Muscle Groups Research Articles

Lumbo-Pelvic-Hip Complex Endurance and Diaphragm Contractility in Females with Patellofemoral Pain Syndrome: A Case-Control Study

Background: The diaphragm muscle constitutes the internal component of the Lumbo-Pelvic-Hip Complex (LPHC), and its stability is suggested to influence lower limb joint function, particularly the alignment of the patellofemoral joint and the tracking path mechanism of the patella. Objectives: To compare the endurance of the LPHC and diaphragm contractility in females with patellofemoral pain syndrome (PFPS) and a healthy control group. Methods: Fifty-six females, including twenty-eight diagnosed with patellofemoral pain syndrome and twenty-eight healthy females matched as controls (aged 15 - 45), were invited to participate in this case-control study. Endurance scores of trunk extensor, flexor, and lateral flexor muscles, endurance ratios, and the percentage of diaphragm muscle contractility using the ultrasonography method were compared between the two groups. Results: The endurance time of trunk flexors and right and left lateral muscle groups in the PFPS group significantly differed compared to the control group (P < 0.05). Diaphragm contractility in both the right (Mean ± SD: 21.82 ± 3.61; P < 0.001) and left (Mean ± SD: 22.92 ± 2.99; P = 0.007) sides was significantly lower in the PFPS group compared to the control group. Conclusions: Lumbo-Pelvic-Hip Complex stability and diaphragm respiratory function and contractility were impaired in females with PFPS.

Evaluating the Repeatability of Musculoskeletal Modelling Force Outcomes in Gait among Chronic Stroke Survivors: Implications for Contemporary Clinical Practice

This study aims to evaluate the consistency of musculoskeletal modelling outcomes during walking in chronic post-stroke patients, focusing on both affected and unaffected sides. Understanding the specific muscle forces involved is crucial for designing targeted rehabilitation strategies to improve balance and mobility after a stroke. Musculoskeletal modelling provides valuable insights into muscle and joint loading, aiding clinicians in analysing essential biomarkers and enhancing patients’ functional outcomes. However, the repeatability of these modelling outcomes in stroke gait has not been thoroughly explored until now. Twelve post-stroke, hemiparetic survivors were included in the study, which consisted of a gait analysis protocol to capture kinematic and kinetic variables. Two generic full body MSK models—Hamner (Ham) and Rajagopal (Raj)—were used to compute joint angles and muscle forces during walking, with combinations of two muscle force estimation algorithms (Static Optimisation (SO) and Computed Muscle Control (CMC)) and different joint degrees-of-freedoms (DOF). The multiple correlation coefficient (MCCoef) was used to compute repeatability for all forces, grouped based on anatomical function. Regardless of models and DOFs, the mean minimum (0.75) and maximum (0.94) MCCoefs denote moderate-to-excellent repeatability for all muscle groups. The combination of the Ham model and SO provided the most repeatable muscle force estimations of all the muscle groups except for the hip flexors, adductors and internal rotators. DOF configuration did not generally affect muscle force repeatability in the Ham–SO case, although the 311 seemed to relate to the highest values. Lastly, the DOF setting had a significant effect on some muscle groups’ force output, with the highest magnitudes reported for the 321 and 322 of non-paretic and paretic hip adductors and extensors, knee flexors and ankle dorsiflexors and paretic knee flexors. The primary findings of our study can assist users in selecting the most suitable modelling workflow and encourage the widespread adoption of MSK modelling in clinical practice.

Strength of the Uninvolved Limb Following Return to Activity After ACL Injury: Implications for Symmetry as a Marker of Sufficient Strength.

Muscular strength deficits are common after ACL injury. While the Limb Symmetry Index (LSI), using the uninvolved limb as a reference, is widely used, negative strength adaptations may affect both limbs post-injury. It is uncertain how the strength of the uninvolved limb in those with an ACL injury compares to uninjured individuals, making it unclear whether it is appropriate as a benchmark for determining sufficient strength. To compare the strength of key lower extremity muscles of the uninvolved limb in those with history of ACL injury (ACL-I) to the dominant limb in individuals with no history of ACL injury (control). Cross-sectional study. Methods: A total of 5,727 military cadets were examined, with 82 females and 126 males in the ACL-I group and 2,146 females and 3,373 males in the control group. Maximum isometric strength was assessed for six muscle groups measured with a hand-held dynamometer. Separate two-way ANOVAs with limb and sex were performed for each muscle group. Significant main effects for limb were observed with the uninvolved limb in the ACL-I group displaying greater strength compared to the dominant limb in the control group for the quadriceps, hamstrings, and gluteus medius, but effect sizes were small (Cohen's d <0.25). Significant main effects for sex were observed with greater male muscular strength in all six muscle groups with small to large effect sizes (Cohen's d 0.49-1.46). No limb-by-sex interactions were observed. There was no evidence of reduced strength in the uninvolved limb in those with a history of ACL injury compared to the dominant limb in those with no prior ACL injury. This finding suggests that, after clearance to return to activities, the uninvolved limb can be used as a standard for comparison of sufficient strength, including when using the LSI. Level of Evidence: Level 3.

The Duration of Non-Local Muscle Fatigue Effects.

Non-local muscle fatigue (NLMF) refers to a transient decline in the functioning of a non-exercised muscle following the fatigue of a different muscle group. Most studies examining NLMF conducted post-tests immediately after the fatiguing protocols, leaving the duration of these effects uncertain. The aim of this study was to investigate the duration of NLMF (1-, 3-, and 5-minutes). In this randomized crossover study, 17 recreationally trained participants (four females) were tested for the acute effects of unilateral knee extensor (KE) muscle fatigue on the contralateral homologous muscle strength, and activation. Each of the four sessions included testing at either 1-, 3-, or 5-minutes post-test, as well as a control condition for non-dominant KE peak force, instantaneous strength (force produced within the first 100-ms), and vastus lateralis and biceps femoris electromyography (EMG). The dominant KE fatigue intervention protocol involved two sets of 100-seconds maximal voluntary isometric contractions (MVIC) separated by 1-minute of rest. Non-dominant KE MVIC forces showed moderate and small magnitude reductions at 1-min (p < 0.0001, d = 0.72) and 3-min (p = 0.005, d = 0.30) post-test respectively. The KE MVIC instantaneous strength revealed large magnitude, significant reductions between 1-min (p = 0.021, d = 1.33), and 3-min (p = 0.041, d = 1.13) compared with the control. In addition, EMG data revealed large magnitude increases with the 1-minute versus control condition (p = 0.03, d = 1.10). In summary, impairments of the non-exercised leg were apparent up to 3-minutes post-exercise with no significant deficits at 5-minutes. Recovery duration plays a crucial role in the manifestation of NLMF.

Isometric muscle torque in Chilean children and adolescents evaluated by manual maintenance dynamometry: a reliability study

to determine the reliability of hand-held dynamometry to obtain the maximal isometric torque of upper and lower limb muscle groups in Chilean children and adolescents. Crosssectional study. Seventy-two participants aged between 7 and 15 years were selected from a school in Talca. Maximal isometric torque was recorded in 15 muscle groups of upper and lower limbs through hand-held dynamometry. Intra- and inter-rater evaluation was used, applying the intraclass correlation coefficient (ICC) to determine the reliability of the tests and Bland-Altman plots to evaluate concordance. The results demonstrated good to excellent inter-rater reliability (ICC = 0.850.98) and intra-rater reliability (ICC = 0.87-0.98). Only two groups, hip extensors and abductors, showed good inter-rater reliability (ICC = 0.85 and ICC = 0.88, respectively); and one group, the ankle dorsiflexors, showed good intra-rater reliability (ICC = 0.87). 100% of the tests presented at least 95.8% inter- and intra-rater agreement on the Bland-Altman plots. The evaluation of isometric muscle torque using hand-held dynamometry is a reliable procedure for use in different growth periods.

Advanced subject-specific neck musculoskeletal modeling unveils sex differences in muscle moment arm and cervical spine loading

Neck pain and injuries are growing healthcare burdens with women having a higher incidence rate and poorer treatment outcomes than males. A better understanding of sex differences in neck biomechanics, foundational for more targeted, effective prevention or treatment strategies, calls for more advanced subject-specific musculoskeletal modeling. Current neck musculoskeletal models are based on generic anatomy, lack subject specificity beyond anthropometric scaling, and are unable to accurately reproduce neck strengths exhibited in vivo without arbitrary muscle force scaling factors or residual torque actuators. In this work, subject-specific neck musculoskeletal models of 23 individuals (11 male, 12 female) were constructed by integrating multi-modality imaging and biomechanical measurements. Each model simulated maximal voluntary neck static exertions in three postures: neck flexion in a neutral posture, flexion in a 40° extended posture, and extension in a 40° flexed posture. Quantitative model validation showed close agreement between model-predicted muscle activation and EMG measurement. The models unveiled that (1) males have greater moment arms in one flexor muscle group and five extensor muscle groups, (2) females exhibited higher cervical spinal compression per unit exertion force in the flexed posture, and (3) the variability of compression force was much greater in females in all three exertions but most notably in the extension with a flexed “dropped head” position. These insights illuminated a plausible pathway from sex differences in neck biomechanics to sex disparities in the risk and prevalence of neck pain.

Relationship between facet joint osteoarthritis and lumbar paraspinal muscle atrophy: a cross-sectional study.

The paraspinal muscles play an essential role in the stabilization of the lumbar spine. Lumbar paraspinal muscle atrophy has been linked to chronic back pain and degenerative processes within the spinal motion segment. However, the relationship between the different paraspinal muscle groups and facet joint osteoarthritis (FJOA) has not been fully explored. In this cross-sectional study, the authors analyzed adult patients who underwent lumbar spinal surgery between December 2014 and March 2023 for degenerative spinal conditions and had preoperative MRI and CT scans. The fatty infiltration (FI) and functional cross-sectional area (fCSA) of the psoas, erector spinae, and multifidus muscles were assessed on axial T2-weighted MR images at the level of the upper endplate of L4 based on established studies and calculated using custom-made software. Intervertebral disc degeneration at each lumbar level was evaluated using the Pfirrmann grading system. The grades from each level were summed to report the cumulative lumbar Pfirrmann grade. Weishaupt classification (0-3) was used to assess FJOA at all lumbar levels (L1 to S1) on preoperative CT scans. The total lumbar FJOA score was determined by adding the Weishaupt grades of both sides at all 5 levels. Correlation and linear regression analyses were conducted to assess the relationship between FJOA and paraspinal muscle parameters. A total of 225 patients (49.7% female) with a median age of 61 (IQR 54-70) years and a median BMI of 28.3 (IQR 25.1-33.1) kg/m2 were included. After adjustment for age, sex, BMI, and the cumulative lumbar Pfirrmann grade, only multifidus muscle fCSA (estimate -4.69, 95% CI -6.91 to -2.46; p < 0.001) and FI (estimate 0.64, 95% CI 0.33-0.94; p < 0.001) were independently predicted by the total FJOA score. A similar relation was seen with individual Weishaupt grades of each lumbar level after controlling for age, sex, BMI, and the Pfirrmann grade of the corresponding level. Atrophy of the multifidus muscle is significantly associated with FJOA in the lumbar spine. The absence of such correlation for the erector spinae and psoas muscles highlights the unique link between multifidus muscle quality and the degeneration of the spinal motion segment. Further research is necessary to establish the causal link and the clinical implications of these findings.

Local Tetanus Begins with a Neuromuscular Junction Paralysis around the Site of Tetanus Neurotoxin Release due to Cleavage of the Vesicle-Associated Membrane Protein

Local tetanus develops when limited amounts of tetanus neurotoxin (TeNT) are released by Clostridium tetani generated from spores inside a necrotic wound. Within days, a spastic paralysis restricted to the muscles of the affected anatomical area develops. This paralysis follows the retrograde transport of TeNT inside the axons of spinal cord motoneurons and its uptake by inhibitory interneurons with cleavage of VAMP, a synaptic vesicle protein required for neurotransmitter release. Consequently, incontrollable excitation of motoneurons causes contractures of innervated muscles and to local spastic paralysis.Here, the initial events occurring close to the site of TeNT release were investigated in a mouse model of local tetanus. A peripheral flaccid paralysis was found to occur, before or overlapping, the spastic one. At variance from the confined TeNT proteolytic activity at the periphery, central VAMP cleavage can be detected within inhibitory interneurons controlling motor neuron efferents innervating muscle groups distant from the site of TeNT release. These results indicate that TeNT does have a peripheral activity in tetanus and explains why the spastic paralysis observed in local tetanus, although confined to single limbs, generally affects multiple muscles. The initial TeNT neuroparalytic activity can be detected by measuring the compound muscle action potential providing a very early diagnosis and therapy thus preventing the ensuing life-threatening generalized tetanus.

White matter characteristics in children with cerebral palsy prior to selective dorsal rhizotomy: a multicenter diffusion tensor imaging study.

The aims of this study were to 1) assess and quantify white matter (WM) microstructural characteristics derived from diffusion tensor imaging (DTI) in children with cerebral palsy (CP) prior to selective dorsal rhizotomy (SDR), and 2) investigate potential associations between WM diffusion properties and gross motor function and spasticity in children with spastic CP who underwent SDR. This study is a multisite study based on DT images acquired prior to SDR as well as postoperative outcome data. DTI data collected from two sites were harmonized using the ComBat approach to minimize intersite scanner difference. The DTI abnormalities between children with spastic CP and controls were analyzed and correlated with the severity of impaired mobility based on the Gross Motor Function Classification System (GMFCS). The improvement in gross motor function and spasticity after SDR surgery was assessed utilizing the Gross Motor Function Measure-66 (GMFM-66), the Modified Tardieu Scale (MTS), and the modified Ashworth scale (MAS). Alterations in these outcome measures were quantified in association with DTI abnormalities. Significant DTI alterations, including lower fractional anisotropy (FA) in the genu of the corpus callosum (gCC) and higher mean diffusivity (MD) in the gCC and posterior limb of the internal capsule (PLIC), were found in children in the SDR group when compared with the age-matched control group (all p < 0.05). Greater DTI alterations (FA in gCC and MD in gCC and PLIC) were associated with lower mobility levels as determined based on GMFCS level (p < 0.05). The pre- to post-SDR improvement in motor function based on GMFM-66 was statistically significant (p = 0.006 and 0.002 at 6-month and 12-month follow-ups, respectively). The SDR efficacy was also identified as improving spasticity in lower-extremity muscle groups assessed with the MTS and MAS. Partial correlation analysis presented a significant association between pre- to post-SDR MTS alteration and DTI abnormalities. The findings in the present study provided initial quantitative evidence to establish the WM microstructural characteristics in children with spastic CP prior to SDR surgery. The study generated data for the association between baseline DTI characteristics and mobility in children with CP prior to SDR surgery. The study also demonstrated SDR efficacy in improving motor function and spasticity based on the GMFM-66, MTS, and MAS, respectively, in association with DTI data.

Interhemispheric inhibition and gait adaptation associations in people with multiple sclerosis.

Multiple sclerosis is a neurodegenerative disease that damages the myelin sheath within the central nervous system. Axonal demyelination, particularly in the corpus callosum, impacts communication between the brain's hemispheres in persons with multiple sclerosis (PwMS). Changes in interhemispheric communication may impair gait coordination which is modulated by communication across the corpus callosum to excite and inhibit specific muscle groups. To further evaluate the functional role of interhemispheric communication in gait and mobility, this study assessed the ipsilateral silent period (iSP), an indirect marker of interhemispheric inhibition and how it relates to gait adaptation in PwMS. Using transcranial magnetic stimulation (TMS), we assessed interhemispheric inhibition differences between the more affected and less affected hemisphere in the primary motor cortices in 29 PwMS. In addition, these same PwMS underwent a split-belt treadmill walking paradigm, with the faster paced belt moving under their more affected limb. Step length asymmetry (SLA) was the primary outcome measure used to assess gait adaptability during split-belt treadmill walking. We hypothesized that PwMS would exhibit differences in iSP inhibitory metrics between the more affected and less affected hemispheres and that increased interhemispheric inhibition would be associated with greater gait adaptability in PwMS. No statistically significant differences in interhemispheric inhibition or conduction time were found between the more affected and less affected hemisphere. Furthermore, SLA aftereffect was negatively correlated with both average percent depth of silent period (dSP%AVE) (r = -0.40, p = 0.07) and max percent depth of silent period (dSP%MAX) r = -0.40, p = 0.07), indicating that reduced interhemispheric inhibition was associated with greater gait adaptability in PwMS. The lack of differences between the more affected and less affected hemisphere indicates that PwMS have similar interhemispheric inhibitory capacity irrespective of the more affected hemisphere. Additionally, we identified a moderate correlation between reduced interhemispheric inhibition and greater gait adaptability. These findings may indicate that interhemispheric inhibition may in part influence responsiveness to motor adaptation paradigms and the need for further research evaluating the neural mechanisms underlying the relationship between interhemispheric inhibition and motor adaptability.

SEMG as complementary tool for VFSS: A synchronized study in patients with neurogenic oropharyngeal dysphagia

The neurogenic oropharyngeal dysphagia is a prevalent functional swallowing disorder resulting from neurological causes. The conventional diagnosis involves ionizing radiation in Videofluoroscopy Swallowing Studies (VFSS). Surface electromyography (sEMG) offers a non-invasive alternative by recording muscle activity. This research compares bolus passage timing through anatomical structures using VFSS and sEMG-related activation times. Fifty confirmed oropharyngeal dysphagia patients underwent synchronized VFSS and sEMG, evaluating muscle groups during cracker and fluid ingestion. sEMG revealed activation patterns in masseters, suprahyoid, and infrahyoid muscles, occurring before bolus passage through the mandibular line and concluding near the upper esophageal sphincter complex. sEMG identified differences in dysphagia severity (EAT-10 score), age, and diagnosis, contrasting VFSS results. Results indicate potential complementarity between sEMG and VFSS for dysphagia screening, diagnosis, and monitoring.

Patient reported outcomes for anterior and postpectoral prosthesis implantation in single-port laparoscopic breast.

e12601 Background: Breast reconstruction surgery is on the rise and can significantly improve patients' quality of life, and single-port lumpectomy breast reconstruction surgery is becoming more widely used because of its minimally invasive nature, clear field of view, and aesthetics. However, patient-reported outcome studies of anterior versus posterior pectoralis muscle in this procedure are still scarce, and more evidence is needed to provide guidance to clinicians. Methods: Patients who underwent single-port laparoscopic breast reconstruction surgery at Xijing Hospital between March 2021 to December 2023 were included and divided into two groups according to the position of the prosthesis in the pectoral muscle. Patient safety was assessed for surgical safety and tumor safety. Patient Reported Outcome (PRO) was assessed using the BREAST-Q questionnaire. Results: General situation: This study was included in 58 patients with a single -hole laparoscopic breast reconstruction, and 48 patients were included in the post -pectoral muscle group. Tumor safety: 100% recurrence-free survival, 100% disease-free survival, and 100% overall survival in the follow-up patients; there was no significant difference between the anterior and posterior pectoral muscle groups in the single-port cavity. Surgical safety: there was no significant difference between the pre-pectoral and post-pectoral groups in terms of operative time, intraoperative bleeding, nipple areola complex ischemia, periosteal contracture. there were significant differences in postoperative infection, postoperative pain, and flap ischemia between the two groups, with the anterior pectoralis muscle group having a lower rate of postoperative infection, less pain, and a lower rate of flap ischemia. Patient-reported outcomes: The breast satisfaction of the breast reconstruction of the thoracic muscles under the laparoscopy, the higher social psychological health score, and the lower score in chest pain. Conclusions: In our research, the two groups of patients with single -hole laparoscopic breast reconstruction did not have a bad ending, and the single -hole laparoscopic pectoral muscle reconstruction had lower postoperative complications, and had better patient reporting ending Therefore, without considering the economic situation, we recommend the reconstruction of a single -hole laparoscopic pectoral muscles.

Percutaneous thermal radiofrequency rhizotomy of L2-S1 spinal nerve roots in children with cerebral palsy.

This study presents the results of an evaluation of the effectiveness of percutaneous thermal radiofrequency (RF) ablation of spinal nerve roots to reduce spasticity and improve motor function in children with cerebral palsy (CP). A retrospective analysis was conducted on the surgical treatment outcomes of 26 pediatric patients with severe CP (Gross Motor Function Classification System levels IV-V). The assessment protocol included muscle tone assessment using the modified Ashworth scale (MAS), evaluation of passive and active range of motion, gait video recording, and locomotor status evaluation using the Gross Motor Function Measure (GMFM)-88 scale. Thermal RF rhizotomy (ablation of spinal nerve roots) was performed on all patients at the L2-S1 levels at 70°C for 90 seconds. The statistical data analysis was conducted using the t-test and Mann-Whitney U-test. A p value < 0.05 was considered statistically significant. Before the operation, the average level of spasticity in the lower-limb muscles of all patients was 3.0 ± 0.2 according to the MAS. In the early postoperative period, the spasticity level in all examined muscle groups significantly decreased to a mean of 1.14 ± 0.15 (p < 0.001). In the long-term postoperative period, the spasticity level in the examined muscle groups averaged 1.49 ± 0.17 points on the MAS (p < 0.001 compared to baseline, p = 0.0416 compared to the early postoperative period). Despite the marked reduction of spasticity in the lower limbs, no significant change in locomotor status according to the GMFM-88 scale was observed in the selected category of patients. In the long-term period, during the control examination of patients, the GMFM-88 level increased on average by 3.6% ± 1.4% (from 22.2% ± 3.1% to 25.8% ± 3.6%). The findings of this study offer preliminary yet compelling evidence that RF ablation of spinal nerve roots can lead to a significant and enduring decrease in muscle tone among children with severe spastic CP. Further studies and longer-term data of the impact on functionality and quality of life of patients with CP after spinal root RF ablation are needed.

Periscapular Strength Profile Changes in Collegiate Baseball Pitchers Over the Course of a Season.

Repetitive application of high forces to the shoulder and scapular musculature during the pitching motion over the course of a collegiate baseball season may lead to changes in strength and increased fatigue, potentially predisposing pitching athletes to injury. The purpose of this study was to investigate periscapular strength profiles of Division I collegiate baseball players over the course of a season. This study was a retrospective data analysis of 18 Division I baseball pitchers. Isometric scapular plane abduction (scaption), external rotator, internal rotator, middle trapezius, and lower trapezius isometric strength was measured on throwing arm of each subject using a MicroFET 2 handheld dynamometer. Data were collected in a single session at the preseason, midseason, and postseason of the college baseball season, which spanned a five-month period. A repeated measures ANOVA was utilized to determine if there was a significant change in periscapular strength across the baseball season. Over the three time-points, all strength values decreased for each muscle group, with decreases ranging from 3-14%. Changes in scaption strength values were statistically significant (p=0.018, partial eta squared =0.284) with an 8% reduction over the entire season, specifically with a 5% decline from mid-season to post-season. While external rotator, internal rotator, middle trapezius, and lower trapezius strength values all decreased over the course of the season (range 0.02kg to 1.8kg), these differences were not statistically significant. However, the middle trapezius strength value change (1.3kg loss) exceeded the minimal detectible change. Periscapular muscles in baseball pitchers diminish in strength over the course of a collegiate baseball season. Understanding strength changes over the course of a season may influence training and therapeutic interventions. 3b.

Focal selective dorsal rhizotomy and concurrent deformity correction: a combined approach.

Selective dorsal rhizotomy (SDR) is a neurosurgical procedure to reduce spasticity in children with cerebral palsy and spastic diplegia. The authors developed a procedure called focal SDR for children with spasticity predominantly in the L5 or S1 motor distribution, which can be combined with orthopedic correction of fixed soft-tissue or bony deformity. The authors describe in detail the technique of minimally invasive focal SDR and propose selection criteria. The authors conducted a retrospective study of patients who underwent focal SDR at their institution and underwent baseline and 1-year postoperative 3D gait analysis. Modified Ashworth scale (MAS) and Gait Deviation Index (GDI) scores were the primary outcome measures. Ten patients met the study criteria, all with an underlying diagnosis of cerebral palsy. All underwent focal SDR at the unilateral or bilateral S1 level, and 4 additionally underwent focal SDR at the L5 level unilaterally or bilaterally. All but 1 patient underwent concurrent orthopedic surgery. The improvement in spasticity of the plantar flexors, as measured by the MAS score, was 2.2 (p < 0.001). In the patients who underwent L5 focal SDR, there was an improvement in the hamstring MAS score of 1.4 (p = 0.004). The mean improvement in the GDI score following focal SDR was 11 (range -6 to 29, p < 0.001). Focally impairing spasticity in the gastrocsoleus complex and/or hamstrings muscle group in the setting of less functionally impactful proximal tone is extremely common in cerebral palsy. The novel technique of focal SDR, combined with orthopedic intervention, improves spasticity scores and overall gait mechanics. Further investigation is warranted to define the ideal candidacy and outcomes.

Comparison of Electromyographic Characteristics of Volleyball Players in Stop-jumps: An Analysis at Different Speeds

The stop-jump is a crucial skill in volleyball, and analyzing its motion can greatly benefit the training of volleyball players. This paper analyzed 30 players from the volleyball team at Chongqing Normal University. To study the impact of running speed on lower limb muscle activity during stop-jumps, the players were randomly assigned the low-speed running group, the medium-speed running group, and the high-speed running group. Surface electromyography sensors were employed to collect electromyographic signals from the rectus femoris, vastus lateralis, and gastrocnemius muscles of the players during the execution of the stop-jump. The electromyographic indicators were calculated using the surface electromyography system’s built-in program, including the root-mean-square (RMS) electromyographic value and integral electromyographic (IEMG) value. The former represents the effective discharge value of motor units, which depends on the electromyographic amplitude and is related to the number of recruited motor units. The latter represents the discharge capacity of motor units involved in muscle activity per unit of time, reflecting the degree of muscle activation during exercise. Then, statistical analysis was performed on these calculated indicators using SPSS software. It was found that the stop-jump comprised three distinct stages: stop, jump, and flight. Regardless of the stage, the results indicated that the higher the speed of running, the greater the electromyographic indexes of the muscle groups. Additionally, when comparing electromyographic indexes across different stages, it was observed that the index values gradually decreased with the progression of each stage.

Interplay between Pitx2 and Pax7 temporally governs specification of extraocular muscle stem cells.

Gene regulatory networks that act upstream of skeletal muscle fate determinants are distinct in different anatomical locations. Despite recent efforts, a clear understanding of the cascade of events underlying the emergence and maintenance of the stem cell pool in specific muscle groups remains unresolved and debated. Here, we invalidated Pitx2 with multiple Cre-driver mice prenatally, postnatally, and during lineage progression. We showed that this gene becomes progressively dispensable for specification and maintenance of the muscle stem (MuSC) cell pool in extraocular muscles (EOMs) despite being, together with Myf5, a major upstream regulator during early development. Moreover, constitutive inactivation of Pax7 postnatally led to a greater loss of MuSCs in the EOMs compared to the limb. Thus, we propose a relay between Pitx2, Myf5 and Pax7 for EOM stem cell maintenance. We demonstrate also that MuSCs in the EOMs adopt a quiescent state earlier that those in limb muscles and do not spontaneously proliferate in the adult, yet EOMs have a significantly higher content of Pax7+ MuSCs per area pre- and post-natally. Finally, while limb MuSCs proliferate in the mdx mouse model for Duchenne muscular dystrophy, significantly less MuSCs were present in the EOMs of the mdx mouse model compared to controls, and they were not proliferative. Overall, our study provides a comprehensive in vivo characterisation of MuSC heterogeneity along the body axis and brings further insights into the unusual sparing of EOMs during muscular dystrophy.

Preemptive dual therapy for children at risk for infantile-onset spinal muscular atrophy.

Compare efficacy of gene therapy alone (monotherapy) or in combination with an SMN2 augmentation agent (dual therapy) for treatment of children at risk for spinal muscular atrophy type 1. Eighteen newborns with biallelic SMN1 deletions and two SMN2 copies were treated preemptively with monotherapy (n = 11) or dual therapy (n = 7) and followed for a median of 3 years. Primary outcomes were independent sitting and walking. Biomarkers were serial muscle ultrasonography (efficacy) and sensory action potentials (safety). Gene therapy was administered by 7-43 postnatal days; dual therapy with risdiplam (n = 6) or nusinersen (n = 1) was started by 15-39 days. Among 18 children enrolled, 17 sat, 15 walked, and 44% had motor delay (i.e., delay or failure to achieve prespecified milestones). Those on dual therapy sat but did not walk at an earlier age. 91% of muscle ultrasounds conducted within 60 postnatal days were normal but by 3-61 months, 94% showed echogenicity and/or fasciculation of at least one muscle group; these changes were indistinguishable between monotherapy and dual therapy cohorts. Five children with three SMN2 copies were treated with monotherapy in parallel: all sat and walked on time and had normal muscle sonograms at all time points. No child on dual therapy experienced treatment-associated adverse events. All 11 participants who completed sensory testing (including six on dual therapy) had intact sural sensory responses. Preemptive dual therapy is well tolerated and may provide modest benefit for children at risk for severe spinal muscular atrophy but does not prevent widespread degenerative changes.

Comparison of resistance training using barbell half squats and trap bar deadlifts on maximal strength, power performance, and lean mass in recreationally active females: an eight-week randomised trial

BackgroundThe aim of this study was to investigate the effect of high load resistance training using barbell half squats compared with trap bar deadlifts on maximal strength, power performance, and lean mass in recreationally active females.MethodsTwenty-two recreationally active female participants (age: 26.9 ± 7.7 yrs.; height: 166.0 ± 5.1 cm; weight: 68.6 ± 9.9 kg) were randomly assigned to either a barbell half squat group (SG: n = 10) or trap bar deadlift group (DG: n = 12). Training consisted of twice-weekly sessions for eight weeks. Both groups completed one-repetition maximum (1RM) testing for both barbell half squat and trap bar deadlift groups. Countermovement jump (CMJ) and sprint performance were also assessed. Total body (TBLM) and leg lean mass (LLM) were measured with dual-energy x-ray absorptiometry. Between-group differences were analysed using analysis of covariance.ResultsSG tended to improve 1RM half squat (21.0 ± 11.5 kg vs. 13.1 ± 7.5 kg) more than DG (mean difference (MD): 8.0 kg, 95% CI: -0.36 – 16.3 kg). A similar pattern in favour of DG (18.4 ± 11.2 vs. 11.7 ± 8.1 kg) compared to SG was observed (MD: 6.5 kg, 95% CI: -2.5 – 15.6 kg). No between-group differences for sprint, jump or lean body mass changes was observed. For groups combined, the following changes in CMJ (2.0 ± 2.4 cm), 5-m sprint (-0.020 ± 0.039 s), 15-m sprint (-0.055 ± 0.230 s), TBLM (0.84 ± 1.12 kg), and LLM (0.27 ± 0.59 kg) was observed.ConclusionsAn exercise intervention consisting of half squats or trap bar deadlift were associated with improved muscle strength, power, and lean mass. Our findings suggests that in recreationally active females, exercise selection is less of a concern provided that heavy loads are applied, and relevant muscle groups are targeted.

Biomechanics‐based study of muscle activation under different driving conditions for Chinese percentiles

AbstractIn this paper, we determined the adjustment levels of the human–machine layout under the preferred driving posture for individuals with different body sizes. We also comparatively analyzed the maximum activation levels of various muscles under straight‐line driving and steering conditions. To increase the accuracy of the results, AnyBody biomechanics software was used to establish a human skeletal muscle mechanics model, which we analyzed for consistency with rig test results. The results showed that people with larger body sizes preferred a driving position with the seat reclined back. Steered driving was associated with a significant (p &lt; .05) increase in the maximum activation of the wrist extensors, serratus anterior, deltoid, and triceps brachii, which are the main force‐generating muscle groups for steered driving, compared with straight driving. Moreover, the measured and simulated results of maximum muscle activation were relatively consistent, with the error between them within a 15% margin. In summary, this study explored the relationship between different driving conditions and preferred driving postures from a biomechanical perspective. A combined experimental and simulation approach was adopted to ensure the reliability of the findings. The insights from this study can inform ergonomic considerations for the comfort and health of Chinese drivers with varying physical characteristics.