Limb Muscles Research Articles

Quantification of gait characteristics and muscle activation in patients with chronic ankle instability during walking on sand: A randomized crossover trial.

Limited evidence exists regarding the movement control patterns of individuals with chronic ankle instability (CAI) during sand walking. This study aimed to analyze gait characteristics and muscle activation in patients with CAI while walking on sand. This study recruited 30 participants, including 15 patients with CAI and 15 healthy controls. Patients with CAI were selected based on having experienced at least a lateral ankle sprain within 12 months before recruitment. They also had to scoring ≤ 27 on the Cumberland ankle instability tool. This study was conducted using a randomized crossover trial. All participants were asked to walk three times each at their natural speed on both sand and paving blocks for a distance of 50m. There was at least a week between each trial. The lower limb gait kinematics, spatiotemporal, and muscle activity parameters while walking on sand and paving blocks were compared between both groups. Significant differences in knee angle were observed between 60.83% and 75.34% of the gait cycle during walking on sand in the patients with CAI. Regarding spatiotemporal parameters, cadence (P = .001) and stride length (P = .049) showed significant differences as the main effect. In the CAI group, the recruitment threshold for the peroneus longus muscle was significantly lower during walking on sand than on paving blocks (P < .001). In contrast, the motor unit action potential (MUAP) was significantly higher (P < .001). For the tibialis anterior muscle, the recruitment threshold and number of motor units were significantly lower during walking on sand than on paving blocks (P = .006 and P = .003, respectively), and the MUAP was significantly higher (P < .001). During walking on sand, patients with CAI exhibited increased knee flexion angle, stride length, and MUAP, along with decreased cadence and recruitment thresholds. These results suggest that sand can influence gait characteristics and muscle activation in patients with CAI. Our findings indicate that gait characteristics and muscle activation changes in patients with CAI could potentially benefit CAI rehabilitation.

Advances in pathogenic mechanisms and pulmonary rehabilitation strategies for skeletal muscle dysfunction in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a complex heterogeneous chronic respiratory disease and third leading cause of death worldwide. In addition to damage to the respiratory system, COPD has significant extra-pulmonary effects, of which skeletal muscle dysfunction is one of the most prominent. Skeletal muscle dysfunction in COPD can manifest as impaired muscle strength, loss of muscle mass, or decreased endurance, etc. Possible pathogenic mechanisms include abnormal neuro-muscular stimulation, dysregulated protein synthesis, hypoxia, inflammation, oxidative stress, mitochondrial dysfunction, impaired regenerative capacity, etc. Pulmonary rehabilitation (PR) can improve limb muscle function, exercise tolerance and quality of life of COPD patients. Exercise training is usually the main component of any PR program. Currently, PR is the main intervention for skeletal muscle dysfunction in COPD and could be executed in PR center, at home, or in the community using state-of-the-art technology. In this review, we summarized recent advances in pathogenic mechanisms and pulmonary rehabilitation strategies for skeletal muscle dysfunction in COPD, in particular exercise training protocols, respiratory support and feedback in PR, and so on.

The effects of dynamic stretching performed before and between the sets of exercises on vertical jump performance

The purpose of this study was to investigate the effects of dynamic stretching (DS) performed before and between the sets of exercises on vertical jump performance. Twelve healthy adult males performed DS on their lower limb muscles, with 10 repetitions on each side before and between four sets of three repetitions of vertical jumps. Vertical jump height was measured. Additionally, the percent change in jump height for each set was determined based on the baseline score from set 1. Heart rate was also measured at rest, before exercise, and before each set of vertical jumps. Vertical jump height was significantly higher in the latter half of the sets (p &lt; .05) compared to the condition in which DS was only performed before exercise and to the control condition in which the participants were refrained from performing DS throughout. In addition, when DS was only performed before exercise, vertical jump height was significantly lower in set 4 compared to set 1 (p = .001). These findings suggest that DS performed between sets, in addition to performing before the exercise, produces a higher power output in vertical jump performance in the latter half of multiple sets.

Applying both the 30-s and the 5-repetition sit-to-stand tests captures dissimilar groups and abroader spectrum of physical abilities inmobility-limited older individuals: results from the BIOFRAIL study.

We aimed to assess differences among older patients demonstrating low STS performance in the 30s-STS and/or the5r-STS. 30s-STS and 5r-STS wereused to assess lower limb muscle strength and function in older adults. Analysis involved 376 patients (≥ 65years) from a geriatric outpatient clinic for fall assessment. The mean age of patients was 79.8 (± 6.1) years (67% female). In total, 40.6% had low STS performance with 9.3% presenting only low 30s-STS, 9.8% only low 5r-STS, and 21.5% low STS performance in both tests. Patients with low STS performance in both tests had lower gait speed, were more often frail, and had more prior falls compared to patients with low STS performance in one test only. The two STS tests are not interchangeable, and the use of both STS tests capture a wider range of physical abilities in mobility-limited older adults. NCT05795556.

The impact of eccentric muscle contractions on peripheral nerve integrity.

Besides muscle damage, eccentric contractions also impose significant mechanical loads on peripheral nerves. However, the impact of eccentric contractions on peripheral nerve properties remains unclear. We aimed to reveal the immediate (i.e., <2 h and short-term (i.e., <10 days) effects of eccentric contractions on functional, structural, morphological, physiological and biomechanical properties of peripheral nerves. Four electronic databases (PubMed, Science Direct, PEDro and Cochrane) were searched for animal and human studies which evaluated the immediate and/or short-term impact of eccentric contractions of upper or lower limb muscles on outcomes related functional, structural, morphological, physiological and biomechanical properties of peripheral nerves. From a total of 2415 articles, two human and two animal studies met the selection criteria. Several signs of nerve damage following eccentric exercises were observed, such as reductions in myelin sheath thickness, nerve fibre diameter, sensory and motor nerve conduction velocity, and protein zero levels, alongside increased levels of macrophage-related protein and tropomyosin receptor kinase C. No significant changes were identified in growth-associated protein 43. It is worth noting that some variables exhibited differences in their time course between human and animal studies. Animal studies revealed that the effects were more pronounced when eccentric contractions were performed at higher velocities. Current evidence is suggestive that eccentric contractions has the potential to alter the peripheral nerves structural, morphological, functional and physiological properties, which are indicative of nerve damage. CRD42021285767.

An adult myogenic cell line of the Japanese fire-bellied newt Cynops pyrrhogaster

Adult myogenic cell lines are useful to study muscle development, repair and regeneration. In newts, which are known for their high regenerative capacity, myogenic cell lines have not been established in species other than the Eastern newt Notophthalmus viridescens. In this study, we established another myogenic cell line, named CpM01, from the skeletal muscle of the forearm of the adult Japanese fire-bellied newt Cynops pyrrhogaster. CpM01 maintained high proliferative ability even after numerous passages, and could be induced to differentiate into myotubes by changing the culture medium. CpM01 expressed myogenic regulatory factors (MRFs) such as Myf5, MRF4 and myogenin. Changes in the immunorectivities of MRFs during differentiation of CpM01 into myotubes were consistent with those during new muscle generation in limb regeneration. In newts, myogenic cells have two origins, muscle fibers or satellite cells. CpM01 expressed Pax7, suggesting the origin might be satellite cells. scRNA-seq analysis deeply characterized CpM01 and demonstrated that the expression patterns of myogenic genes (Pax3, Pax7, myocyte-specific enhancer factor 2 A, and genes encoding MRFs) in CpM01 are related to progress of the cell cycle. CpM01 can be a useful tool for future studies of limb muscle regeneration in adult newts.

SIX transcription factors are necessary for the activation of DUX4 expression in facioscapulohumeral muscular dystrophy

BackgroundFacioscapulohumeral muscular dystrophy (FSHD) is a common and progressive muscle wasting disease that is characterized by muscle weakness often first noticed in the face, the shoulder girdle and upper arms before progressing to the lower limb muscles. FSHD is caused by the misexpression of the Double Homeobox 4 (DUX4) transcription factor in skeletal muscle. While epigenetic derepression of D4Z4 macrosatellite repeats underlies DUX4 misexpression, our understanding of the complex transcriptional activation of DUX4 is incomplete.MethodsTo identify potential DUX4-regulatory factors, we used small interfering RNAs (siRNAs) to knockdown SIX family transcription factors (SIX1, 2, 4, 5) in patient-derived FSHD1 and FSHD2 myoblasts that were differentiated to form multinucleated myotubes. Quantitative real-time polymerase chain reaction was used to measure changes in DUX4 mRNA, DUX4 target gene expression and myogenic markers. Staining for SIX1 and SIX2 with specific antibodies was performed in FSHD myoblasts and myotubes. To assess reciprocal effects of DUX4 on SIX1, 2, and 4 expression, we utilized a doxycycline-inducible DUX4 myoblast cell line.ResultWe show that SIX1, 2 and 4 transcription factors, regulators of embryonic development, muscle differentiation, regeneration and homeostasis, are necessary for myogenic differentiation-dependent DUX4 expression in FSHD muscle cells. Using siRNA, we demonstrate SIX1, SIX2, and SIX4 to be critical factors involved in the induction of DUX4 transcription in differentiating FSHD myotubes in vitro. siRNA dual knockdown of SIX1 and SIX2 resulted in a ~ 98% decrease of DUX4 and DUX4 target genes, suggesting that SIX1 and SIX2 are the most critical in promoting DUX4 expression. Importantly, we show that DUX4 downregulates SIX RNA levels, suggesting negative feedback regulation.ConclusionsIn this study, we identified a family of developmental regulators that promote aberrant DUX4 expression in FSHD1 and FSHD2 differentiating muscle cells. Our findings highlight the critical involvement of SIX transcription factors (SIX1, 2, 4) in the pathogenesis of FSHD by serving as necessary factors that function in the promotion of DUX4 expression following epigenetic derepression of the D4Z4 repeats.

Epidural electrical stimulation combined with photobiomodulation restores hindlimb motor function in rats with thoracic spinal cord injury.

Epidural electrical stimulation (EES) could restore motor function of paralyzed limbs of patients with spinal cord injury (SCI). However, its invasiveness limits its application in early stage of injury. Photobiomodulation (PBM) utilizes infrared light for percutaneous irradiation of the spinal cord to protect nerve tissue, delay muscle atrophy, and can be applied in early stage of SCI due to its non-invasiveness. This study tested the effect of the combination of EES and PBM on promoting motor function recovery in SCI rats. Severe contusion was induced at the T9 spinal segment in female rats, EES (applied to the L2 and S1 spinal cord segments) with treadmill training was conducted one week after the injury, and PBM percutaneous irradiation started at the injured segment on the day of surgery. In the third week post-injury, electromyographic and gait performance during training were recorded. Besides, the muscles of the hind limbs and the spinal cord on the caudal side of the injured segment were extracted. The results demonstrate that compared to the EES- or PBM-only group, this combined therapy led to several indicators returning to intact levels, including behavioral and electrophysiological, the gait patterns was also closer to intact rats. Additionally, the combined treatment group showed minimal muscle atrophy and maximal preservation of the injured spinal cord on the caudal side, with this histological improvement correlated with motor function recovery. Taken together, our results showed that this combined therapy was a more effective treatment for improving motor dysfunction after SCI which could protect the damaged spinal cord and promote the recovery of motor function in rats with SCI.

Efficacy of Blood Flow Restriction Exercise for Improving Lower Limb Muscle Strength and Function in Chronic Spinal Cord Injury: A Randomized Controlled Trial.

The objective of the present study was to evaluate the efficacy of low-load (LL) blood flow restriction exercise (BFRE) for improving lower limb muscle strength, muscle thickness and physical function in individuals with spinal cord injury (SCI). In a randomized sham-controlled trial, 21 participants (age ≥ 18 years, SCI duration ≥ 1 year, knee extensor strength grade 2-4, ASIA A-D) were randomized to either 45-min LL-BFRE (n = 11) or sham BFRE (n = 10) twice/week for 8 weeks. The exercise protocol consisted of four sets (30 × 15 × 15 × 15 repetitions) of unilateral seated leg extensions and leg curls at 30%-40% of 1RM performed with pneumatic cuffs applied proximally on the trained limb and inflated to 40% of total arterial occlusion pressure (BFRE) or non-inflated (sham exercise). Maximal voluntary isometric quadriceps and hamstring muscle strength, quadriceps muscle thickness, thigh circumference, and physical function were assessed at baseline, after 4 and 8 weeks of training and at 4-week follow-up. No significant between-group differences were found between BFRE and sham exercise in quadriceps or hamstring muscle strength, 10-m walking test, timed up & go, 6-min walking test or the spinal cord independence measure. In contrast, a significant between-group difference favoring BFRE was present for muscle thickness and thigh circumference from baseline to 4-week follow-up (0.76 cm (95% CI: 0.32; 1.20, p = 0.002) and 2.42 cm (0.05; 4.79, p = 0.05), respectively). In conclusion, there was no significant difference in the effect of LL-BFRE and sham exercise on muscle strength and physical function in individuals with SCI. However, significant increases in muscle thickness and thigh circumference were observed in favor of BFRE. Trial Registration: ClinicalTrials.gov identifier: NCT03690700.

Association between muscle strength and echogenicity using greyscale ultrasound software: a diagnostic accuracy study in kidney transplant candidates.

Advanced chronic kidney disease disrupts the delicate equilibrium between protein anabolism and catabolism, leading to alterations in muscle quantity, quality, and function. Musculoskeletal ultrasound emerges as a promising assessment tool due to its widespread availability and high reliability. To evaluate the efficacy of rectus femoris (RF) echogenicity, measured using greyscale software, in identifying diminished muscle quality and strength in candidates for kidney transplant. Post-hoc diagnostic accuracy study. Outpatients in a multimodal prehabilitation program pre kidney transplantation (KT). Patients on the waiting list for KT. Sensitivity, specificity, likelihood ratios and area under the curve (AUC) for diagnostic efficacy of echogenicity (index test) assessed with the ImageJ software greyscale as a potential marker of quadriceps muscle weakness (reference test) were calculated. Muscle weakness was considered as maximal voluntary isometric contraction of the quadriceps (Q-MVIC) <40% of body weight. Other variables included body composition parameters derived from multifrequency electrical bioimpedance, upper limb muscle strength (handgrip), and RF thickness assessed by ultrasound. Chi-square, t-Student, Pearson correlation coefficients (r), bivariate and multivariate logistic regression models. Statistical significance level ≤0.05. Of 112 patients (mean age: 63.6, 76% male), 72 (63.7%) exhibited quadriceps weakness, while 80 (70.8%) had some degree of overhydration (extracellular water/total body water ratio >0.390). The echogenicity cut-off point of highest concordance with muscle weakness was 70, boasting a sensitivity of 83%, specificity of 57%, and AUC of 0.671 (CI 95% 0.570-0.772 [P=0.003]). Echogenicity >70 was associated with a 3.4-fold higher risk of muscle weakness (crude OR = 3.4 [CI95% 1.4 to 8.0]), which persisted after adjusting for age, height, weight and RF thickness. The RF echogenicity exhibits fair validity in identifying muscle weakness among candidates for KT. However, it cannot be endorsed as a standalone diagnostic tool in this population. Early identification of muscle weakness would advance efforts to mitigate morbidity and mortality through targeted measures.

Comprehensive RNA-seq Analysis Identifies Network Hub Genes and Biomarkers Differentiating Desmoid-type Fibromatosis from Reactive Fibrosis

Desmoid-type fibromatosis (DTF) is a benign but locally aggressive neoplasm characterized by the persistent fibroblast activation, unlike reactive fibrosis (RF), where fibroblast activation is transient. Although the Wnt/β-catenin signaling pathway is known to play a role in DTF pathogenesis, the specific genetic drivers contributing to this abnormal fibroblast activation are not fully understood.To identify additional driver genes that underlie the persistent activation of fibroblasts in DTF, we conducted a comparative transcriptome analysis between 29 DTF and 14 RF tissue samples, identifying 4,267 differentially expressed genes (DEGs) specific to DTF. These DTF-specific DEGs were significantly associated with pathways involved in embryonic limb morphogenesis and muscle contraction, whereas RF-specific DEGs were linked to immune response and apoptosis.Using weighted gene co-expression network analysis (WGCNA) to further elucidate the key regulatory circuits associated with the persistent activation of DTF fibroblasts, we identified a highly DTF-specific gene module comprising 120 genes. This module was also significantly enriched in other fibro-proliferative conditions showing the persistent fibroblasts activation, such as keloid disease and idiopathic pulmonary fibrosis. Subsequent analyses identified seven driver transcription factors (ZNF536, IRX5, TWIST2, NKD2, PAX9, SHOX2, and SALL4) within this DTF-specific module that may contribute to the sustained activation of DTF fibroblasts.We further assessed the utility of five key genes from this module (TWIST2, LRRC15, CTHRC1, SHOX2, and SALL4) as potential biomarkers to distinguish DTF from RF using immunohistochemistry. All markers demonstrated excellent diagnostic performance, with TWIST2 showing exceptionally high sensitivity and specificity, surpassing β-catenin, the current standard biomarker for DTF.In conclusion, our study identifies gene modules and driver transcription factors that are highly specific to DTF, offering new insights into the genetic underpinnings of abnormal fibroblast activation in DTF. We also propose novel biomarkers that could improve the diagnostic accuracy and clinical management of DTF.

Predictors of Quality of Life among Older Residents in Rural and Urban Areas in Indonesia: An Approach Using the International Classification of Functioning, Disability, and Health.

The International Classification of Functioning, Disability, and Health (ICF) model provides a comprehensive framework for understanding health and quality of life (QoL) in older adults in both rural and urban settings, each presenting unique advantages and challenges. This study aimed to explore the relationship between factors based on the ICF model and QoL among older residents of these areas. A cross-sectional study was conducted, involving 286 older adults aged 60 years or older from rural and urban areas of Surakarta, Central Java, Indonesia. The WHOQoL-BREF was utilized to assess QoL. The co-factors included personal factors, impairments, and activity limitations. Multiple linear regression analysis indicated that lower limb muscle strength was the most significant factor associated with QoL in older adults in rural areas (B=0.681, standard error [SE]=0.301, p=0.026), followed by static balance (B=0.085, SE=0.034, p=0.014). In urban areas, gender emerged as the most significant factor influencing QoL (B=-13.643, SE=2.499, p<0.001), followed by hemoglobin level (B=-1.847, SE=0.760, p=0.017), age (B=-0.935, SE=0.246, p<0.001), and cognitive function (B=0.493, SE=0.179, p=0.007). Efforts to improve QoL for older adults in rural areas should focus on enhance physical performance through exercise. In urban areas, the maintenance of QoL is influenced by personal factors. It is crucial to address physical performance through exercise to enhance QoL in rural settings. Meanwhile, focusing on mental health, financial security, and social connections is recommended to improve QoL for older adults in urban areas.

Analysis of anticipatory and compensatory postural adjustment in women of different age groups using surface electromyography

Postural balance is crucial for daily activities, relying on the coordination of sensory systems. Balance impairment, common in the elderly, is a leading cause of mortality in this population. To analyze balance, methods like postural adjustment analysis using electromyography (EMG) have been developed. With age, women tend to experience reduced mobility and greater muscle loss compared to men. However, few studies have focused on postural adjustments in women of different ages using EMG of the lower limbs during laterolateral and anteroposterior movements. This gap could reveal a decrease in muscle activation time with aging, as activation time is vital for postural adjustments. This study aimed to analyze muscle activation times in women of different ages during postural adjustments. Thirty women were divided into two groups: young and older women. A controlled biaxial force platform was used for static and dynamic balance tests while recording lower limb muscle activity using EMG. Data analysis focused on identifying muscle activation points and analyzing postural adjustment times. Results showed significant differences in muscle activation times between the two groups across various muscles and platform tilt conditions. Younger women had longer muscle activation times than older women, particularly during laterolateral platform inclinations. In anteroposterior movements, older women exhibited longer activation times compared to their laterolateral performance, with fewer differences between the groups. Overall, older women had shorter muscle activation times than younger women, suggesting a potential indicator of imbalance and increased fall risk.

Lower limb muscle activity during neurointerface control: neurointerface based on motor imagery of walking

The question of the activity of muscles that provide the realization of imaginary movement is essential in the rehabilitation of motor disorders using neurointerfaces. The literature data on this issue are contradictory. The paper analyzes the EMG activity of the shin and thigh muscles of 40 healthy volunteers when working with a neurointerface based on kinesthetic motor imagery of walking in place and supplemented with the «Biokin» robotic limb movement device (mechanotherapy), activated in case of successful motor imagery. It is shown that working with a neurointerface, on average for subjects, leads to an increase in muscle activity when motor imagery of walking compared to rest, and activation of the mechanical training device (AM) further increases muscle activity, with its effect being more pronounced in the muscles of the leg from which motor imagery of walking begins. The nature of muscle reactions to the task of motor imagery of walking is individual. AM when working with a neurointerface, the number of subjects with pronounced EMG activity increases, as does the number of significant correlations between the activity of the muscles of the lower limbs. Thus, the use of neurointerfaces based on motor imagery of walking and the addition of AM as feedback allows activating the muscles of the lower extremities, which is important in clinical practice in the rehabilitation of movements.

Influence of Body Composition and Muscle Power Performance on Multiple Frequency Speed of Kick Test in Taekwondo Athletes

The Multiple Frequency Speed of Kick Test (FSKTmult) is used to investigate which characteristics are necessary for, contribute to, or limit the ability to repeat high-intensity intermittent efforts in taekwondo. This cross-sectional study investigated the relationship between anthropometric and body composition characteristics, muscle power performance, and sport-specific anaerobic performance. Nineteen black belt taekwondo athletes (mean ± SD age: 17.2 ± 2.4 years) volunteered to participate. Anthropometric and body composition characteristics (i.e., body height (BH), body mass (BM), fat mass (FM), body fat (BF%), and muscle mass (MM)) and physical performance (squat jump (SJ), countermovement jump (CMJ) tests, and FSKTmult) were assessed. Data were analyzed with correlation coefficients and simple linear regression. The statistical significance was set at p &lt; 0.05. The total number of kicks in FSKTmult (FSKTtotal) was significantly and positively correlated with MM (r = 0.521, R2 = 0.27, p &lt; 0.05) and negatively with BF% (r = −0.499, R2 = 0.25, p &lt; 0.05). The FSKTtotal was significantly and positively correlated with SJ (r = 0.520, R2 = 0.27, p &lt; 0.05) and CMJ (r = 0.508, R2 = 0.26, p &lt; 0.05) performance. Body composition optimization, with appropriate physical training and dietary planning, is relevant in taekwondo as the improvement in the ability to repeat high-intensity intermittent efforts depends on MM, and its worsening on BF%. Lower limb muscle power positively influences the ability to repeat high-intensity intermittent efforts. Therefore, training programs should emphasize ballistic and plyometric exercises.

Successful mobility in a wheelchair and the health status of people with paraplegia

Introduction. Possession of a wheelchair allows disabled people with paraplegia to compensate for mobility limitations. In order to build the rehabilitation process, it is important to know what factors hinder and what factors facilitate the development of a wheelchair. Aim. To determine functional independence, quality of life and secondary health conditions in persons with lower paraplegia and to assess their relationships with the degree of difficulty when moving around in a wheelchair. Materials and methods. We examined 396 patients with spinal cord injury (SCI) and lower paraplegia who used a wheelchair. The level of independence of the patients was determined using Functional Independence Measure (FIM) and Spinal Cord Independence Measure (SCIM III), quality of life was assessed using the SF-36 questionnaire, secondary health conditions were determined using the SCI SCS scale and the presence of problems moving around in the wheelchair was assessed using category d465 «moving around using equipment» of the International Classification of Functioning, Disability and Health. Results. Half of the examined patients with SCI had a sufficiently high level of independence when performing daily activities. 43.5 % of the patients showed either moderate, severe or absolute problems moving around in the wheelchair and 65.4 % demonstrated the presence of more than three secondary health conditions. We found negative correlations between the degree of difficulty experienced by the patients when moving around in the wheelchair and the levels of independence in daily life and the indicators of quality of life such as vitality, social functioning and mental health. In binary logistic regression it was ascertained that the significant independent factors associated with difficulty when using the wheelchair were spasticity, contractures of the muscles of the lower limb and circulatory disorders. Conclusion. The success in using the wheelchair is limited by spasticity, contractures of the muscles of the lower limb and circulatory disorders.

Myeloid Drp1 deficiency limits revascularization in ischemic muscles via inflammatory macrophage polarization and metabolic reprograming.

Macrophage plays a crucial role in promoting perfusion recovery and revascularization after ischemia through anti-inflammatory polarization, a process essential for the treatment of peripheral arterial disease (PAD). Mitochondrial dynamics, particularly regulated by the fission protein DRP1, are closely linked to macrophage metabolism and inflammation. However, the role of DRP1 in reparative neovascularization remains unexplored. Here we show that DRP1 expression was increased in F4/80+ macrophages within ischemic muscle at day 3 after hindlimb ischemia (HLI), an animal model of PAD. Mice lacking Drp1 in myeloid cells exhibited impaired limb perfusion recovery, angiogenesis and muscle regeneration post-HLI. These effects were associated with increased pro-inflammatory M1-like macrophages, p-NFkB and TNFα, and reduced anti-inflammatory M2-like macrophages and p-AMPK in ischemic muscle of myeloid Drp1-/- mice. In vitro, Drp1-deficient macrophages under hypoxia serum starvation (HSS), an in vitro PAD model, demonstrated enhanced glycolysis via reducing p-AMPK as well as mitochondrial dysfunction, and excessive mitochondrial ROS production, resulting in increased pro-inflammatory M1-gene and reduced anti-inflammatory M2-gene expression. Conditioned media from HSS-treated Drp1-/- macrophages exhibited increased pro-inflammatory cytokine secretion, leading to suppressed angiogenesis in endothelial cells. Thus, macrophage DRP1 deficiency under ischemia drives pro-inflammatory metabolic reprogramming and macrophage polarization, limiting revascularization in experimental PAD.

Effect of blood flow restriction training on insulin resistance in men with metabolic syndrome: a randomized controlled trial

Introduction. Metabolic syndrome is defined as a pathological condition characterized by abdominal obesity, hypertension, dyslipidemia, and impaired glucose tolerance. Insulin resistance is hypothesized to underlie metabolic syndrome. Modern studies, including Mendelian randomization, have demonstrated that muscle strength and muscle mass may play an important role in the mechanisms of insulin resistance. Aim. To establish the relationship between relative upper limb muscle strength and triglyceride/glucose index, and to evaluate the effects of different resistance exercise regimens on alternative measures of insulin resistance in men with metabolic syndrome. Materials and methods. At the first stage of the study, 216 men aged from 25 to 50 years were examined. The relative muscle strength of the upper limbs in the bench press exercise and the triglyceride/glucose index were assessed. At the second stage, a randomized controlled trial was conducted, for which 60 men who met the criteria for metabolic syndrome. Men with metabolic syndrome were divided into three groups: low-intensity strength training with blood flow restriction (n = 20), high-intensity strength training (n = 20), low-intensity strength training without blood flow restriction (n = 20). Training was carried out 2 times a week for 12 weeks. Before and after the study, the triglycerides/glucose index, the ratio of triglycerides to high-density lipoproteins, and the combination of the triglycerides/glucose index with body mass index were assessed. Results and discussion. It was found that the relative muscle strength of the upper limbs was inversely proportional to the triglycerides/glucose index (r = –0.52; p 0.05) in the examined men. After 12 weeks of resistance training, statistically significant reductions in triglyceride/glucose index, triglyceride/high-density lipoprotein ratio, and triglyceride/glucose index/body mass index combination were found for the low-intensity resistance training with blood flow restriction and high-intensity resistance training groups (both, p 0,01). Changes in body composition, an increase in the proportion of muscle fibers I and IIa and a decrease in the proportion of muscle fibers IIx, an increase in the activity of glucose transporters, and a decrease in systemic inflammation are the main potential mechanisms for the beneficial effects of resistance training, including in combination with blood flow restriction, on insulin resistance in men with metabolic syndrome. Conclusion. There is an inverse relationship between muscle strength and triglycerides/glucose index; resistance training is an effective and safe tool for reducing alternative indicators of insulin resistance and can be included in comprehensive correction programs for men with metabolic syndrome.

Increased Variability in Lower Limb Muscle Activation Is Observed with Increasing Walking Speed in Fall-Risk Older Adults

This study is a cross-sectional study and aims to determine the differences in lower limb muscle activation and variability at preferred, slow, and fast walking speeds according to age and fall risk. We divided 301 participants into groups based on fall risk (fall-risk vs. non-fall-risk). We measured muscle activation and its coefficients of variation (CV) for the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius muscle (GCM) at speeds 20% slower, 20% faster, and 40% faster than the preferred speed (PS). When compared by fall risk, fall-risk older adults had significantly lower GCM activity and higher CVs of RF, BF, TA, and GCM in PS. With changes in gait speed, fall-risk older adults had significantly increased CVs of RF, BF, and GCM. Our findings provide new evidence that variability rather than muscle activity increases with walking speed in older adults at risk of falls, highlighting the importance of decreasing muscle activity variability in preventing fall risk.

Effects of electrical muscle stimulation exercise on lower limb muscles and lumbar movement in older adults with disabilities: A pre- and post-test controlled experimental study

In older adults with disabilities, muscle weakness reduces mobility and causes postural issues. Electrical muscle stimulation (EMS) training is effective for increasing strength by inducing involuntary skeletal muscle contractions. Thus, this study aimed to examine changes in lumbar movement, muscle activity during walking, and maximum muscle strength of lower-limb joints based on an 8-week EMS exercise program for older adults with physical disabilities. Sixteen older adults (aged 56–78 years) with physical disabilities were selected and randomly assigned to either the exercise group (EG, n = 8) or the control group (CG, n = 8). EG participants were instructed to wear EMS suits and participate in an elastic band and bare-body exercise program, whereas CG participants performed the exercise program without the EMS suits. Lumbar range of motion (ROM), body circumference, partial volume, maximum muscle strength, and muscle activity were measured. Statistical analysis was performed using SPSS 28.0 for Windows, with the critical value of α = 0.05. Compared to CG participants, EG participants had a superior ROM, body volume, partial volume, maximum muscle strength (knee joints), and muscle activity while walking. These positive outcomes highlight the efficacy of combining EMS with an exercise program for strength and rehabilitation training in older adults with physical disabilities.