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Purpose: To gather information on practices and perceptions of high-performance experts regarding their athletes' muscle fiber-type composition (MFTC) and its estimation. Methods: A questionnaire on the noninvasive versus invasive estimation of MFTC was completed by 446 experts including coaches and sport-science/sports-medicine staff. Moreover, the perceived importance of MFTC for training and performance optimization was assessed. Differences between sport types (individual and team sports) were analyzed using chi-square tests. Results: Forty percent of the experts implemented MFTC assessment in pursuit of performance optimization, while 50% did not know their athletes' MFTC but expressed a desire to implement it if they would be able to assess MFTC. Ten percent did not perceive value in MFTC assessment. Only 18% of experts believed that their athletes would undergo a muscle biopsy, leading to the adoption of alternative noninvasive techniques. Experts primarily relied on their experience to estimate MFTC (65%), with experts working in individual sports using their experience more frequently than those working in team sports (68% vs 51%; P =.009). Jump tests emerged as the second-most commonly employed method for estimating MFTC (56%). When only considering experts who are currently using MFTC, 87% use MFTC to individualize training volume and 84% to individualize training intensity. Conclusions: Experts value MFTC assessment primarily to individualize training but mainly rely on noninvasive methods to estimate MFTC. Some of these methods lack scientific validity, suggesting a continuing need for education and further research in this area. [ABSTRACT FROM AUTHOR]

Vertical loading rate (VLR) and pelvic floor muscle activity (PFA) increase with running velocity, which may indicate a relationship between VLR and PFA. Foot strike pattern has been shown to influence VLR while running, but little is known about its influence on PFA. Twenty healthy women ran on a treadmill for 2 conditions: with a rearfoot strike and with a forefoot strike. PFA was measured with electromyography. Running kinematics associated with VLR were collected using inertial measurement units and tibial accelerometers. Change scores between conditions were calculated for average PFA and running kinematics: peak vertical tibial acceleration, vertical excursion of the center of mass (VO), and cadence. Paired t tests assessed differences between running conditions for all variables. Pearson correlations assessed the relationships between changes in PFA and running kinematics. PFA was significantly higher during the forefoot compared with the rearfoot strike condition. Change in vertical tibial acceleration was positively correlated with change in PFA during the right stance. Change in cadence was negatively correlated, and change in vertical excursion of the center of mass was positively correlated with change in PFA during left stance. The average PFA increased during the forefoot strike pattern condition. Changes in PFA were correlated with changes in running kinematics associated with VLR. [ABSTRACT FROM AUTHOR]

Muscle fiber conduction velocity (MFCV) can be affected by muscle fiber geometry at different joint angles and during joint movements. This study aimed to investigate MFCV during electrically evoked contraction at different joint angles, during joint movements, and during voluntary contractions. Sixteen healthy young men participated. A stimulation electrode was attached on the innervation zone of the vastus lateralis, and a linear electrode array was attached on the vastus lateralis. Under a static condition, electrically evoked electromyography signals were recorded at knee joint angles set every 15° between 0° and 105°. Under a passive movement condition, signals were recorded during knee extension and flexion passively. Under a voluntary contraction condition, signals were recorded while performing 30% or 60% of maximum voluntary contraction. MFCV was calculated using cross-correlation coefficients. Under the static condition, there were no differences in MFCV among various joint angles. Under the passive movement condition, MFCV was significantly greater during high velocity or shortening. Under the voluntary contraction condition, MFCV was significantly greater during high-intensity voluntary contraction and with a shortened muscle length. Joint angles do not influence MFCV markedly during relaxation, but it is possible to overestimate MFCV during movement or voluntary contraction. [ABSTRACT FROM AUTHOR]

A correction to the article "Match Running Performance in Australian Football is Related to Muscle Fiber Typology" that was published in the October 10, 2023 online issue is presented.

Recognizing that conventional understanding of animal and human locomotion is based on a dated and reductionist machine modeling of organisms, we set out to create a theory of locomotion by reasoning from first principles. We center on the constraints necessitated by 1) the 2nd law of thermodynamics, 2) the theory of evolution, 3) a systems science view of organisms, and 4) the laws of motion, but we also look for compatibility these constraints might find in emerging areas of scientific inquiry (ecological psychology, processual biology, soft matter, biotensegrity), and in the wisdom embedded in various movement traditions and ancient philosophy. Applying and synthesizing these, we propose an updated "bouncing bones" (BB) model for walking and running, which corresponds with maximum efficiency and conservation of energy. [ABSTRACT FROM AUTHOR]

Adaptations in muscle physiology due to long-term physical training have been monitored using various methods: ranging from invasive techniques, such as biopsy, to less invasive approaches, such as electromyography (EMG), to various quantitative magnetic resonance imaging (qMRI) parameters. Typically, these latter parameters are assessed immediately after exercise. In contrast, this work assesses such adaptations in a set of qMRI parameters obtained at rest in the lumbar spine muscles of volunteers. To this end, we developed a multiparametric measurement protocol to extract quantitative values of (water) T2, fat fraction, T1, and Intra Voxel Incoherent Motion (IVIM) diffusion parameters in the lumbar back muscle. The protocol was applied to 31 healthy subjects divided into three differently trained cohorts: two groups of athletes (endurance athletes and powerlifters) and a control group with a sedentary lifestyle. Significant differences in muscle water T2, fat fraction, and pseudo-diffusion coefficient linked to microcirculatory blood flow in muscle tissue were found between the trained and untrained cohorts. At the same time, diffusion coefficients (resolved along different directions) provided additional differentiation between the two groups of athletes. Specifically, the strength-trained athletes showed lower axial and higher radial diffusion components compared to the endurance-trained cohort, which may indicate muscle hypertrophy. In conclusion, utilizing multiparametric information revealed new insights into the potential of quantitative MR parameters to detect and quantify long-term effects associated with training in differently trained cohorts, even at rest. [ABSTRACT FROM AUTHOR]

Recent research has highlighted the essential role of the microbiome in maintaining skeletal muscle physiology. The microbiota influences muscle health by regulating lipid metabolism, protein synthesis, and insulin sensitivity. However, metabolic disturbances such as obesity can lead to dysbiosis, impairing muscle function. Time‐restricted feeding (TRF) has been shown to mitigate obesity‐related muscle dysfunction, but its effects on restoring healthy microbiomes remain poorly understood. This study utilizes 16S microbiome analysis and bacterial supplementation to investigate the bacterial communities influenced by TRF that may benefit skeletal muscle physiology. In wild‐type and obese Drosophila models (axenic models devoid of natural microbial communities), the absence of microbiota influence muscle performance and metabolism differently. Specifically, axenic wild‐type Drosophila exhibited reduced muscle performance, higher glucose levels, insulin resistance, ectopic lipid accumulation, and decreased ATP levels. Interestingly, in obese Drosophila (induced by a high‐fat diet or predisposed obesity mutant Sk2), the absence of microbiota improved muscle performance, lowered glucose levels, reduced insulin resistance, and increased ATP levels. TRF was found to modulate microbiota composition, notably increasing Acetobacter pasteurianus (AP) and decreasing Staphylococcus aureus (SA) in both obesity models. Supplementation with AP improved muscle performance and reduced glucose and insulin resistance, while SA supplementation had the opposite effect. This study provides novel insights into the complex interactions between TRF, microbiota, and skeletal muscle physiology in different Drosophila models. [ABSTRACT FROM AUTHOR]

The document "Advances in Muscle Research in Health and Disease" published in the journal Cells highlights the critical role of muscle tissue in maintaining overall health and explores recent advancements in muscle research. Key areas of focus include myogenesis, muscle as an endocrine organ, non-invasive treatments for muscle-related diseases, and the impact of lysine on myogenic differentiation in fast and slow muscles. The research presented in this special issue provides valuable insights into muscle biology, potential therapeutic strategies, and innovative approaches for managing muscle-related diseases, ultimately aiming to improve muscle health and overall well-being. [Extracted from the article]

Key points A fundamental question in cardiovascular and muscle physiology is how the heart operates in synchrony with distinct muscles to regulate homeostasis, enable movement and adapt to exercise demands and fatigue. Here we investigate how autonomic regulation of cardiac function synchronizes and integrates as a network with the activity of distinct muscles during exercise. Further, we establish how the network of cardio‐muscular interactions reorganizes with fatigue. Thirty healthy young adults performed two body weight squat tests until exhaustion. Simultaneous recordings were taken of a 3‐lead electrocardiogram (EKG) along with electromyography (EMG) signals from the left and right vastus lateralis, and left and right erector spinae. We first obtained instantaneous heart rate (HR) derived from the EKG signal and decomposed the EMG recordings in 10 frequency bands (F1–F10). We next quantified pair‐wise coupling (cross‐correlation) between the time series for HR and all EMG spectral power frequency bands in each leg and back muscle. We uncovered the first profiles of cardio‐muscular network interactions, which depend on the role muscles play during exercise and muscle fibre histochemical characteristics. Additionally, we observed a significant decline in the degree of cardio‐muscular coupling with fatigue, characterized by complex transitions from synchronous to asynchronous behaviour across a range of timescales. The network approach we utilized introduces new avenues for the development of novel network‐based markers, with the potential to characterize multilevel cardio‐muscular interactions to assess global health, levels of fatigue, fitness status or the effectiveness of cardiovascular and muscle injury rehabilitation programmes. The heart operates in synchrony with muscles to regulate homeostasis, enable movement, and adapt to exercise demands and fatigue. However, the precise mechanisms regulating cardio‐muscular coupling remain unknown. This study introduces a pioneering approach to assess cardio‐muscular network interactions by examining the synchronization of cardiac function with muscle activity during exercise and fatigue. We uncover the first profiles of cardio‐muscular interactions characterized by specific hierarchical organization of link strength. We observe a significant decline in the degree of cardio‐muscular coupling with fatigue, marked by complex transitions from synchronous to asynchronous behaviour. This network approach offers new network‐based markers to characterize multilevel cardio‐muscular interactions to assess global health, levels of fatigue, fitness status or the effectiveness of cardiovascular and muscle injury rehabilitation programmes. [ABSTRACT FROM AUTHOR]

Background: Vaginal noise (VN) is a natural phenomenon that arises when air is forced into the vagina and then expelled as the vaginal wall muscles naturally contract. It has been described as involuntarily passing gas from the vagina. VN is a symptom of pelvic floor (PF) dysfunction and can cause social and psychological issues. Data on it is limited, and women rarely voluntarily report it. So, this study was conducted to determine the prevalence, bother, and relation between VN and PF muscle dysfunction. Material and methods: It was a cross-sectional study that included females with age ranges from 30 to 60 years old, body mass index (BMI) ranges from 18 to 30 kg/m2, married, single, virgin, nulliparous, and multiparous women; those with previous one or more vaginal deliveries or cesarean sections (CS) or history of anterior and/or posterior vaginal wall prolapses; and those who had undergone medical interventions such as vaginal surgeries (e.g., pelvic floor reconstruction, hysterectomy), stress urinary incontinence, urge incontinence, and fecal incontinence. The Vaginal Wind Questionnaire, Pelvic Floor Impact Questionnaire-Short Form 7 (PFIQ-7), and Pelvic Floor Bother Questionnaire were used as methods of evaluating the VN prevalence and bother and its relation to PF dysfunction. Results: It was noted that there was a 76.3% prevalence of VN and 75% bother among the study population. Eighty-eight percent of them did not seek any treatment, and VN occurred in 84.3% of females with pelvic floor muscle weakness. Conclusion: VN is common in middle-aged Egyptian women, most frequently occurring with sexual intercourse, vaginal delivery, and pelvic floor muscle weakness. [ABSTRACT FROM AUTHOR]

In the pathophysiology of osteoarthritis and osteoporosis, articular cartilage and bone represent the target tissues, respectively, but muscle is also involved. Since many changes in energy metabolism occur in muscle with aging, the aim of the present work was to investigate the involvement of carnitine palmitoyl transferase 1b (Cpt1b) in the muscle pathophysiology of the two diseases. Healthy subjects (CTR, n = 5), osteoarthritic (OA, n = 10), and osteoporotic (OP, n = 10) patients were enrolled. Gene expression analysis conducted on muscle and myoblasts showed up-regulation of CPT1B in OA patients; this result was confirmed by immunohistochemical and immunofluorescence analyses and enzyme activity assay, which showed increased Cpt1b activity in OA muscle. In addition, CPT1B expression resulted down-regulated in cultured OP myoblasts. Given the potential involvement of Cpt1b in the modulation of oxidative stress, we investigated ROS levels, which were found to be lower in OA myoblasts, and gene expression of nicotinamide adenine dinucleotide phosphate hydrogen oxidase 4 (Nox4), which resulted up-regulated in OA cells. Finally, the immunofluorescence of BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (Bnip3) showed a decreased expression in OP myoblasts, with respect to CTR and OA. Contextually, through an ultrastructural analysis conducted by Transmission Electron Microscopy (TEM), the presence of aberrant mitochondria was observed in OP muscle. This study highlights the potential role of Cpt1b in the regulation of muscle homeostasis in both osteoarthritis and osteoporosis, allowing for the expansion of the current knowledge of what are the molecular biological pathways involved in the regulation of muscle physiology in both diseases. [ABSTRACT FROM AUTHOR]

Introduction: Increases in skeletal muscle size occur in response to prolonged exposure to resistance training that is typically ascribed to increased muscle fiber size. Whether muscle fiber number also changes remains controversial, and a paucity of data exists about myofibrillar structure. This cross-sectional study compared muscle fiber and myofibril characteristics in long-term resistance-trained (LRT) versus untrained (UNT) individuals. Methods: The maximal anatomical cross-sectional area (ACSAmax) of the biceps brachii muscle was measured by magnetic resonance imaging in 16 LRT (5.9 ± 3.5 yr’ experience) and 13 UNT males. A muscle biopsy was taken from the biceps brachii to measure muscle fiber area, myofibril area, and myosin spacing. Muscle fiber number, and myofibril number in total and per fiber were estimated by dividing ACSAmax by muscle fiber area or myofibril area, and muscle fiber area by myofibril area, respectively. Results: Compared with UNT, LRT individuals had greater ACSAmax (+70%, P < 0.001), fiber area (+29%, P = 0.028), fiber number (+34%, P = 0.013), and myofibril number per fiber (+49%, P = 0.034) and in total (+105%, P < 0.001). LRT individuals also had smaller myosin spacing (−7%, P = 0.004; i.e., greater packing density) and a tendency toward smaller myofibril area (−16%, P = 0.074). ACSAmax was positively correlated with fiber area (r = 0.526), fiber number (r = 0.445), and myofibril number (in total r = 0.873 and per fiber r = 0.566), and negatively correlated with myofibril area (r = −0.456) and myosin spacing (r = −0.382) (all P < 0.05). Conclusions: The larger muscles of LRT individuals exhibited more fibers in cross-section and larger muscle fibers, which contained substantially more total myofibrils and more packed myofilaments than UNT participants, suggesting plasticity of muscle ultrastructure. [ABSTRACT FROM AUTHOR]

Background: Chronic pelvic pain (CPP) is a common and debilitating condition, and sufferers present to healthcare professionals with variable complex symptoms and co-morbidities. This study aimed to investigate the current beliefs and practice behaviours of healthcare professionals towards the management of CPP in Australian females. Methods: We distributed an online survey to Australian healthcare professionals. Participants were questioned regarding their beliefs, the importance of various contributing factors and assessment variables, and their management preferences for two CPP vignettes. Demographic information and responses were analysed with descriptive statistics. Results: Complete data were obtained and analysed from 446 respondents including gynaecologists (n = 75), general practitioners (GPs) (n = 184) and physiotherapists (n = 187). Most of the respondents were female (88.1%), with male (11.7%) and other (0.2%) making up a smaller representation. Physiotherapists rated themselves higher in understanding mechanisms of CPP (64.7% very good to excellent) compared to gynaecologists (41.3%) and GPs (22.8%). Physiotherapists also reported higher levels of confidence in managing patients with CPP (57.8% quite or extremely confident) compared to 41.3% of gynaecologists and 22.3% of GPs who reported being quite or extremely confident. All three professions rated patient's beliefs (89.8%), nervous system sensitisation (85.7%), stress/anxiety/depression (91.9%), fear avoidance (83.3%), history of sexual/emotional/physical abuse (94.1%) and pelvic floor muscle function (85.0%) as very/extremely important factors in the development of chronic pelvic pain. Most gynaecologists (71.0%) and GPs (70.2%) always referred for pelvic ultrasound during assessment. Physiotherapists assessed goal setting (88.8%) and screened for patients' beliefs (80.9%) more often than gynaecologists (30.4% and 39.1% respectively) and GPs (46.5% and 29.0% respectively). Conclusions: All three groups of healthcare professionals demonstrated a good understanding of pain mechanisms and incorporated a biopsychosocial and multidisciplinary approach to management of females with chronic pelvic pain. However, both gynaecologists and GPs were less confident in their understanding of and management of CPP, and less likely to consider patient beliefs and goals. The findings of this online survey may assist in the provision of more targeted education to further improve management of this condition. Chronic pelvic pain (CPP) is a common, debilitating condition. Sufferers present to healthcare professionals with variable complex symptoms and co-morbidities. This online survey demonstrated that Australian healthcare professionals (HCPs) demonstrated good knowledge of pain mechanisms, largely followed guideline recommended care, but lacked confidence treating patients with CPP. Patient experiences suggest discrepancy exists between HCPs beliefs and actual practice behaviours. A collaborative approach is needed to help guide targeted research and education to further improve confidence in the management of CPP. [ABSTRACT FROM AUTHOR]

Therapeutic development for skeletal muscle diseases is challenged by a lack of ex vivo models that recapitulate human muscle physiology. Here, we engineered 3D human skeletal muscle tissue in the Biowire II platform that could be maintained and electrically stimulated long‐term. Increasing differentiation time enhanced myotube formation, modulated myogenic gene expression, and increased twitch and tetanic forces. When we mimicked exercise training by applying chronic electrical stimulation, the "exercised" skeletal muscle tissues showed increased myotube size and a contractility profile, fatigue resistance, and gene expression changes comparable to in vivo models of exercise training. Additionally, tissues also responded with expected physiological changes to known pharmacological treatment. To our knowledge, this is the first evidence of a human engineered 3D skeletal muscle tissue that recapitulates in vivo models of exercise. By recapitulating key features of human skeletal muscle, we demonstrated that the Biowire II platform may be used by the pharmaceutical industry as a model for identifying and optimizing therapeutic drug candidates that modulate skeletal muscle function. [ABSTRACT FROM AUTHOR]

The increasing global population and demand for meat have led to the need to find sustainable and viable alternatives to traditional production methods. One potential solution is cultivated meat (CM), which involves producing meat in vitro from animal stem cells to generate products with nutritional and sensory properties similar to conventional livestock‐derived meat. This article examines current approaches to CM production and investigates how using insect cells could enhance the process. Cell sources are a critical issue in CM production, alongside advances in culture media, bioreactors for scalability, and scaffold development. Insect cells, compared to commonly used mammalian cells, may offer advantages in overcoming technological challenges that hinder cell culture development and expansion. The objective of this review is to emphasize how insects, as a cell source for CM production, could offer a more sustainable option. A crucial aspect for achieving this goal is a comprehensive understanding of the physiology of muscle and fat cells. In this work, the characteristics of insect and mammalian cells are compared, focusing particularly on muscle and fat cell development, regulatory pathways, hormonal regulation, and tissue composition. Insect cells are a promising source for CM, offering a sustainable and environmentally friendly alternative. [ABSTRACT FROM AUTHOR]

We examined the effect of prolonged tennis playing on lower limb muscles' activity during the execution of first and second tennis serves. Ten male competitive tennis players executed five first and second serves before (pretest) and after (posttest) a 3‐h tennis match. Surface electromyographic (EMG) activity of four lower limb muscles (vastus lateralis, rectus femoris, gastrocnemius lateralis, and soleus muscles) on each leg was recorded along with maximum ball velocity measured by a radar gun and peak vertical forces recorded by a force platform. For the vastus lateralis, gastrocnemius lateralis, and soleus muscles of the left leg as well as the vastus lateralis muscle of the right leg, EMG amplitude decreased from pre‐ to posttests (p ≤ 0.033). These reductions in the EMG signal were generally more pronounced in the first serve (i.e., ranging from −10% to −40%) compared to the second serve (0% to −25%). Maximum ball velocity for both first (159 ± 12 vs. 154 ± 12 km/h) and second (126 ± 20 vs. 125 ± 15 km/h) serves remained unchanged from pre‐ to posttests (p = 0.638) Similarly, peak vertical forces did not differ between pretest and posttest for both first (1.78 ± 0.30 vs. 1.72 ± 0.29 body weight) and second (1.62 ± 0.25 vs. 1.75 ± 0.23 body weight) serves (p = 0.730). In conclusion, a 3‐h tennis match led to decreased activation levels in various leg muscles during serves, particularly in first serves compared to second serves. Despite consistent maximum ball velocity and peak vertical forces, these reductions in EMG signals suggest that skilled tennis players may adopt compensatory strategies after prolonged play. Highlights: A 3‐h tennis match resulted in reduced relative electromyographic (EMG) amplitudes for various knee extensor and plantar flexor muscles on both sides during the serve.Reductions in EMG signals were more prominent in the first serve (−10% to −40%) compared to the second serve (0% to −25%).Despite unchanged maximum ball velocities and peak vertical forces, muscle recruitment adjustments occurred in the vastus lateralis, gastrocnemius lateralis, and soleus muscles in the left leg and the vastus lateralis muscle in the right leg.Understanding changes in lower extremity muscle activation following prolonged play can help players and coaches develop strategies, such as targeted strength and conditioning protocols, to maintain effective serve technique. [ABSTRACT FROM AUTHOR]

Introduction: Pelvic floor muscle training (PFMT) for urinary incontinence (UI) is recommended in combination with biofeedback to visualize pelvic floor muscles. The focus is on non‐invasive hand‐held ultrasound (US) measurement methods for PFMT, which can be performed at home. Recently, self‐performed US measurements in which the patient applies the US to themself have gradually spreading. This study aimed to develop an educational program for the biofeedback method using self‐performed US and to evaluate its feasibility. Methods: This study was an observational study. The ADDIE model (Analysis, Design, Development, Implementation, and Evaluation) was utilized to create an e‐learning program for women aged ≥40 years with UI. Participants self‐performed bladder US via e‐learning, using a hand‐held US device with a convex probe. The primary outcome was the number of times the bladder area was successfully extracted using an existing automatic bladder area extraction system. The secondary outcome was the total score of the technical evaluation of the self‐performed US, which was evaluated across three proficiency levels. Descriptive statistics were conducted for participant characteristics, presenting categorical variables as percentages and continuous variables as means ± SD. Results: We included 11 participants with a mean age of 56.2 years. Nine participants were able to record US videos, and two were unable to record bladder videos. Regarding the technical evaluation scores, all participants scored ≥80%; four had perfect scores. Conclusions: This study showed that transabdominal self‐performed bladder US can be performed in 81.8% of women with UI in their 40–60s by using an e‐learning program. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the relative muscular effort (RME) of the hip and knee extensor and ankle plantarflexor muscle groups during the back squat (BS) and split squat (SS) exercises across four external load conditions. Motion capture and force plate data were collected as participants performed the BS and SS at 0%, 25%, 50%, and 75% of their body-mass. These data were used to calculate net joint moments (NJM) at the hip, knee, and ankle of the front leg during the SS and the matched leg during the BS. A musculoskeletal model, which accounted for force-length-velocity properties of 52 muscles, was used to estimate the maximal possible NJM (NJMmax) of the hip and knee extensor and ankle plantarflexor muscle groups. RME was calculated as the ratio between NJM and NJMmax, and compared across exercises and loads. The results indicated that while hip extensor RME increased across all loads, the increases in hip extensor RME were disproportionately greater during the SS at loads of 50% and 75%. Knee extensor RME increased linearly across loads and did not differ between exercises. These results provide coaches and athletes with detailed information about how to optimise resistance training specificity. [ABSTRACT FROM AUTHOR]

Objective: This systematic review and meta-analysis aimed to evaluate the influence of core muscle training on throwing ball velocity among overhead throwing athletes. Design: A literature search was performed from inception to July 2023 for randomized controlled trials investigating the effects of core muscle training on overhead throwing ball velocity. The primary outcome was the change in standing throwing ball velocity. The secondary outcome focused on the enhancement of step/jump throwing ball velocity. Results: Ten randomized controlled trials were included, revealing a significant improvement in standing throwing ball velocity in the group undergoing core muscle training (Hedges’ g = 0.701, 95% confidence interval = 0.339 to 1.063, P < 0.001). Longer treatment duration and a higher frequency of core muscle training sessions per week contributed to improved standing throwing ball velocity. However, core muscle training did not show significant benefits for step (Hedge’s g = 0.463, 95% confidence interval = −0.058 to 0.985, P = 0.082) and jump throwing ball velocity (Hedges’ g = 0.550, 95% confidence interval = −0.051 to 1.152, P = 0.073). Conclusions: Core muscle training significantly enhanced standing ball throwing velocity. However, its effect on step/jump throwing ball velocity was less certain. Further research is needed to explore the impact of core muscle training (especially its long-term effects) on throwing ball velocity. [ABSTRACT FROM AUTHOR]

Slow and sustainable intermittent swimming has recently been described in several Centrarchid fishes, such as bluegill and largemouth bass. This swimming behavior involves short periods of body‐caudal fin undulation alternating with variable periods of coasting. This aerobic muscle powered swimming appears to reduce energetic costs for slow, sustainable swimming, with fish employing a "fixed‐gear" or constant tailbeat frequency and modulating swimming speed by altering the length of the coasting period. We asked if this swimming behavior was found in other fish species by examining volitional swimming by brook trout in a static swimming tank. Further, we employed muscle mechanics experiments to explore how intermittent swimming affects muscle power output in comparison to steady swimming behavior. Brook trout regularly employ an intermittent swimming form when allowed to swim volitionally, and consistently showed a tailbeat frequency of ~2 Hz. Coasting duration had a significant, inverse relationship to swimming speed. Across a range of slow, sustainable swimming speeds, tailbeat frequency increased modestly with speed. The duration of periods of coasting decreased significantly with increasing speed. Workloop experiments suggest that intermittent swimming reduces fatigue, allowing fish to maintain high power output for longer compared to continuous activity. This study expands the list of species that employ intermittent swimming, suggesting this behavior is a general feature of fishes. Research Highlights: This is the first analysis of muscle function during intermittent swimming in a salmonid. Intermittent muscle activity reduces fatigue during extended bouts of aerobic, sustained swimming. [ABSTRACT FROM AUTHOR]

Background: It is unclear whether chronically training close to volitional failure influences motor unit recruitment strategies during fatigue. Purpose: We compared resistance training to near volitional failure vs. non-failure on individual motor unit action potential amplitude (MUAP) and surface electromyographic excitation (sEMG) during fatiguing contractions. Methods: Nineteen resistance-trained adults (11 males, 8 females) underwent 5 weeks (3×/week) of either low repetitions-in-reserve (RIR; 0–1 RIR) or high RIR training (4–6 RIR). Before and after the intervention, participants performed isometric contractions of the knee extensors at 30% of maximal peak torque until exhaustion while vastus lateralis sEMG signals were recorded and later decomposed. MUAP and sEMG excitation for the vastus lateralis were quantified at the beginning, middle, and end of the fatigue assessment. Results: Both training groups improved time-to-task failure (mean change = 43.3 s, 24.0%), with no significant differences between low and high RIR training groups (low RIR = 28.7%, high RIR = 19.4%). Our fatigue assessment revealed reduced isometric torque steadiness and increased MUAP amplitude and sEMG excitation during the fatiguing task, but these changes were consistent between groups. Conclusion: Both low and high RIR training improved time-to-task failure, but resulted in comparable motor unit recruitment during fatiguing contractions. Our findings indicate that both low and high RIR training can be used to enhance fatiguability among previously resistance-trained adults. [ABSTRACT FROM AUTHOR]

Background: Animal research suggests that repeated heat exposures may stimulate skeletal muscle protein synthesis and downregulate protein degradation. Hypothesis: Repeated heat exposures during ankle immobilization and rehabilitation would preserve human muscle strength and mass. Study Design: Controlled laboratory study. Methods: A total of 20 male participants (age, 33.6 ± 2.8 years; weight, 83.8 ± 9.2 kg; height, 182 ± 6 cm) underwent 4 weeks of supervised training, 2 weeks of single-lower leg immobilization, and 2 weeks of supervised rehabilitation before return to sports (RTS). Participants were split into 2 groups: (1) whole-body heat therapy (HEAT) and (2) sham treatment (SHAM) throughout the immobilization and rehabilitation periods. Measures of muscle strength (isometric and isokinetic), volume (magnetic resonance imaging and ultrasound), and muscle biopsies were obtained preimmobilization, postimmobilization, and at RTS. Results: Maximal isometric strength of the plantarflexors was lower at RTS compared with preimmobilization in SHAM (P =.027) but not HEAT (P =.301). Isokinetic strength during a fatigue test was higher at RTS compared with preimmobilization in HEAT (P =.039) but not SHAM (P =.245). Pennation angle and muscle thickness were lower at postimmobilization compared with preimmobilization only in SHAM (P ≤.027). Muscle cross-sectional area decreased in soleus and both gastrocnemius medialis and lateralis (all P ≤.035) in SHAM, but only in gastrocnemius medialis in HEAT. There was a large (d = 0.91) but not significant (P =.054) decrease in the ratio of phosphorylated/total nuclear factor-kappa B (NFκB) from preimmobilization to postimmobilization in HEAT only. There was an increase in phosphorylated fork head box O proteins (FoxO) only in HEAT (P =.034), suggesting a decrease in FoxO activity. Caspase 3 expression increased from preimmobilization to postimmobilization in SHAM only (P =.004). Conclusion: These results indicate that using heat therapy throughout immobilization and rehabilitation reduces skeletal muscle atrophy and maintains plantarflexor strength in healthy humans. Moreover, heat therapy may lead to the inactivation of the FoxO and NFκB signaling pathways involved in atrophy. Clinical Relevance: Repeated heat exposures should be considered a novel therapeutic intervention to counteract muscle atrophy during immobilization. [ABSTRACT FROM AUTHOR]

Context Housing temperature is a critical regulator of mouse metabolism and thermoneutral housing can improve model translation to humans. However, the impact of housing temperature on the ability of wheel running exercise training to rescue the detrimental effect of diet-induced obese mice is currently not fully understood. Objective To investigate how housing temperature affects muscle metabolism in obese mice with regard to calcium handling and exercise training (ET) adaptations in skeletal muscle, and benefits of ET on adiposity and glucometabolic parameters. Methods Lean or obese female mice were housed at standard ambient temperature (22 °C) or thermoneutrality (30 °C) with/without access to running wheels. The metabolic phenotype was investigated using glucose tolerance tests, indirect calorimetry, and body composition. Molecular muscle adaptations were measured using immunoblotting, qPCR, and spectrophotometric/fluorescent assays. Results Obese female mice housed at 22 °C showed lower adiposity, lower circulating insulin levels, improved glucose tolerance, and elevated basal metabolic rate compared to 30 °C housing. Mice exposed to voluntary wheel running exhibited a larger fat loss and higher metabolic rate at 22 °C housing compared to thermoneutrality. In obese female mice, glucose tolerance improved after ET independent of housing temperature. Independent of diet and training, 22 °C housing increased skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) activity. Additionally, housing at 22 °C elevated the induction of training-responsive muscle proteins in obese mice. Conclusion Our findings highlight that housing temperature significantly influences adiposity, insulin sensitivity, muscle physiology, and exercise adaptations in diet-induced obese female mice. [ABSTRACT FROM AUTHOR]

Background/Objectives: The main aim of our study was to analyze the stabilometric parameters in relation to hip and knee muscle force in children with unilateral slipped capital femoral epiphysis (SCFE) who had undergone surgical treatment. Another objective was to compare the stabilometry in three testing situations (eyes open, eyes closed, and head retroflexed). Methods: In total, 26 patients with unilateral right SCFE treated via in situ fixation with one percutaneous screw performed stabilometry assessments under three different situations (with their eyes open, with their eyes closed, and with their head retroflexed) and isometric muscle force assessment of the bilateral hip flexors, extensors, abductors and adductors and bilateral knee flexors and extensors. Results: No significant differences between the right side (affected hip) and left side (non-affected hip) were recorded for all of the tested muscle groups. We found significant negative correlations between the 90% confidence ellipse area (eyes open condition) and left knee extensors (p = 0.028), right knee flexors (p = 0.041), and left knee flexors (p = 0.02), respectively. When performing the comparison between the eyes open and eyes closed situations, there were significant differences in CoP path length (p < 0.0001) and maximum CoP speed (p = 0.048); the parameters increased in the eyes closed situation. Conclusions: Better postural stability is acquired when assessed with eyes open or with the head retroflexed in contrast with eyes closed testing. [ABSTRACT FROM AUTHOR]

Background: Our understanding of facial anatomy has significantly evolved, yet the detailed contraction patterns of facial muscles and their presentation during clinical imaging remain largely unexplored. Understanding the contraction patterns and visual presentation of these muscles, particularly the zygomaticus major could enhance pre-surgical facial assessments and the development of new treatment strategies. Methods: A total of 34 healthy young individuals (17 female, 17 male) with a mean age of 23.6 (2.4) years [range: 20–30] were investigated regarding the length, thickness, width, and angle of the zygomaticus major muscle in five different facial expressions (i.e., repose, anger, joy, surprise, and sadness) utilizing MR imaging. Results: Joyful expressions caused a reduction in muscle length to 85.6% of its original length and an increase in width (103.4%), thickness (108.4%), and facial angle (2.72°) when compared to that in repose, suggesting isotonic contraction. Conversely, expressions of anger, surprise, and sadness generally led to muscle stretching, seen through changes in length (98.9%, 104.3%, and 102.7%, respectively), width (98.8%, 96.5%, and 99.4%, respectively), and thickness (91.2%, 91.0%, and 102.7%, respectively), with variable alterations in facial angle (0.55°, 1.85°, and 1.00°, respectively) depending on the specific expression. Conclusion: This MRI-based study indicates that the zygomaticus major muscle experiences isotonic contraction, characterized by decreased length and increased width and thickness. The findings underline the importance of muscle thickness as a reliable parameter in assessing facial muscle function and offer valuable guidance for practitioners in accurately evaluating muscle performance during different facial expressions. No Level Assigned: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266. [ABSTRACT FROM AUTHOR]

The impact of the long-term historical contamination of the Mrežnica River with textile industry wastewaters on metal/metalloid bioaccumulation in the muscles of the young northern pike (Esox lucius) (0+ to 3+) was evaluated, as well as the association of bioaccumulated metal/metalloid concentrations in the muscle with fish physiology. Increased levels of several elements (As, Bi, Cs, Co, Cu, Zn), bioaccumulated in fish muscle, were occasionally found in front of the former factory, but the obtained metal/metalloid concentrations in muscle were in general either comparable or even lower than in the fish from moderately contaminated freshwaters. Calculated target hazard quotients indicated that the current risk for humans, arising from consumption of the northern pike meat originating from a historically contaminated section of the Mrežnica River, was negligible. The influence of biological factors, especially seasonal physiological changes, on metal/metalloid bioaccumulation was confirmed, indicating the importance of the involvement of these parameters in the freshwater pollution assessment, but also in the estimation of the human health hazard. The increased bioaccumulation of several metals/metalloids in fish muscle at a historically contaminated site pointed to the need for continuous supervision of fish health and biodiversity in freshwaters impacted by currently suspended long-term contamination sources. [ABSTRACT FROM AUTHOR]

Movement is integral to animal life, and most animal movement is actuated by the same engine: striated muscle. Muscle input is typically mediated by skeletal elements, resulting in musculoskeletal systems that are geared: at any instant, the muscle force and velocity are related to the output force and velocity only via a proportionality constant G , the "mechanical advantage". The functional analysis of such "simple machines" has traditionally centered around this instantaneous interpretation, such that a small vs large G is thought to reflect a fast vs forceful system, respectively. But evidence is mounting that a comprehensive analysis ought to also consider the mechanical energy output of a complete contraction. Here, we approach this task systematically, and deploy the theory of physiological similarity to study how gearing affects the flow of mechanical energy in a minimalist model of a musculoskeletal system. Gearing influences the flow of mechanical energy in two key ways: it can curtail muscle work output, because it determines the ratio between the characteristic muscle kinetic energy and work capacity; and it defines how each unit of muscle work is partitioned into different system energies, that is, into kinetic vs "parasitic" energy such as heat. As a consequence of both effects, delivering maximum work in minimum time and with maximum output speed generally requires a mechanical advantage of intermediate magnitude. This optimality condition can be expressed in terms of two dimensionless numbers that reflect the key geometric, physiological, and physical properties of the interrogated musculoskeletal system, and the environment in which the contraction takes place. Illustrative application to exemplar musculoskeletal systems predicts plausible mechanical advantages in disparate biomechanical scenarios, yields a speculative explanation for why gearing is typically used to attenuate the instantaneous force output (⁠|$G_{\text{opt}} \lt 1)$|⁠ , and predicts how G needs to vary systematically with animal size to optimize the delivery of mechanical energy, in superficial agreement with empirical observations. A many-to-one mapping from musculoskeletal geometry to mechanical performance is identified, such that differences in G alone do not provide a reliable indicator for specialization for force vs speed—neither instantaneously, nor in terms of mechanical energy output. The energy framework presented here can be used to estimate an optimal mechanical advantage across variable muscle physiology, anatomy, mechanical environment, and animal size, and so facilitates investigation of the extent to which selection has made efficient use of gearing as a degree of freedom in musculoskeletal "design." [ABSTRACT FROM AUTHOR]

Carbohydrates are critical for high‐intensity exercise performance. However, the effects of carbohydrate supplementation on muscle metabolism and performance during short‐duration high‐intensity intermittent exercise remain inadequately explored. Our aim was to address this aspect in a randomized, counterbalanced, double‐blinded crossover design. Eleven moderately‐to‐well‐trained males performed high‐intensity intermittent cycling receiving carbohydrate (CHO, ~55 g/h) or placebo (PLA) fluid supplementation. Three exercise periods (EX1‐EX3) were completed comprising 10 × 45 s at ~105% Wmax interspersed with 135 s rest between bouts and ~20 min between periods. Repeated sprint ability (5 × 6 s sprints with 24 s recovery) was assessed at baseline and after each period. Thigh muscle biopsies were obtained at baseline and before and after EX3 to determine whole‐muscle and fiber‐type‐specific glycogen depletion. No differences were found in muscle glycogen degradation at the whole‐muscle (p = 0.683) or fiber‐type‐specific level (p = 0.763–0.854) with similar post‐exercise whole‐muscle glycogen concentrations (146 ± 20 and 122 ± 15 mmol·kg−1 dw in CHO and PLA, respectively). Repeated sprint ability declined by ~9% after EX3 with no between‐condition differences (p = 0.971) and no overall differences in ratings of perceived exertion (p = 0.550). This was despite distinctions in blood glucose concentrations throughout exercise, reaching post‐exercise levels of 5.3 ± 0.2 and 4.1 ± 0.2 mmol·L−1 (p < 0.001) in CHO and PLA, respectively, accompanied by fivefold higher plasma insulin levels in CHO (p < 0.001). In conclusion, we observed no effects of carbohydrate ingestion on net muscle glycogen breakdown or sprint performance during short‐duration high‐intensity intermittent exercise despite elevated blood glucose and insulin levels. These results therefore question the efficacy of carbohydrate supplementation strategies in high‐intensity intermittent sports. [ABSTRACT FROM AUTHOR]

The elongation of Caenorhabditis elegans embryos allows examination of mechanical interactions between adjacent tissues. Muscle contractions during late elongation induce the remodeling of epidermal circumferential actin filaments through mechanotransduction. Force inputs from the muscles deform circumferential epidermal actin filament, which causes them to be severed, eventually reformed, and shortened. This squeezing force drives embryonic elongation. We investigated the possible role of the nonmuscle myosins NMY-1 and NMY-2 in this process using nmy-1 and nmy-2 thermosensitive alleles. Our findings show these myosins act redundantly in late elongation, since double nmy-2(ts); nmy-1(ts) mutants immediately stop elongation when raised to 25°C. Their inactivation does not reduce muscle activity, as measured from epidermis deformation, suggesting that they are directly involved in the multistep process of epidermal remodeling. Furthermore, NMY-1 and NMY-2 inactivation is reversible when embryos are kept at the nonpermissive temperature for a few hours. However, after longer exposure to 25°C double mutant embryos fail to resume elongation, presumably because NMY-1 was seen to form protein aggregates. We propose that the two C. elegans nonmuscle myosin II act during actin remodeling either to bring severed ends or hold them. [ABSTRACT FROM AUTHOR]

The objective of this work was to investigate myonuclear permanence and transcriptional regulation as mechanisms for cellular muscle memory after strength training in humans. Twelve untrained men and women performed 10 weeks of unilateral elbow‐flexor strength training followed by 16 weeks of de‐training. Thereafter, 10 weeks' re‐training was conducted with both arms: the previously trained arm and the contralateral untrained control arm. Muscle biopsies were taken from the trained arm before and after both training periods and from the control arm before and after re‐training. Muscle biopsies were analysed for fibre cross‐sectional area (fCSA), myonuclei and global transcriptomics (RNA sequencing). During the first training period, myonuclei increased in type 1 (13 ± 17%) and type 2 (33 ± 23%) fibres together with a 30 ± 43% non‐significant increase in mixed fibre fCSA (P = 0.069). Following de‐training, fCSA decreased in both fibre types, whereas myonuclei were maintained, resulting in 33% higher myonuclear number in previously trained vs. control muscle in type 2 fibres. Furthermore, in the previously trained muscle, three differentially expressed genes (DEGs; EGR1, MYL5 and COL1A1) were observed. Following re‐training, the previously trained muscle showed larger type 2 fCSA compared to the control (P = 0.035). However, delta change in type 2 fCSA was not different between muscles. Gene expression was more dramatically changed in the control arm (1338 DEGs) than in the previously trained arm (822 DEGs). The sustained higher number of myonuclei in the previously trained muscle confirms myonuclear accretion and permanence in humans. Nevertheless, because of the unclear effect on the subsequent hypertrophy with re‐training, the physiological benefit remains to be determined. Key points: Muscle memory is a cellular mechanism that describes the capacity of skeletal muscle fibres to respond differently to training stimuli if the stimuli have been previously encountered.This study overcomes past methodological limitations related to the choice of muscles and analytical procedures.We show that myonuclear number is increased after strength training and maintained during de‐training.Increased myonuclear number and differentially expressed genes related to muscle performance and development in the previously trained muscle did not translate into a clearly superior responses during re‐training. Because of the unclear effect on the subsequent hypertrophy and muscle strength gain with re‐training, the physiological benefit remains to be determined. [ABSTRACT FROM AUTHOR]

Objective: It was aimed to investigate the relationship between online gaming addiction, core muscle endurance, and reaction time in adolescents. Methods: The study was designed as a descriptive-correlational study and was conducted with 67 adolescents who play online games daily. The Online Gaming Addiction Scale, core muscle endurance tests, and hand and foot reaction time tests were performed. Results: The overall score of the Online Gaming Addiction Scale was 64.79±17.38, which corresponds as moderate negative reflections on the individual's life. A statistically significant difference was observed in online gaming addiction (p<0.001) and hand reaction time (p=0.004) according to the daily time allocated to video games. There was a negative correlation between the score of Online Gaming Addiction Scale and the hand reaction time test (r=-0.588; p<0.001) and the trunk extension test (r= -0.335; p=0.006) of the core muscle endurance tests. Conclusion: It was observed that the hand reaction time performance of adolescents was significantly impacted by the time spent in online games. Besides that, online gaming addiction may have a detrimental impact on adolescents' core muscle endurance. [ABSTRACT FROM AUTHOR]

Meat quality holds significant importance for both consumers and meat producers. Various factors influence meat quality, and among them, mitochondria play a crucial role. Recent studies have indicated that mitochondria can sustain their functions and viability for a certain duration in postmortem muscles. Consequently, mitochondria have an impact on oxygen consumption, energy metabolism, and apoptotic processes, which in turn affect myoglobin levels, oxidative stress, meat tenderness, fat oxidation, and protein oxidation. Ultimately, these factors influence the color, tenderness, and flavor of meat. However, there is a dearth of comprehensive summaries addressing the effects of mitochondria on postmortem muscle physiology and meat quality. Therefore, this review aims to describe the characteristics of muscle mitochondria and their potential influence on muscle. Additionally, a suitable method for isolating mitochondria is presented. Lastly, the review emphasizes the regulation of oxygen consumption, energy metabolism, and apoptosis by postmortem muscle mitochondria, and provides an overview of relevant research and recent advancements. The ultimate objective of this review is to elucidate the underlying mechanisms through which mitochondria impact meat quality. [ABSTRACT FROM AUTHOR]

Objective: To assess the efficacy of pelvic floor muscle training and physical therapy interventions in patients with low back pain. Data sources: The Ovid–Medline, Ovid–Embase, Cochrane Library, CINAHL, Web of Science, and PEDro databases were searched for randomised, controlled trials published in English or Korean between database inception and September 2024. Review Methods: Studies providing pelvic floor muscle training in individuals with low back pain were included. The risk of bias using the Cochrane Risk of Bias 2 tool and the grading of recommendation, assessment, development, and evaluation (GRADE) system was used to evaluate the quality of evidence. The meta-analysis was performed using Review Manager software 5.4. Results: Nineteen studies were included in this review. Pelvic floor muscle training showed low certainty evidence for improving pain (standardised mean difference = −0.73, 95% CI [−1.10, −0.36]) and reflected a clinically meaningful reduction in pain. The evidence for disability improvement had a low certainty (mean difference = −5.21, 95% CI [−7.15, −3.26]) due to high heterogeneity. Substantial improvements in pain and disability were observed when pelvic floor muscle training was added to standard physical therapy, with low certainty of evidence supporting these findings. Whereas pelvic floor muscle training substantially improved pain compared to other interventions, there was no marked improvement in disability. Conclusion: Pelvic floor muscle training is potentially beneficial in addition to physical therapy for reducing low back pain, particularly in pregnancy-related cases. However, the evidence should be interpreted considering the quality and risk of bias. [ABSTRACT FROM AUTHOR]

Context: In athletes, postural control impairment and knee muscle dysfunction are the most common disorders following anterior cruciate ligament (ACL) injury. Because of functional changes in the motor cortex following ACL injury, physiotherapy (PT) is not enough for treatment and using neuromodulators, such as trans-cranial direct current stimulation (tDCS) may be necessary. The present study focused on the effects of anodal tDCS (a-tDCS) over the primary motor cortex (M1) concurrent with PT on postural control and muscular performance in the athletes with ACL injury. Design: In this study, 34 athletes with ACL injury were randomly assigned in 2 groups of intervention group (active M1 a-tDCS concurrent with PT, n = 16) and control group (sham M1 a-tDCS concurrent with PT, n = 16). Methods: The participants of all groups received 20-minute 2 mA M1 a-tDCS with PT during 10 sessions, while tDCS was turned off after 30 seconds in the sham group. Before, immediately following, and 1 month after the interventions, the center of pressure and the average of power of flexor and extensor muscles at 2 velocities of 30°/s and 60°/s were measured by force plate and isokinetic devices, respectively. Results: One month after treatment, the displacement of center of pressure was decreased in the intervention group (P < .05), while there were no changes in the control group. Y-axis of center of pressure decreased in the intervention group relative to the control group, although average of power of flexor and extensor muscles increased immediately in both groups, but the rise in the intervention group was larger than that in the control group (P < .05). Conclusion: The findings indicated that M1 a-tDCS can induce the efficacy of PT, which has a lasting effect on the improvement of the postural control in athletes with ACL injury. [ABSTRACT FROM AUTHOR]

Abstract Multiple sclerosis (MS) is a demyelinating and neurodegenerative disease due to an autoimmune chronic inflammatory response, yet the etiology is currently not completely understood. It is already known that physical activity plays an essential role in improving quality of life, especially in neuropathological conditions. The study was aimed to investigate the possible benefits of high-intensity interval training (HIIT) in bone and lipid metabolism markers, and neuromotor abilities in MS patients. 130 participants were recruited; 16 subjects with MS met the inclusion criteria and were included in the data analysis. The patients were randomly assigned to two groups: a Control group (CG) (34.88 ± 4.45 yrs) that didn’t perform any physical activity and the Exercise group (EG) (36.20 ± 7.80 yrs) that performed HIIT protocol. The training program was conducted remotely by a kinesiologist. It was performed three times a week for 8 weeks. At the beginning (T0) and the end of the study (T1) physical function tests, bone remodelling markers, and lipid markers analyses were performed. After 8 weeks of training the wall squat (s) (T0 = 27.18 ± 4.21; T1 = 41.68 ± 5.38, p ≤ 0.01) and Time Up and Go test (s) (T0 = 7.65 ± 0.43; T1 = 6.34 ± 0.38 p ≤ 0.01) performances improved; lipid markers analysis showed a decrease in Total (mg/dl) (T0 = 187.22 ± 15.73; T1 = 173.44 ± 13.03, p ≤ 0.05) and LDL (mg/dl) (T0 = 108 ± 21.08; T1 = 95.02 ± 17.99, p

A growing body of research has provided evidence that de novo expression of connexin hemichannels and upregulation of pannexin hemichannels (Cx HCs and Panx HCs, respectively) in the cytoplasmic membrane of skeletal muscle (sarcolemma) are critical steps in the pathogenesis of muscle dysfunction of many genetic and acquired muscle diseases. This review provides an overview of the current understanding of the molecular mechanisms regulating the expression of Cx and Panx HCs in skeletal muscle, as well as their roles in both muscle physiology and pathologies. Additionally, it addresses existing gaps in knowledge and outlines future challenges in the field. [ABSTRACT FROM AUTHOR]

Skeletal muscle stem cells (MuSCs) display distinct behavior crucial for tissue maintenance and repair. Upon activation, MuSCs exhibit distinct modes of division: symmetric division, facilitating either self-renewal or differentiation, and asymmetric division, which dictates divergent cellular fates. This review explores the nuanced dynamics of MuSC division and the molecular mechanisms governing this behavior. Furthermore, it introduces a novel phenomenon observed in a subset of MuSCs under hypertrophic stimuli termed division-independent differentiation. Insights into the underlying mechanisms driving this process are discussed, alongside its broader implications for muscle physiology. [ABSTRACT FROM AUTHOR]

The purpose of this review is to delineate aspects of energy metabolism at rest and during exercise that may be subject to sex differences and the potential underlying mechanisms involved. It focuses on distinct aspects of female physiology with an oriented discussion following the reproductive life stages of healthy, eumenorrheic females, including premenopausal time frames, pregnancy, perimenopause, and menopause. Finally, this review aims to address methodological challenges surrounding sexual dimorphism in energy metabolism investigations and confounding factors in this field. During resting conditions, females tend to have higher rates of non-oxidative free fatty acid clearance, which could contribute to lower respiratory exchange ratio measures. At the same time, carbohydrate energy metabolism findings are mixed. In general, females favor lipid energy metabolism during moderate-intensity exercise, while men favor carbohydrate energy metabolism. Factors such as age, dietary intake, genetics, and methodological decisions confound study findings, including properly identifying and reporting the menstrual cycle phase when female subjects are eumenorrheic. Pregnancy presents a unique shift in physiological systems, including energy metabolism, which can be observed at rest and during exercise. Changes in body composition and hormonal levels during the post-menopausal period directly impact energy metabolism, specifically lipid metabolism. This change in physiological state factors into the evidence showing a reduction in our understanding of sex differences in lipid metabolism during exercise in older adults. This review reveals a need for a focused understanding of female energy metabolism that could help exercise and nutrition professionals optimize female health and performance across the lifespan. [ABSTRACT FROM AUTHOR]

Copy number variations (CNVs) are large‐scale changes in the DNA sequence that can affect the genetic structure and phenotype of an organism. The purpose of this study was to investigate the existing CNVs and their associations with the shank diameter (ShD) and shank length (ShL) traits using data from an F2 crossbred chicken population. To carry out the study, 312 chickens were genotyped using the Illumina 60k SNP Beadchip. The shank traits of the birds were measured from day 1 to 12 weeks of age. penncnv and cnvruler tools were used to find copy numbers and regions with copy number changes (CNVR), respectively. The CNVRanger package was used to perform a genome‐wide association study between shank traits and CNVs. Gene ontology research in CNVRs was carried out using the david database. In this investigation, 966 CNVs and 606 regions with copy number changes were discovered. The copy number states and variations were randomly distributed along the length of the autosomal chromosomes. Weeks 1–4, 9 and 12 of growth revealed a significant association of copy number variations with shank traits, false discovery rate (FDR‐corrected p‐value < 0.01), and the majority of CNVs that were statistically significant were found on chromosomes 1–3. These CNV segments are nearby genes such as KCNJ12, FGF6 and MYF5, which are fundamental to growth and development. In addition, gene set analyses revealed terms related to muscle physiology, regulation of cellular processes and potassium channels. [ABSTRACT FROM AUTHOR]

Supersonic shear image (SSI) ultrasound elastography provides a quantitative assessment of tissue stiffness using the velocity of shear waves. SSI's great potential has allowed researchers in fields like biomechanics and muscle physiology to study the function of complex muscle groups in different conditions. The aim of this study is to use SSI to investigate changes in the stiffness of the vastus lateralis (VL) muscle as a consequence of passive elongation, isometric contraction, and repeated muscle activity. In a single session, 15 volunteers performed a series of isometric, concentric, and eccentric contractions. SSI images were collected from the VL to assess its stiffness before and after the contractions and at various knee angles. Two-way within-subjects ANOVA was used to test the effects of muscle contraction type and knee angle on VL stiffness. Linear regression analysis was employed to assess the relationship between muscle stiffness and the intensity of isometric contractions. After maximal contractions, VL stiffness increased by approximately 10% compared to baseline values, and following maximal isometric (p < 0.01) and eccentric contractions (p < 0.05). Yet, there was no change in VL shear modulus at the end of concentric contractions. The relaxed VL shear modulus increased with knee flexion both before and after the knee extensor contractions (p < 0.001). A linear relationship between the shear modulus and the degree of isometric contraction was observed, although with notable individual variation (R2 = 0.125). Maximal contractile activity produces modest increases in relaxed muscle stiffness. The SSI-measured shear modulus increases linearly with the degree of isometric contraction. [ABSTRACT FROM AUTHOR]

The complex compositional and functional nature of skeletal muscle makes this organ an essential topic of study for biomedical researchers and clinicians. An additional layer of complexity is added with the consideration of sex as a biological variable. Recent research advances have revealed sexual dimorphisms in developmental biology, muscle homeostasis, adaptive responses, and disorders relating to skeletal muscle. Many of the observed sex differences have hormonal and molecular mechanistic underpinnings, whereas others have yet to be elucidated. Future research is needed to investigate the mechanisms dictating sex-based differences in the various aspects of skeletal muscle. As such, it is necessary that skeletal muscle biologists ensure that both female and male subjects are represented in biomedical and clinical studies to facilitate the successful testing and development of therapeutics for all patients. [ABSTRACT FROM AUTHOR]

Background: Personalized medicine, an emerging approach, considers individual differences to tailor treatments optimally. Persian medicine (PM) incorporates individual differences through Mizāj (temperament). A comprehensive understanding of each Mizaj type's characteristics is essential in designing standardized diagnostic tools. Objectives: This study aims to explore the attributes of one of the most significant Mizaj groups, namely cold-wet Mizaj, and its subtypes, including cold-wet Su-e-Mizaj (dystemperament), as well as phlegm dominance in PM sources. Methods: Persian medicine literature, including the Canon of Medicine, was reviewed for relevant concepts. Reliable scientific databases, including PubMed, Scopus, and MagIran, were searched using keywords such as Mizaj, temperament, Su-e-Mizaj, dystemperament, cold-wet dystemperament, phlegm, and Balgham. The obtained results were studied and categorized. Results: Out of the 196 articles obtained related to Mizaj, 16 investigated indices. No studies were found on the indices of coldwet Mizaj and phlegm dominance separately. PM sources exhibit high congruence in describing the characteristics of cold-wet Mizaj. Specifically, emphasis is placed on characteristics such as coldness and softness of the skin to the touch, high fat mass, pale and white complexion, excessive body secretions, weakness and slowness of physical and physiological actions, low vitality, timidity, poor memory, and slow-wittedness. In cold-wet dystemperament, symptoms are more severe, and in the presence of phlegm, a feeling of heaviness is also mentioned as a specific symptom. Conclusions: By compiling indices of cold-wet Mizaj/dystemperament and phlegm dominance, this study can contribute to the development of standardized PM questionnaires, facilitating a personalized approach to the diagnosis and treatment of diseases. [ABSTRACT FROM AUTHOR]

The term Delayed Onset Muscle Soreness (DOMS) refers to a complex injury entity which is based on ultrastructural injury patterns. The injury is usually harmless and heals within a few days without sequelae. However, at the time of the manifestation there are (sometimes considerable) performance limitations and the risk of possible secondary injuries is increased. Thus, prevention and treatment of DOMS, especially in high-performance sports, are of particular value. Insights into muscle biomechanics are necessary to understand the background and mechanisms of DOMS. The definition and classification of overload-related muscle injuries has not yet been uniformly determined. Fluid transitions between physiological, metabolic and neuromuscular fatigue as well as the actual occurrence of injuries with clinical symptoms make clear delineation difficult. The “Munich Classification” terms Delayed Onset Muscle Soreness (DOMS) as Type 1b muscle injury, “delayed onset muscle pain”. The central target of prevention of DOMS is to prevent or alleviate the onset of the initial damage, known as “Exercise Induced Muscle Damage” (EIMD). In case of manifest DOMS, the intention is both to relieve the attendant symptoms and to promote rapid restoration of muscle function. In clinical practice as in scientific research, diverse procedures and interventions have proven valuable, whereby especially physical therapy procedures like cryotherapy, heat therapy or compression therapy show promising study results. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the efficacy and user's impression of an arm-support exoskeleton in complex and realistic ceiling construction tasks. 11 construction workers performed 9 tasks. We determined objective and subjective efficacy of the exoskeleton by measuring shoulder muscle activity and perceived exertion. User's impression was assessed by questionnaires on expected support, perceived support, perceived hindrance and future intention to use the exoskeleton. Wearing the exoskeleton yielded persistent reductions in shoulder muscle activity of up to 58% and decreased perceived exertion. Participants reported limited perceived hindrance by the exoskeleton, as also indicated by no increase in antagonistic muscle activity. The findings demonstrate the high potential of an arm-support exoskeleton for unloading the shoulder muscles when used in the dynamic and versatile working environment of a ceiling construction worker, which is in line with the consistent intention of the workers to use the exoskeleton in the future. Practitioner Summary: The majority of research focuses on the effect of using an arm-support exoskeleton during isolated postures and prescribed movements. We investigated the efficacy of an exoskeleton during a complex and realistic work, namely ceiling construction. Shoulder muscle activity was lower in almost all tasks when wearing the exoskeleton. [ABSTRACT FROM AUTHOR]

Ulnar collateral ligament (UCL) tears occur due to the prolonged exposure and overworking of joint stresses, resulting in decreased strength in the flexion and extension of the elbow. Current rehabilitation approaches for UCL tears involve subjective assessments (pain scales) and objective measures such as monitoring joint angles and range of motion. The main goal of this study is to find out if using wearable near-infrared spectroscopy technology can help measure digital biomarkers like muscle oxygen levels and heart rate. These measurements could then be applied to athletes who have been injured. Specifically, measuring muscle oxygen levels will help us understand how well the muscles are using oxygen. This can indicate improvements in how the muscles are healing and growing new blood vessels after reconstructive surgery. Previous research studies demonstrated that there remains an unmet clinical need to measure biomarkers to provide continuous, internal data on muscle physiology during the rehabilitation process. This study's findings can benefit team physicians, sports scientists, athletic trainers, and athletes in the identification of biomarkers to assist in clinical decisions for optimizing training regimens for athletes that perform overarm movements; the research suggests pathways for possible earlier detection, and thus earlier intervention for injury prevention. [ABSTRACT FROM AUTHOR]

Background: Orthodontic and surgical technical advances in recent years have resulted in treatment opportunities for a whole range of craniofacial skeletal disorders either in the adolescent or adult patient. In the growing child, these can include myofunctional orthodontic appliance therapy or distraction osteogenesis procedures, while in the adult, the mainstay approach revolves around orthognathic surgery. The literature agrees that for a change in craniofacial morphology to remain stable, the muscles acting upon the facial skeleton must be capable of adaptation in their structure and, therefore, their function. Failure of the muscles to adapt to the change in their length or orientation will place undesirable forces on the muscle attachments leading to potential instability of the skeleton. Adaptation can occur through various processes including those within the neuromuscular feedback mechanism, through changes within muscle structure or through altered muscle physiology, and through changes at the muscle/bone interface. It is now accepted that because there is no single method of assessing masticatory function, several measures should be taken, and whenever possible, simultaneously. Methods: This investigation was designed to apply several, newly developed and more sophisticated methods of measuring muscle structure and function to a situation where adaptation of muscle is pivotal to the success of a therapeutic approach. Patients attending the combined orthodontic/orthognathic surgery clinic at the Clitrofa – Centro Médico, Dentário e Cirúrgico, in Trofa, Portugal, were screened. Ten patients scheduled for a bimaxillary osteotomy involving a combination of maxillary Le Fort I impaction procedure coupled with a sagittal split advancement of the mandible were selected to form the study group. The patients have MRI of the masseter muscle to evaluate the masseter muscle volume and fibre orientation changes. This exam was taken before surgery (T0), 6 to 12 months after surgery (T1), and 3 years after surgery (T2), by two independent observers, according to the protocol jointly developed between the Eastman Dental Institute – University of London and the MRI Centre - Department of Radiology at John Radcliffe Hospital – University of Oxford. Results: Significant differences (p < 0.05) have been identified between Time 0 (pre-op) and Time 1 (6–12 months post-op) regarding the masseter area (mm2). The differences against Time 0 (pre-op) seem to disappear at Time 2 (3 years post-op). Conclusions: MRI therefore seems to be a valid tool for measuring differences in the masseter muscle area and volume associated with high-severity occlusal deformities, although showing not to be as efficient in detecting the same differences in cases of low-severity occlusal deformities. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is a demyelinating and neurodegenerative disease due to an autoimmune chronic inflammatory response, yet the etiology is currently not completely understood. It is already known that physical activity plays an essential role in improving quality of life, especially in neuropathological conditions. The study was aimed to investigate the possible benefits of high-intensity interval training (HIIT) in bone and lipid metabolism markers, and neuromotor abilities in MS patients. 130 participants were recruited; 16 subjects with MS met the inclusion criteria and were included in the data analysis. The patients were randomly assigned to two groups: a Control group (CG) (34.88 ± 4.45 yrs) that didn't perform any physical activity and the Exercise group (EG) (36.20 ± 7.80 yrs) that performed HIIT protocol. The training program was conducted remotely by a kinesiologist. It was performed three times a week for 8 weeks. At the beginning (T0) and the end of the study (T1) physical function tests, bone remodelling markers, and lipid markers analyses were performed. After 8 weeks of training the wall squat (s) (T0 = 27.18 ± 4.21; T1 = 41.68 ± 5.38, p ≤ 0.01) and Time Up and Go test (s) (T0 = 7.65 ± 0.43; T1 = 6.34 ± 0.38 p ≤ 0.01) performances improved; lipid markers analysis showed a decrease in Total (mg/dl) (T0 = 187.22 ± 15.73; T1 = 173.44 ± 13.03, p ≤ 0.05) and LDL (mg/dl) (T0 = 108 ± 21.08; T1 = 95.02 ± 17.99, p < 0.05) cholesterol levels. Additionally, the levels of osteocalcin (µg/L), a marker of bone formation increased (T0 = 20.88 ± 4.22; T1 = 23.66 ± 6.24, p < 0.05), 25-OH Vitamin D (µg/L) improved after 8 weeks (T0 = 21.11 ± 7.11; T1 = 27.66 ± 7.59, p < 0.05). HIIT had an effect on lower limb strength and gait control, improved bone formation, and lipid management, in MS patients. [ABSTRACT FROM AUTHOR]

Muscle-tendon unit (MTU) morphology and physiology are likely major determinants of locomotor performance and therefore Darwinian fitness. However, the relationships between underlying traits, performance, and fitness are complicated by phenomena such as coadaptation, multiple solutions, and trade-offs. Here, we leverage a long-running artificial selection experiment in which mice have been bred for high levels of voluntary running to explore MTU adaptation, as well as the role of coadaptation, multiple solutions, and trade-offs, in the evolution of endurance running. We compared the morphological and contractile properties of the triceps surae complex, a major locomotor MTU, in four replicate selected lines to those of the triceps surae complex in four replicate control lines. All selected lines have lighter and shorter muscles, longer tendons, and faster muscle twitch times than all control lines. Absolute and normalized maximum shortening velocities and contractile endurance vary across selected lines. Selected lines have similar or lower absolute velocities and higher endurance than control lines. However, normalized shortening velocities are both higher and lower in selected lines than in control lines. These findings potentially show an interesting coadaptation between muscle and tendon morphology and muscle physiology, highlight multiple solutions for increasing endurance running performance, demonstrate that a trade-off between muscle speed and endurance can arise in response to selection, and suggest that a novel physiology may sometimes allow this trade-off to be circumvented. [ABSTRACT FROM AUTHOR]

Background: Disruption of external anal sphincter muscle (EAS) is an important factor in the multifactorial etiology of fecal incontinence (FI). Objectives: We categorize FI patients into four groups based on the location of lesion in neuromuscular circuitry of EAS to determine if there are differences with regards to fecal incontinence symptoms severity (FISI) score, age, BMI, obstetrical history, and anal sphincter muscle damage. Methods: Female patients (151) without any neurological symptoms, who had undergone high‐resolution manometry, anal sphincter EMG, and 3D ultrasound imaging of the anal sphincter were assessed. Patients were categorized into four groups: Group 1 (normal)—normal cough EMG (>10 μV), normal squeeze EMG (>10 μV), and normal anal squeeze pressure (>124 mmHg); Group 2 (cortical apraxia, i.e., poor cortical activation)—normal cough EMG, low squeeze EMG, and low anal squeeze pressure; Group 3 (muscle damage)—normal cough EMG, normal squeeze EMG, and low anal squeeze pressure; and Group 4 (pudendal nerve damage)—low cough EMG, low squeeze EMG, and low anal squeeze pressure. Results: The four patient groups were not different with regards to the patient's age, BMI, parity, and FISI scores. 3D ultrasound images of the anal sphincter complex revealed significant damage to the internal anal sphincter, external anal sphincter, and puborectalis muscles in all four groups. Conclusion: The FI patients are a heterogeneous group; majority of these patients have significant damage to the muscles of the anal sphincter complex. Whether biofeedback therapy response is different among different patient groups requires study. [ABSTRACT FROM AUTHOR]

Muscle isometric torque fluctuates according to time-of-day with such variation owed to the influence of circadian molecular clock genes. Satellite cells (SCs), the muscle stem cell population, also express molecular clock genes with several contractile-related genes oscillating in a diurnal pattern. Currently, limited evidence exists regarding the relationship between SCs and contractility, although long-term SC ablation alters muscle contractile function. Whether there are acute alterations in contractility following SC ablation and with respect to the time-of-day is unknown. We investigated whether short-term SC ablation affected contractile function at two times of day and whether any such alterations led to different extents of eccentric contraction-induced injury. Using an established mouse model to deplete SCs, we characterized muscle clock gene expression and ex vivo contractility at two times-of-day (morning: 0700 and afternoon: 1500). Morning-SC+ animals demonstrated ∼25%–30% reductions in tetanic/eccentric specific forces and, after eccentric injury, exhibited ∼30% less force-loss and ∼50% less dystrophinnegative fibers versus SC− counterparts; no differences were noted between Afternoon groups (Morning-SC+: −5.63 ± 0.61, Morning-SC−: −7.93 ± 0.61; N/cm2; P < 0.05) (Morning-SC+: 32 ± 2.1, Morning-SC−: 64 ± 10.2; dystrophinnegative fibers; P < 0.05). As Ca++ kinetics underpin force generation, we also evaluated caffeine-induced contracture force as an indirect marker of Ca++ availability and found similar force reductions in Morning-SC+ vs. SC− mice. We conclude that force production is reduced in the presence of SCs in the morning but not in the afternoon, suggesting that SCs may have a time-of-day influence over contractile function. NEW & NOTEWORTHY: Muscle isometric torque fluctuates according to time-of-day with such variation owed to molecular clock regulation. Satellite cells (SCs) have recently demonstrated diurnal characteristics related to muscle physiology. In our work, force production was reduced in the presence versus absence of SCs in the morning but, not in the afternoon. Morning-SC+ animals, producing lower force, sustained lesser degrees of injury versus SC− counterparts. One potential mechanism underpinning lower forces produced appears to be lower calcium availability. [ABSTRACT FROM AUTHOR]