ECSS Paris 2023: OP-AP29
INTRODUCTION: The force–velocity (F-v) relationship provides a theoretical and practical model to describe the interaction between muscle force and contraction velocity, offering key insights into maximal strength (F₀), maximal velocity (V₀), and maximal power (Pmax). While this concept has been extensively validated in field tests such as jumps and sprints, its application to isokinetic dynamometry remains limited. Establishing valid and reliable F-v profiles from isokinetic testing could enhance the interpretation of neuromuscular function and support individualized rehabilitation and performance strategies. This study aimed to evaluate the validity and intra-session reliability of F-v profiles derived from isokinetic dynamometry METHODS: A prospective, cross-sectional, single-center study was conducted at the Orthosport Center (France) between June and August 2025. Twelve healthy, physically active male athletes (mean ± SD: 26.5 ± 3.8 years; 1.81 ± 0.06 m; 76.3 ± 5.9 kg) volunteered to participate. Inclusion criteria comprised a Tegner activity score ≥ 7, Marx Activity Rating Scale ≥ 12, and no history of lower-limb injury or surgery within six months. After a standardized warm-up (10 min cycling at 1.5 W/kg + 3 sets of bodyweight squats), participants underwent concentric isokinetic knee extension and flexion testing on a Humac Norm dynamometer (Athlex, France). Each leg was tested separately at five preset angular velocities (30°, 60°, 180°, 240°, 300°/s). For each velocity, three maximal trials were performed following a submaximal familiarization repetition. Participants were stabilized with straps at the trunk, pelvis, and thigh, ensuring alignment of the knee joint with the dynamometer axis. Torque–velocity data from the five test conditions were extracted and averaged per limb and muscle group. Individual linear regressions were computed (torque = f(velocity)) in Microsoft Excel to derive F₀ (y-intercept), V₀ (x-intercept = −slope/F₀), and Pmax = (F₀ × V₀)/4. The coefficient of determination (R²) was calculated to quantify model linearity. All analyses were performed separately for quadriceps and hamstrings. RESULTS: High linearity of the F-v relationship was observed (mean R² = 0.98 ± 0.02 for dominant quadriceps and 0.97 ± 0.01 for dominant hamstrings). Mean F₀, V₀, and Pmax for the quadriceps were 234.8 ± 31.8 N, 598.7 ± 102.9°/s, and 2418.7 ± 345.8 W, respectively. For the hamstrings, mean F₀ = 178.8 ± 37.9 N, V₀ = 861.7 ± 698.0°/s, and Pmax = 2351.7 ± 972.0 W. ICC values ranged from 0.79 to 0.98 for quadriceps and 0.74 to 0.98 for hamstrings. SEM% values were generally below 10%, and CV values remained acceptable (< 20%) across velocities. CONCLUSION: Isokinetic F-v profiling is a valid and reliable method for characterizing neuromuscular performance in healthy athletes. This approach bridges laboratory-based and field-based assessments by integrating mechanical variables into a single framework.
Read CV Ayrton MOIROUX--SAHRAOUIECSS Paris 2023: OP-AP29
INTRODUCTION: Isokinetic dynamometry is a well-established method for evaluating muscle strength. It enables monitoring of function in training and sports medicine, by measuring joint moments during constant angular velocity [1]. However, the recent emergence of novel electromechanical isokinetic systems requires rigorous validation to ensure they replicate consistent physiological responses, before clinical implementation [2]. Therefore, this study aimed to assess (a) the concurrent validity and test–retest repeatability of a novel isokinetic device (Kineo; Globus, Italy) and (b) muscle activation (EMG) and neuromuscular efficiency (NME) of dynamic contractions, to ensure physiological consistency with a gold-standard device. METHODS: Thirty-one healthy, physically active participants (17 males, 14 females; 19–33 years) completed one familiarization and a testing session on the Kineo system and the Cybex dynamometer (CSMI, USA). Knee extensor peak torque (PT) and vastus lateralis surface EMG were recorded during maximal effort under concentric (60°/s – CON60, 180°/s – CON180) and eccentric (60°/s – ECC60) conditions in a randomized, counterbalanced order. Reliability was assessed by repeating the protocol on the Kineo system one week later under identical conditions. Repeated measures ANOVA, intraclass correlation coefficients (ICC), and standard error of measurement (SEM) were used to evaluate between-device differences and absolute reliability. RESULTS: PT showed high accuracy during CON60 (mean difference Kineo-Cybex: -3.33 ± 41.29 Nm; 2% difference; p > 0.05), whereas Kineo produced higher values during CON180 (mean difference Kineo-Cybex: +10.52 ± 11.85 Nm; 8% difference; p < 0.01) and ECC60 (mean difference Kineo-Cybex: +14.78 ± 27.52 Nm; 7% difference; p = 0.01). Despite small PT differences, measurement accuracy was high (ICC3,1 = 0.81–0.90) and repeatability was excellent (ICC3,1= 0.97). SEM (8.25–17.03 Nm) and minimal detectable change (MDC; 22.86–47.20 Nm) supported test–retest reliability. EMG activity (%MVIC) and NME (PT/%MVIC) did not differ between devices (p > 0.05), mean NME values for Kineo were within the expected physiological range (CON60 2.82 ± 0.99, CON180 2.02 ± 0.82, ECC60 4.35 ± 1.43), consistently with Cybex. CONCLUSION: Isokinetic testing on the Kineo system showed very high repeatability and strong agreement with the gold standard device for PT. Importantly, EMG activity and NME displayed comparable behaviours between devices, with greater activation and lower torque per unit of activation during concentric contractions and vice versa for eccentric contractions. These findings indicate that the device accurately reproduces knee extensors physiological muscle activation characteristics and supports its use for monitoring strength and recovery in training and rehabilitative settings. References 1. Baltzopoulos V. In: Biomechanical Evaluation of Movement in Sport and Exercise. 2017:140–167. 2. Ratitch B et al. Digit Biomark. 2023; 7:74–91.
Read CV Camilla CostagliolaECSS Paris 2023: OP-AP29
INTRODUCTION: Despite the well-established importance of physical and dual-task neurocognitive demands in athletic performance, neurocognitive assessments for upper extremity performance remain limited. We aimed to develop tests that combine motor and cognitive tasks simultaneously to assess functional upper quadrant stability (UQS) in athletes and to determine their test–retest reliability. Furthermore, the effect of neurocognitive load on Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST) performance and the association between the Neurocognitive Upper Quadrant Y Balance Test (NC-UQYBT) and the traditional Upper Quadrant Y Balance Test (UQYBT) were investigated. METHODS: Nineteen healthy male athletes (age: 19.8±0.4 years; body mass index: 24.9±0.6 kg/m²; dominant shoulder: right 100%; Kerlan–Jobe Shoulder and Elbow Score: 74.1±7.2; Tegner Activity Level: 8.8±0.1) participated in the study. Neurocognitive test protocols were developed based on the UQYBT and CKCUEST and integrated with standardized cognitive tasks targeting attention, reaction, and decision-making. The NC-UQYBT assessed bilateral reaction time (ms), while the Neurocognitive Closed Kinetic Chain Stability Test (NC-CKCUEST) measured reaction time (ms) and total touches. Test performance was evaluated under single-task and dual-task conditions. For reliability analysis, all participants completed the tests twice within a one-week interval. Neurocognitive load was calculated as the percentage change in performance between the single-task and dual-task performance. Pearson and Spearman correlation analysis was performed to examine the relationship between the NC-UQYBT and the UQYBT. RESULTS: For the NC-UQYBT, test–retest reliability was excellent for the dominant [(ICC = 0.91 (95% CI: 0.80–0.96; SEM: 30.46; MDC: 84.43)], and non-dominant sides [ICC = 0.96 (95% CI: 0.88–0.98; SEM: 24.41; MDC: 67.66)]. For the NC-CKCUEST, test–retest reliability was good for reaction time [ICC = 0.88 (95% CI: 0.71–0.95; SEM: 39.12; MDC: 108.43)], and touches [ICC = 0.75 (95% CI: 0.47–0.89; SEM: 0.93; MDC: 2.57)]. Neurocognitive load resulted in a 54.92 ± 1.75% reduction in CKCUEST performance. No significant correlations were found between the NC-UQYBT and UQYBT for either the dominant (r=-0.22, p=0.36) or non-dominant side (r=-0.26, p=0.27). CONCLUSION: The neurocognitive UQS Tests demonstrated good to excellent test–retest reliability in athletes, indicating that they are reliable tools for assessing upper extremity performance under combined motor and cognitive demands. The substantial reduction in performance under neurocognitive load highlights the importance of incorporating cognitive challenges into UQS assessments. However, the lack of correlation between the neurocognitive and traditional Y Balance Tests suggests that these assessments may capture distinct aspects of upper quadrant function. Therefore, the proposed neurocognitive test battery may be useful in clinical and sports settings for performance assessments.
Read CV CANSU AKKUŞECSS Paris 2023: OP-AP29