men (age = 21–26 years) were randomly assigned to the intervention group (n = 18) and control group (n = 14). Participants in the intervention group performed EMS to stimulate the bilateral lower limb muscle for four weeks (20 min/3 days/week). The control group received no EMS intervention. To understand the effects of EMS, the following measurements were made at baseline and four weeks: knee extension torque, muscle mass, and spatial distribution of neuromuscular activation during a target torques [10%, 30%, 50%, and 70% of the maximal voluntary contraction (MVC)] using multi-channel SEMG. The knee extension torque was significantly increased in intervention group compared with control group (p < 0.0001). However, the muscle mass did not show a significant difference between pre and post intervention in each group. The muscle activation patterns of 50% and 70% MVC task showed significant enhancement between baseline and four weeks in the intervention group. Furthermore, a moderate correlation between Δ knee extension torque and Δ spatial distribution pattern of electromyographic activity of 50% and 70% MVC in the intervention group was observed. These results suggested EMS intervention induced different distribution of muscle activity at high-intensity muscle contraction compared with low-intensity muscle contraction.

Personalized Prevention in Mercury-Induced Amyotrophic Lateral Sclerosis: A Case Report

Chronic exposure to low levels of mercury is involved in the development of motor neuron diseases (MND). Genetic alterations may have a crucial role in the onset and progression. We presented a case of a TANK-binding kinase 1 (TBK1)-mutated 54-year-old male worker who developed a MND due to chronic mercury exposure at work. He was employed in a chlor-alkali plant in Central Italy. After two years of employment he had acute mercury intoxication with suggestive neurological symptoms and a high urinary level of the metal. Through years, many episodes of intoxication occurred, but he continued to perform the same job and be exposed to mercury. After yet another episode of intoxication in 2013, he showed fasciculations of the upper limbs and trunk, and electromyographic activity patterns were consistent with amyotrophic lateral sclerosis (ALS). In 2016, a genetic test revealed a mutation of TBK1, an ALS-related gene. This case highlights the important role of genetics in personalized occupational medicine. Occupational physicians should use genetic tests to identify conditions of individual susceptibility in workers with documented frequent episodes of mercury intoxication recorded during health surveillance programs to customize prevention measures in the workplace and act before damage appears.

Implied Evidence of the Functional Role of the Rectus Capitis Posterior Muscles.

Osteopathic physicians often target the rectus capitis posterior minor (RCPm) and rectus capitis posterior major (RCPM) muscles when using muscle energy or soft tissue cervical techniques to treat patients with head and neck pain. The RCPm and RCPM muscles are located deep within the posterior occipitoatlantal and atlantoaxial interspaces, respectively. To characterize the functional role of RCPm and RCPM muscles by comparing electromyographic (EMG) activation patterns of these muscles with EMG activation patterns of specific flexor and extensor muscles of the head and neck, the sternocleidomastoid (SCM), and the splenius capitis (SC) muscles, respectively. Asymptomatic participants were recruited from the Michigan State University College of Osteopathic Medicine student body. Disposable 25-gauge, bipolar fine-wire intramuscular electrodes were used to collect EMG data from the right and left RCPm and RCPM muscles. Surface electrodes were used to collect EMG data from the right and left SCM and SC muscles. Data were collected as participants performed 4 cycles of flexion and extension with an external 4-lb force applied to the back of the head and the forehead. In RCPM muscles, EMG activity was significantly greater (P<.003) during flexion and extension of the head and neck when an external force was applied to the back of the head. EMG activity in SCM muscles was significantly greater (P<.0001) during flexion and extension of the head and neck when an external force was applied to the forehead. The authors observed that EMG activity in SC muscles was significantly greater (P<.015) during flexion and extension of the head and neck when an external force was applied to the back of the head. No significant difference was found in EMG activity in RCPm muscles (P<.834) during flexion and extension of the head and neck, regardless of whether the external force was applied to the back of the head or the forehead. The EMG activation patterns of the RCPm muscles suggest that their functional role may be to stabilize the occipitoatlantal joint by helping maintain congruency of the joint surfaces. In contrast, the EMG activation patterns of the RCPM muscles suggest that their functional role may be to contribute to extension of the head, primarily at the occipitoatlantal and the atlantoaxial joints.

Transfer learning using low-dimensional subspaces for EMG-based classification of hand posture.

This study proposes a novel approach for evaluating the task invariance of muscle synergies, vital for potential implementation in improving prosthetic hand control. We do this by using a transfer learning paradigm to test for invariance across a relatively small set of hand/forearm muscle synergies, derived from electromyographic (EMG) activation patterns during voluntary behaviors such as finger spelling and grasp mimicking postures and unconstrained exploration. EMG for each task were decomposed using non-negative matrix factorization into synergy and weight matrices, and cross-task weights for each task were then reconstructed by employing the base matrices from different tasks. Support Vector Machine and Extreme Learning Machine classifiers were used to classify the resulting weights in order to compare their performance, as well as their behaviors as a function of synergy rank. Both algorithms showed robust and significantly higher performance, compared to two distinct randomized controls, with lower rank EMG representations, both within and between tasks/postures, supporting hypotheses of functional invariance of multi-muscle synergies. Our results suggest that this invariance could be leveraged to efficiently calibrate postures for prosthetic hand implementation by transferring learned EMG patterns from unconstrained movements to other tasks.

Rapid maxillary expansion in the treatment of the functional posterior crossbite: joint noise and electromyographic activity analysis

Abstract Introduction The rapid maxillary expansion (RME) reduces the risk of developing structural and functional disorders in the stomatognathic system. Objective To examine the effects of the RME as a treatment for the posterior crossbite, related with the electromyographic activity of the masticatory muscles and the TMJ noises in a population of children. Material and method 13 girls and 7 boys, regardless of the type of malocclusion, with a mean age of 9 years old (± 3), were treated with RME. The electrovibratography analyzed the TMJ noise, and the electromyography analyzed the masticatory muscles before treatment (T0) and after three months of a short-term follow-up (T1). The comparisons of the affected and unaffected sides by the crossbite were performed using Mann-Whitney’s test, and to compare data before and after treatment the Wilcoxon’s test was used (level of significance: 5%). Result No significant differences were found in the parameters of joint noise in comparison to the sides affected and unaffected by the crossbite, in both T0 and T1 (p&gt;0.05); only the side without the crossbite observed decrease in the peak amplitude of the joint noises after treatment. In the static electromyographic analysis, inter-side differences were observed before and after treatment, since the deliberate unilateral chewing showed greater asymmetry activity in T0 for both sides, which has been corrected after treatment, improving the functional chewing. Conclusion The proposed treatment did not lead to the occurrence of joint noises and improved the functional pattern of electromyographic activity during chewing at the end of treatment.

The effect of medication on vastus lateralis muscle activation patterns in Parkinson’s disease patients

The effect of levodopa on muscle activity patterns in Parkinson’s disease (PD) patients is currently unclear. The aim of the present study was to compare the spatial distribution pattern of electromyographic activity during sustained isometric contraction in PD patients during on- and off-medication periods using multi-channel surface electromyography (SEMG). Ten female PD patients were recruited for the present study. All patients performed a sustained isometric knee extension at 10% maximum voluntary contraction task for 60 s. To evaluate alterations in the spatial SEMG potential distribution, the coefficient of variation (CV) of force, normalized root mean square (RMS), modified entropy, CV of the RMS, and correlation coefficients were calculated at during contraction task. The off-medication period exhibited more fluctuation during the contraction task than those in the on-medication period. The off-medication period exhibited less change in modified entropy, the CV of RMS, the correlation coefficient and patterns of spatial SEMG distribution. These data demonstrated that the heterogeneity and changes in the activation pattern are smaller in the off-medication period than in those in the on-medication period. These findings might indicate that levodopa enhanced the activation of muscle action potentials during force production.

Association of electromyographic activation patterns with pain and functional disability in people with chronic neck pain

This study examined the activation patterns of the cervical and thoracic muscles in people with and without chronic neck pain during functional activities and their associations with pain intensity and functional disability. Thirty-four adults with chronic neck pain and 34 asymptomatic adults were recruited. They were requested to perform active cervical movements and an upper limb lifting task. Electromyographic activation patterns (EMG) of bilateral upper trapezius, cervical erector spinae, sternocleidomastoid, and thoracic erector spinae were recorded during these tasks. Correlation and multiple regression analysis were used to examine the associations between EMG variables and severity of pain and functional disability. When performing the cervical movements, the neck pain group displayed lower EMG activity levels, especially in the cervical and thoracic extensors. In addition, significantly prolonged activation was observed in seven of the ten muscles during the upper limb lifting task. The changes in EMG amplitude and activation duration were found to be significantly correlated with severity of pain (R2 = 0.716) and functional disability (R2 = 0.623). Significant differences in the activation patterns of multiple cervical and thoracic muscles were found in individuals with neck pain compared with those without neck pain. These were significantly associated with their degree of pain and functional limitation. The findings of this study highlight the importance of assessing and optimising the neuromuscular activation of these muscles in the rehabilitation of those suffering from chronic neck pain.

Effect of Fatigue on Electromyographic Activity Patterns of the Knee Joint Muscles in Anterior Cruciate Ligament Reconstructed and Deficient Patients during Landing Task

Lower extremity fatigue causes a number of neuromuscular alterations that may increase the risk of knee (re)injury. It has therefore been suggested that fatigue-resistance training be incorporated into injury prevention and rehabilitation programs. The purpose of this study was to determine the effects of fatigue on knee-muscle activity patterns after anterior cruciate ligament injury (ACL). Twelve healthy, 12 ACL reconstructed (ACLR) and 12 ACL deficient (ACLD) recreationally active male volunteers participated in this case-control study. Fatigue was induced via repetitive sets of double-leg squats and drop landings. Muscle activity was assessed via surface electromyography during a single-leg drop landing task pre- and post-fatigue. After fatigue, medial hamstring, lateral hamstring and vastus lateralis muscles turned on significantly earlier in ACLR compared to the control group. Significantly greater vastus medialis muscle activity was observed in ACLD compared to ACLR and control participants post-fatigue. Finally, fatigue decreased lateral gastrocnemius muscle activity in ACLD and control participants. It seems ACLR patients rely on earlier muscle pre-activation to establish knee joint stability upon landing after fatigue. This feed-forward strategy should be emphasized during post-operative rehabilitation in ACLR patients. Furthermore, according to our results, quadriceps and gastrocnemius muscles play an important role in establishing knee joint stability post impact in ACLD patients.

Isolated Infraspinatus Atrophy Secondary to Suprascapular Nerve Neuropathy Results in Altered Shoulder Muscles Activity.

Isolated infraspinatus atrophy (IIA) is a common condition among overhead activity athletes, which affects the hitting shoulder and is caused by suprascapular nerve injury. The loss of infraspinatus function could lead to altered activity of the glenohumeral and scapulothoracic (ST) muscles and compromise the optimal shoulder function. To assess the surface electromyographic (sEMG) activity patterns, relationships, and response latencies of relevant shoulder girdle muscles in professional volleyball players with IIA and in healthy control players. Cross-sectional study. Research laboratory. Twenty-four male professional volleyball players (12 players with diagnosed IIA and 12 healthy players) recruited from local volleyball teams. sEMG activity of anterior, middle, and posterior deltoid; upper, middle, and lower trapezius; and serratus anterior (SA) was recorded and evaluated during a movement of shoulder abduction in the scapular plane, monitored with an optoelectronic motion capture system. sEMG activity, relationships, and response latencies of the selected muscles were analyzed with analysis of variance models to highlight statistical differences within and between groups. Athletes with IIA demonstrated significant higher deltoid and trapezius muscles activity and lower SA activity compared with the contralateral shoulder and healthy athletes. The shoulder with IIA also showed a higher activity ratio between the upper trapezius and other ST muscles in addition to anticipated activation of the upper trapezius and delayed activation of the SA, with regard to the onset of shoulder movement. This study highlighted altered shoulder muscle activity levels, ST muscles imbalances, and abnormal ST recruitment patterns in the hitting shoulder of professional volleyball players with IIA, secondary to suprascapular nerve neuropathy. Such shoulder girdle muscles' impairments may compromise the optimal scapulohumeral rhythm and function, increasing the risk of acute and overuse shoulder injuries.