Lower Limb Muscle Research Articles

Characteristics of Changes in Contractile Properties of Muscle after Anaerobic Exercise

Tensiomyography (TMG) has been described as an effective method for identifying differences in muscle response to athletic training stimuli. However, there is a lack of studies that evaluated changes in muscle contractile properties in response to anaerobic effort and related these changes to Wingate test parameters in more than one lower limb superficial muscle. The main contribution of this work is to evaluate changes in the contractile properties of muscles in response to anaerobic exercise. In a group of 20 physically active men, the body composition analysis was performed using a Tanita DC-360 device. The anaerobic effort was assessed by a Wingate test (30 s), and the contractile properties of muscles were measured using a TMG S2 device. The TMG parameters were measured in selected superficial muscles of the dominant lower limb. The study also calculated indices of the differences (d) and the size of the effect (r). An anaerobic effort in the form of the Wingate test resulted in greater stiffness (Dm) in the vastus lateralis muscle (p = 0.0365; r = 0.47) and a delayed response to stimulus (Td) in the vastus lateralis (p = 0.0239; r = 0.51) and vastus medialis (p = 0.0031; r = 0.66) muscles. The half relaxation time (Tr) (p = 0.0478; r = 0.44) and sustained contraction time (Ts) (p = 0.0276; r = 0.49) in the rectus femoris muscle were also increased. In contrast, a prolonged stimulus-response time (Td) with a decrease in sustained contraction time (Ts) was observed in the gastrocnemius lateralis (Td: p = 0.0054; r = 0.64 and Ts: p = 0.0012; r = 0.74) and gastrocnemius medialis (Td: p = 0.0229; r = 0.52 and Ts: p = 0.0054; r = 0.64) muscles. A significant decrease in contraction time (Tc) (p = 0.0051; r = 0.63) occurred only in the soleus muscle. In addition, significant correlations were shown between selected changes in contractile properties of muscle and parameters of the Wingate anaerobic test. Anaerobic exercise has a significant effect on changes in skeletal muscle contractility parameters. TMG is an effective method for identifying differences in muscle response to sports training stimuli.

Brisk walking improves motor function and lower limb muscle strength in Chinese women aged 80years and older.

This study investigates the effects of a 12-week brisk walking exercise regimen on motor function improvements in elderly women. Twenty-six elderly women, aged 84.2 ± 3.2years, participated in a 12-week brisk walking exercise program. Fitness assessments and blood biomarker analyses (including CHO, HDLC, LDLC, TC) were conducted pre- and post-intervention. Additionally, targeted metabolomics was employed to measure short-chain fatty acids, amino acids, and vitamin metabolites. The intervention led to significant enhancements in participants' flexibility (p < 0.05), lower limb muscle strength (p < 0.01), and cardiorespiratory endurance (p < 0.01), while muscle mass showed no significant changes. Fifteen significant differential metabolites were identified (VIP > 1.0, FC > 1.2 or < 0.8, and p < 0.05), with arginine, ornithine, aspartic acid, glutamine, phenylalanine, tyrosine, and pantothenic acid playing key roles across seven metabolic pathways. A 12-week brisk walking exercise program significantly enhanced flexibility, lower limb muscle strength, and cardiorespiratory endurance among elderly women. These improvements did not extend to muscle mass or upper limb muscle strength. The observed enhancement in exercise capacity may be attributed to improved regulation of neurotransmitters.

Preliminary comparative study of lower extremity pressure measurements under the conditions using former models and new lithotomy stirrups in rectal cancer surgery

BackgroundThis study aimed to investigate the effect of the use of new lithotomy stirrups-2 on the pressure dispersal on lower limbs, which may lead to the prevention of well-leg compartment syndrome (WLCS) and deep venous thrombosis (DVT), which are the most commonly associated adverse events with laparoscopic and robot-assisted rectal surgery.MethodsA total of 30 healthy participants were included in this study. The pressure (mmHg) applied on various lower limb muscles when using conventional lithotomy stirrups-1 and new type stirrups-2 was recorded in various lithotomy positions; 1) neutral position, 2) Trendelenburg position (15°) with a 0° right inferior tilt, and 3) Trendelenburg position (15°) with a 10° right inferior tilt. Using a special sensor pad named Palm Q®, and the average values were compared between two types of stirrups.ResultsThe use of new lithotomy stirrups-2 significantly reduced the pressure applied on the lower limb muscles in various lithotomy positions compared with the use of lithotomy stirrups-1. The most pressured lower limb muscle when using both lithotomy stirrups was the central soleus muscle, which is the most common site for the development of WLCS and DVT. In addition, when using the conventional lithotomy stirrups-1, the pressure was predominantly applied to the proximal soleus muscle; however, when using lithotomy stirrups-2, the pressure was shifted to the more distal soleus muscle.ConclusionThese results suggest that the new lithotomy stirrups-2 is useful in reducing the pressure load on leg muscles, especially on the proximal to central soleus, and may reduce the incidence of WLCS and DVT after rectal surgery performed in the lithotomy position. Further clinical studies are needed to determine whether the use of lithotomy stirrups-2 prevents these complications in various clinical settings.

Automatic segmentation of lower limb muscles from MR images of post-menopausal women based on deep learning and data augmentation.

Individual muscle segmentation is the process of partitioning medical images into regions representing each muscle. It can be used to isolate spatially structured quantitative muscle characteristics, such as volume, geometry, and the level of fat infiltration. These features are pivotal to measuring the state of muscle functional health and in tracking the response of the body to musculoskeletal and neuromusculoskeletal disorders. The gold standard approach to perform muscle segmentation requires manual processing of large numbers of images and is associated with significant operator repeatability issues and high time requirements. Deep learning-based techniques have been recently suggested to be capable of automating the process, which would catalyse research into the effects of musculoskeletal disorders on the muscular system. In this study, three convolutional neural networks were explored in their capacity to automatically segment twenty-three lower limb muscles from the hips, thigh, and calves from magnetic resonance images. The three neural networks (UNet, Attention UNet, and a novel Spatial Channel UNet) were trained independently with augmented images to segment 6 subjects and were able to segment the muscles with an average Relative Volume Error (RVE) between -8.6% and 2.9%, average Dice Similarity Coefficient (DSC) between 0.70 and 0.84, and average Hausdorff Distance (HD) between 12.2 and 46.5 mm, with performance dependent on both the subject and the network used. The trained convolutional neural networks designed, and data used in this study are openly available for use, either through re-training for other medical images, or application to automatically segment new T1-weighted lower limb magnetic resonance images captured with similar acquisition parameters.

Clinical experience of Tianxiong Granules in treatment of hypertension based on treatment principle of supressing Yang and promoting blood circulation

Hypertension is the most common chronic disease in clinics and has become the most common risk factor for cardiovascular diseases. Because of its high incidence rate, disability rate, and mortality, it has attracted worldwide attention. Despite continuous progress in modern medicine in the treatment of hypertension with new antihypertensive drugs such as Zilebesiran, a nucleic acid drug that acts on microRNA, direct renin inhibitors, and renal sympathetic blockade, the control rate is still not ideal. How to effectively prevent and control hypertension has become one of the urgent clinical challenges to be solved. Traditional Chinese medicine(TCM) has a long record of treating hypertension and has accumulated rich experience, including theoretical understanding, effective single medicine, compound medicine, traditional Chinese patent medicines, and classic famous prescriptions. In TCM, hypertension belongs to the categories of diseases such as dizziness and headache. Previous literature and clinical studies have found that hypertension has key pathogenesis such as fire syndrome, fluid syndrome, deficiency syndrome, and blood stasis syndrome. Among them, the hyperactivity of liver Yang is closely related to blood pressure fluctuations, blood pressure variability, inflammation, and sympathetic activity stimulation. Internal obstruction by blood stasis is closely related to the damage of target organs such as the heart, brain, and kidneys in hypertension. Therefore, the two key pathogenesis of liver yang hyperactivity and internal obstruction by blood stasis run through the entire process of hypertension. Previous studies have found that the effective empirical formula Tianxiong Granules, based on the principles of suppressing Yang and promoting blood circulation, originated from the classic formula Xiongqiong Tianma Pills in Yu Yao Yuan Fang. It is composed of Gastrodiae Rhizoma, Chuanxiong Rhizoma, Puerariae Lobatae Radix, Achyranthis Bidentatae Radix, and Cyathulae Radix and has significant therapeutic effects in the treatment of hypertension. The clinical indications include headache, dizziness, bloating, strong neck, and weak waist and legs. At the same time, it may be accompanied by poor speech, thirst, normal or loose stools, soreness in the waist and legs, lower limb pain, muscle and pulse spasm, menstrual and abdominal pain, dark red tongue, strong pulse strings, or straight and long pulse strings that pass through the mouth of an inch. In the combination rule, it can be used according to the different pathogenesis stages of hypertension patients. In the fire syndrome stage, it is often combined with Tianma Gouteng Decoction and Chaihu Jia Longgu Muli Decoction. In the fluid syndrome stage, it is often combined with Banxia Baizhu Tianma Decoction. In the deficiency syndrome stage, it is often combined with Liuwei Dihuang Pills and Shenqi Pills. In terms of dosage, it is important to focus on the main symptoms and adjust the dosage of key drugs based on blood pressure values. Some drugs can be used in sufficient quantities. By analyzing the compatibility of Tianxiong Granules, clinical application indications, combined formula experience, and dosage application experience, we provide effective treatment methods and more options for TCM to treat hypertension with Yang hyperactivity and blood stasis syndrome.

Spatiotemporal modulation of a common set of muscle synergies during unpredictable and predictable gait perturbations in older adults.

Muscle synergies as functional low-dimensional building blocks of the neuromotor system regulate the activation patterns of muscle groups in a modular structure during locomotion. The purpose of the current study was to explore how older adults organize locomotor muscle synergies to counteract unpredictable and predictable gait perturbations during the perturbed steps and the recovery steps. Sixty-three healthy older adults (71.2±5.2 years) participated in the study. Mediolateral and anteroposterior unpredictable and predictable perturbations during walking were introduced using a treadmill. Muscle synergies were extracted from the electromyographic activity of 13 lower limb muscles using Gaussian non-negative matrix factorization. The four basic synergies responsible for unperturbed walking (weight acceptance, propulsion, early swing and late swing) were preserved in all applied gait perturbations, yet their temporal recruitment and muscle contribution in each synergy were modified (P<0.05). These modifications were observed for up to four recovery steps and were more pronounced (P<0.05) following unpredictable perturbations. The recruitment of the four basic walking synergies in the perturbed and recovery gait cycles indicates a robust neuromotor control of locomotion by using activation patterns of a few and well-known muscle synergies with specific adjustments within the synergies. The selection of pre-existing muscle synergies while adjusting the time of their recruitment during challenging locomotor conditions may improve the effectiveness to deal with perturbations and promote the transfer of adaptation between different kinds of perturbations.

Exploring the relationship between lower limb strength, strength asymmetries, and curvilinear sprint performance: Findings from a pilot study.

Team sports involve various sprinting actions, including curvilinear sprints, yet their neuromuscular factors have been understudied. The aim of this cross-sectional study was to investigate the relationship between lower limb muscle strength, strength asymmetries, linear sprint and curvilinear sprint performance. At two visits 12 male (age: 24.8 ± 4.7 years, height: 1.82 ± 0.06 m, body mass: 80 ± 6.58 kg) and 6 female (age: 20.8 ± 1.33 years, body height: 1.60 ± 0.02 m, body mass: 55.3 ± 2.88 kg) student-athletes completed isometric strength measurements of the knee flexors (KF), knee extensors (KE), hip abductors (HABD), hip adductors (HADD), as well as linear sprint and curvilinear sprint to the right and left. Sprint split times over 30 m (t30) were measured and curvilinear sprint split time deficits (t30deficit) and inter-limb strength asymmetries were calculated. Very large negative correlations were observed between HADD and HABD strength on one side and t30 of curvilinear sprint to the left (r = -0.75 and -0.71; p < 0.001) and right (ρ = -0.81 and -0.70; p < 0.001) on the other. The regression model consisting of HADD, HABD, and KF explained 76% and 67% of the variance in left and right curvilinear sprint t30, respectively. Similarly, 59% of the left curvilinear sprint t30deficit variance was explained by the HABD and KF strength. High inter-limb HABD strength symmetry was related to better left and right curvilinear sprint t30 (r = 0.71 and ρ = 0.75, p < 0.001). These results highlight the pivotal role of hip strength for curvilinear sprint speed, and emphasize the need of symmetrical HABD muscle strength to optimize neuromuscular function during curvilinear sprint.

Lower-Limb Muscle Force is related with Physical Activity in Older Adults Undergone Total Knee Replacement

Lower-Limb Muscle Force is related with Physical Activity in Older Adults Undergone Total Knee Replacement

Leveraging Knowledge Management Techniques for Developing Multimedia Exercise Guides for Elderly Fall Prevention

In this research study, the primary objective was to develop a comprehensive exercise program specifically designed for elderly individuals. The focus was on evaluating various exercise postures and validating their impact on muscle groups. By integrating knowledge management systems with knowledge engineering methodologies, the aim was to optimize the design of exercise postures and promote optimal health outcomes for the elderly. Divided into three distinct experiments, the study employed a systematic approach to acquire, represent, and validate knowledge related to exercise postures for the elderly population. The use of knowledge management systems and engineering methodologies facilitated the design of effective exercise postures tailored to meet the unique needs and capabilities of elderly individuals. Experiment I focused on knowledge acquisition through structured interviews with physical therapists. The acquired knowledge was used to screen and prioritize exercise postures suitable for elderly individuals. Expert recommendations and analysis were employed to select a set of exercise postures. Using a matrix combination approach, 189 possible exercise postures were generated by combining aerobic and dance postures. Through a screening process, 52 postures were selected as suitable for elderly individuals. Experiment II utilized kinesthetic representation techniques to visually represent the 52 selected exercise postures for the elderly. Additionally, frame representation was employed to capture muscle specifications associated with each posture. The representation design was validated by physical exercise experts. In the first step of Experiment III, a total of 52 exercise postures were implemented and evaluated with elderly participants. The implementation and validation process aimed to identify the best and most appropriate postures for the elderly, considering factors such as satisfaction levels, difficulty levels, and safety considerations. Through this rigorous evaluation, the initial selection of 52 postures was narrowed down to a final set of 21 suitable postures. The validation results provided valuable insights into the effectiveness of the exercise postures and their impact on the elderly participants. It ensured that the chosen postures were not only effective in promoting optimal health outcomes but also minimized the risk of injury. The iterative assessment and refinement process contributed to the development of an evidence-based exercise program specifically tailored to the unique needs and capabilities of elderly individuals. For the second step of Experiment III, the effects of the selected exercise postures on different muscle groups were validated. Three physical exercise experts evaluated the impact on upper limb, trunk, and lower limb muscles. Specific muscle groups, such as brachioradialis, deltoid, quadriceps, and hamstring, were found to be strongly focused on during the exercises, while trunk muscles were rated as poor overall. The evaluation involved implementing and evaluating a total of 52 exercise postures with elderly participants. The selection of the final 21 postures was based on the evaluation results and provided insights into satisfaction levels, difficulty levels, and safety considerations for each exercise posture. The validation outcomes showed a high level of agreement among the experts, ranging from 79% to 91%. For conclusion, this research aimed to enhance exercise programs for the elderly by developing more effective methodologies for designing exercise postures. By considering the specific requirements of the elderly population and utilizing knowledge management systems, the study successfully created exercise postures that maximize health benefits and overall well-being. Through the implementation of knowledge engineering methodologies and the utilization of knowledge management systems, the research optimized the design of exercise postures for elderly individuals. The division of the study into three experiments enabled a comprehensive analysis of the acquired knowledge, leading to the development of exercise postures specifically tailored to the needs of the elderly population.

Improving lower limb muscle strength according to number of weeks of core stability exercises in female athletes with and without ACL injury

Improving lower limb muscle strength according to number of weeks of core stability exercises in female athletes with and without ACL injury

A Field Study to Assess Physical Activity Levels During Weekdays Among Students in the First Cycle and its Relationship with Lower Limb Muscle Strength

This study aimed to assess physical activity levels during 3 school days among first cycle students and its relationship with lower limb muscle strength. Twenty-eight students from the Governor of Muscat were participated in this study, (age: 11.8±0.3 years, height: 9.0±148 cm, mass Body: 14.5±34.8 kg, BMI: 5.3±19.2 kg.m-2 To assess physical activity levels, the ActiGraph GT3X device was used for 3 school days during the week (from 8:00 am to 12:00 pm, daily). All participating performed two tests of lower limb muscle strength (CMJ - FCM). Study results showed that the average physical activity levels of students during 3 school days were (455.9± 56.7minutes) and (26.3±6.6 minutes) for both sedentary physical behavior (SPA) and high-intensity physical activity (VPA), respectively. The results also revealed that the level of moderate and vigorous physical activity level (MVPA) during 3 days of school reached (67.9 ±17.01minutes), which is approximately (22.6 minutes per day), meaning that there was a noticeable decrease in the levels of physical activity practiced during school days (3 days). per week for first cycle students. The results also showed that there was no relationship between all physical activity levels (SPA, LPA, MPA, VPA, MVPA) and lower limb muscle strength tests (CMJ - FCM) among the students (0.05&lt;p).

Muscular strength, balance, and functionality in post-COVID-19 patients: An observational case-control protocol

Background: Persistent and systemic impairments have been reported in individuals recovering from COVID-19, including balance and muscle strength dysfunctions. However, the implications for static and dynamic Balance and their potential associations with muscle strength and functional assessments in patients with severe disease during the acute phase remain poorly understood in the existing scientific literature. Objectives: This study evaluates static and dynamic balance, lower limb muscle strength, and physical capacity in post COVID volunteers who experienced severe and critical forms of the disease. Additionally, it seeks to identify potential correlations between functional outcomes and demographic characteristics. Methods: This observational case-control study will enroll individuals who had experienced severe and critical forms of COVID-19 during the acute phase of the illness. Static Balance will be assessed using a Portable Baropodometry and Stabilometry platform, while dynamic Balance will be evaluated through the MiniBest Test. Muscle strength will be measured by Isometric Quadriceps Muscle Strength during contraction of knee extension, flexion, and physical capacity utilizing the 1-minute Sit-to-Stand Test (1MST). Hypothesis: We hypothesize that Long COVID volunteers who endured severe and critical forms of the disease during the acute phase will exhibit: 1)Impaired static and dynamic Balance compared to a control group of individuals without a history of COVID-19, as evidenced by significantly different scores on Baropodometry and Stabilometry assessments, as well as the MiniBest Test. 2)Reduced lower limb muscle strength compared to the control group. 3) Decreased physical capacity as assessed by the 1-minute Sit-to-Stand Test (1MST) when compared to individuals without a history of COVID-19. 4) Possible associations between demographic characteristics (age, gender, and physical activity level) and the observed functional outcomes. We anticipate that these findings will contribute to a better understanding of the long-term effects of severe and critical COVID-19 on Balance, muscle strength, and physical capacity.

Optimization of direct cortical stimulation using tibial versus median nerve sensory mapping during midline brain tumor resection: illustrative case.

During brain tumor resection, neurophysiological mapping and monitoring help surgeons locate, characterize, and functionally assess eloquent brain areas in real time. The selection of mapping and monitoring targets has implications for successful surgery. Here, the authors compare direct cortical stimulation (DCS) as suggested by median nerve (MN) with posterior tibial nerve (PTN) cortical sensory mapping (SM) during mesial lesion resection. Recordings from a 6-contact cortical strip served to generate an MN and a PTN sensory map, which indicated the strip was anterior to the central sulcus. Responses exhibited an amplitude gradient with no phase reversal (PR). DCS, elicited through a stimulus probe or contact(s) of the strip, yielded larger responses from the corresponding sensory mapped limb; that is, PTN SM resulted in larger lower limb muscle responses than those suggested by MN SM. SM of the MN and PTN is effective for localizing eloquent cortical areas wherein the PTN is favored in surgery for mesial cortical tumors. The recorded amplitude of the cortical somatosensory evoked potential is a valuable criterion for defining the optimal location for DCS, despite an absent PR. The pathway at risk dictates the specifics of SM, which subsequently defines the optimal location for DCS.

Is There an Effect of the Trampoline Program for Autism Spectrum Disorder Children in Portugal?

Trampoline-based therapies have demonstrated the potential to enhance motor skills in children with autism by promoting the development of control, stability, and muscle power. This research aimed to investigate the impact of different trampoline therapies on motor abilities competency, lower limb muscle power, and body mass index (BMI) in a group of 25 children with autism (aged 6.9 ± 2.3 years old). Respondents were separated into two groups to participate in the experiment: Group A consisted of six children who underwent a 20-week program, while Group B comprised eight children who received a 32-week program. Additionally, an 11-member control group received no treatment. The Bruininks-Oseretsky Test of Motor Ability-2 otherwise stated (BOT-2), the Standing Long Jump test, and Mass Index of Body (BMI) assessments was administered at three time points: baseline (T1), during the program (T2), and after the program (T3). The results showed that both experimental groups demonstrated significant improvements scores in BOT-2 and lengthy standing jump workout performance after 20 and 32 weeks of trampoline-based therapy, respectively, compared to the control group. However, there were no significant changes in mass index of body before and after the programs in any of the three groups. Based on the results of this study, it can be concluded that engaging in trampoline training for a minimum duration of 20 weeks could potentially serve as an efficacious therapeutic approach to enhance motor skills among children diagnosed with autism spectrum disorder.

Phenotype variability and natural history of X-linked myopathy with excessive autophagy.

X-linked myopathy with excessive autophagy (XMEA) linked to the VMA21 gene leads to autophagy failure with progressive vacuolation and atrophy of skeletal muscles. Current knowledge of this rare disease is limited. Our objective was to define the clinical, radiological, and natural history of XMEA. We conducted a retrospective study collecting clinical, genetic, muscle imaging, and biopsy data of XMEA patients followed in France and reviewed the literature for additional cases. Eighteen males had genetically confirmed XMEA in France, carrying four different VMA21 variants. Mean age at disease onset was 9.4 ± 9.9 (range 1-40) years. In 14/18 patients (77.8%), onset occurred during childhood (< 15years); however in four patients, the disease started in adulthood. Patients had anterior and medial compartment thigh muscle weakness, distal contractures (56.3%), elevated CK levels (1287.9 ± 757.8U/l) and autophagic vacuoles with sarcolemmal features on muscle histopathology. Muscle MRI (n = 10) showed a characteristic pattern of lower limb muscle involvement. In 11 patients, outcome measures were available for an average follow-up period of 10.6 ± 9.8years and six of them show disease progression. Mean change of functional outcomes was 0.5 ± 1.2 points for Brooke and 2.2 ± 2.5 points for Vignos score, 7/16 patients (43.8%) needed a walking aid and 3/16 (18.8%) were wheelchair-bound (median age of 40years old, range 39-48). The variant c.164-7T > G was associated with a later onset of symptoms. Respiratory insufficiency was common (57.1%) but cardiac involvement rare (12.5%). XMEA has variable age of onset, but a characteristic clinical, histopathological, and muscle imaging presentation, guiding the diagnosis. Although slowly, motor disability progresses with time, and relevant genotype-phenotype correlations will help design future clinical trials.

Local Muscle Oxygenation Differences between Lower Limbs according to Muscle Mass in Breath-Hold Divers

Oxidative potential and anaerobic capacity could be influential to the training regimen and performance of breath-hold diving (BHD) athletes. Therefore, this study aimed to determine the differences in local muscle oxygenation between the lower limbs according to the muscle mass percentage in spearfishermen and freedivers. The sample of participants included 21 BHD athletes (13 freedivers; 8 spearfishermen; 4 females). Their chronological age was 35.5 ± 8.6 years, body mass was 79.3 ± 9.1 kg, and height was 182.5 ± 13.0 cm. Participants’ training experience was 10.6 ± 9.5 years. The variables in this study included anthropometric indices, the Wingate anaerobic test, and muscle oxygen dynamics parameters. The results show significant differences for freedivers between the lower limbs (muscle mass percentage, p &lt; 0.00; minimal SmO2%, p = 0.05; and maximal SmO2%, p = 0.04). However, when observing only spearfisherman, there is only one significant difference between the dominant and non-dominant lower limb (percentage of lower limb muscle mass, 85.73 ± 2.42, 85.16 ± 2.40%, respectively; p = 0.02). The results of this study demonstrate that freedivers have significant asymmetries between the lower limbs in muscle oxygenation parameters when observing the lower limb dominance in relation to the percentage of muscle mass. These findings suggest different muscular oxygenation adaptations to the load set upon athletes.

The Lower Limb Muscle Co-Activation Map during Human Locomotion: From Slow Walking to Running.

The central nervous system (CNS) controls movements and regulates joint stiffness with muscle co-activation, but until now, few studies have examined muscle pairs during running. This study aims to investigate differences in lower limb muscle coactivation during gait at different speeds, from walking to running. Nineteen healthy runners walked and ran at speeds ranging from 0.8 km/h to 9.3 km/h. Twelve lower limb muscles' co-activation was calculated using the time-varying multi-muscle co-activation function (TMCf) with global, flexor-extension, and rostro-caudal approaches. Spatiotemporal and kinematic parameters were also measured. We found that TMCf, spatiotemporal, and kinematic parameters were significantly affected by gait speed for all approaches. Significant differences were observed in the main parameters of each co-activation approach and in the spatiotemporal and kinematic parameters at the transition between walking and running. In particular, significant differences were observed in the global co-activation (CIglob, main effect F(1,17) = 641.04, p < 0.001; at the transition p < 0.001), the stride length (main effect F(1,17) = 253.03, p < 0.001; at the transition p < 0.001), the stride frequency (main effect F(1,17) = 714.22, p < 0.001; at the transition p < 0.001) and the Center of Mass displacement in the vertical (CoMy, main effect F(1,17) = 426.2, p < 0.001; at the transition p < 0.001) and medial-lateral (CoMz, main effect F(1,17) = 120.29 p < 0.001; at the transition p < 0.001) directions. Regarding the correlation analysis, the CoMy was positively correlated with a higher CIglob (r = 0.88, p < 0.001) and negatively correlated with Full Width at Half Maximum (FWHMglob, r = -0.83, p < 0.001), whereas the CoMz was positively correlated with the global Center of Activity (CoAglob, r = 0.97, p < 0.001). Positive and negative strong correlations were found between global co-activation parameters and center of mass displacements, as well as some spatiotemporal parameters, regardless of gait speed. Our findings suggest that walking and running have different co-activation patterns and kinematic characteristics, with the whole-limb stiffness exerted more synchronously and stably during running. The co-activation indexes and kinematic parameters could be the result of global co-activation, which is a sensory-control integration process used by the CNS to deal with more demanding and potentially unstable tasks like running.

An alternative EMG normalization method: Heterogeneous recurrence quantification analysis of isometric maximum voluntary contraction movements

This study presents an alternative method of normalizing Surface Electromyography (EMG) signals, which provide valuable insights into the musculoskeletal properties of the human body. Traditional normalization through the peak maximum voluntary contraction (MVC) method may result in variable outcomes due to its dependence on pre-processing steps such as smoothing and window length. To address this issue, the study standardizes the EMG pre-processing steps by using non-linear techniques, namely recurrence quantification analysis (RQA) and heterogeneous RQA (HRQA). RQA, specifically HRQA, functions as EMG feature extractors to explore the nonlinear dynamical system and state space trajectories of chaotic EMG signals. Principal component analysis (PCA) and kernel PCA (KPCA) were further applied to the RQA and HRQA results to obtain data with more information. The results show that the first principal components (PC1 and KPC1) of HRQA have a very strong relationship with peak MVC (ρ > |0.90|, p < 0.001), indicating their potential compared to the traditional EMG normalization technique for lower limb muscle groups. Additionally, the study investigated the dynamic differences among isometric MVC movements in lower limb muscle groups and found that the RQA and HRQA methods indicated a greater separation for detecting these differences compared to peak MVC. This study offers a valuable method for assessing the musculoskeletal characteristics of individuals who may have difficulty with activities like walking or providing maximum force during EMG data collection, such as those suffering from Parkinson's disease or walking disabilities. This enhances our understanding of their musculoskeletal properties.

Physical fitness levels and trends of kindergarteners in Hong Kong during the COVID-19 pandemic

Background/objectivesThe study aimed to examine the physical fitness and activity levels of kindergarteners in Hong Kong during the coronavirus disease 2019 pandemic. MethodsA total of 2052 kindergarteners (48% girls; 32.9% Grade 1, 34% Grade 2, and 33.1% Grade 3) were recruited from July 2020 to November 2021. Participants completed the physical fitness tests, including body composition, flexibility, lower-limb muscle strength, upper-limb muscle strength, lower-limb muscle endurance, and agility. Children's physical activity and overall well-being were examined using parental proxy reports. Parents also reported their physical activity and parental support to children's physical activity engagement, as well as their perception of children's kindergarten physical activity environment. Fitness differences by age and gender were analyzed using one-way ANOVA and ANCOVA measuring effect size with partial eta-squared. Additionally, correlations assessed the relationship between children's fitness and parents' proxy reports. ResultsThe results of the physical fitness tests were higher than those in previous studies conducted by the Physical Fitness Association of Hong Kong in 2015–2018. Gender-based differences were observed in most tests for children aged 4 years and older, with boys showing higher scores in the standing long jump, shot put, and balance tests, while girls had higher scores in the sit-and-reach test. Parents' proxy questionnaire answers indicated that children's continuous jump test performances were significantly related to their frequency of physical activity per week (r = 0.19, p < 0.001), and that children's health was significantly and positively correlated with their fitness level (r = 0.179, p < 0.009). Inadequate school physical activity was associated with poor upper-limb strength (r = 0.078, p < 0.005). Moreover, a high level of parental support for their children's participation in physical activity was correlated with a high level of parental participation in vigorous-intensity physical activities (r = 0.167, p < 0.005). ConclusionThe physical fitness of children in Hong Kong was less affected by the epidemic. Parents' healthy behaviors and support were related to children's participation in PA. Efforts to improve children's physical fitness and motor development should include parent education and physical activity involvement.

Activation of a Rhythmic Lower Limb Movement Pattern during the Use of a Multimodal Brain-Computer Interface: A Case Study of a Clinically Complete Spinal Cord Injury.

Brain-computer interfaces (BCIs) that integrate virtual reality with tactile feedback are increasingly relevant for neurorehabilitation in spinal cord injury (SCI). In our previous case study employing a BCI-based virtual reality neurorehabilitation protocol, a patient with complete T4 SCI experienced reduced pain and emergence of non-spastic lower limb movements after 10 sessions. However, it is still unclear whether these effects can be sustained, enhanced, and replicated, as well as the neural mechanisms that underlie them. The present report outlines the outcomes of extending the previous protocol with 24 more sessions (14 months, in total). Clinical, behavioral, and neurophysiological data were analyzed. The protocol maintained or reduced pain levels, increased self-reported quality of life, and was frequently associated with the appearance of non-spastic lower limb movements when the patient was engaged and not experiencing stressful events. Neural activity analysis revealed that changes in pain were encoded in the theta frequency band by the left frontal electrode F3. Examination of the lower limbs revealed alternating movements resembling a gait pattern. These results suggest that sustained use of this BCI protocol leads to enhanced quality of life, reduced and stable pain levels, and may result in the emergence of rhythmic patterns of lower limb muscle activity reminiscent of gait.