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Background: Accurately measuring shoulder strength in overhead athletes is critical, as sufficient strength is essential for safe and sustained performance during repetitive athletic movements. Isokinetic dynamometry (ID) offers dynamic strength assessments that surpass the capabilities of static methods, such as manual muscle testing and handheld dynamometry. The dynamic assessment provided by ID may enhance upper extremity evaluation, aiding in the prediction of injury risk and the determination of return-to-sport criteria for overhead athletes. Purpose: The purpose of this review was to examine the existing literature concerning the application of isokinetic shoulder strength testing in rehabilitation and clinical decision-making processes among youth athletes who perform repetitive overhead activities. Study Design: Scoping review Methods: A comprehensive literature search was conducted using PubMed and EBSCO Host databases, covering publications from 2000-2024. Search terms included "isokinetic dynamometry," "shoulder," and "youth athlete." Inclusion criteria focused on youth athletes (<18 years) engaged in overhead sports, excluding those with neurological conditions or those designated as college or professional athletes. The PRISMA-ScR guidelines were followed. Results: A total of 23 articles met the inclusion criteria. Volleyball and swimming were the most studied sports, with the most common testing position being the seated 90/90 position. Variations in testing speeds and outcome measures, such as peak torque and external rotation (ER) ratios, were identified. Conclusions: Isokinetic dynamometry is a valuable tool for assessing shoulder strength in youth overhead athletes. It provides critical insights into muscle strength dynamics, aiding in injury prevention and rehabilitation. Further research is needed to optimize strength assessment protocols and enhance clinical decision-making for safe return-to-sport practices. [ABSTRACT FROM AUTHOR]

Background: Three-dimensional gait analysis, supported by advanced sensor systems, is a crucial component in the rehabilitation assessment of post-stroke hemiplegic patients. However, the sensor data generated from such analyses are often complex and challenging to interpret in clinical practice, requiring significant time and complicated procedures. The Gait Deviation Index (GDI) serves as a simplified metric for quantifying the severity of pathological gait. Although isokinetic dynamometry, utilizing sophisticated sensors, is widely employed in muscle function assessment and rehabilitation, its application in gait analysis remains underexplored. Objective: This study aims to investigate the use of sensor-acquired isokinetic muscle strength data, combined with machine learning techniques, to predict the GDI in hemiplegic patients. This study utilizes data captured from sensors embedded in the Biodex dynamometry system and the Vicon 3D motion capture system, highlighting the integration of sensor technology in clinical gait analysis. Methods: This study was a cross-sectional, observational study that included a cohort of 150 post-stroke hemiplegic patients. The sensor data included measurements such as peak torque, peak torque/body weight, maximum work of repeated actions, coefficient of variation, average power, total work, acceleration time, deceleration time, range of motion, and average peak torque for both flexor and extensor muscles on the affected side at three angular velocities (60°/s, 90°/s, and 120°/s) using the Biodex System 4 Pro. The GDI was calculated using data from a Vicon 3D motion capture system. This study employed four machine learning models—Lasso Regression, Random Forest (RF), Support Vector regression (SVR), and BP Neural Network—to model and validate the sensor data. Model performance was evaluated using mean squared error (MSE), the coefficient of determination (R2), and mean absolute error (MAE). SHapley Additive exPlanations (SHAP) analysis was used to enhance model interpretability. Results: The RF model outperformed others in predicting GDI, with an MSE of 16.18, an R2 of 0.89, and an MAE of 2.99. In contrast, the Lasso Regression model yielded an MSE of 22.29, an R2 of 0.85, and an MAE of 3.71. The SVR model had an MSE of 31.58, an R2 of 0.82, and an MAE of 7.68, while the BP Neural Network model exhibited the poorest performance with an MSE of 50.38, an R2 of 0.79, and an MAE of 9.59. SHAP analysis identified the maximum work of repeated actions of the extensor muscles at 60°/s and 120°/s as the most critical sensor-derived features for predicting GDI, underscoring the importance of muscle strength metrics at varying speeds in rehabilitation assessments. Conclusions: This study highlights the potential of integrating advanced sensor technology with machine learning techniques in the analysis of complex clinical data. The developed GDI prediction model, based on sensor-acquired isokinetic dynamometry data, offers a novel, streamlined, and effective tool for assessing rehabilitation progress in post-stroke hemiplegic patients, with promising implications for broader clinical application. [ABSTRACT FROM AUTHOR]

Isokinetic metrics are suggested to be related to vertical jump performance, but little is known about the possible sex differences in this relationship in adolescent track and field athletes. The aim of the study was to examine the possible sex differences in the strength of the relationship between the kinetic parameters of the vertical squat jump with arms akimbo, the countermovement jump with arms akimbo, and the countermovement jump with free arm swing with the isokinetic parameters of the knee extensor and flexor muscles (angular velocities: 60°/s and 300°/s). In total, 35 (males: 21, females: 14) U18 track and field athletes were examined. The results revealed that the Men U18 group had higher vertical jump performance, higher values in the kinetic parameters of the vertical jump tests, higher knee extensor torque, and higher knee flexor torque in the non-dominant leg compared to the Women U18 group. Significant (p < 0.05) sex differences were observed in the relationship between the isokinetic parameters and the vertical jump performance metrics, as the Women U18 athletes relied more on the knee flexor torque than Men U18 athletes, and demonstrated a stronger negative relationship between selected isokinetic metrics and the pre-stretch gain in the vertical jump tests. In conclusion, it is recommended that young female track and field athletes minimize interlimb asymmetry and improve the convention ratio in their non-dominant leg to optimize vertical jump performance. [ABSTRACT FROM AUTHOR]

Short-term fatigue protocols simulating sports participation are scarce and not well-documented in jumplanding sports. Therefore, this study investigated physiological and physical responses following high-intensity, intermittent exercise protocols (HIIPs) with a standardized level of subjective exhaustion (Borg ≥18/20) and a modified fixed version of five circuits (HIIP-5) for future inclusion in biomechanical screening protocols. Twenty male volleyball and basketball players participated in this study to complete the HIIP and the HIIP-5. Physiological and physical variables were assessed before and up to 30 min after cessation of both protocols. Regarding physiological variables, heart rate values increased (+104 bpm, p < 0.001) and remained elevated up to 30 min (+34 bpm, p < 0.001), and blood lactate levels increased (+17 mmol/l, p < 0.001) compared to baseline. Regarding physical variables, decreased jump height (-4 cm, p = 0.001-0.009) and quadriceps muscle strength (p = 0.001-0.050) were observed up to 30 min compared to baseline. The type of the fatigue protocol did not have an effect on the investigated variables (p > 0.05). To conclude, both the HIIP and the HIIP-5 seem valuable tools to induce acute and long-lasting responses, providing a sufficiently large time window of 30 min within which biomechanical markers of injury can be assessed under fatigued conditions in future risk factor screenings. In practice, the fatigue protocol can be terminated after only five circuits if athletes had not yet been stopped at that point due to exhaustion (Borg ≥18/20). [ABSTRACT FROM AUTHOR]

Background/Objectives: High-precision measurement tools are needed to measure relevant changes in strength and power in children with neuromuscular diseases. The aim of this study was to determine the feasibility (i), reproducibility (ii), and validity (iii) of isokinetic dynamometry in this population. Methods: Isometric and isokinetic knee and elbow flexion and extension were measured twice on the same day. Feasibility was based on completion rate and acceptability. Acceptability was measured with a 100 mm visual analog scale. We measured reproducibility as the intraclass correlation coefficient (ICC-agreement), standard error of measurement (SEM), and smallest detectable change (SDC). We investigated relationships between isometric strength and isokinetic power with Pearson's correlation coefficient. ROC curves were used to determine the cutoff of isometric strength to conduct isokinetic measurements. Results: Fifty children with NMDs participated with completion rates of 78–90% for isometric and 39–75% for isokinetic measurements. Acceptability was high (mean (SD) = 73 (19) mm). The ICCs for all measurements were over 0.9 (95% confidence interval (CI) = 0.932–0.998). The SEM% ranged from 5 to 14% and the SDC% from 14 to 28%. The correlations of strength and power were high (Pearson's correlation coefficient >0.9 (95% CI: 0.89–0.98)). The isometric strength needed to conduct isokinetic measurements ranged from 11.1 N in elbow flexors to 24.9 N in knee extensors. Conclusions: Isokinetic dynamometry is a feasible and reproducible method for measuring isometric strength in children with neuromuscular diseases with moderate weakness to normal strength, and isokinetic measurements are only feasible in knee extension for children with moderate weakness to normal strength. The convergent validity between isometric strength and power at low velocities is high. [ABSTRACT FROM AUTHOR]

Background: High-intensity anaerobic physical training frequently leads to muscle fatigue among boxers and kickboxers. Vibrational therapy (VT) and passive rest (PR) have been employed as methods to enhance muscular recovery and performance. This study evaluates the effectiveness of these two recovery methods on upper limb muscle strength and lactate levels in plasma after high-intensity exertion. Methods: Eighteen elite boxers and kickboxers, aged 19–32 years, underwent tests employing VT and PR as recovery methods in a controlled, crossover study. Muscle performance was assessed via isokinetic dynamometry, and lactate levels were measured pre-exercise, post-exercise, and post-recovery. The study adhered to the Declaration of Helsinki guidelines and was approved by the relevant bioethics committee. Results: The results showed that VT led to a faster recruitment of muscle fibers and improved muscle endurance as indicated by decreased fatigue work indices compared to PR. However, no significant differences were observed in peak torque or lactate levels between the two recovery methods. The VT group exhibited quicker recovery times in torque generation and better performance in fatigue resistance. Conclusions: VT appears to provide superior muscular recovery compared to PR following intense anaerobic effort, particularly in terms of muscle strength endurance and activation speed. These findings support the potential of VT in sports recovery protocols, although similar lactate response suggests that metabolic recovery rates are not significantly affected. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to examine the test−retest reliability in lower limb muscle strength and rate of torque development (RTD) using isokinetic dynamometry in adults with obesity, with a body mass index (BMI) ≥ 35 kg/m2. Method: Thirty‐two adults with a BMI of 43.8 ± 6.6 kg/m2 eligible for bariatric surgery were enroled in the study. Isokinetic and isometric knee extensor (KE) and flexor (KF) strength were assessed in an isokinetic dynamometer (Biodex 4) during three test sessions separated by 3−7 days. Results: There were no statistical differences in peak KE and KF torque for any test modalities between sessions. Intraclass correlation (ICC) was 0.91−0.94 between sessions 1 and 2 and 0.94−0.97 between sessions 2 and 3. Standard error of measurement (SEM%) and coefficient of variation (CV) ranged across test sessions from 4.3% to 7.3%. KE RTD showed high test−retest reliability following familiarization, with ICC, CV and SEM% values ranging from 0.84 to 0.90, 13.3%−20.3% and 14.6%−24.9%, respectively. Conclusion: Maximal lower limb muscle strength measured by isokinetic dynamometry showed excellent test−retest reliability manifested by small measurement errors and low CV. Reliability was slightly improved by including a familiarization session. KE RTD but not KF RTD demonstrated high test−retest reliability following familiarization. The present data indicate that isokinetic dynamometry can be used to detect even small changes in lower limb muscle strength in adults with obesity. [ABSTRACT FROM AUTHOR]

Background: Abnormal gait is prevalent among the elderly population, leading to reduced physical activity, increased risk of falls, and the potential development of dementia and disabilities, thus degrading the quality of life in later years. Numerous studies have highlighted the crucial roles of lower limb muscle strength asymmetry and static postural control in gait, and the reciprocal influence of lower limb muscle strength asymmetry on static postural control. However, research exploring the interrelationship between lower limb muscle strength asymmetry, static postural control, and gait performance has been limited. Methods: A total of 55 elderly participants aged 60 to 75 years were recruited. Isokinetic muscle strength testing was used to assess bilateral knee extension strength, and asymmetry values were calculated. Participants with asymmetry greater than 15% were categorized as the Asymmetry Group (AG), while those with asymmetry less than 15% were classified in the Symmetry Group (SG). Gait parameters were measured using a plantar pressure gait analysis system to evaluate gait performance, and static postural control was assessed through comfortable and narrow stance tests. Results: First, participants in the AG demonstrated inferior gait performance, characterized by slower gait speed, longer stance time and percentage of stance time in gait, and smaller swing time and percentage of swing time in gait. Spatial-temporal gait parameters of the weaker limb tended to be abnormal. Second, static postural control indices were higher in AG compared to SG in all aspects except for the area of ellipse during the comfortable stance with eyes open test. Third, abnormal gait parameters were associated with static postural control. Conclusion: Firstly, elderly individuals with lower limb muscle strength asymmetry are prone to abnormal gait, with the weaker limb exhibiting poorer gait performance. Secondly, lower limb muscle strength asymmetry contributes to diminished static postural control in the elderly. Thirdly, the mechanism underlying abnormal gait in the elderly due to lower limb muscle strength asymmetry may be linked to a decline in static postural control. [ABSTRACT FROM AUTHOR]

Context: The assessment of pediatric muscle strength is necessary in a range of applications, including rehabilitation programs. Handheld dynamometry (HHD) is considered easy to use, portable, and low cost, but validity to measure lower limb muscle strength in children has not been assessed. Objective: To determine the concurrent validity of lower limb torque from HHD compared with isokinetic dynamometry (ID) in children aged from 7 to 11 years old. Design: A descriptive assessment of concurrent validity of lower limb joint torques from HHD compared with ID. Methods: Sixty-one typically developing children underwent assessment of maximal hip, knee, and ankle isometric torque by HHD and ID using standardized protocols. Joint positions were selected to represent maximal strength and were replicated between devices. Concurrent validity was determined by Pearson correlation, limits of agreement, and Bland–Altman plots. Results: Correlations between HHD and ID were moderate to large for knee extension (r 95% CI, .39 to .73), small to large for plantar flexion (r 95% CI, .29 to .67), knee flexion (r 95% CI, .16 to .59), hip flexion (r 95% CI, .21 to .57), hip extension (r 95% CI, .18 to .54), and hip adduction (r 95% CI, .12 to .56), and small to moderate for dorsiflexion (r 95% CI, −.11 to .39) and hip abduction (r 95% CI, −.02 to .46). Limits of agreement for all joint torques were greater than 10% indicating large error in HHD measured torque compared with ID. A positive proportional bias was detected for plantarflexion, indicating that HHD underestimated torque to a greater extent in participants with higher torque values. Conclusions: Maximal torque values from HHD and ID are consistent with those previously reported in the literature. Poor concurrent validity of HHD may have arisen from issues around joint position, joint stabilization, and the experience of the tester to prevent an isokinetic contraction. Pediatric lower limb muscle strength assessed by HHD should be interpreted with caution. [ABSTRACT FROM AUTHOR]

be important in planning return to sport. The aim of this study was to (1) determine the test–retest reliability of clinically relevant, angle-specific rotational and peak torque measurements in a cohort of uninjured collision and contact athletes; (2) develop a normal descriptive profile of angle-specific rotational torque measurements in the same cohort; and (3) examine the effects of direction and joint angle on shoulder rotational strength interlimb asymmetries. Twenty-three collision and contact athletes were recruited for the interday reliability substudy and 47 athletes were recruited for the remaining substudies. We used intraclass correlation coefficients with 95% confidence intervals to quantify interday reliability of all variables. We used a 2-way repeated-measures analysis of variance to analyze differences in absolute interlimb asymmetries. Interday reliability for the isokinetic strength variables was good to excellent (0.78–0.90) on the dominant side and moderate to good (0.63–0.86) on the nondominant side. Maximum angle-specific torque (as well as peak torque) can be measured reliably in internally and externally rotated positions. A normal profile of clinically relevant, angle-specific shoulder rotational torque measurements for collision and contact athletes has been established which provides a reference when assessing shoulder strength in this population. [ABSTRACT FROM AUTHOR]

Background and study aim. Shoulder injuries are common in women volleyball players, often resulting from repetitive overhead movements. Effective strength training methods can help prevent these injuries. This study aimed to investigate the efficacy of an eight-week resistance band training program on shoulder muscle strength enhancement and injury prevention in women volleyball athletes. Material and Methods. Forty collegiate women volleyball players, aged 18-25, were randomly assigned to either an intervention group (n=20) or a control group (n=20). The intervention group underwent a structured resistance band training program targeting shoulder strength, which included exercises like shoulder presses, lateral raises, internal and external rotations, and scapular retractions. Isokinetic dynamometry was used to assess shoulder muscle strength before and after the intervention, measuring peak torque of the shoulder flexors, extensors, internal rotators, and external rotators. Injury rates were monitored throughout the volleyball season, documenting the number and severity of shoulder injuries. Results. Significant improvements in shoulder muscle strength were observed in the intervention group across all measured parameters (p < 0.001), while the control group showed minimal changes (p > 0.05). Moreover, the intervention group exhibited a significant reduction in shoulder injury rates post-intervention (p = 0.041), whereas the control group's injury rates remained stable (p = 0.768). Conclusions. The findings suggest that resistance band training effectively enhances shoulder muscle strength and reduces injury rates in women volleyball athletes. Integrating targeted strength training, such as resistance band exercises, into regular training routines may help enhance athlete performance and mitigate injury risk in sports characterized by repetitive overhead movements. Further research is needed to explore the long-term effects and optimal implementation strategies of resistance band training in athletic contexts. [ABSTRACT FROM AUTHOR]

Background: Previous research has established good test–retest reliability for isokinetic dynamometry in fibromyalgia. However, the reliability of this test under dual-task conditions has not been investigated in fibromyalgia. Methods: A total of 10 women with fibromyalgia participated in this study. Participants completed the concentric/concentric test. The dual-task condition involved subtracting two by two while performing the test. Results: Reliability analysis under the single condition showed "poor" to "excellent" values for maximum peak torque in knee extension and "moderate" to "excellent" values for average. "Poor" to "excellent" reliability values were found in knee flexion for the maximum and average. Dual-task condition in knee extension ranged from "moderate" to "excellent" for maximum and average values, and in knee flexion, it ranged from "poor" to "excellent" for maximum value and from "moderate" to "excellent" for average value. Conclusions: Isokinetic dynamometry demonstrated sufficient reliability for measuring strength in knee extension maximum and average during single-task and dual-task conditions, along with knee flexion dual-task average in fibromyalgia. For knee flexion single-task maximum and average and knee flexion dual-task maximum, we did not obtain sufficiently reliable measurements. Only the concentric/concentric test has been studied, and future studies with a larger sample size are needed in order to generalize the results. [ABSTRACT FROM AUTHOR]

Background Abnormal gait is prevalent among the elderly population, leading to reduced physical activity, increased risk of falls, and the potential development of dementia and disabilities, thus degrading the quality of life in later years. Numerous studies have highlighted the crucial roles of lower limb muscle strength asymmetry and static postural control in gait, and the reciprocal influence of lower limb muscle strength asymmetry on static postural control. However, research exploring the interrelationship between lower limb muscle strength asymmetry, static postural control, and gait performance has been limited. Methods A total of 55 elderly participants aged 60 to 75 years were recruited. Isokinetic muscle strength testing was used to assess bilateral knee extension strength, and asymmetry values were calculated. Participants with asymmetry greater than 15% were categorized as the Asymmetry Group (AG), while those with asymmetry less than 15% were classified in the Symmetry Group (SG). Gait parameters were measured using a plantar pressure gait analysis system to evaluate gait performance, and static postural control was assessed through comfortable and narrow stance tests. Results First, participants in the AG demonstrated inferior gait performance, characterized by slower gait speed, longer stance time and percentage of stance time in gait, and smaller swing time and percentage of swing time in gait. Spatial-temporal gait parameters of the weaker limb tended to be abnormal. Second, static postural control indices were higher in AG compared to SG in all aspects except for the area of ellipse during the comfortable stance with eyes open test. Third, abnormal gait parameters were associated with static postural control. Conclusion Firstly, elderly individuals with lower limb muscle strength asymmetry are prone to abnormal gait, with the weaker limb exhibiting poorer gait performance. Secondly, lower limb muscle strength asymmetry contributes to diminished static postural control in the elderly. Thirdly, the mechanism underlying abnormal gait in the elderly due to lower limb muscle strength asymmetry may be linked to a decline in static postural control.

This research investigates functional strength ratios in young elite athletes across different sports disciplines with different movement characteristics, focusing on the relationship between these ratios and physical performance. Purpose: the study aims to examine the differences in functional ipsilateral and bilateral strength ratios among athletes in symmetrical, asymmetrical, and hybrid sports and assess how these disparities impact strength parameters. Material & Methods: the study comprised 56 male athletes aged 18-28, excluding those with lower limb injuries or limitations affecting performance. The participants were divided into symmetrical, asymmetrical, and hybrid sports categories. Strength assessment utilised an isokinetic dynamometer, focusing on quadriceps-to-hamstring strength and bilateral strength ratios. The study employed MANOVA as the major statistical test for the purpose of the study. Results: athletes in asymmetrical sports demonstrated higher bilateral symmetry in knee extensors compared to symmetrical (0.94±5.98) and hybrid sports (4.9±10.32), with values of 12.89±8.56. The functional hamstring to quadriceps (H:Q) strength ratio showed lower ratios in hybrid sports (right limb: 0.60±0.12, left limb: 0.61±0.09) compared to symmetrical (right limb: 0.79±0.16, left limb: 0.94±0.27) and asymmetrical sports (right limb: 1.05±0.26, left limb: 1.03±0.24), yet within normative values. These findings suggest that sport-specific demands significantly influence functional strength ratios, highlighting the importance of tailored training and rehabilitation programs. The observed strength asymmetries, particularly in sports with unilateral movements, underline the need for sport-specific training approaches to address these imbalances. Conclusion: the study revealed that sport-specific training can lead to strength asymmetries within normal ranges, suggesting that they may not substantially induce muscular imbalances. However, the distinct H:Q ratio patterns in hybrid sports emphasise the need for customised training and rehabilitation strategies.

Exercise intolerance in chronic obstructive pulmonary disease (COPD) is associated with dyspnea, reduced inspiratory capacity (IC) and occurs with a neuromuscular "power reserve," i.e., an acute ability to increase isokinetic locomotor power. This power reserve is associated with resting forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) suggesting that treatments to target pulmonary function may protect neuromuscular performance and extend whole body exercise in COPD. We, therefore, tested whether combination long-acting β-agonist and muscarinic antagonist bronchodilator therapy [long-acting muscarinic antagonist (LAMA) + long-acting β-agonist (LABA); Stiolto Respimat] would ameliorate the decline in neuromuscular performance and increase endurance time during constant power cycling at 80% peak incremental power. Fourteen patients with COPD (4 female; 64 [58, 72] yr; FEV1 67% [56%, 75%] predicted; median [25th, 75th percentile]) participated in a randomized, placebo-controlled crossover trial (NCT02845752). Pulmonary function and cardiopulmonary exercise responses were assessed before and after 1 wk of treatment, with 2 wk washout between conditions. Performance fatigue was assessed using an ∼4-s maximal isokinetic cycling effort at preexercise, isotime, and intolerance. Isotime was the shorter exercise duration of the two treatment conditions. Significance was assessed using ANOVA with treatment as fixed factor and subject as random factor. FEV1 was greater with LAMA + LABA versus placebo (1.81 [1.58, 1.98] L vs. 1.72 [1.29, 1.99] L; P = 0.006), but IC at isotime, performance fatigue at isotime, and constant power endurance time were not different between conditions (each P > 0.05). A modest (∼95 mL) increase in FEV1 following 1 wk of combination LAMA + LABA treatment did not alleviate neuromuscular performance fatigue or enhance cycle exercise tolerance in patients with mild-to-severe COPD with largely preserved "static" lung volumes.NEW & NOTEWORTHY Bronchodilation is known to increase forced expiratory volume in 1 s (FEV1) and reduce hyperinflation in COPD. In a randomized controlled trial, we investigated whether combined inhaled long-acting β-agonist and muscarinic antagonist would alleviate maximal voluntary neuromuscular performance fatigue or enhance maximal muscle activation during cycling in patients with COPD. Despite increased FEV1, combination bronchodilator therapy did not reduce neuromuscular performance fatigue or enhance muscle activity or exercise tolerance in patients with mild-to-severe COPD.

Isokinetic metrics are suggested to be related to vertical jump performance, but little is known about the possible sex differences in this relationship in adolescent track and field athletes. The aim of the study was to examine the possible sex differences in the strength of the relationship between the kinetic parameters of the vertical squat jump with arms akimbo, the countermovement jump with arms akimbo, and the countermovement jump with free arm swing with the isokinetic parameters of the knee extensor and flexor muscles (angular velocities: 60°/s and 300°/s). In total, 35 (males: 21, females: 14) U18 track and field athletes were examined. The results revealed that the Men U18 group had higher vertical jump performance, higher values in the kinetic parameters of the vertical jump tests, higher knee extensor torque, and higher knee flexor torque in the non-dominant leg compared to the Women U18 group. Significant (p < 0.05) sex differences were observed in the relationship between the isokinetic parameters and the vertical jump performance metrics, as the Women U18 athletes relied more on the knee flexor torque than Men U18 athletes, and demonstrated a stronger negative relationship between selected isokinetic metrics and the pre-stretch gain in the vertical jump tests. In conclusion, it is recommended that young female track and field athletes minimize interlimb asymmetry and improve the convention ratio in their non-dominant leg to optimize vertical jump performance.

Background: High-intensity anaerobic physical training frequently leads to muscle fatigue among boxers and kickboxers. Vibrational therapy (VT) and passive rest (PR) have been employed as methods to enhance muscular recovery and performance. This study evaluates the effectiveness of these two recovery methods on upper limb muscle strength and lactate levels in plasma after high-intensity exertion. Methods: Eighteen elite boxers and kickboxers, aged 19–32 years, underwent tests employing VT and PR as recovery methods in a controlled, crossover study. Muscle performance was assessed via isokinetic dynamometry, and lactate levels were measured pre-exercise, post-exercise, and post-recovery. The study adhered to the Declaration of Helsinki guidelines and was approved by the relevant bioethics committee. Results: The results showed that VT led to a faster recruitment of muscle fibers and improved muscle endurance as indicated by decreased fatigue work indices compared to PR. However, no significant differences were observed in peak torque or lactate levels between the two recovery methods. The VT group exhibited quicker recovery times in torque generation and better performance in fatigue resistance. Conclusions: VT appears to provide superior muscular recovery compared to PR following intense anaerobic effort, particularly in terms of muscle strength endurance and activation speed. These findings support the potential of VT in sports recovery protocols, although similar lactate response suggests that metabolic recovery rates are not significantly affected.

Purpose: The aim of this report is to measure and analyse the isometric and isokinetic (concentric) peak torque (PT) of knee extensors and flexors of the involved and uninvolved limb of twin professional football players over one year post anterior cruciate ligament reconstruction (ACLR). To calculate the unilateral and bilateral asymmetry indexes and compare the athlete's PT values with sport-specific and position-specific data. Case description: Strength measurements of the knee extensors and flexors were conducted on two ACLR football players (twins) on the involved and uninvolved limbs in isometric and concentric modes of muscle contractions, and unilateral/bilateral asymmetry indexes were calculated. Results: The peak torque isometric data indicated that the strength characteristics of the involved leg extensors in both patients were significantly lower compared to the uninvolved limb and were indicators of higher secondary injury risk. The first athlete's concentric peak torque values showed relatively good return-to-sport results, while the second football player returned to sport having not met the recovery criteria. Both athletes require additional specific muscle strength exercises on the extension and flexion muscle groups to reach the ACL reconstruction recovery targets. Conclusions: In this case report, the possibilities of isokinetic dynamometric testing in an isometric and concentric mode of football players to more accurately assess the extent of the muscle strength deficiency and asymmetry are demonstrated. This more precise information allows to the creation of correct training and therapeutic program to recover the knee muscle groups' strength and unilateral/bilateral strength balance to avoid reinjury.

The total number of confirmed cases of COVID-19 caused by SARS-CoV-2 virus infection is over 621 million. Post-COVID-19 syndrome, also known as long COVID or long-haul COVID, refers to a persistent condition where individuals experience symptoms and health issues after the acute phase of COVID-19. The aim of this study was to assess the strength and fatigue of skeletal muscles in people recovered from COVID-19. A total of 94 individuals took part in this cross-sectional study, with 45 participants (referred to as the Post-COVID Cohort, PCC) and 49 healthy age-matched volunteers (Healthy Control Cohort, HCC). This research article uses the direct dynamometry method to provide a detailed analysis of post-COVID survivors' strength and power characteristics. The Biodex System 4 Pro was utilized to evaluate muscle strength characteristics during the fatigue test. The fatigue work in extensors and flexors was significantly higher in the PCC. The PCC also showed significantly less power in both extensors and flexors compared to the HCC. In conclusion, this study provides compelling evidence of the impact of post-COVID-19 fatigue on muscle performance, highlighting the importance of considering these effects in the rehabilitation and care of individuals recovering from the virus. PCC achieved lower muscle strength values than HCC. [ABSTRACT FROM AUTHOR]

Giordano, KA, Cassidy, MM, and Oliver, GD. Length-tension differences between concentric and eccentric shoulder rotation strength. J Strength Cond Res 38(2): 253-258, 2024--Eccentric contractions generally produce more force than concentric contractions. However, if length-tension relationships affect both contractions equally remains unknown. Therefore, our purpose was to compare concentric versus eccentric shoulder external and internal rotation strength across a continuous 90° arc. Fifty-two physically active individuals performed isokinetic concentric and eccentric shoulder external rotation and internal rotation through a 90° arc (forearm horizontal to forearm vertical) with the shoulder elevated in both the frontal and scapular planes. Statistical parametric mapping analysis compared concentric and eccentric trials within subjects. Frontal plane eccentric external rotation torque was greater than concentric 30°-90° (p, 0.01) external rotation, and concentric external rotation torque was greater 5°-15° external rotation (p50.01). Frontal plane, eccentric internal rotation torque was greater than concentric 15°-55° external rotation (p < 0.01), and concentric torque was greater at forearm horizontal (p50.05) and 70°-90° external rotation (p < 0.01). Scapular plane eccentric external rotation torque was greater than concentric 30°-90° external rotation (p, 0.01) and concentric external rotation torque was greater 5°-20° external rotation (p < 0.01). Scapular plane eccentric internal rotation torque was greater than concentric 15°-60° external rotation (p < 0.01), and concentric torque was greater at forearm horizontal (p50.05) and 78°-90° external rotation (p50.02). Coaches, clinicians, and researchers should interpret data from studies reporting isokinetic data with the understanding that isokinetic peak strength values are not comparing the same muscle length and are not an appropriate measure for all muscle lengths. Furthermore, shoulder stability is affected through decreased eccentric force production at end ranges of shoulder rotation. [ABSTRACT FROM AUTHOR]

Resistance training is a widely used method to enhance muscle strength, with acute program variables influencing muscle adaptations. This study focused on the often-neglected variable of inter-set rest interval duration and its impact on muscle strength gains. Existing literature presents conflicting findings, with some studies advocating for longer rest intervals, while the others show comparable strength increases with shorter rests. Methodological differences in prescription and sample groups contributed to these inconsistencies. This study investigated the effect of short and long inter-set rests on maximal isokinetic strength gains of the upper and lower extremities during slow and fast angular velocities after eight weeks of resistance training. The research involved 26 healthy strength-trained males (age=20±1 year, body mass=81.5±8.8 kg, body height=184.4±6.1 cm) randomly assigned to G1m (1-minute rest) or G3m (3-minute rest). The resistance training programs were matched for all acute program variables, emphasizing the rest interval as the primary difference. Isokinetic dynamometry pre- and post-training assessed knee and elbow extensor and flexor maximal strength at 60°/s and 120°/s. The training program consisted of seven exercises performed at 70% 1RM until muscle failure three times per week over eight weeks. The most important result was that G3m, in contrast to G1m, led to a higher increase in peak torque of the knee (p=.037) and elbow extensors (p=.007) as well as the elbow flexors (p=.045) at 60°/s. Furthermore, G3m and G1m similarly increased the peak torque of the knee and elbow extensors and flexors at 120°/s and of the knee flexors at 60°/s (p>.138). In conclusion, the study suggests that strength training with longer inter-set rest intervals may lead to similar strength gains as strength training with shorter inter-set rest intervals. Nonetheless, individuals who prioritize maximizing their strength gains are advised to utilize longer rest intervals. However, shorter rest intervals may still yield significant strength enhancements, particularly for those who are limited by time. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Investigación Cuerpo, Cultura y Movimiento is the property of Universidad Santo Tomas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of German Journal of Sports Medicine / Deutsche Zeitschrift fur Sportmedizin is the property of Verein zur Forderung der Sportmedizin Hannover e.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Age-related declines in the musculoskeletal system may place additional demands on the lumbar spine during everyday activities such as walking. This study aimed to investigate age-related differences in the functional demand (FD) of walking on the lumbar spine in older and younger adults. A motion analysis system with integrated force plates was used to acquire kinematic and kinetic data on 12 older (67.3 ± 6.0 years) and 12 younger (24.7 ± 3.1 years) healthy men during walking at a self-selected speed along a 10 m walkway. Isokinetic dynamometry was used to acquire the maximal joint moment capacity of the lumbar spine. The FD of the lumbar spine was calculated as the muscle moment during key phases of the gait cycle (GC) relative to the maximum moment capacity of the lumbar spine. The difference in FD between age groups was not significant (p = 0.07) and there were no significant differences between the young group (YG) and older group (OG) for any individual phase in the GC. Despite the lack of statistical significance, the results indicate that a practical difference may exist, as walking was approximately 20% more functionally demanding on the lumbar spine in the OG compared to the YG. Therefore, older adults may employ modified gait strategies to reduce mechanical load whilst walking to fall within the limits of their maximal force-producing capacity in the lumbar spine, which may have implications for injury risk.

Context: The effect of local cooling on muscle strength presents conflicting debates, with literature undecided as to the potential implications for injury, when returning to play following cryotherapy application. Objective: To investigate concentric muscle strength following local cooling over the anterior thigh compared with the knee joint in males and females and the temporal pattern over a 30-minute rewarming period. Design: Repeated-measures crossover design. Method: Twelve healthy participants randomly assigned to receive cooling intervention on one location, directly over either the anterior thigh or the knee, returning 1 week later to receive the cooling intervention on opposite location. Muscle strength measured via an isokinetic dynamometer at multiple time points (immediately post, 10-, 20-, and 30-min post) coincided with measurement of skin surface temperature (Tsk) using a noninvasive infrared camera. Results: Significant main effects for time (P ≤.001, η2 =.126) with preice application higher than all other time points (P ≤.05) were demonstrated for both peak torque and average torque. There were also significant main effects for isokinetic testing speed, sex of the participant, and position of the ice application for both peak torque and average torque (P ≤.05). Statistically significant decreases in Tsk were reported in both gender groups across all time points compared with preintervention Tsk for the anterior thigh and knee (P <.05). Conclusions: Reductions reported for concentric peak torque and average torque knee-extensor strength in males and females did not fully recover to baseline measures at 30-minute postcryotherapy interventions. Sports medicine practitioners should consider strength deficits of the quadriceps after wetted ice applications, regardless of cooling location (joint/muscle) or gender. [ABSTRACT FROM AUTHOR]

Background. Whole-body vibration (WBV) has proven to be an efficient tool in improving the physical qualities of the neuromuscular system, such as increasing muscle strength, performance, joint stability, electromyographic signal, proprioception, among others. Its use in the upper limbs and joint instabilities has shown good immediate results in a single session. The aim of this study was to analyze the acute effects of the use of mechanical vibration on the muscle strength of subjects with shoulder instability. Methods. 10 athletes in the process of post-surgical rehabilitation of shoulder instability were volunteers in this study. Muscle strength was tested in the internal (IR) and external (ER) rotation movements in the neutral position using isokinetic dynamometry at two angular velocities - 60 and 180º/s in three moments: before, immediately after, and 10 minutes after the application of WBV. The WBV was applied only once, using a frequency of 30 Hz, with the patient assuming the arm flexion position on the platform during 5 series of 30 seconds of stimulation. Results. The limb with shoulder instability benefited in both movements - ER and IR - and in both angular velocities. The limb without instability, on the other hand, had increased strength only in the RI movements at 60º/s and RE at 180º/s. Conclusions. It is concluded that a single session of WBV applied directly to the upper limbs is capable of acutely improving muscle strength in both limbs in subjects with shoulder instability, with the affected limb being the most benefited. [ABSTRACT FROM AUTHOR]

Handball athletes are subjected to high loads, especially during the process of throwing or shooting overhead. These athletes often complain of pain and report unexplained loss of throwing velocity and throwing control. Shoulder dyskinesia and overuse syndrome have been identified as risk factors among elite handball athletes. Understanding the dynamics and kinematics of the throwing phase is vital for the exercise professional. This study evaluates the effect of an interventional exercise program on shoulder girdle biomechanics and overhead shooting. The sample consisted of 20 high level handball athletes from Greece. The athletes were divided into two groups: 10 in the study group, who were given the exercise program, and 10 in the control group, who only engaged in in-team handball training. Before and after the program, the following measurements were performed: a) angular measurements of abduction, adduction, flexion and extension of the shoulder; b) isokinetic evaluation of abduction flexion and adduction extension of the shoulder joint, at three angular velocities (60°/sec, 180°/sec and 300°/sec). Inferential statistics showed that there was a statistically significant difference in angular measurements with a reduction in range of motion for 10 of the study group. In the isokinetic assessment there was a statistically significant difference, in the 180°/sec velocities in flexion and extension, and in the deficit of flexion of both shoulders. In conclusion, the interventional exercise program had, to some extent, a beneficial effect on muscle strengthening of the shoulder girdle. The results of this study may suggest training guidelines, provide important information to exercise professionals, and provide feedback to handball athletes. [ABSTRACT FROM AUTHOR]

Abstract Background Robotic-assisted unicompartmental knee arthroplasty (UKA) improves implant accuracy, however whether this translates to patient function is less clear. Various outcomes have been reported but muscle recovery has not been previously investigated. Objective To explore sequential change in lower limb muscle strength following robotic-assisted UKA with isokinetic dynamometry. Results 12 participants undergoing rUKA for medial compartment osteoarthritis were assessed pre-operatively, and at 6- and 12-weeks post-operatively. Maximal muscle strength changed over time in both quadriceps (p = 0.006) and hamstrings (p = 0.018) muscle groups. Quadriceps strength reduced from 88.52(39.86)Nm to 74.47(27.58)Nm by 6-weeks (p = 0.026), and then recovered to 90.41(38.76)Nm by 12-weeks (p = 0.018). Hamstring strength reduced from 62.45(23.18)Nm to 54.12(20.49)Nm by 6-weeks (p = 0.016), and then recovered to 55.07(17.99)Nm by 12-weeks (p = 0.028). By 12-weeks quadriceps strength was 70% and hamstrings 83% of the values achieved in the un-operated limb. Substantial improvement was seen in all other measures over time, with sequential positive change in Timed-up-and-go test (p = 0.015), 10 m walk test (p = 0.021), range of knee flexion (p = 0.016) and PROMs (p

The purpose of this study was to identify velocity-specific changes in electromyographic root mean square (EMG RMS), EMG frequency (EMG MPF), mechanomyographic RMS (MMG RMS), and MMG MPF during maximal unilateral isokinetic muscle actions performed at 60° and 240°·s-1 velocities within the right and left vastus lateralis (VL) after 4 weeks of dynamic constant external resistance (DCER) bilateral leg press training. Twelve resistance-trained men (age: mean ± SD = 21.4 ± 3.6 years) visited the laboratory 3d·wk-1 to perform resistance training consisting of 3 sets of 10 DCER leg presses. Four, three-way analysis of variance were performed to evaluate changes in neuromuscular responses (EMG RMS, EMG MPF, MMG RMS, and MMG MPF) from the right and left VL during 1 single-leg maximal isokinetic leg extension performed at 60° and 240°·s-1 before and after 4 weeks of DCER leg press training (p < 0.05). The results indicated a 36% increase in EMG RMS for the right leg, as well as a 23% increase in MMG RMS and 10% decrease in MMG MPF after training, collapsed across velocity and leg. In addition, EMG RMS was 65% greater in the right leg than the left leg following training, whereas EMG MPF was 11% greater for the left leg than the right leg throughout training. Thus, 4 weeks of DCER leg press training provides sufficient stimuli to alter the neuromuscular activation process of the VL but not velocity-specific neuromuscular adaptations in trained males. [ABSTRACT FROM AUTHOR]

Handball athletes are subjected to high loads especially during the process of overhead throwing. Female and male athletes often complain of pain and report unexplained loss of speed and control of ball transfer. Shoulder blade dyskinesia and overuse syndrome have been identified as risk factors for injury among elite handball athletes. Understanding the dynamics of ball transfer and its kinematic phase is crucial for health professionals. In this study, the effect of an interventional exercise program was evaluated to investigate its effect on the range of motion and muscle activation of the shoulder girdle, elements that are major components of ball transfer in handball. The sample consisted of 20 high level handball athletes from Greece. The athletes were divided into two groups, 10 study 10 control group and were given the exercise program. Before and after the application of the program, the following measurements were performed: a) Angular external and internal rotation b)Isokinetic evaluation of shoulder at external and internal rotation in 90° abduction, at 60°/sec, 180°/sec and 300°/sec angular velocities. Statistically significant difference showed: a) in external rotation of 180°/sec, b) the deficit internal rotation of 300°/sec and c) in the deficit of external and internal rotator muscles, after inferential statistics was contacted. Statistically significant difference also showed in 300°/sec ratio of left shoulder, increasing the external towards the internal torque. In conclusion, from the angular evaluation, it appeared that the results in the range of motion were not as expected. The interventional program was not as beneficial as it would expect. This contradicts the results in the deficits and ratio in both the internal and external rotation of both shoulders, in witch was sufficiently beneficial. The results of the study suggest training guidelines giving important information to the health professionals involved, while providing feedback to the handball athletes. [ABSTRACT FROM AUTHOR]

Purpose: Limb dominance and consequent between-limbs muscle strength in soccer players should be explored to determine a standard musculoskeletal profile to maintain and establish during screening protocols and postinjury rehabilitation. The primary aim of this review was to identify dominant- vs non-dominant-lower-extremity muscle-strength characteristics of healthy soccer players, with secondary aims to consider available between-limbs outcome measures and directions for future research. Methods: Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Five electronic databases were used for study identification with guidance from a medical librarian. Inclusion criteria consisted of studies employing a cross-sectional design assessing soccer players of all ages, genders, and levels of play that identified limb dominance and associated lower-extremity muscle strength as a main purpose of the experiment. Results: The literature search identified 3471 articles. After screening titles, abstracts, and full texts, 17 articles were included in the review. Peak torques and hamstring-to-quadriceps ratios via isokinetic dynamometry were commonly used, and subsequent meta-analyses were conducted to yield remarkable between-limbs symmetry. Additional results of individual studies also demonstrate symmetry, except 1 article of velocity-dependent measures that reported greater strength in the dominant limb. Conclusions: In soccer, between-limbs muscle strength measured by maximal isokinetic dynamometry demonstrates symmetry across ages, genders, and levels of play. Future testing using alternative measures that more specifically replicate the movement demands of soccer players may further classify between-limbs characteristics. [ABSTRACT FROM AUTHOR]

Background: Robotic-assisted unicompartmental knee arthroplasty (UKA) improves implant accuracy, however whether this translates to patient function is less clear. Various outcomes have been reported but muscle recovery has not been previously investigated. Objective: To explore sequential change in lower limb muscle strength following robotic-assisted UKA with isokinetic dynamometry. Results: 12 participants undergoing rUKA for medial compartment osteoarthritis were assessed pre-operatively, and at 6- and 12-weeks post-operatively. Maximal muscle strength changed over time in both quadriceps (p = 0.006) and hamstrings (p = 0.018) muscle groups. Quadriceps strength reduced from 88.52(39.86)Nm to 74.47(27.58)Nm by 6-weeks (p = 0.026), and then recovered to 90.41(38.76)Nm by 12-weeks (p = 0.018). Hamstring strength reduced from 62.45(23.18)Nm to 54.12(20.49)Nm by 6-weeks (p = 0.016), and then recovered to 55.07(17.99)Nm by 12-weeks (p = 0.028). By 12-weeks quadriceps strength was 70% and hamstrings 83% of the values achieved in the un-operated limb. Substantial improvement was seen in all other measures over time, with sequential positive change in Timed-up-and-go test (p = 0.015), 10 m walk test (p = 0.021), range of knee flexion (p = 0.016) and PROMs (p < 0.025). [ABSTRACT FROM AUTHOR]

Older individuals fatigue more rapidly during, and recover more slowly from, dynamic exercise. Women are particularly vulnerable to these deleterious effects of aging, which increases their risk of falling. We have shown that dietary nitrate (NO3−), a source of nitric oxide (NO) via the NO3− → nitrite (NO2−) → NO pathway, enhances muscle speed and power in older individuals in the non‐fatigued state; however, it is unclear if it reduces fatigability and/or improves recoverability in this population. Using a double‐blind, placebo‐controlled, crossover design, we studied 18 older (age 70 ± 4 years) women who were administered an acute dose of beetroot juice (BRJ) containing either 15.6 ± 3.6 or <0.05 mmol of NO3−. Blood samples were drawn throughout each ~3 h visit for plasma NO3− and NO2− analysis. Peak torque was measured during, and periodically for 10 min after, 50 maximal knee extensions performed at 3.14 rad/s on an isokinetic dynamometer. Ingestion of NO3−‐containing BRJ increased plasma NO3− and NO2− concentrations by 21 ± 8 and 4 ± 4 fold, respectively. However, there were no differences in muscle fatigue or recovery. Dietary NO3− increases plasma NO3− and NO2− concentrations but does not reduce fatigability during or enhance recoverability after high intensity exercise in older women. [ABSTRACT FROM AUTHOR]

Isokinetic dynamometry is used during exercise testing and rehabilitation to obtain a quantitative strength measurement on which progressive strength training programs can be based. This study assesses the test–retest reliability of isokinetic leg function in the knee flexors and extensors at 150°/s in children and young adults with severe burns to be used for rehabilitation exercise program prescription. In 39 severely burned patients (49 ± 14% total body surface area burn [TBSA], mean ± SD; 34 ± 21% TBSA 3rd degree; 14 ± 5 years, 153.3 ± 16.5 cm height; 53.8 ± 17.9 kg) knee flexion/extension isokinetic dynamometry at 150°/s was performed on each patient's dominant leg in two sessions. The patient was acquainted with the test and performed 1 set of 10 repetitions at 150°/s. A second session of 1 set of 10 repetitions at 150°/ was performed within 24 h of the first. Muscle function outcomes were knee flexion/extension peak torque, average peak torque, and average power. One-sample paired t tests were performed for all muscle function outcomes; intraclass correlation coefficients and r 2 values with session two as a function of session one were calculated. Sessions did not differ significantly in knee extension or flexion for any muscle function outcome or the hamstrings to quadriceps ratio. All intraclass correlation coefficients were >0.89 and r 2 > 0.79. Test–retest isokinetic dynamometry functional measurements in the knee flexors and extensors at 150°/s are reliable in the burn population and may aid resistance rehabilitation program prescriptions. [ABSTRACT FROM AUTHOR]

Isokinetic dynamometry represents the clinical gold standard for strength assessment but testing lack consensus. Elite youth male football players (n = 28) completed 20 repetitions (analysed as four epochs) of eccentric knee flexor (eccKF) and concentric knee extensor (conKE) trials at 60, 180 and 270°∙s−1, quantifying peak torque (PT) and functional range (FR). There was a significant (P < 0.001) main effect for fatigue and angular velocity in conKE PT; eccKF PT was not significant across epoch (P = 0.35) and velocity (P = 0.12) and a velocity x epoch interaction highlighted more repetitions were required to elicit fatigue as velocity increased. FR decreased with fatigue (P < 0.001) and velocity (P < 0.01) in conKE and eccKF, indicative of a narrowing of the strength curve. Clinical interpretation advocates an isokinetic test comprising at least 15 reps at a velocity ≥ 180°∙s−1 and analysis beyond the peak of the strength curve (PT) to inform clinical reasoning and individualized exercise prescription. [ABSTRACT FROM AUTHOR]

Sprinting at maximum velocity requires fast angular motion of the thigh and effective hamstring function for optimum performance and injury prevention. In this cross-sectional investigation of 21 male sprinters, we acquired thigh angular kinematics while sprinting at top speed (range: 8.96–10.17 m/s), and then measured eccentric hamstring strength capacities using an isokinetic dynamometer during the same test session. In agreement with the hypotheses, thigh angular motion rates and the associated eccentric hamstring strength capacities were both significantly correlated with top speed (r -values: ∼0.5; p < 0.05). Additionally, when the participants were sorted by top speed, there were significant differences between the faster group and the slower group. Notably, on average the faster group showed faster thigh motion (angular acceleration: 10.3 kdeg/s2, 11 % greater than slower group) and higher eccentric hamstring strength capacities (peak moment: 2.26 Nm/kg, 14 % greater than slower group). This investigation indicates that fast thigh angular motion and eccentric hamstring strength are both important for sprint performance. [ABSTRACT FROM AUTHOR]

This study aimed to determine the test–retest reliability of a range of transcranial magnetic stimulation (TMS) outcomes in the biceps femoris during isometric, eccentric and concentric contractions. Corticospinal excitability (active motor threshold 120% [AMT120%] and area under recruitment curve [AURC]), short‐ and long‐interval intracortical inhibition (SICI and LICI) and intracortical facilitation (ICF) were assessed from the biceps femoris in 10 participants (age 26.3 ± 6.0 years; height 180.2 ± 6.6 cm, body mass 77.2 ± 8.0 kg) in three sessions. Single‐ and paired‐pulse stimuli were delivered under low‐level muscle activity (5% ± 2% of maximal isometric root mean squared surface electromyography [rmsEMG]) during isometric, concentric and eccentric contractions. Participants were provided visual feedback on their levels of rmsEMG during all contractions. Single‐pulse outcomes measured during isometric contractions (AURC, AMT110%, AMT120%, AMT130%, AMT150%, AMT170%) demonstrated fair to excellent reliability (ICC range,.51 to.92; CV%, 21% to 37%), whereas SICI, LICI and ICF demonstrated good to excellent reliability (ICC range,.62 to.80; CV%, 19 to 42%). Single‐pulse outcomes measured during concentric contractions demonstrated excellent reliability (ICC range,.75 to.96; CV%, 15% to 34%), whereas SICI, LICI and ICF demonstrated good to excellent reliability (ICC range,.65 to.76; CV%, 16% to 71%). Single‐pulse outcomes during eccentric contractions demonstrated fair to excellent reliability (ICC range,.56 to.96; CV%, 16% to 41%), whereas SICI, LICI and ICF demonstrated good to excellent (ICC range,.67 to.86; CV%, 20% to 42%). This study found that both single‐ and paired‐pulse TMS outcomes can be measured from the biceps femoris muscle across all contraction modes with fair to excellent reliability. However, coefficient of variation values were typically greater than the smallest worthwhile change which may make tracking physiological changes in these variables difficult without moderate to large effect sizes. [ABSTRACT FROM AUTHOR]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

After anterior cruciate ligament reconstruction (ACLR), there are differences in the neuromuscular deficits observed in patients with bone‐patellar tendon‐bone (BPTB) and with hamstring tendon (HT) autografts. The differences in knee extensor and flexor strength are commonly reported, but analyses have largely focused on peak torque metrics despite the requirement to generate torque through range when returning to sport. The aim of this study was to investigate the angle‐specific strength and strength asymmetry differences between BPTB and HT around the time of return to play after ACLR. A total of 357 male field sport athletes with either a BPTB (n = 297) or an HT (n = 60) autograft underwent concentric knee flexor and extensor isokinetic strength testing 9 months post‐ACLR. Angle‐specific torques were compared between grafts and limbs using 1D Statistical Parametric Mapping and discrete‐point variables. Inter‐limb extensor torque asymmetry was greater in BTPB than HT at knee angles of >30° (p = 0.001, peak d = 5.53), with flexor torque asymmetry lower in BPTB than HT at flexion angles of >25° (p = 0.001, peak d = 2.68). Angle of maximum asymmetry and angle of operated limb peak torque differed in knee extension for BPTB (p < 0.001, d = 0.32) but not HT, whereas knee flexion angle of maximum asymmetry and operated limb peak torque differed in both BTPB (p < 0.001, d = 0.75) and HT (p < 0.001, d = 0.43). Graft type affected extensor torque at knee angles of 67°–85° and flexor torque at knee angles of 27°–85°. Angle‐specific strength analysis may inform the rehabilitation process and improve rehabilitation and return‐to‐play decision making strategies in comparison with the use of peak torque values alone. [ABSTRACT FROM AUTHOR]

Purpose: Chronic Achilles tendon rupture with a 2–5 cm gap is usually repaired using a V-Y advancement flap. This study examined the clinical outcomes after a V-Y advancement flap for a chronic Achilles tendon rupture and compared the postsurgical muscle strength of the affected limb with the unaffected side using a constant velocity dynamometer. Materials and Methods: Twenty patients (14 male, six female) who underwent a V-Y advancement flap for chronic Achilles tendon rupture between March 2011 and September 2019 were reviewed retrospectively. The following clinical outcomes were evaluated preinjury, preoperatively, and postoperatively: the Foot and Ankle Ability Measure (FAAM) daily living and sports subscales, Thermann score, American Orthopaedic Foot and Ankle Society score, and Achilles Tendon Total Rupture Score. At the last follow-up, the muscle torque at an ankle plantar flexion of 30°, 60°, and 120° was measured on both sides using a constant velocity dynamometer (HUMAC® ) to determine the gastrocnemius-soleus complex strength. Results: The postoperative average deficiency of plantar flexion strength in the affected side was 10.40% for plantar flexion peak torque at 30°/s, and 15.89% for peak torque at 120°/s. The mean FAAM daily living subscale improved to 98.81±1.54 from 94.28±5.48 pre-injury (p<0.001). On the other hand, the mean FAAM sports subscale decreased to 85.28±4.47 from 95.71±4.27 pre-injury (p<0.001). Conclusion: Chronic Achilles tendon rupture repair by a V-Y advancement flap leads to successful return to pre-injury daily life activities without additional treatment. [ABSTRACT FROM AUTHOR]

Background: Running is a very popular activity and muscle strength imbalance has been treated with caution to prevent injuries. Aim: The present study aimed to compare and correlate knee flexion and extension strength imbalance based on peak torque (PT) and total work (TW) in running athletes. Methods: Thirty-eight male amateur running athletes (38 ± 6 years; 80.6 ± 8.3 kg; 177 ± 7 cm; 7.8 ± 8.4 years of training; 3.5 ± 0.9 training sessions a week; 33.5 ± 13.4 km of training per week) took part in the present study. Knee flexion eccentric and concentric PT and TW, as well as concentric knee extension PT and TW were assessed. PT- and TW-based hamstring-to-quadriceps ratios (H:Q), as well as PT and TW contralateral imbalance were quantified. Results: A significant correlation was observed between TW and PT concentric knee flexion contralateral deficits (r = 0.52, p < 0.001). No further correlations were found among TW- and PT-based muscle strength imbalance variables (p > 0.05). All mean comparisons of H:Q and contralateral imbalances using TW or PT were significantly different (p < 0.05). Conclusions: Our results showed that TW and PT muscle strength imbalance were unrelated, and the H:Q and contralateral imbalance profile of endurance runners may differ based on the isokinetic variable analyzed. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether repeated carbohydrate (CHO) mouth rinsing would improve neuromuscular performance during high-intensity fatiguing contractions. Methods: Eighteen young men (age 26.1 ± 5.0 y, BMI 22.9 ± 1.9) performed 3 maximal voluntary isometric contractions (MVICPRE). Immediately after, they completed 10-second mouth rinse with 6.4% maltodextrin solution (MAL), 7.1% glucose solution (GLU), water (W), artificially sweetened solution (PLA), or a control trial with no rinse (CON) in a crossover protocol. Subjects performed 5 sets of 30 isokinetic fatiguing contractions at 180°/s, and an MVICPOST with their elbow flexors was performed after each mouth rinse. Mechanical and electromyographic (EMG) signals were recorded from the biceps brachii and parameters of interest analyzed. Results: When rinsing the mouth with a solution containing CHO, independently of the sweetness, isokinetic performance was enhanced as shown by the greater total work achieved in comparison with CON. The decay of torque and mean fiber-conduction velocity (MFCV) recorded at the end of the fatiguing task was lower when rinsing the mouth with GLU than with CON. The torque recorded during the MVICPOST was greater with CHO with respect to CON, and this was associated to a lower decay of MFCV. Conclusions: CHO mouth rinse counteracts fatigue-induced decline in neuromuscular performance, supporting the notion that CHO rinse may activate positive afferent signals able to modify motor output. Repeated mouth rinsing with sweet and nonsweet CHO-containing solutions can improve neuromuscular performance during an isokinetic intermittent fatiguing task. [ABSTRACT FROM AUTHOR]

Purpose: Multiple sclerosis (MS) disrupts joint position sense (JPS). The aims were: - to assess the JPS of knee extensors, using three target angles in MS patients and in healthy; - to estimate the changes in reproducing the joint position by using absolute (AE), constant (CE) and variable error (VE) and the effect of sex on knee JPS acuity. Subjects and Methods: Twenty MS patients and twenty healthy were tested, by knee joint angle reproduction with three targets (20o, 60o, 75o), by passive and active mode, without visual and verbal feedback. JPS measurement was done using isokinetic dynamometry. Deviations from the targets were calculated as AE, VE and CE, which correspond to accuracy, precision and direction of the bias, respectively. Results: Increased values of AE and sex differences in JPS accuracy in MS individuals, as compared with healthy, were: - at targets 20o and 60o in females in passive mode in both legs; - at 60o in the involved leg in males (more pronounced as compared with females); and – at 75o in the less involved leg, in passive reproduction in women and active in men. The significantly increased negative CE indicates a more pronounced deficit in males with MS at 60o in the involved leg and at 75o in less involved leg. Increased VE in passive repositioning was also proved (p

Exercise intolerance in chronic obstructive pulmonary disease (COPD) is associated with dyspnea, reduced inspiratory capacity (IC) and occurs with a neuromuscular "power reserve," i.e., an acute ability to increase isokinetic locomotor power. This power reserve is associated with resting forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) suggesting that treatments to target pulmonary function may protect neuromuscular performance and extend whole body exercise in COPD. We, therefore, tested whether combination long-acting β-agonist and muscarinic antagonist bronchodilator therapy [long-acting muscarinic antagonist (LAMA) þ long-acting β-agonist (LABA); Stiolto Respimat] would ameliorate the decline in neuromuscular performance and increase endurance time during constant power cycling at 80% peak incremental power. Fourteen patients with COPD (4 female; 64 [58, 72] yr; FEV1 67% [56%, 75%] predicted; median [25th, 75th percentile]) participated in a randomized, placebo-controlled crossover trial (NCT02845752). Pulmonary function and cardiopulmonary exercise responses were assessed before and after 1 wk of treatment, with 2 wk washout between conditions. Performance fatigue was assessed using an -4-s maximal isokinetic cycling effort at preexercise, isotime, and intolerance. Isotime was the shorter exercise duration of the two treatment conditions. Significance was assessed using ANOVA with treatment as fixed factor and subject as random factor. FEV1 was greater with LAMA þ LABA versus placebo (1.81 [1.58, 1.98] L vs. 1.72 [1.29, 1.99] L; P = 0.006), but IC at isotime, performance fatigue at isotime, and constant power endurance time were not different between conditions (each P > 0.05). A modest (-95 mL) increase in FEV1 following 1 wk of combination LAMA þ LABA treatment did not alleviate neuromuscular performance fatigue or enhance cycle exercise tolerance in patients with mild-to-severe COPD with largely preserved "static" lung volumes. [ABSTRACT FROM AUTHOR]

The hip abductor muscles control the pelvis in the frontal plane and allow the maintenance of trunk position and dynamic balance during weight-bearing activities. To compare the side-lying and standing positions for hip abductor strength assessment with regards to torque production and myolectric activity. Concentric and eccentric hip abductor peak torque and total work, and myoelectric activity of the tensor fascia lata, gluteus medius, and inferior and superior portions of the gluteus maximus muscles were measured during maximal isokinetic tests for hip abductor strength in the side-lying and standing positions. The Wilcoxon test was used to compare variables between the positions. Peak torque values did not differ between side-lying and standing positions for both concentric and eccentric contraction modes (p >.05). During standing position, greater concentric total work was observed (p =.013). This position resulted in a lower activity of the tensor fascia lata muscle (p =.005) compared to side lying position. Myoelectric activity of gluteus medius, and inferior and superior portions of the gluteus maximus was similar between positions (p >.05). Both positions presented similar peak torque values and, during the standing position, a greater concentric total work and lesser activation of the tensor fascia lata was observed. Standing position can be used when emphasis on the superior portion of gluteus maximus over the tensor fascia lata is intended. • Standing can be used when emphasis on the superior gluteus over the tensor fascia lata is intended. • Side-lying and standing positions are comparable in terms of peak torque values. • Maximal hip abductor concentric work is greater during standing compared to side-lying position. • Reduced activity of the tensor fascia lata is achieved at standing position. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine blood pressure (BP) and heart rate (HR) responses triggered during an isokinetic testing protocol in professional soccer players and compare cardiovascular parameters at completion of this isokinetic protocol with those during a treadmill test. Using purposive sampling, 63 professional soccer players were recruited. Cardiovascular responses were measured noninvasively during a bilateral testing protocol of knee flexion and extension. Treadmill ergospirometry following an incremental speed protocol was performed to analyze the same cardiovascular parameters at rest and at completion of this test. There were significant differences in diastolic blood pressure (DBP) and HR according to field position. The parameters presented high homogeneity at both competitive levels. Systolic blood pressure, mean arterial pressure, HR, and rate pressure product at completion of the treadmill test were significantly higher than those at completion of the isokinetic protocol. Intermittent isokinetic testing protocol of the knee triggers normal and safe BP and HR responses in healthy professional soccer players. The HR of the defenders was higher than those of the forwards and midfielders but was independent of the competitive level. The values of cardiovascular parameters at isokinetic protocol completion were lower than those during the treadmill test. [ABSTRACT FROM AUTHOR]

The present study aimed to explore the possibility of comprehensively assessing whole-body muscle strength by testing as few muscle groups as possible, using a single testing method (isometric or isokinetic dynamometry) and a single variable (maximal force or rate of force development). Knee, hip, shoulder and elbow extensors and flexors were evaluated in males with high (n = 26) and low strength levels (n = 32). The principal component analysis revealed three factors that explained 62.5% of the total variance, while the main factors were loaded by the different testing methods and strength variables for the muscles acting on the knee (first component), hip (second component) and arm joints (third component). These results were confirmed by a three-way ANOVA which revealed a significant factor of group (P < 0.001) and the interaction test type × group (P = 0.002), but not of test type (P = 0.644), muscle group (P = 0.999), or their interactions (P > 0.205). The correlations of strength outcomes across the muscles ranged from trivial to very large (r range = −0.17, 0.84), being generally higher for the antagonistic muscles. Overall, a comprehensive assessment of whole-body muscle strength can be obtained using isometric dynamometry and maximal force, but it should consider at least one muscle group from the antagonistic pair. [ABSTRACT FROM AUTHOR]

Persistent deficits in strength and voluntary activation have been observed in athletes with a history of hamstring strain injury. The mechanisms contributing to these deficits are poorly understood and consequently may not be appropriately addressed during rehabilitation. This study aimed to investigate the impact of intended knee flexor contraction mode (concentric, eccentric or isometric) on the rate of torque development and surface electromyography (sEMG) rise in athletes with and without a history of unilateral hamstring strain injury. The impact of the previous injury on hip extensor rate of torque development was also investigated. Previously injured limbs exhibited a slower rate of torque development (mean difference = −31%, p = 0.02, Cohen's d = 0.62) and biceps femoris rate of sEMG rise (mean difference = −181% · s−1, p = 0.003, Cohen's d = 1.10) during intended eccentric knee flexor contractions compared with control limbs. Previously injured (mean difference = −29%, p = 0.01, Cohen's d = 0.85) and contralateral uninjured limbs (mean difference = −31%, p = 0.007, Cohen's d = 0.73) exhibited a slower rate of torque development during isometric hip extensor contractions compared with control limbs. These findings may highlight lower levels of descending input to hamstring motoneurons in previously injured athletes. [ABSTRACT FROM AUTHOR]