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Context: Anterior cruciate ligament injuries are directly related to the control of dynamic knee valgus in the landing of a jump, and this is mainly due to the correct activation and neuromuscular function of the lower-extremity muscles. The aim of the study is to assess the relationship between lower limb muscle activity during a single-legged drop jump and knee frontal plane projection angle (FPPA). Design: A correlation study. Methods: Thirty healthy collegiate female athletes were included in the study. Main outcomes measures were peak knee FPPA and muscle activity (% of maximal voluntary isometric contraction). Peak knee FPPA during a single-legged drop jump test was identified using a 2-dimensional motion analysis system. Muscle activity was assessed using a surface electromyograph for gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius, and lateral gastrocnemius. All variables were assessed for both dominant and nondominant limbs. A correlation analysis between peak knee FPPA and muscle activity was performed. Statistical significance was set at P <.05. Results: A mean peak knee FPPA of 14.52° and 13.38° was identified for dominant and nondominant limb single-legged drop jump test, respectively. Muscle activity (% of maximal voluntary isometric contraction) for muscles assessed ranged from 43.97% to 195.71% during the single-legged drop jump test. The correlation analysis found no significant correlation between any of the muscles assessed and peak knee FPPA during the single-legged drop jump test (Pearson coefficient between −.3 and.1). Conclusions: There is no association between muscle activity from the lower limb muscles and the knee FPPA during a single-legged drop jump in female athletes. Thus, different muscle properties should be assessed in order to understand such an important movement as the knee FPPA during a jump. [ABSTRACT FROM AUTHOR]

Firefighter work-related fatigue can be measured by objective physical performance or subjective perceptions of fatigue; however, the two fatigue constructs are not related. Excess adiposity is common among career firefighters and negatively impacts performance fatigability. Objective: The purpose of this study was to (1) examine the relationship between perceived work-related fatigue and performance fatigability, and (2) assess the impact of percent body fat (%BF) on perceived fatigue constructs in career firefighters. Methods: Thirty-nine career firefighters completed body composition testing, the Occupational Fatigue Exhaustion Recovery (OFER15) scale assessing three subscales of work-related fatigue (acute fatigue, chronic fatigue, and inter-shift recovery), and maximal leg extensor isometric strength testing prior to and following an isotonic fatiguing protocol. Results: Performance fatigability was not associated with any of the OFER15 perceived work-related fatigue variables (P ≥ 0.513). Greater %BF was associated with greater %∆ peak torque (r = −0.41, P = 0.010) but none of the OFER15 perceived work-related fatigue variables (P ≥ 0.638). Conclusions: Performance fatigability was not associated with OFER15 perceived work-related fatigue, and greater adiposity negatively impacted performance fatigability but not perceived fatigability. [ABSTRACT FROM AUTHOR]

Purpose: The effects of low-intensity exercise, heat-induced hypo-hydration and rehydration on maximal strength and the underlying neurophysiological mechanisms are not well understood. Methods: To assess this, 12 participants took part in a randomised crossover study, in a prolonged (3 h) submaximal (60 W) cycling protocol under 3 conditions: (i) in 45 °C (achieving ~ 5% body mass reduction), with post-exercise rehydration in 2 h (RHY2), (ii) with rehydration across 24 h (RHY24), and (iii) a euhydrated trial in 25 °C (CON). Dependent variables included maximal voluntary contractions (MVC), maximum motor unit potential (MMAX), motor evoked potential (MEPRAW) amplitude and cortical silent period (cSP) duration. Blood–brain-barrier integrity was also assessed by serum Ubiquitin Carboxyl-terminal Hydrolase (UCH-L1) concentrations. All measures were obtained immediately pre, post, post 2 h and 24 h. Results: During both dehydration trials, MVC (RHY2: p < 0.001, RHY24: p = 0.001) and MEPRAW (RHY2: p = 0.025, RHY24: p = 0.045) decreased from pre- to post-exercise. MEPRAW returned to baseline during RHY2 and CON, but not RHY24 (p = 0.020). MEP/MMAX ratio decreased across time for all trials (p = 0.009) and returned to baseline, except RHY24 (p < 0.026). Increased cSP (p = 0.011) was observed during CON post-exercise, but not during RHY2 and RHY24. Serum UCH-L1 increased across time for all conditions (p < 0.001) but was not significantly different between conditions. Conclusion: Our findings demonstrate an increase in corticospinal inhibition after exercise with fluid ingestion, but a decrease in corticospinal excitability after heat-induced hypo-hydration. In addition, low-intensity exercise increases peripheral markers of blood–brain-barrier permeability. [ABSTRACT FROM AUTHOR]

Introduction The menstrual cycle influences various physiological systems, including energy metabolism, neuromuscular function, and psychological states, which collectively impact athletic performance. Despite increased research in this area, findings remain inconsistent due to individual variability and methodological differences. This review synthesizes current evidence on the effects of menstrual cycle phases on athletic performance to identify actionable strategies for female athletes. Materials and Methods A systematic review of 35 studies published between 2019 and 2025 was conducted using PubMed and PMC databases. Inclusion criteria focused on studies examining the physiological, psychological, or performance-related effects of menstrual cycle phases. Each study was evaluated for its methodology, population, and outcomes to ensure a comprehensive analysis. Analysis of the Literature This review explores the influence of hormonal fluctuations during the menstrual cycle on energy metabolism, neuromuscular function, endurance, strength, and psychological aspects. It highlights individualized recovery strategies and long-term adaptations to phase-specific training. Conclusions Menstrual cycle phases exert significant, though variable, effects on athletic performance. While the follicular phase favors carbohydrate metabolism and high-intensity activities, the luteal phase supports fatigue resistance and fat utilization. Personalized training protocols informed by hormonal profiling can optimize outcomes, though further research is needed to standardize methodologies and evaluate long-term adaptations. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess if ischaemic preconditioning (IPC) can reduce pain perception and enhance corticospinal excitability during voluntary contractions. In a randomised, within-subject design, healthy participants took part in three experimental visits after a familiarisation session. Measures of pressure pain threshold (PPT), maximum voluntary isometric force, voluntary activation, resting twitch force, corticospinal excitability and corticospinal inhibition were performed before and ≥10 min after either, unilateral IPC on the right leg (3 × 5 min); a sham protocol (3 × 1 min); or a control (no occlusion). Pain perception was then assessed in response to a hypertonic saline injection into the vastus lateralis muscle. In the right (occluded) leg, PPT was 10% greater after IPC compared to sham (P = 0.004). PPTs were also 9.5% greater in the contralateral leg for IPC compared to sham (P = 0.031). Maximum voluntary force, voluntary activation and resting twitch force were not different between conditions (all P ≥ 0.133). Measures of corticospinal excitability and inhibition also revealed no significant differences between conditions (all P ≥ 0.240). Hypertonic saline evoked pain revealed no difference in reported intensity or duration between conditions (P ≥ 0.082). IPC can reduce pain sensitivity in local and remote areas but does not subsequently impact neurophysiological measures of excitability or inhibition. [ABSTRACT FROM AUTHOR]

Females typically live longer than males but, paradoxically, spend a greater number of later years in poorer health. The neuromuscular system is a critical component of the progression to frailty, and motor unit (MU) characteristics differ by sex in healthy young individuals and may adapt to ageing in a sex‐specific manner due to divergent hormonal profiles. The purpose of this study was to investigate sex differences in vastus lateralis (VL) MU structure and function in early to late elderly humans. Intramuscular electromyography signals from 50 healthy older adults (M/F: 26/24) were collected from VL during standardized submaximal contractions and decomposed to quantify MU characteristics. Muscle size and neuromuscular performance were also measured. Females had higher MU firing rate (FR) than males (P = 0.025), with no difference in MU structure or neuromuscular junction transmission (NMJ) instability. All MU characteristics increased from low‐ to mid‐level contractions (P < 0.05) without sex × level interactions. Females had smaller cross‐sectional area of VL, lower strength and poorer force steadiness (P < 0.05). From early to late elderly, both sexes showed decreased neuromuscular function (P < 0.05) without sex‐specific patterns. Higher VL MUFRs at normalized contraction levels previously observed in young are also apparent in old individuals, with no sex‐based difference of estimates of MU structure or NMJ transmission instability. From early to late elderly, the deterioration of neuromuscular function and MU characteristics did not differ between sexes, yet function was consistently greater in males. These parallel trajectories underscore the lower initial level for older females and may offer insights into identifying critical intervention periods. Key points: Females generally exhibit an extended lifespan when compared to males, yet this is accompanied by a poorer healthspan and higher rates of frailty.In healthy young people, motor unit firing rate (MUFR) at normalized contraction intensities is widely reported to be higher in females than in age‐matched males.Here we show in 50 people that older females have higher MUFR than older males with little difference in other MU parameters. The trajectory of decline from early to late elderly does not differ between sexes, yet function is consistently lower in females.These findings highlight distinguishable sex disparities in some MU characteristics and neuromuscular function, and suggest early interventions are needed for females to prevent functional deterioration to reduce the ageing health–sex paradox. [ABSTRACT FROM AUTHOR]

This systematic literature review (SLR) aimed to comprehensively synthesize existing studies that have reported on TMG-derived parameters of lower extremities in soccer players. The PubMed, Web of Science, and EBSCOHost (including MEDLINE, SPORTDiscuss, ERIC, DOAJ, and SCOPUS) databases were... [ABSTRACT FROM AUTHOR]

BACKGROUND: The maximum muscle strength is typically used for evaluating the recovery of muscle function after anterior cruciate ligament reconstruction. Recent studies have suggested that neuromuscular function should also be considered, such as rate of force development, which measures the slope of the force time curve at different time intervals under conditions of isometric muscle contraction. OBJECTIVE: To elaborate on the current research status and shortcomings of muscle isometric rate of force development in patients undergoing anterior cruciate ligament reconstruction surgery, and analyze the degree of defects in quadriceps femoris and hamstring isometric rate of force development at different times after surgery; to analyze the effect of isometric rate of force development on postoperative functional performance, thereby providing important information for optimizing postoperative rehabilitation following anterior cruciate ligament reconstruction, reducing secondary injury to patients, and reducing the incidence of knee osteoarthritis. METHODS: Literature retrieval of CNKI, VIP, WanFang and PubMed was performed using “anterior cruciate ligament, rate of force development” as Chinese search terms and “anterior cruciate ligament, rate of force development, rate of torque development” as English search terms. Finally, 69 articles were included according to inclusion and exclusion criteria. RESULTS AND CONCLUSION: Most studies have found defects in bilateral muscle isometric rate of force development in patients undergoing anterior cruciate ligament reconstruction within 6 months. Early isometric rate of force development of the bilateral hamstring muscles (i.e. the slope of the force time curve at any time interval during muscle contraction of 100 ms) showed significant improvement after 6 months. However, long-term defects in early isometric rate of force development of the bilateral quadriceps indicate long-term damage to the neuromuscular function of the quadriceps after surgery. There is limited research on late isometric rate of force development (the slope of the force time curve at any time interval after 100 ms of muscle contraction), and conclusions cannot be drawn. Regarding landing exercises (jumping to the ground, lateral cutting, etc.) and daily activities (walking, running), early isometric rate of force development of the quadriceps is more correlated with isometric peak torque. Abnormal biomechanical changes during exercise are considered an important risk factor for secondary injury and traumatic knee osteoarthritis in patients. Actively improving early isometric rate of force development of the quadriceps may reduce the incidence of secondary injury and traumatic knee osteoarthritis. Currently, there is limited evidence to suggest that wholebody vibration training can improve early isometric rate of force development of the quadriceps femoris in patients undergoing anterior cruciate ligament reconstruction. It is recommended to use neuromuscular electrical stimulation to intervene in the quadriceps and hamstring in the early postoperative stage and implement explosive force and high resistance training in the late postoperative stage, which may improve the isometric rate of force development in patients. Generating sufficient muscle strength in a short period of time is necessary to effectively protect the anterior cruciate ligament, while the relationship between isometric rate of force development in the hamstring muscle and functional performance is still unclear, which may provide information on preventing secondary injury in patients. It is recommended to use the isometric rate of force development as one of the evaluation indicators for guiding rehabilitation and restoring movement. In addition to focusing on improving symmetry and differences from normal individuals, the hamstring to quadriceps strength ratio should also be considered. An appropriate range of ratios can ensure the balance of muscles during rapid muscle exertion, which may reduce the occurrence of secondary injuries. However, the normal range of ratios is not yet clear. Future research should consider the effects of graft type and knee flexion angle on isometric rate of force development, in order to identify neuromuscular dysfunction in patients as much as possible and help them recover better. [ABSTRACT FROM AUTHOR]

Patients with schizophrenia exhibit functional impairments in their locomotory tasks, which decreases their quality of life. Due to the limited current research, the neuromuscular mechanisms behind the functional impairments in patients is not fully understood. Thus, this review aims to summarize the neuromuscular mechanisms that underlie these deficits in daily functioning. These deficits are speculated to stem from abnormalities at various levels from neurons through to the skeletal muscles. The neurological abnormalities are exhibited as lower motor neuron dysfunction whereas the skeletal muscle pathology is shown as increased muscle fibre (type 1 and type 2) atrophy, reduction in maximal force generation, and increased strength loss per decade. Although antipsychotics effectively reduce positive symptoms, functional impairments remain unresolved. Both endurance and resistance training have shown potential benefits in alleviating deficits in daily functioning by increasing muscular strength, increasing fat-free mass, and preserving neuromuscular properties from degradation. In summary, the review elucidates various possible mechanisms for the onset of functional impairment experienced by patients with schizophrenia and highlights the potential utility of endurance and resistance training to alleviate these deficits in daily functioning. [ABSTRACT FROM AUTHOR]

Hand-Eye Coordination (HEC) and Hand Grip Strength (HGS) are among the most important skills in Taekwondo. On a technical level, HEC reflects neuromuscular coordination ability which enables quick responses, and HGS reflects muscle strength which indicates the strength and overall health of the athletes. Combined together, HEC and HGS likely allow Taekwondo athletes to perform better. The aim of this study was to identify if there is a relationship between HEC and HGS in elite Taekwondo athletes. 166 elite Taekwondo athletes (141 males, 25 females) voluntarily participated in this study and were divided into two categories: seniors (age >17 years) and juniors (age =17 years). HEC was assessed by hand-eye coordination manual dexterity test (Lafayette, IN, US) and HGS was measured using a hand dynamometer (Takei, Niigata, Japan). The results revealed that no significant relationship was observed between HEC and HGS (p>0.05) in elite Taekwondo athletes. Despite the several strength and neuromuscular adaptations acquired during Taekwondo practice, HEC and HGS are not significantly correlated, and hence there is no relationship between HEC and HGS in elite Taekwondo athletes. The results obtained may benefit Taekwondo coaches and athletes in improving their training strategies. [ABSTRACT FROM AUTHOR]

Introduction The menstrual cycle influences various physiological systems, including energy metabolism, neuromuscular function, and psychological states, which collectively impact athletic performance. Despite increased research in this area, findings remain inconsistent due to individual variability and methodological differences. This review synthesizes current evidence on the effects of menstrual cycle phases on athletic performance to identify actionable strategies for female athletes. Materials and Methods A systematic review of 35 studies published between 2019 and 2025 was conducted using PubMed and PMC databases. Inclusion criteria focused on studies examining the physiological, psychological, or performance-related effects of menstrual cycle phases. Each study was evaluated for its methodology, population, and outcomes to ensure a comprehensive analysis. Analysis of the Literature This review explores the influence of hormonal fluctuations during the menstrual cycle on energy metabolism, neuromuscular function, endurance, strength, and psychological aspects. It highlights individualized recovery strategies and long-term adaptations to phase-specific training. Conclusions Menstrual cycle phases exert significant, though variable, effects on athletic performance. While the follicular phase favors carbohydrate metabolism and high-intensity activities, the luteal phase supports fatigue resistance and fat utilization. Personalized training protocols informed by hormonal profiling can optimize outcomes, though further research is needed to standardize methodologies and evaluate long-term adaptations.

Mastour Saeed Alshahrani,1,&ast; Ravi Shankar Reddy,1,&ast; Adel Alshahrani,2,&ast; Saud F Alsubaie3,&ast; 1Department of Medical Rehabilitation Sciences, College of Applied Medical Sciences, King Khalid University, Abha, 61421, Saudi Arabia; 2Department of Medical Rehabilitation Sciences-Physiotherapy Program, College of Applied Medical Sciences, Najran University, Najran, 55461, Saudi Arabia; 3Department of Health and Rehabilitation Sciences, College of Applied Medical Sciences, Prince Sattam Bin Abdulaziz University, Al-Kharj, 11942, Saudi Arabia&ast;These authors contributed equally to this workCorrespondence: Ravi Shankar Reddy, Department of Medical Rehabilitation Sciences, College of Applied Medical Sciences, King Khalid University, Abha, 61421, Saudi Arabia, Tel +966 503587903, Email rshankar@kku.edu.saIntroduction: Shoulder proprioception is vital and this cross-sectional study investigated the association between glycemic control and shoulder joint proprioception in Type 2 Diabetes Mellitus (T2DM).Methods: A total of 120 participants, including 60 with T2DM and 60 healthy individuals, were assessed for shoulder joint position sense (JPS) using a digital inclinometer. The T2DM group exhibited significantly greater mean shoulder joint position errors in flexion (4.32° vs 2.15°), abduction, medial rotation, and lateral rotation compared to the healthy group (p < 0.001).Results: The study found significantly greater shoulder joint position errors in the T2DM group compared to the healthy group, highlighting notable proprioceptive deficits in individuals with T2DM. Additionally, a significant positive correlation was found between HbA1c levels and shoulder joint position errors in the T2DM group, suggesting a link between long-term glycemic control and proprioceptive accuracy.Discussion: The significant positive correlation between HbA1c levels and shoulder joint position errors suggests that poor glycemic control is associated with impaired proprioception in T2DM patients. This underscores the need for comprehensive management strategies to mitigate proprioceptive deficits and improve the quality of life in individuals with T2DM.Keywords: joint position sense, diabetes complications, sensory feedback, neuromuscular function, HbA1c Levels

This study's goals were to determine the health status of a group of heart transplant recipients (HTRs) and their level of physical activity and to compare the health status among them and with a group of healthy sedentary individuals. Fifty-four HTRs and eighteen sedentary individuals (S) were assigned to four groups, according to their level of physical activity (determined with the International Physical Activity Questionnaire); patients with a low, moderate, and high level of physical activity (HTRL, HTRM, and HTRH, respectively) and S participants underwent a basic blood analysis and several tests to assess their cardiovascular, neuromuscular, and functional mobility condition and their quality of life. The S and HTRH were very similar in terms of BP, HR, and blood analysis while HTRM and HTRL differed from both S and HTRH in these parameters. Regarding the cardiovascular, neuromuscular, functional mobility, and quality of life variables assessed in this study, HTRH showed the best results across all of them, followed by S, HTRM, and HTRL. It is suggested that the weekly level of physical activity of HTRs should be high, which might help them to enhance their health and quality of life. [ABSTRACT FROM AUTHOR]

The distinct and specialized movements performed in different sports disciplines may significantly influence nerve performance, potentially affecting nerve responses and the overall function within the respective athletic activities. The purpose of this study is to find the effect of forearm supination and pronation across the elbow joint on ulnar and median nerve conduction velocity (NCV) in throwers, archers, and non-athletes. A total of 34 participants both male and females were recruited with a body mass index (BMI) between 18.5 and 24.9 kg/m2. Nerve conduction study (NeuroStim NS2 EMG/NCV/EP System) was used for measuring ulnar and median NCV across the elbow joint at different angles with the forearm in supination and pronation. Repeated measure analysis of variance (RMANOVA) revealed that there are statistically significant differences in mean values of forearm positions, angles, nerves and groups (p <.05). This study illuminates distinctive NCV variations across diverse athletic groups during forearm supination and pronation movements. Pronation consistently exhibited faster ulnar NCV compared to the median nerve across throwers, archers, and non-athletes, while in supination specific joint positions revealed notable differences within sports groups and nerve function. [ABSTRACT FROM AUTHOR]

Purpose: Approximately 30%of people infected with COVID-19 require hospitalization, and 20% of them are admitted to an intensive care unit (ICU). Most of these patients experience symptoms of fatigue weeks post-ICU, so understanding the factors associated with fatigue in this population is crucial. Methods: Fifty-nine patients (38-78 yr) hospitalized in ICU for COVID-19 infection for 32 (6-80) d, including 23 (3-57) d of mechanical ventilation, visited the laboratory on two separate occasions. The first visit occurred 52 ± 15 d after discharge and was dedicated to questionnaires, blood sampling, and cardiopulmonary exercise testing, whereas measurements of the knee extensors neuromuscular function and performance fatigability were performed in the second visit 7 ± 2 d later. Results: Using the FACIT-F questionnaire, 56% of patients were classified as fatigued. Fatigued patients had worse lung function score than non-fatigued (i.e., 2.9 ± 0.8 L vs 3.6 ± 0.8 L; 2.4 ± 0.7 L vs 3.0 ± 0.7 L for forced vital capacity and forced expiratory volume in 1 s, respectively), and forced vital capacity was identified as a predictor of being fatigued. Maximal voluntary activation was lower in fatigued patients than non-fatigued patients (82% ± 14% vs 91% ± 3%) and was the only neuromuscular variable that discriminated between fatigued and non-fatigued patients. Patient-reported outcomes also showed differences between fatigued and non-fatigued patients for sleep, physical activity, depression, and quality of life (P < 0.05). Conclusions: COVID-19 survivors showed altered respiratory function 4 to 8 wk after discharge, which was further deteriorated in fatigued patients. Fatigue was also associated with lower voluntary activation and patient-reported impairments (i.e., sleep satisfaction, quality of life, or depressive state). The present study reinforces the importance of exercise intervention and rehabilitation to counteract cardiorespiratory and neuromuscular impairments of COVID-19 patients admitted in ICU, especially individuals experiencing fatigue. [ABSTRACT FROM AUTHOR]

Background: Quadriceps neuromuscular function is negatively affected after anterior cruciate ligament reconstruction (ACLR). The specific effect that the ACLR has on the quadriceps femoris rate of force production and its impact on functional recovery is unknown. Hypothesis: The anterior cruciate ligament (ACL) limb would present persistent deficits in the rate of torque development (RTD), when compared with the non-ACL limb before ACLR until 9 months (9M) post-ACLR. Study Design: Prospective cohort study. Level of Evidence: Level 3. Methods: Twenty-eight participants performed quadriceps maximum voluntary isometric contractions (MVICs) before (PRE), at 5 months (5M) and at 9M after ACLR. Single-leg hop distance was also assessed at 9M. Quadriceps RTD was calculated at 50, 100, and 200 ms after the onset of torque production. Maximum RTD was also calculated. A 2 (limb) × 3 (time) repeated-measures analysis of variance was used for RTD50, RTD100, RTD200, and RTDmax. Linear regressions were used to evaluate the associations of MVIC and RTD values at 5M and 9M with single-leg hop distance at 9M. Results: The ACL limb had lower RTD values at all times compared with the non-ACL limb (P < 0.05). RTD of the ACL limb significantly decreased from PRE to 5M, and then recovered to PRE levels at 9M (P < 0.05). The non-ACL limb displayed no differences from baseline to either 5M or 9M. MVIC and RTD200 at 5M predicted (R 2 = 0.313 and R 2 = 0.262, respectively) single-leg hop distance at 9M, better than the strength and RTD at 9M (R 2 = 0.235 and R 2 = 0.128, respectively). Conclusion: Quadriceps RTD is negatively affected after ACLR, and deficits may persist at the time of return to activity. Strength and RTD during recovery at 5M may predict more than 25% of the variance in single-leg hop distance at 9M, independently; hence, both provide important information to monitor functional recovery post-ACLR. Clinical Relevance: RTD should be measured to understand the changes in neuromuscular capacity after ACLR, and rehabilitation strategies that target quick force production, ie, quick muscle activation and functional tasks, should be implemented. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To probe into the clinical efficacy of Wenyang Huoxue Tongluo decoction combined with transcutaneous electrical acupoint stimulation in the treatment of discogenic low back pain and its effects on serum prostaglandin E2 (PGE2) and 6-keto-prostaglandin F1α (6-keto-PGF1ɑ). METHODS: A total of 112 patients with discogenic low back pain admitted into the hospital from Jun. 2021 to Jun. 2022 were extracted to be divided into the control group and study group via the random number method, with 56 cases in each group. The control group was treated with transcutaneous electrical acupoint stimulation, while the research group received Wenyang Huoxue Tongluo decoction combined with transcutaneous electrical acupoint stimulation. The course of treatment in both groups was 2 weeks. The curative effect was statistical at the end of the course of treatment. The traditional Chinese medicine syndrome scores, efficacy index and brain low-frequency fluctuations(ALFF), neuromuscular function, serum sclerostatin (SOST), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), PGE2 and 6-keto-PGF1ɑ before and after treatment were compared between two groups. RESULTS: The total effective rate of the research group was 96. 43% (54 / 56), significantly higher than 83. 93% (47 / 56) of the control group, the difference was statistically significant (P < 0. 05). After treatment, the scores of cold limbs, numb limbs, local fixation tingling and purple dark limbs in research group were significantly lower than those in control group, with statistically significant differences (P<0. 05). After treatment, JOA score and leg lift in research group were significantly higher than those in control group, sitting time was significantly longer than that in control group, and VAS score was significantly lower than that in control group; the mean iEMG and mean RMS of muscle dorsal group were significantly higher than those of control group, serum levels of SOST, TNF-α and IL-6 were significantly lower than those of control group, serum levels of PGE2, 6-keto-PGF1ɑ were significantly lower than those of control group, the ALEF of left and right middle occipital gyrus was higher than that of control group, with statistically significant differences (P<0. 05). CONCLUSIONS: The efficacy of Wenyang Huoxue Tongluo decoction combined with transcutaneous electrical acupoint stimulation in the treatment of patients with discogenic low back pain is significant, which can reduce the levels of serum PGE2 and 6-keto-PGF1ɑ, and relieve pain. The mechanism may be by changing the ALEF of the resting state of the brain, while enhancing neuromuscular function and decreasing SOST expression levels. [ABSTRACT FROM AUTHOR]

Objective. This study aims to investigate the effects of ACL injury on force fluctuation measures (stability and complexity) of the quadriceps muscle, and how these measures relate to functional performance. Methods. Forty-two athletes (14 females) with unilateral ACL injury were assessed. Quadriceps maximal isometric contraction was performed for both limbs before any surgical intervention. A 1.5s window from maximal torque signal was used to compute average torque (AT), force stability (coefficient of variation, CV), and complexity (sample entropy, SE), from which the limb symmetry index (LSI, % of contralateral limb) was estimated. The single hop test (SHT) was also performed and expressed as LSI. A nonparametric approach was used for between-limb comparison (Wilcoxon test) and to assess the relationship between force variables and SHT (Spearman correlation). Results. Significant limb asymmetry was found, with the injured limb exhibiting smaller AT (p < 0.001) and higher SE (p = 0.044) than the contralateral limb. A significant, moderate association was found only for LSI-SE and LSI-SHT (rho = -0.535, p = 0.002). Conclusions. In summary, along with the average torque, force complexity was altered in ACL-injured limbs of professional athletes, and was associated with larger asymmetries in functional performance, corroborating its relevance as a marker of ACL injury-related neuromuscular deficits. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to investigate a) the associations between bilateral performance utilizing countermovement jump (CMJ), squat jump (SJ), speed and unilateral CMJ, isokinetic peak torque in knee extension and flexion with angular velocities of 60°/s and 180°/s and tensiomyography (TMG) parameters; b) whether the asymmetries derived from unilateral tests are associated with bilateral CMJ, SJ and speed in elite female soccer players. Methods: Thirty-five elite female soccer players (average age: 20 ± 5 years) completed CMJ, SJ, speed, isokinetic muscle strength and TMG tests. Results: Compared to the non-dominant leg, the dominant leg demonstrated greater peak torque output in both knee flexion (7.4%) and knee extension (5.6%) isokinetic tasks, as well as m. vastus medialis contraction time (7.6%), and soccerspecific agility test (4.1%). Conversely, the hamstring to quadriceps peak torque ratio at 180°/s (8.5%) was significantly greater in the non-dominant leg. The associations between CMJ, SJ and speed performance were positive and ranged from weak (r = 0.350) to high (r = 0.710). For speed and TMG-derived variables, correlations were negative and ranged from weak (r = −0.345, p = 0.042, for vastus medialis contraction time) to moderate (r = −0.530, p = 0.001, for biceps femoris contraction time). Furthermore, both bilateral CMJ and SJ negatively correlated with TMG-derived variables, ranging from weak (r = −0.350, p = 0.039, for vastus lateralis contraction time) to moderate (r = −0.537, p = 0.003, for rectus femoris contraction time). Conclusion: The overall significant, albeit inconsistent, correlations between the diverse performance scores obtained highlight the necessity for a multifaceted and thorough diagnostic strategy in female soccer players. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of maturity status on force-velocity relationships in a ballistic lower limb (BLL) test in high-level soccer adolescents and young adults. The population was 61 adolescents (13.0–17.9 years) and 23 young adults (18.0–26.2 years). Subjects completed the BLL test on a ballistic ergometer equipped with two force plates and a linear encoder. Following Samozino's method, maximal power output (Pmax), force (F0) and velocity (v0) were determined. An allometric model was applied to Pmax and F0 with body mass (BM) and fat-free mass (FFM). Significant effects of maturity status were found for absolute Pmax, F0, relative Pmax to BM and FFM, relative F0 to FFM and F0 allometrically scaled to BM and FFM (p = 0.02 to p < 0.001; $\eta $ η = 0.10 to $\eta $ η = 0.49). There was no significant effect for Pmax allometrically scaled to BM and FFM, F0 relative to BM and v0. Body dimensions explain group differences in Pmax whereas for F0, qualitative factors explain the differences between the groups. As maturity status and body dimensions influence Pmax, these factors should be considered when assessing explosive short efforts. This could help to better identify potential athletic talent and adapt training content. [ABSTRACT FROM AUTHOR]

Background: High-intensity sprint exercises (HIS) are central to sprinter training and require careful monitoring of athlete muscle fatigue to improve performance and prevent injury. While the countermovement jump (CMJ) may be used to monitor neuromuscular fatigue (NMF), little is known about the specific effects from HIS. The purpose of this study is to investigate the effects of HIS on the CMJ to assess its utility for assessing NMF following HIS. Methods: Ten male collegiate 400 m sprinters completed a 400 m sprint fatigue protocol and underwent five CMJ-testing sessions (baseline, 3 minutes, 10 minutes, 1 hour and 24 hours) over two days. Three CMJ trials, performed on a force plate, were completed each trial, with rating of perceived exertion (RPE) recorded as a subjective fatigue measure. Changes in RPE, CMJ variables, force-time and power-time curves at baseline and post fatigue were assessed. Results: Significant changes were observed in most variables following the fatigue protocol. In particular, concentric mean power remained significantly lower after 24 hours compared to baseline. In addition, the force-time curves exhibited a significant reduction in all conditions following the fatigue protocol. This decline was most pronounced within 50–75%of the concentric phase relative to baseline measurements. Conclusion. Results indicate that the CMJ may be a useful tool for monitoring fatigue in at least 400 m sprinters. These data also indicate that HIS may disproportionately reduce force output in during concentric movement. These insights may improve training prescriptions and injury prevention strategies for sprint athletes. [ABSTRACT FROM AUTHOR]

(1) Background: The countermovement jump (CMJ) on a force plate could be a sensitive assessment for detecting early lower-limb muscle mechanical deficits in the early stages of multiple sclerosis (MS). CMJ performance is known to be influenced by various anthropometric, physiological, and biomechanical factors, mostly investigated in children and adult athletes. Our aim was to investigate the association of age, sex, and BMI with muscle mechanical function using CMJ to provide a comprehensive overview of lower-limb motor function in people with multiple sclerosis (pwMS). (2) Methods: A cross-sectional study was conducted with pwMS (N = 164) and healthy controls (N = 98). All participants performed three maximal CMJs on a force plate. Age, sex, and BMI were collected from all participants. (3) Results: Significant age, sex, and BMI effects were found for all performance parameters, flight time, and negative and positive power for pwMS and HC, but no significant interaction effects with the group (pwMS, HC) were detected. The highest significant effects were found for sex on flight time (η2 = 0.23), jump height (η2 = 0.23), and positive power (η2 = 0.13). PwMS showed significantly lower CMJ performance compared to HC in middle-aged (31–49 years), with normal weight to overweight and in both women and men. (4) Conclusions: This study showed that age, sex, and BMI are associated with muscle mechanical function in pwMS and HC. These results may be useful in developing reference values for CMJ. This is a crucial step in integrating CMJ into the diagnostic assessment of people with early MS and developing individualized and effective neurorehabilitative therapy. [ABSTRACT FROM AUTHOR]

Background: Surface electromyography (sEMG) can provide an objective and quantitative image of the functional state of neuromuscular balance in the stomatognathic system. The objective of this systematic review is to examine current scientific evidence regarding the effects of orthodontic treatment on muscle electromyographic (EMG) activity in children. Methods: The search strategy included the PubMed, PubMed Central, Web of Science, Scopus, and Embase databases. The inclusion criteria were studies assessing EMG muscle activity in children undergoing orthodontic treatment compared with untreated children. The Cochrane risk-of-bias tool (RoB2) and the Newcastle–Ottawa Scale (NOS) were used to evaluate the quality of the studies. The quality of evidence assessment was performed using GRADE analysis. The PRISMA diagram visually represented the search strategy, as well as screening and inclusion process. Results: The search strategy identified 540 potential articles. Fourteen papers met the inclusion criteria. Six studies were judged at a low risk of bias. The certainty of evidence was rated as moderate to low, according to the GRADE criteria. Studies showed alterations in EMG muscle activity in children undergoing orthodontic treatment. Conclusions: Orthodontic treatment appears to affect muscle activity in children undergoing orthodontic treatment. However, the quality of evidence is low and, therefore, it is not possible to definitively state this effect. Further long-term studies are needed to confirm the findings of this review. Study protocol number in PROSPERO database: CRD42023491005. [ABSTRACT FROM AUTHOR]

Purpose: The main aim of the present study was to describe the Vertical Force-velocity (F-v) profile in male Under-20 (U-20) national team rugby XV union players. Also, as a secondary aim, we proposed to establish the relationships between anthropometric variables with F-v profile parameters. Methods: Ten elite rugby union players from Uruguayan National male U-20 team [age: 18.9 ± 0.3 years; body mass: 90.03 ± 9.09 kg; body mass index (BMI): 26.28 ± 1.33 kg·m-2] were assessed in their force-velocity profile employing squat jump (SJ) with incremental loads. Moreover, we performed correlations between anthropometric variables [height, body mass, BMI, lower-limb length fully extended position (LL length), starting position of the jump (hs), and vertical push-off distance (hpo)] with the F-v profile variables [theoretical maximal force (F0), theoretical maximal velocity (V0), maximal mechanical power output (Pmax), deviation from the optimal profile (Dev), force-velocity imbalance (FVimb), SJ height (SJ0 h) and SJ power (SJ0 P)]. Results: Among the 10 rugby union players evaluated, 7 of them presented a force deficit, 2 were well balanced, and only one presented a velocity deficit. Thus, five athletes presented a high force deficit (37-52%), 2 a low force deficit (64 and 66%), 2 were well balanced (95 and 96%) and only one showed a low velocity deficit (136%). Furthermore, we found large to very large significant correlations between hs with F0, V0, FVimb and Dev (r > 0.6; p < 0.05). Additionally, we found a very large significant correlation between SJ0 h with Pmax (r = 0.757; p = 0.011). Conclusion: Male U-20 union rugby players presented force imbalance, which could suggest a greater emphasis of maximal strength performance for this sample.

Abstract Background This study aimed to evaluate the characteristics of mandibular protrusive condylar trajectory in adolescents with skeletal Class II Division 1 malocclusion and the changes of condylar trajectory during mandibular advancement (MA) treatment using clear functional aligners. Methods This prospective study consisted of a cross-sectional study and a longitudinal study. In cross-sectional study, sixty-one adolescents were divided into two groups: Class I (n = 30) and Class II Division 1 (n = 31). The condylar trajectory was measured and compared using the Mann–Whitney U test. The longitudinal study was the MA treatment group using clear functional aligner and consisted of 16 participants from Class II Division 1group. The condylar trajectory was collected at three-time points: pre-treatment (T1), during MA treatment at approximately 3 months (T2, 105.6 days average), and at the end of MA treatment (T3, 237.6 days average). The changes at T1, T2, and T3, as well as the symmetry between the left and right condyles across all groups, were examined using the Wilcoxon paired test. Results A greater increase in the anteroposterior displacement and space displacement during protrusive movements was observed in the Class II Division 1 group compared with that in the Class I group, with a large difference being observed in the left and right condylar movements. The condylar anteroposterior displacement and space displacement decreased significantly at T2 and increased significantly at T3; however, no significant difference was observed between T1 and T3. A significant difference was observed between the condylar movement on the left and right sides at T1; however, no significant difference was observed at T2 and T3. Conclusions Adolescents with Class II Division 1 malocclusion had higher protrusive capacity than those with Class I. Moreover, their left and right condylar motion was more asymmetric. The range of condyle motion decreased first and then increased during MA therapy, and the left and right condyle movement became more symmetrical, which may be the adaptive response of neuromuscular function to the changes in jaw position.

Abstract To identify biomarkers that precede the decline of human function and independence during the lifespan, two important concepts have been introduced in recent decades: sarcopenia and dynapenia. While the former is originally focused on skeletal muscle loss, the latter is on maximal strength loss. Although the dynapenia concept implies the inclusion of skeletal muscle power, in practical terms, this has not been specifically addressed. For instance, only 2 out of 220 studies published between 2008 and 2023 have directly measured muscle power to classify individuals with dynapenia. As previous studies have shown a greater relevance of skeletal muscle power in healthy aging, we hereby propose the introduction of the term “powerpenia” to specifically reflect the loss of skeletal muscle power along lifespan, but also with disease and/or physical inactivity. Together with sarcopenia and dynapenia, we contend that powerpenia should be considered a biomarker of healthy aging.

The author talks about the treatment of anterior cruciate ligament (ACL) injuries. He discusses the amount of research on ACL injury, prevention, and treatment; the goals of ACL reconstruction surgery, in which the injured ACL is replaced with a tendon graft; and the distinct functions of ACL. He also mentions the possibility to improve ACL reconstruction outcomes.

PurposeThe present study aimed to investigate a) the associations between bilateral performance utilizing countermovement jump (CMJ), squat jump (SJ), speed and unilateral CMJ, isokinetic peak torque in knee extension and flexion with angular velocities of 60°/s and 180°/s and tensiomyography (TMG) parameters; b) whether the asymmetries derived from unilateral tests are associated with bilateral CMJ, SJ and speed in elite female soccer players.MethodsThirty-five elite female soccer players (average age: 20 ± 5 years) completed CMJ, SJ, speed, isokinetic muscle strength and TMG tests.ResultsCompared to the non-dominant leg, the dominant leg demonstrated greater peak torque output in both knee flexion (7.4%) and knee extension (5.6%) isokinetic tasks, as well as m. vastus medialis contraction time (7.6%), and soccer-specific agility test (4.1%). Conversely, the hamstring to quadriceps peak torque ratio at 180°/s (8.5%) was significantly greater in the non-dominant leg. The associations between CMJ, SJ and speed performance were positive and ranged from weak (r = 0.350) to high (r = 0.710). For speed and TMG-derived variables, correlations were negative and ranged from weak (r = −0.345, p = 0.042, for vastus medialis contraction time) to moderate (r = −0.530, p = 0.001, for biceps femoris contraction time). Furthermore, both bilateral CMJ and SJ negatively correlated with TMG-derived variables, ranging from weak (r = −0.350, p = 0.039, for vastus lateralis contraction time) to moderate (r = −0.537, p = 0.003, for rectus femoris contraction time).ConclusionThe overall significant, albeit inconsistent, correlations between the diverse performance scores obtained highlight the necessity for a multifaceted and thorough diagnostic strategy in female soccer players.

Background High-intensity sprint exercises (HIS) are central to sprinter training and require careful monitoring of athlete muscle fatigue to improve performance and prevent injury. While the countermovement jump (CMJ) may be used to monitor neuromuscular fatigue (NMF), little is known about the specific effects from HIS. The purpose of this study is to investigate the effects of HIS on the CMJ to assess its utility for assessing NMF following HIS. Methods Ten male collegiate 400 m sprinters completed a 400 m sprint fatigue protocol and underwent five CMJ-testing sessions (baseline, 3 minutes, 10 minutes, 1 hour and 24 hours) over two days. Three CMJ trials, performed on a force plate, were completed each trial, with rating of perceived exertion (RPE) recorded as a subjective fatigue measure. Changes in RPE, CMJ variables, force-time and power-time curves at baseline and post fatigue were assessed. Results Significant changes were observed in most variables following the fatigue protocol. In particular, concentric mean power remained significantly lower after 24 hours compared to baseline. In addition, the force-time curves exhibited a significant reduction in all conditions following the fatigue protocol. This decline was most pronounced within 50–75%of the concentric phase relative to baseline measurements. Conclusion. Results indicate that the CMJ may be a useful tool for monitoring fatigue in at least 400 m sprinters. These data also indicate that HIS may disproportionately reduce force output in during concentric movement. These insights may improve training prescriptions and injury prevention strategies for sprint athletes.

To identify biomarkers that precede the decline of human function and independence during the lifespan, two important concepts have been introduced in recent decades: sarcopenia and dynapenia. While the former is originally focused on skeletal muscle loss, the latter is on maximal strength loss. Although the dynapenia concept implies the inclusion of skeletal muscle power, in practical terms, this has not been specifically addressed. For instance, only 2 out of 220 studies published between 2008 and 2023 have directly measured muscle power to classify individuals with dynapenia. As previous studies have shown a greater relevance of skeletal muscle power in healthy aging, we hereby propose the introduction of the term "powerpenia" to specifically reflect the loss of skeletal muscle power along lifespan, but also with disease and/or physical inactivity. Together with sarcopenia and dynapenia, we contend that powerpenia should be considered a biomarker of healthy aging. Key Points: • Skeletal muscle power is more influential than muscle strength and mass in enhancing physical function and reducing falls in older adults, and is a more sensitive marker of disease presence and/or physical inactivity; • The existing concepts of sarcopenia and dynapenia are commonly accepted and used among professionals and researchers in the fields of health and physical exercise. However, concept of dynapenia has been focused on skeletal muscle maximal strength rather than power, and sarcopenia does not include muscle power as a criterion. • We propose the introduction of the term powerpenia to specifically address the loss of skeletal muscle power with aging, disease, and/or physical inactivity. [ABSTRACT FROM AUTHOR]

Background: This study aimed to evaluate the characteristics of mandibular protrusive condylar trajectory in adolescents with skeletal Class II Division 1 malocclusion and the changes of condylar trajectory during mandibular advancement (MA) treatment using clear functional aligners. Methods: This prospective study consisted of a cross-sectional study and a longitudinal study. In cross-sectional study, sixty-one adolescents were divided into two groups: Class I (n = 30) and Class II Division 1 (n = 31). The condylar trajectory was measured and compared using the Mann–Whitney U test. The longitudinal study was the MA treatment group using clear functional aligner and consisted of 16 participants from Class II Division 1group. The condylar trajectory was collected at three-time points: pre-treatment (T1), during MA treatment at approximately 3 months (T2, 105.6 days average), and at the end of MA treatment (T3, 237.6 days average). The changes at T1, T2, and T3, as well as the symmetry between the left and right condyles across all groups, were examined using the Wilcoxon paired test. Results: A greater increase in the anteroposterior displacement and space displacement during protrusive movements was observed in the Class II Division 1 group compared with that in the Class I group, with a large difference being observed in the left and right condylar movements. The condylar anteroposterior displacement and space displacement decreased significantly at T2 and increased significantly at T3; however, no significant difference was observed between T1 and T3. A significant difference was observed between the condylar movement on the left and right sides at T1; however, no significant difference was observed at T2 and T3. Conclusions: Adolescents with Class II Division 1 malocclusion had higher protrusive capacity than those with Class I. Moreover, their left and right condylar motion was more asymmetric. The range of condyle motion decreased first and then increased during MA therapy, and the left and right condyle movement became more symmetrical, which may be the adaptive response of neuromuscular function to the changes in jaw position. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is available in the text. Sudlow, A, Galantine, P, Del Sordo, G, Raymond, J-J, Dalleau, G, Peyrot, N, and Duché, P. Influence of growth, maturation, and sex on maximal power, force, and velocity during overground sprinting. J Strength Cond Res 38(3): 491–500, 2024—In pediatric populations maximal anaerobic power, force, and velocity capabilities are influenced by changes in body dimensions and muscle function. The aim of this study was to investigate the influences of growth, maturation, and sex on short-term anaerobic performance. One hundred forty children pre-, mid-, and postpeak height velocity performed two 30-m sprints concurrently measured using a radar device. Maximal power (P max), force (F 0), and velocity (v 0) were calculated from sprint velocity-time data and normalized using sex-specific, multiplicative, allometric models containing body mass, fat-free mass (FFM), or height, and chronological age. Absolute values for P max, F 0, and v 0 were higher with increasing maturity (p < 0.01; d ≥ 0.96), and boys had greater outputs than girls (p < 0.01; d ≥ 1.19). When P max and v 0 were scaled all maturity-related and sex-related differences were removed. When F 0 was scaled using models excluding age, all maturity-related differences were removed except for the least mature group (p < 0.05; d ≥ 0.88) and boys maintained higher values than girls (p < 0.05; d ≥ 0.92). All maturity-related and sex-related differences were removed when F 0 was scaled using models including age. Maturity-related and sex-related variance in P max and v 0 can be entirely explained when FFM, height, and chronological age are accounted for. Regarding F 0, there seems to be a threshold after which the inclusion of age is no longer necessary to account for maturity-related differences. In young prepubertal children, the inclusion of age likely accounts for deficits in neuromuscular capacities and motor skills, which body dimensions cannot account for. Practitioners should focus on eliciting neural adaptations and enhancing motor coordination in prepubertal children to improve anaerobic performance during overground sprinting. [ABSTRACT FROM AUTHOR]

Background: Quadriceps strength deficits are known for patients with knee osteoarthritis (OA), whereas findings on hamstrings are less clear. The Adaptive Force (AF) as a special neuromuscular function has never been investigated in OA before. The maximal adaptive holding capacity (max. isometric AF; AFisomax) has been considered to be especially vulnerable to disruptive stimuli (e.g., nociception). It was hypothesized that affected limbs of OA patients would show clear deficits in AFisomax. Methods: AF parameters and the maximal voluntary isometric contraction (MVIC) of hamstrings were assessed bilaterally comparing 20 patients with knee OA (ART) vs. controls (CON). AF was measured by a pneumatically driven device. Participants were instructed to maintain a static position despite an increasing load of the device. After reaching AFisomax, the hamstrings merged into eccentric action whereby the force increased further to the maximum (AFmax). MVIC was recorded before and after AF trials. Mixed ANOVA was used to identify differences between and within ART and CON (comparing 1st and 2nd measured sides). Results: AFisomax and the torque development per degree of yielding were significantly lower only for the more affected side of ART vs. CON (p ≤ 0.001). The percentage difference of AFisomax amounted to − 40%. For the less affected side it was − 24% (p = 0.219). MVIC and AFmax were significantly lower for ART vs. CON for both sides (p ≤ 0.001). Differences of MVIC between ART vs. CON amounted to − 27% for the more, and − 30% for the less affected side; for AFmax it was − 34% and − 32%, respectively. Conclusion: The results suggest that strength deficits of hamstrings are present in patients with knee OA possibly attributable to nociception, generally lower physical activity/relief of lower extremities or fear-avoidance. However, the more affected side of OA patients seems to show further specific impairments regarding neuromuscular control reflected by the significantly reduced adaptive holding capacity and torque development during adaptive eccentric action. It is assumed that those parameters could reflect possible inhibitory nociceptive effects more sensitive than maximal strengths as MVIC and AFmax. Their role should be further investigated to get more specific insights into these aspects of neuromuscular control in OA patients. The approach is relevant for diagnostics also in terms of severity and prevention. [ABSTRACT FROM AUTHOR]

An emerging alternative to conventional animal models in toxicology research is the zebrafish. Their accelerated development, regenerative capacity, transparent physical appearance, ability to be genetically manipulated, and ease of housing and care make them feasible and efficient experimental models. Nonetheless, their most esteemed asset is their 70% (+) genetic similarity with the human genome, which allows the model to be used in a variety of clinically relevant studies. With these attributes, we propose the zebrafish is an excellent model for analyzing cognitive and neuromuscular responses when exposed to toxicants. Neurocognition can be readily analyzed using visual discrimination, memory and learning, and social behavior testing. Neuromuscular function can be analyzed using techniques such as the startle response, assessment of activity level, and evaluation of critical swimming speed. Furthermore, selectively mutated zebrafish is another novel application of this species in behavioral and pharmacological studies, which can be exploited in toxicological studies. There is a critical need in biomedical research to discover ethical and cost-effective methods to develop new products, including drugs. Through mutagenesis, zebrafish models have become key in meeting this need by advancing the field in numerous areas of biomedical research. [ABSTRACT FROM AUTHOR]

Background Rehabilitation clinicians that work with physically active populations are challenged with how to safely return patients back to performing deadlift movements following low back injury. Application of reliable and valid tests and measures to quantify impairments related to low back pain (LBP) enhances clinical decision making and may affect outcomes. Myotonometry is a non-invasive method to assess muscle stiffness which has demonstrated significant associations with physical performance and musculoskeletal injury. Hypothesis/Purpose The purpose of this study was to compare the stiffness of trunk (lumbar multifidus [LM] and longissimus thoracis [LT]) and lower extremity (vastus lateralis [VL] and biceps femoris [BF]) muscles between individuals with and without LBP during the lying, standing, and deadlifting body positions. Study Design Cross-sectional cohort comparison Methods Muscle stiffness measures were collected in the VL, BF, LM, and LT muscles with participants in lying (supine and prone), standing, and the trap bar deadlift position. Separate analyses of covariance were conducted to compare absolute and relative muscle stiffness between the groups for each muscle and condition. Results Sixty-eight participants (41 female, 21.3 years, 34 LBP) volunteered for the study. Within the deadlift condition there was a significantly greater increase in the percent-muscle stiffness change in the VL (p = .029, 21.9%) and BF (p = .024, 11.2%) muscles in the control group than in the LBP group. There were no differences in percent-muscle stiffness changes for the standing condition nor were there any absolute muscle stiffness differences between the two groups for the three conditions. Conclusion No differences in muscle stiffness were identified in the lying, standing, or deadlifting conditions between participants with and without LBP. Differences in percent stiffness changes were noted between groups for the deadlift position, however the differences were modest and within measurement error. Future studies should investigate the utility of myotonometry as a method to identify LBP-related impairments that contribute to chronic and/or recurrent low back injury. Level of Evidence Level 3 [ABSTRACT FROM AUTHOR]

Context: Traditionally, quadriceps activation failure after anterior cruciate ligament reconstruction (ACLR) is estimated using discrete isometric torque values, providing only a snapshot of neuromuscular function. Sample entropy (SampEn) is a mathematical technique that can measure neurologic complexity during the entirety of contraction, elucidating qualities of neuromuscular control not previously captured. Objective: To apply SampEn analyses to quadriceps electromyographic activity in order to more comprehensively characterize neuromuscular deficits after ACLR. Design: Cross-sectional. Setting: Laboratory. Participants: ACLR: n = 18; controls: n = 24. Interventions: All participants underwent synchronized unilateral quadriceps isometric strength, activation, and electromyography testing during a superimposed electrical stimulus. Main Outcome Measures: Group differences in strength, activation, and SampEn were evaluated with t tests. Associations between SampEn and quadriceps function were evaluated with Pearson product–moment correlations and hierarchical linear regressions. Results: Vastus medialis SampEn was significantly reduced after ACLR compared with controls (P =.032). Vastus medialis and vastus lateralis SampEn predicted significant variance in activation after ACLR (r2 =.444; P =.003). Conclusions: Loss of neurologic complexity correlates with worse activation after ACLR, particularly in the vastus medialis. Electromyographic SampEn is capable of detecting underlying patterns of variability that are associated with the loss of complexity between key neurophysiologic events after ACLR. [ABSTRACT FROM AUTHOR]

This study’s goals were to determine the health status of a group of heart transplant recipients (HTRs) and their level of physical activity and to compare the health status among them and with a group of healthy sedentary individuals. Fifty-four HTRs and eighteen sedentary individuals (S) were assigned to four groups, according to their level of physical activity (determined with the International Physical Activity Questionnaire); patients with a low, moderate, and high level of physical activity (HTRL, HTRM, and HTRH, respectively) and S participants underwent a basic blood analysis and several tests to assess their cardiovascular, neuromuscular, and functional mobility condition and their quality of life. The S and HTRH were very similar in terms of BP, HR, and blood analysis while HTRM and HTRL differed from both S and HTRH in these parameters. Regarding the cardiovascular, neuromuscular, functional mobility, and quality of life variables assessed in this study, HTRH showed the best results across all of them, followed by S, HTRM, and HTRL. It is suggested that the weekly level of physical activity of HTRs should be high, which might help them to enhance their health and quality of life.

Context: Altered neural signaling is known to have a direct impact on psychological wellness. Therefore, disruptions in neural signaling after anterior cruciate ligament reconstruction may influence psychological dysfunction, in some cases manifesting as learned helplessness. Helplessness is a psychological paradigm that presents as altered neuromuscular control, reduced motivation, and psychological deficits. Objectives: The authors sought to evaluate the relationship between helplessness, neural activity, and quadriceps function at different time points after anterior cruciate ligament reconstruction. Evidence acquisition: Twenty-nine individuals with unilateral anterior cruciate ligament reconstruction were categorized into early group (<2 y, age: 19.13 [2.18] y; height: 1.77 [0.11] m; mass: 76.903 [11.87] kg) or late group (>2 y, age: 22 [23] y; height: 1.67 [0.07] m; mass: 65.66 [11.33] kg). Quadriceps function (activation and strength), spinal-reflexive and corticospinal excitability (active motor thresholds and motor evoked potentials), and helplessness were obtained. A principal component analysis was performed by group (early and late) to identify which factors of helplessness were most associated with neural activity and quadriceps function. Pearson product moment correlation analyses were performed by group to determine associations between individual components and main outcomes. Evidence synthesis: In the early group, cognitive readiness was associated with quadriceps strength of the injured limb (r² = .513, P = .004), and self-awareness/management was associated with motor threshold of the injured limb (r² = .238, P = .05). In the late group, intrinsic helplessness was associated with motor output of injured limb (r² = .653, P = .01). Conclusion: Helplessness is made up of several attributional constructs, which are altered at different phases of recovery. Helplessness constructs interact differently with neural activity and quadriceps function across time. These findings are preliminary and do not establish a causal link between neural alterations and learned helplessness. Future studies should serially evaluate both changes in neural activity and learned helplessness attributes throughout recovery. [ABSTRACT FROM AUTHOR]

Background: The prevalence of older (>60 years) people with multiple sclerosis (pwMS) is increasing. This introduces numerous challenges, as both MS and ageing independently contribute to the deterioration of neuromuscular function. Aim: The aim was to compare the neuromuscular function in pwMS and healthy controls (HC) across three age groups: young, middle-aged, and old. Methods: Using a cross-sectional study design, the maximal muscle strength (Fmax) and rate of force development (RFD) of the knee extensors (KE) and plantar flexors (PF) were assessed using an isokinetic dynamometer. In addition, voluntary activation (VA) and resting twitch (RT) were measured using the interpolated twitch technique. Results: The Fmax, RFD, and VA of the KE were reduced in pwMS compared to HC across age groups. In pwMS, reductions were observed in PF Fmax, RFD, and RT, predominantly in the middle-aged and old age groups. Reductions increased with age in KE for both groups (except for VA) but in PF only for pwMS. The “trajectory” differed between pwMS and HC, as pwMS showed reductions from young to middle age, while HC showed reductions from middle to old age in KE. Conclusion: The combined negative effects of MS and ageing on neuromuscular function were especially present in the PF but also substantial in the KE. RFD showed large deficits for pwMS compared to HC across age groups. The findings can partly be explained by a reduction in VA and RT, but further investigations of neural regulation are needed to explain large RFD deficits.

Background Neuromuscular dysfunction is common in older adults and more pronounced in neurodegenerative diseases. In Parkinson's disease (PD), a complex set of factors often prevents the effective performance of activities of daily living that require intact and simultaneous performance of the motor and cognitive tasks. Methods The cross-sectional study includes a multifactorial mixed-measure design. Between-subject factor grouping the sample will be Parkinson’s Disease (early PD vs. healthy). The within-subject factors will be the task complexity (single- vs. dual-task) in each motor activity, i.e., overground walking, semi-tandem stance, and isometric knee extension, and a walking condition (wide vs. narrow lane) will be implemented for the overground walking activity only. To study dual-task (DT) effects, in each motor activity participants will be given a secondary cognitive task, i.e., a visual discrimination task for the overground walking, an attention task for the semi-tandem, and mental arithmetic for the isometric extension. Analyses of DT effects and underlying neuronal correlates will focus on both gait and cognitive performance where applicable. Based on an a priori sample size calculation, a total N = 42 older adults (55–75 years) will be recruited. Disease-specific changes such as laterality in motor unit behavior and cortical control of movement will be studied with high-density surface electromyography and electroencephalography during static and dynamic motor activities, together with whole-body kinematics. Discussion This study will be one of the first to holistically address early PD neurophysiological and neuromuscular patterns in an ecologically valid environment under cognitive-motor DT conditions of different complexities. The outcomes of the study aim to identify the biomarker for early PD either at the electrophysiological, muscular or kinematic level or in the communication between these systems. Clinical Trial Registration ClinicalTrials.Gov, NCT05477654. This study was approved by the Medical Ethical Committee (106/2021).

Purpose: This study aimed to compare performance and fatigability between young (n = 13; 18-30 yr), old (n = 13; 60-80 yr), and very old (n = 12; >80 yr) men during a single-joint isometric (ISO) and concentric (CON) task per- formed on an isokinetic dynamometer and a cycling (BIKE) task. Methods: Participants randomly performed incremental tasks consisting of stages of 75 contractions (i.e., 120 s, 0.8 s on/0.8 s off) for ISO and CON and 120 s at 37.5 rpm (similar duty cycle) for BIKE. Increments were set as a percentage of body weight. Knee extensor maximal force, voluntary activation, and twitch amplitude were measured at baseline, after each stage, and at task failure (five out of eight contractions below the target force or 6 s in a row at a cadence <37.5 rpm). Results: Compared with young men, performance (number of stages) was 24% and 40% lower in old and very old men in ISO, 54% and 59% lower in CON, and 36% and 60% lower in BIKE (all P <0.05). Performance of old and very old differed only in BIKE (P <0.01). For the last common stages performed, compared with young, force loss was greater for very old men in ISO and for old and very old men in BIKE (all P <0.05). Overall, for the last common stage performed and task failure, old and very old men presented similar force loss, alterations in voluntary activation, and twitch amplitude. Conclusions: Our findings reveal that, with workloads relative to body weight, differences in performance between old and very old men could only be observed during BIKE (i.e., the more ecologically valid task). Results from isometric or concentric conditions might not be transferable to dynamic exercise with large muscle masses. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to determine if aging would lead to greater decline in neuromuscular function during a fatiguing task under severe whole‐body hyperthermia conditions. Methods: Twelve young (aged 19–21 years) and 11 older (aged 65–80 years) males were enrolled in the study, which comprised a randomized control trial under a thermoneutral condition at an ambient temperature of 23°C (CON) and an experimental trial with passive lower body heating in 43°C water (HWI‐43°C). Changes in neuromuscular function and fatigability, and physical performance‐influencing factors such as psychological, thermoregulatory, neuroendocrine, and immune responses to whole‐body hyperthermia were measured. Results: A slower increase in rectal temperature, and a lower heart rate, thermal sensation, and sweating rate were observed in older males than young males in response to HWI‐43°C trial (p < 0.05). Nevertheless, prolactin increased more in response to hyperthermia in young males, while interleukin‐6 and cortisol levels increased more in older males (p < 0.05). Peripheral dopamine levels decreased in older males and increased in young males in response to hyperthermia (p < 0.05). Surprisingly, older males demonstrated greater neuromuscular fatigability resistance and faster maximal voluntary contraction (MVC) torque recovery after a 2‐min sustained isometric MVC task under thermoneutral and severe hyperthermic conditions (p < 0.05). Conclusion: Neuromuscular performance during fatigue‐provoking sustained isometric exercise under severe whole‐body hyperthermia conditions appears to decline in both age groups, but a lower relative decline in torque production for older males may relate to lower psychological and thermophysiological strain along with a diminished dopamine response and prolactin release. [ABSTRACT FROM AUTHOR]

Neuromuscular function is thought to contribute to posttraumatic osteoarthritis (PTOA) risk in anterior cruciate ligament (ACL)-reconstructed (ACLR) patients, but sensitive and easy-to-use tools are needed to discern whether complex muscle activation strategies are beneficial or maladaptive. Using an electromyography (EMG) signal analysis technique coupled with a machine learning approach, we sought to: (1) identify whether ACLR muscle activity patterns differed from those of healthy controls, and (2) explore which combination of patient outcome measures (thigh muscle girth, knee laxity, hop distance, and activity level) predicted the extent of osteoarthritic changes via magnetic resonance imaging (MRI) in ACLR patients. Eleven ACLR patients 10–15 years post-surgery and 12 healthy controls performed a hop activity while lower limb muscle EMG was recorded bilaterally. Osteoarthritis was evaluated based on MRI. ACLR muscle activity patterns were bilaterally symmetrical and differed from those of healthy controls, suggesting the presence of a global adaptation strategy. Smaller ipsilateral thigh muscle girth was the strongest predictor of inferior MRI scores. The ability of our EMG analysis approach to detect meaningful neuromuscular differences that could ultimately be related to thigh muscle girth provides the foundation to further investigate a direct link between muscle activation patterns and PTOA risk. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to characterize the etiology of exercise-induced neuromuscular fatigue and its consequences on the force-duration relationship to provide mechanistic insights into the reduced exercise capacity characterizing early-stage breast cancer patients. Methods: Fifteen early-stage breast cancer patients and fifteen healthy women performed 60 maximal voluntary isometric quadriceps contractions (MVCs, 3 s of contraction, 2 s of relaxation). The critical force was determined as the mean force of the last six contractions, while W' was calculated as the force impulse generated above the critical force. Quadriceps muscle activation during exercise was estimated from vastus lateralis, vastus medialis and rectus femoris EMG. Central and peripheral fatigue were quantified via changes in pre- to postexercise quadriceps voluntary activation (ΔVA) and quadriceps twitch force (ΔQTw) evoked by supramaximal electrical stimulation, respectively. Results: Early-stage breast cancer patients demonstrated lower MVC than controls preexercise (− 15%, P = 0.022), and this reduction persisted throughout the 60-MVC exercise (− 21%, P = 0.002). The absolute critical force was lower in patients than in controls (144 ± 29N vs. 201 ± 47N, respectively, P < 0.001), while W' was similar (P = 0.546), resulting in lower total work done (− 23%, P = 0.001). This was associated with lower muscle activation in the vastus lateralis (P < 0.001), vastus medialis (P = 0.003) and rectus femoris (P = 0.003) in patients. Immediately following exercise, ΔVA showed a greater reduction in patients compared to controls (− 21.6 ± 13.3% vs. − 12.6 ± 7.7%, P = 0.040), while ΔQTw was similar (− 60.2 ± 13.2% vs. − 52.8 ± 19.4%, P = 0.196). Conclusion: These findings support central fatigue as a primary cause of the reduction in exercise capacity characterizing early-stage breast cancer patients treated with chemotherapy. Clinical trials registration : No. NCT04639609—November 20, 2020. [ABSTRACT FROM AUTHOR]

• CMAP amplitude, muscle strength and walking capacity decrease after immobilisation and return to baseline levels after retraining. • Muscle velocity recovery cycles and MScanFit MUNE generally stay stable during short-term immobilisation and retraining. • Measures of the peripheral nervous system do not contribute to the changes observed in muscle strength and walking capacity. To explore the effects of short-term immobilisation and subsequent retraining on peripheral nervous system (PNS) measures using two novel electrophysiological methods, muscle velocity recovery cycles (MVRC) and MScanFit motor unit number estimation (MUNE) alongside lower limb muscle strength, muscle imaging and walking capacity. Twelve healthy participants underwent 1-week of ankle immobilisation and 2-weeks of retraining. Assessments before and after immobilisation, and after retraining, included MVRC [muscle membrane properties; muscle relative refractory period (MRRP), early and late supernormality ], MScanFit, MRI-scans [muscle contractile cross-sectional area (cCSA)], isokinetic dynamometry [dorsal and plantar flexor muscle strength], and 2-minute maximal walk test [physical function]. After immobilisation, compound muscle action potential (CMAP) amplitude reduced (-1.35[-2.00;-0.69]mV); mean change [95%CI]) alongside reductions in plantar (but not dorsal) flexor muscle cCSA (-124[-246;3]mm2), dorsal flexor muscle strength (isometric −0.06[-0.10;-0.02]Nm/kg, dynamic slow −0.08[-0.11;-0.04]Nm/kg, dynamic fast no changes), plantar flexor muscle strength (isometric −0.20[-0.30;-0.10]Nm/kg, dynamic slow −0.19[-0.28;-0.09]Nm/kg, dynamic fast −0.12[-0.19;-0.05]Nm/kg) and walking capacity (-31[-39;–23]m). After retraining, all immobilisation-affected parameters returned to baseline levels. In contrast, neither MScanFit nor MVRC were affected apart from slightly prolonged MRRP in gastrocnemius. PNS do not contribute to the changes observed in muscle strength and walking capacity. Further studies should include both corticospinal and peripheral mechanisms. [ABSTRACT FROM AUTHOR]

(1) Background: The countermovement jump (CMJ) on a force plate could be a sensitive assessment for detecting early lower-limb muscle mechanical deficits in the early stages of multiple sclerosis (MS). CMJ performance is known to be influenced by various anthropometric, physiological, and biomechanical factors, mostly investigated in children and adult athletes. Our aim was to investigate the association of age, sex, and BMI with muscle mechanical function using CMJ to provide a comprehensive overview of lower-limb motor function in people with multiple sclerosis (pwMS). (2) Methods: A cross-sectional study was conducted with pwMS (N = 164) and healthy controls (N = 98). All participants performed three maximal CMJs on a force plate. Age, sex, and BMI were collected from all participants. (3) Results: Significant age, sex, and BMI effects were found for all performance parameters, flight time, and negative and positive power for pwMS and HC, but no significant interaction effects with the group (pwMS, HC) were detected. The highest significant effects were found for sex on flight time (η2 = 0.23), jump height (η2 = 0.23), and positive power (η2 = 0.13). PwMS showed significantly lower CMJ performance compared to HC in middle-aged (31–49 years), with normal weight to overweight and in both women and men. (4) Conclusions: This study showed that age, sex, and BMI are associated with muscle mechanical function in pwMS and HC. These results may be useful in developing reference values for CMJ. This is a crucial step in integrating CMJ into the diagnostic assessment of people with early MS and developing individualized and effective neurorehabilitative therapy.