Changes in isokinetic trunk muscle strength and endurance after two different restoration programs in people with chronic low back pain: A longitudinal retrospective study.

Background: Multidisciplinary functional restoration programs (FRPs) aim to improve pain and function in people with chronic low back pain (CLBP). The intensity and content of FRPs varies; the benefits of one program over another are unclear. Objective: To assess changes in trunk muscle strength and endurance after an intensive (IFRP) (for people on sick leave for >6 months with high levels of fear-avoidance beliefs about physical activity and work) or semi-intensive (SIFRP) (for people working) FRP in people with CLBP. Methods: Longitudinal retrospective study from March 2016 to December 2019. Setting: rehabilitation department of a tertiary care center. Trunk flexor and extensor muscle strength (60°.s-1) and endurance (120°.s-1) were measured with the Humac NORM isokinetic dynamometer at pre and post FRP. Change in isokinetic variables (peak torque, total work and flexor/extensor ratio) after each program was assessed with a paired t-test (p < 0.05). Pearson's rho and multiple linear regression assessed associations between changes in isokinetic and clinical variables and demographic characteristics. Results: 125 individuals, 63.2 % female, age 43.5 (10.3) years, were included. Mean low back pain intensity was 49.8 (24.9) and 37.2 (25.8)/100 and mean activity limitation (QBPDS) was 38.8 (16.4) and 32.0 (14.6)/100 in the IFRP and SFRP groups, respectively. Trunk extensor peak torque, flexor total work, extensor total work and flexor/extensor peak ratio improved significantly in both FRPs, p < 0.001. The flexor/extensor total work ratio improved in the IFRP group only, p = 0.003. Trunk extensor endurance increased more in the IFRP than the SIFRP group, the absolute pre-post differences for extensor total work [95%CI] N.m were 611.7 [495.2; 728.3] in the IFRP group and 380.0 [300.8; 459.3] in the SIFRP group. No variables were correlated and none predicted improvement in extensor total work in either group. Conclusion: This study highlights the short-term independence of clinical and trunk muscle strength and endurance changes.

Subacromial balloon spacer improves isokinetic performance in patients with massive irreparable rotator cuff tear.

PURPOSE: The aim of this study was to analyse clinical, functional and shoulder kinematics results using subacromial balloon spacer in nonreparable massive rotator cuff tears. Subacromial balloon spacer was hypothesised to improve shoulder kinematics and increases clinical and functional outcomes scores in nonreparable massive rotator cuff tears. METHODS: This is a prospective study in massive rotator cuff tears. From October 2021 to October 2022, a total of 127 shoulders suffering massive rotator cuff tears were initially evaluated. All patients were evaluated preoperatively, at 6 and 12 months. Patients' patient-reported outcome measures (PROM) subjective values using visual analogue scale (VAS) and the Spanish Western Ontario Rotator Cuff Index (WORC) version were analysed. We also evaluated objective outcomes: constant score, range of movement and kinematic shoulder analysis (isokinetic test to evaluate internal and external rotation forces). Statistical analysis was conducted using SPSS software; continuous variables were presented as means and standard deviations (SDs). RESULTS: Seventeen nonrepairable massive rotator cuff tears were finally included. Three patients required reverse shoulder arthroplasty before 6 months postoperative. After 1-year follow-up, objective and subjective (PROM) outcome scores and isokinetic measurements improved in 13 patients. Preoperative VAS improved from 6.5 ± 2.1 to 2 ± 1.9 points on average at 1-year follow-up and WORC index from 1603 ± 217.3 to 699 ± 361.6. Constant score from 42.1 ± 13.1 on average and at 1-year follow-up increased to 60.8 ± 14.7. Range of movement also improved in elevation 122.2 ± 39.3 to 166.9 ± 25.8, abduction 120.3 ± 38.6 to 134.6 ± 21.1, external rotation 30.3 ± 19.7 to 86.1 ± 13.8 and internal rotation L4-T12 on average at 1-year follow-up. Isokinetic evaluation showed functional improvement 1 year after implantation. Both internal and external rotation improved compared with their healthy shoulder. External rotation improved from 30.3° ± 19.7° preoperatively to 86.1° ± 13.8° (43.7% in the isokinetic study) and internal rotation from L4 preoperatively to L1 (49.8% in isokinetic study) on average. CONCLUSION: Among the different alternatives for irreparable rotator cuff injuries surgical treatment, subacromial balloon spacer is an effective alternative in selected patients, both in terms of clinical-functional improvement and short-term isokinetic results. LEVEL OF EVIDENCE: Level II.

The Utility of High-Intensity, Intermittent Exercise Protocols to Induce Fatigue for Screening Purposes in Jump-Landing Sports.

Short-term fatigue protocols simulating sports participation are scarce and not well-documented in jump-landing 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).

Knee and Hip Muscle Strength of Male Soccer Players from Different Competitive Levels.

In soccer, knee and hip muscle strength assessments have been recommended for injury prevention. The aims of this study were threefold: (1) to compare knee and hip muscle strength between professional players competing at different levels; (2) to compare strength performance according to the preferred leg (PL) and the non-preferred leg (NPL); and (3) to compare knee and hip muscle strength performance at two moments of the season. This study included 33 professional soccer players: 13 were in the elite group (EG), and 20 were in the sub-elite group (SEG). Body composition, isokinetic knee strength at 60º/s, and hip adduction strength were assessed at two different moments (M1 and M2). Values of peak torque (PT), peak torque/bodyweight (PT/BW), and the hamstring-to-quadriceps strength ratio (H:Q) for knee extensors (KEs) and knee flexors (KFs) for both legs were used for analysis. The statistical analysis included the Mann-Whitney U and the Wilcoxon Signed Rank tests. At M1, the EG presented a significantly better performance in KF PT/BW and in the squeeze strength test for the PL and the NPL (p ≤ 0.01). At M2, the EG performed substantially better in KE PT/BW and KF PT/BW (p ≤ 0.01). No substantial strength differences were observed in knee and hip muscle performance between the PL and the NPL. From M1 to M2, significant increases were found in knee strength in both groups (p ≤ 0.01). Overall, the EG players outperformed significantly their lower-division peers in strength assessments. The results indicate significant knee and hip muscle strength increases during the season, probably as a response to the exposure to training and competition.

Favourable mid-term isokinetic strength after primary THA combined with a modified enhanced recovery after surgery concept (ERAS) in a single blinded randomized controlled trial.

PURPOSE: Muscular deficits as part of severe osteoarthritis of the hip may persist for up to two years following total hip arthroplasty (THA). No study has evaluated the mid-term benefit of a modified enhanced-recovery-after-surgery (ERAS) concept on muscular strength of the hip in detail thus far. We (1) investigated if a modified ERAS-concept for primary THA improves the mid-term rehabilitation of muscular strength and (2) compared the clinical outcome using validated clinical scores. METHODS: In a prospective, single-blinded, randomized controlled trial we compared patients receiving primary THA with a modified ERAS concept (n = 12, ERAS-group) and such receiving conventional THA (n = 12, non-ERAS) at three months and one year postoperatively. For assessment of isokinetic muscular strength, a Biodex-Dynamometer was used (peak-torque, total-work, power). The clinical outcome was evaluated by using clinical scores (Patient-Related-Outcome-Measures (PROMs), WOMAC-index (Western-Ontario-and-McMaster-Universities-Osteoarthritis-Index), HHS (Harris-Hip-Score) and EQ-5D-3L-score. RESULTS: Three-months postoperatively, isokinetic strength (peak-torque, total-work, power) and active range of motion was significantly better in the modified ERAS group. One year postoperatively, the total work for flexion was significantly higher than in the Non-ERAS group, whilst peak-torque and power did not show significant differences. Evaluation of clinical scores revealed excellent results at both time points in both groups. However, we could not detect any significant differences between both groups in respect of the clinical outcome. CONCLUSION: With regard to muscular strength, this study supports the implementation of an ERAS concept for primary THA. The combination with a modified ERAS concept lead to faster rehabilitation for up to one-year postoperatively, reflected by significant higher muscular strength (peak-torque, total-work, power). Possibly, because common scores are not sensitive enough, the results are not reflected in the clinical outcome. Further larger randomized controlled trials are necessary for long-term evaluation.

The mechanism of static postural control in the impact of lower limb muscle strength asymmetry on gait performance in the elderly.

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.

The effects of aerobic gymnastics training on performance-related variables in an elite athlete: a 2-year follow-up study.

This study investigates individual performance adaptations on 2 years of training between European Aerobics Championships. An elite, 22-year-old aerobic gymnast performed postural coordination test, Y-Balance test, squat and countermovement jumps, 60 s test of repeated jumps, an isokinetic leg muscle strength test, and the Wingate test. Postural stability and flexibility improved in terms of increased distance achieved in the Y-Balance test in the anterior (by 6.3%), posteromedial (by 2%), and posterolateral (by 4.8%) directions. Lower limb muscular endurance also increased, which can be corroborated by a reduced fatigue index in the 60 s test of repeated jumps (from 42% to 27% after the 1st and to 22% after the 2nd year of training). In addition, mean power increased during dominant (by 23.2% at 60°/s and by 18.5% at 180°/s) and non-dominant leg extension (by 4.9% at 180°/s and by 15.5% at 300°/s), plus dominant leg flexion (by 2.0% at 60°/s and by 6.9% at 300°/s). Similarly, peak torque/body weight ratio increased during dominant (by 24.9% at 60°/s, by 11.5% at 180°/s, and by 2.1% at 300°/s) and non-dominant leg extension (by 0.5% at 60°/s and by 6.4% at 300°/s), plus dominant leg flexion (by 1.7% at 60°/s and by 5.4% at 300°/s). However, 2 years of training failed to show any significant improvements in the explosive power of lower limbs and anaerobic performance. These findings indicate that general aerobic gymnastics training without any specific inputs leads to performance adaptation, namely, in abilities closely related to competition routine (dynamic balance and strength endurance of lower limbs).

No beneficial effect of aerobic whole-body electromyostimulation on lower limbs strength and power - a randomized controlled trial.

BACKGROUND: Applying whole-body electromyostimulation (wbEMS) to voluntary activation of the muscle is known to impact motor unit recruitment. Thus, wbEMS as an additional training stimulus enhances force-related capacities. This study aimed to evaluate the mono- and multiarticular strength adaptations to a running intervention with wbEMS compared to running without wbEMS. METHODS: In a randomized controlled trial (RCT), 59 healthy participants (32 female/ 27 male, 41 ± 7 years) with minor running experience conducted an eight-week running intervention (2x/ week à 20 min) with a wbEMS suit (EG) or without wbEMS (control group, CG). Maximal isokinetic knee extensor and flexor strength and jump height during countermovement jumps were recorded prior and after the intervention to assess maximal strength and power. RESULTS: Following eight weeks of running, maximal isokinetic knee extension torque decreased significantly over time for both interventions (EG Δ -4%, CG Δ -4%; F(1, 44.14) = 5.96, p = 0.02, η = 0.12). No changes were observed for flexion torque (F(1, 43.20) = 3.93, p = 0.05, η = 0.08) or jump height (F(1, 43.04) = 0.32, p = 0.57, η  = 0.01). CONCLUSIONS: The outcomes indicate that there is no additional effect over neuromuscular function adaptations with the inclusion of wbEMS during running training. Knee extensor strength is even slightly reduced which supports the principle of training specificity in regards to strength adaptation. We conclude that strength improvements cannot be achieved by running with wbEMS. TRIAL REGISTRATION: German Clinical Trials Register, ID DRKS00026827, date 10/26/21.

A deficit to reach the isokinetic velocity in youth wheelchair users with spina bifida.

INTRODUCTION: The self-paced adopted by wheelchair users in their postural transfers and locomotion may require sufficient levels of speed-strength in the upper limbs. In clinical practice, we observed limited functional independence and social participation. OBJECTIVES: This study aimed to investigate and compare the speed-strength relationship between wheelchair users with spina bifida (SB) and typically developing youth. In particular, to analyze if SB wheelchair users reached the preset velocities in the isokinetic evaluation of shoulder and elbow. DESIGN: Cross-sectional observational study. SETTING: Ribeirão Preto Medical School of the University of São Paulo. PARTICIPANTS AND PROCEDURES: SB (SB; n = 11) and controls (CT; n = 22) performed the isokinetic assessment of shoulder abductors (SAB), adductors (SAD), flexors (SFL), extensors (SEX), and elbow flexors (EFL) and extensors (EEX) at velocities of 60 and 120degree.s-1. The analysis of covariance was used to identify the intergroup differences in muscle performance. OUTCOME MEASURES: The values of peak torque (PT), power (Pow), time to peak torque (tPT) and the percentage to reach the isokinetic velocity. RESULTS: The percentage to reach 120degree.s-1 was moderate-to-low for both groups (26-75.9%). CT presented a significantly greater relative risk of reaching the preset velocities than SB. SB presented higher PT and Pow for SAB and SFL at 60degree.s-1, higher PT for SFL and EEX at 120degree.s-1, and lower tPT for SFL at 120degree.s-1 compared to CT. CONCLUSION: SB had difficulty reaching 120degree.s-1, probably related to neuromuscular differences. However, arm movements in their daily tasks seem to maintain the ability to produce PT and Pow.

Reliability of lower limb strength assessment in female team sport athletes.

BACKGROUND: Lower limb injury rates have increased dramatically in line with increased female sport participation levels. Muscle strength is a modifiable lower limb injury risk factor, guiding performance monitoring and rehabilitation. OBJECTIVES: The aim of this study was to investigate the test-retest reliability of isokinetic and isometric lower limb peak torque to body mass of muscles acting on the hip, knee, and ankle in female team sport athletes. It was hypothesised the test-retest reliability would be good (intraclass correlation coefficients (ICC) ≥ 0.75). METHODS: Thirty-eight female athletes (Australian Rules Football = 18, netball = 12, soccer = 8) aged 16-35 years participated in this study. Participants performed isokinetic (60°/s and 120°/s) and isometric testing on a Biodex Isokinetic Dynamometer on three separate days. RESULTS: Poor to good reliability was demonstrated for all joint movements (ICC = 0.38-0.88) with small to moderate effect sizes (0.00-0.43) and typical errors (5.65-24.49). CONCLUSION: Differences in peak torque to body mass were observed between sessions one and two and/or one and three, demonstrating a learning effect. Therefore, three testing sessions, and/or the inclusion of a familiarisation session, is recommended for future assessments in populations unfamiliar with dynamometry.

Comparison of the effects of isokinetic and isotonic strength training in team sport athletes: A randomized controlled trial.

Athletes may benefit from isokinetic training (IK) to improve strength and jump performance. Previous studies comparing IK methods to isotonic resistance training (IT) have utilized high-repetition protocols and a Dynamometer, which are usually reserved for laboratory or rehabilitation settings. This study compared effects of IK and IT using ≤ 6 repetitions on strength and jump performance in 50 male, team-sport athletes (ages 18-35) during COVID-19 lockdown using the commercially-available TechnoGym BioCircuit Dynamometer. This 4-group randomized parallel study assessed the effects of an 8-week isokinetic at 80°/s (IK80; n = 16) and 25°/s (IK25; n = 12) or isotonic training program (IT; n = 15) compared to a control group (CG; n = 7) on anthropometric measurements, peak torque at 80°/s (PT80) and 25°/s (PT25), one-repetition maximum (1-RM) leg extension, and countermovement (CMJ) and squat jump height (SJ). Anthropomorphic data showed minimal differences between groups post-intervention. Strength increased in IT, and IK25 compared to CG, with no difference between intervention groups. SJ increased in all groups compared to the control group, with differences between groups. Counter movement jump (CMJ) improved only in IT and IK80 with no between-group difference. These results do support the hypothesis that low-repetition IK and IT can be used to effectively improve strength and jump performance in athletic populations. However, the efficacy of IK on CMJ depends on training velocity and repetition range, with a higher velocity training protocol (80°/s) being more effective for jump performance and lower speeds potentially more useful for improving maximal strength (25°/s).

Sequential Comparison of Knee Muscle Strength after Anterior Cruciate Ligament Reconstruction between Hamstring Autograft and Tibialis Anterior Allograft: Propensity Score Matched Pair Analysis.

Among the graft options for anterior cruciate ligament reconstruction (ACLR), hamstring autografts are widely regarded as the preferred choice for primary ACLR among orthopedic surgeons worldwide. However, concerns persist regarding postoperative knee flexor weakness. We aimed to compare knee extensor and flexor strengths between hamstring autograft and tibialis anterior allograft groups in ACLR patients, who were propensity score-matched based on baseline characteristics. A retrospective analysis included 58 matched pairs who underwent isokinetic strength tests at 6 and 12 months post operation. Isokinetic muscle strength tests found no significant difference in knee extensor and flexor strength at 6 months post operation between the hamstring autograft and tibial anterior allograft groups. At 12 months, the hamstring autograft group exhibited significantly greater knee flexor deficit (total work and average power) compared to the allograft group, despite no differences in extensor strength or patient-reported outcomes. This study highlights the impact of hamstring autograft harvesting on muscle strength and recovery following ACLR in short-term period.

Torque and power of knee extensor muscles at individualized isokinetic angular velocities.

OBJECTIVE: Existing isokinetic contractions are characterized using standardized angular velocities, which can induce differing adaptations. Here, we characterized the variation in the isokinetic parameters of knee extensors according to individualized angular velocity (IAV). METHODS: We performed a cross-sectional study of 19 young, healthy men. We measured the maximum angular velocity (MAV) of concentric knee extension using the isotonic mode of an isokinetic dynamometer. Isometric and isokinetic (at angular velocities corresponding to 100%, 70%, 40%, and 10% of each individual's MAV) knee extensor contractions were performed, and the peak torque and mean power were recorded. RESULTS: Peak torque significantly decreased with increasing IAV (129.42 ± 25.04, 84.37 ± 20.97, and 56.42 ± 16.18 Nm at 40%, 70%, and 100%, respectively), except for isometric contraction (233.36 ± 47.85) and at 10% of MAV (208 ± 48.55). At the mean power, 10% of MAV (74.52 ± 20.84 W) was significantly lower than the faster IAV (176.32 ± 49.64, 161.53 ± 56.55, and 145.95 ± 50.64 W at 40%, 70%, and 100%, respectively), and 100% was significantly lower than 40%. CONCLUSION: The optimized IAV for isokinetic contraction to improve power output while maintaining torque is 10% to 40% of MAV. IAV may reflect both the velocity and force components of power because individuals do not have the same angular velocity.

Resistance training modalities: comparative analysis of effects on physical fitness, isokinetic muscle functions, and core muscle biomechanics.

Introduction: This study aimed to evaluate the effects of varied resistance training modalities on physical fitness components, body composition, maximal strength assessed by one-repetition maximum (1RM), isokinetic muscle functions of the shoulder and knee joints, and biomechanical properties of core muscles. Methods: Forty participants were randomly assigned to four groups: control group (CG, n = 10), compound set training group (CSG, n = 10), pyramid set training group (PSG, n = 10), and superset training group (SSG, n = 10). Excluding the CG, the other three groups underwent an 8-week resistance training program, three sessions per week, at 60%-80% of 1RM intensity for 60-90 min per session. Assessments included body composition, physical fitness components, 1RM, isokinetic muscle functions, and biomechanical properties (muscle frequency, stiffness, etc.) of the rectus abdominis and external oblique muscles. Results: The PSG demonstrated the most significant improvement in relative peak torque during isokinetic testing of the shoulder and knee joints. Compared to the CG, all exercise groups exhibited positive effects on back strength, sprint performance, 1RM, and core muscle biomechanics. Notably, the PSG showed superior enhancement in external oblique stiffness. However, no significant differences were observed among the exercise groups for rectus abdominis biomechanical properties. Discussion: Structured resistance training effectively improved maximal strength, functional performance, and core muscle biomechanics. The pyramidal training modality conferred specific benefits for isokinetic muscle functions and external oblique stiffness, suggesting its efficacy in enhancing force production capabilities and core stability.

Test-Retest Reliability of an Isometric and Isometric/Vibratory Muscular Strength Protocol with Functional Electro-Mechanical Dynamometry.

The purpose of the study was to analyze the test-retest reliability of an isometric and isometric/vibratory muscular strength protocol in the bilateral seated bench press (BSBP), bilateral seated rowing (BSR), unilateral seated right knee extension (USKER), and left knee extension (USKEL) tests controlled using functional electromechanical dynamometry (FEMD) in healthy young adults. A repeated measures design was used to determine the reliability of a muscular strength protocol in isometric and isometric vibration modes with FEMD. No significant differences were found in test-retest analysis (p > 0.05; ES < 0.20); and high reliability (CV = 4.65-5.02%; ICC = 0.99-0.98) was found for BSBP measures, and acceptable reliability (CV = 3.71-9.61%; ICC = 0.98-0.95) was found for BSR, USKER, and USKEL. Furthermore, the coefficients between the two measures were strong (r = 0.963-0.839) and highly significant (p = 0.001) for maximal strength in the isometric and maximal isometric/vibratory assessment of muscle strength in all muscle strength tests. This study demonstrates that isometric and maximal isometric/vibratory strength in the BSBP, BSR, USKER, and USKEL tests can be measured with high reliability and reproducibility using the FEMD.

Acute patellar dislocation during isokinetic knee strength testing: A case report.

Key Clinical Message: Isokinetic testing is a maximal muscle strength test which requires adequate patient's preparation and observer's care. While the available data suggests that isokinetic devices are safe, their use may rarely cause severe injuries. The screening of predisposing anatomical factors could help preventing injuries before testing. Abstract: A 29-year-old athletic man presented an acute patellar dislocation on a healthy right knee during isokinetic muscle strength testing, which was conducted in the setting of an intensive physical rehabilitation program, for persistent left knee pain after arthroscopic surgery for meniscal tear. This is the first case to occur in an adult male without clear risk factors such as patellar dysplasia. Predisposing factors may include slightly elevated patellar tilt and lateral shift compared to the contralateral knee (researched from subsequent review of pre-injury X-rays), and an elevated quadricipital strength in the context of recreational bodybuilding. The dislocation occurred during eccentric extension phase of testing. Medial patellofemoral ligament reconstruction was conducted 6 months later. Isokinetic muscle strength testing is generally considered as a safe method, despite limited data on the devices' safety. Since severe injuries might rarely occur, adequate patient preparation is needed, as well as the screening of predisposing factors.

Discipline-specific Torque-Velocity Profiles and Musculotendinous Morphology in Athletes.

OBJECTIVES: The aim of this study was to compare torque-velocity profiles, muscle architecture, tendon dimensions, and bilateral-symmetry between competitive cyclists (CY), competitive runners (RN), ice-hockey players (IH), basketball players (BP), and physically-active individuals (CN) (n=10 for each group). METHODS: Vastus lateralis (VL) muscle and patellar tendon (PT) structures were determined with B-mode ultrasonography, and maximal knee extensor isokinetic torque was assessed at three different velocities. RESULTS: Optimal torque and velocity were lower in runners than CY, BP and IH (p<0.05). Maximal power was similar between the athlete groups but greater than CN (p<0.05). Furthermore, RN and BP reached their peak-torque at longer muscle lengths compared to IH and CY (p<0.05). RN had the lowest VL muscle thickness and the greatest fascicle length, while CY had the greatest pennation angle (p<0.05). CY had the greatest PT thickness, particularly at the proximal and medial sites, while BP at the distal point (p<0.05), with similar trends observed for PT cross-sectional-area. CONCLUSIONS: Our findings show that even if power generating capacity is similar between athletic disciplines, there are discipline-specific muscle adaptations, where particularly runners appear to have muscles adapted for speed rather than torque development, while in cyclists, velocity is sacrificed for torque development.

Magnitude and direction of shoulder torque asymmetries between different angular velocities in competitive swimmers.

Asymmetries in swimming can be the result of poor technique or coordination between limbs, reducing the ability to produce propulsive force and increasing resistive drag. Therefore, this study aimed to compare the magnitude and determine the consistency of isokinetic peak torque asymmetries between the angular velocities of in the shoulder joint movements of internal and external rotation, flexion, and extension. Twenty-one competitive swimmers performed concentric actions at 60°/s (3 repetitions) and 180°/s (20 repetitions) in the movements of internal and external rotation, flexion, and extension of the shoulders using an isokinetic dynamometer, with the peak torque and asymmetry index being common metrics across the tests. The results showed a greater magnitude of asymmetry in internal rotation (16.86 vs. 9.86; p = 0.007) and flexion (12.06 vs. 7.35; p = 0.008) at 60 vs. 180°/s, respectively. The agreement levels of the direction of asymmetries between angular velocities were fair to substantial (Kappa: 0.40 to 0.69). Evaluating isokinetic torque in different movements and angular velocities resulted in different levels of asymmetry. Muscle force asymmetries can impact propulsion efficiency and movement coordination during swimming. Understanding muscle asymmetries allows the development of targeted and individualised training programmes to correct strength imbalances.

Sleep restriction reduces voluntary isometric quadriceps strength through reduced neuromuscular efficiency, not impaired contractile performance.

Acute sleep restriction (SR) reduces strength through an unknown mechanism. PURPOSE: To determine how SR affects quadriceps contractile function and recruitment. METHODS: Eighteen healthy subjects (9 M, 9F, age 23.8 ± 2.8y) underwent isometric (maximal and submaximal), isokinetic (300-60°·s-1), and interpolated twitch (ITT) assessment of knee extensors following 3d of adequate sleep (SA; 7-9 h·night-1), 3d of SR (5 h·night-1), and 7d of washout (WO; 7-9 h·night-1). RESULTS: Compared to SA (227.9 ± 76.6Nm) and WO (228.19 ± 62.9Nm), MVIC was lesser following SR (209.9 ± 73.9Nm; p = 0.006) and this effect was greater for males (- 9.8 v. - 4.8%). There was no significant effect of sleep or sleep x speed interaction on peak isokinetic torque. Peak twitch torque was greater in the potentiated state, but no significant effect of sleep was noted. Males displayed greater potentiation of peak twitch torque (12 v. 7.5%) and rate of torque development (16.7 v. 8.2%) than females but this was not affected by sleep condition. ITT-assessed voluntary activation did not vary among sleep conditions (SA: 81.8 ± 13.1% v. SR: 84.4 ± 12.6% v. WO 84.9 ± 12.6%; p = 0.093). SR induced a leftward shift in Torque-EMG relationship at high torque output in both sexes. Compared to SA, females displayed greater y-intercept and lesser slope with SR and WO and males displayed lesser y-intercept and greater slope with SR and WO. CONCLUSIONS: Three nights of SR decreases voluntary isometric knee extensor strength, but not twitch contractile properties. Sex-specific differences in neuromuscular efficiency may explain the greater MVIC reduction in males following SR.

Reliability of Dynamic Shoulder Strength Test Battery Using Multi-Joint Isokinetic Device.

This study aimed to determine the absolute and relative reliability of concentric and eccentric flexion, extension, horizontal abduction, and adduction movements of the shoulder using a functional electromechanical dynamometer (FEMD). Forty-three active male university students (23.51 ± 4.72 years) were examined for concentric and eccentric strength of shoulder flexion, extension, horizontal abduction, and horizontal adduction with an isokinetic test at 0.80 m·s-1. Relative reliability was determined by intraclass correlation coefficients (ICCs) with 95% confidence intervals. Absolute reliability was quantified by the standard error of measurement (SEM) and coefficient of variation (CV). Reliability was very high to extremely high for all movements on concentric and eccentric strength measurements (ICC: 0.76-0.94, SEM: 0.63-6.57%, CV: 9.40-19.63%). The results of this study provide compelling evidence for the absolute and relative reliability of concentric and eccentric flexion, extension, horizontal abduction, and horizontal adduction shoulder isokinetic strength tests in asymptomatic adults. The mean concentric force was the most reliable strength value for all tests.