Peak Moment Research Articles

First tarsometatarsal joint mobility in hallux valgus during gait: A synchronized ultrasound and three-dimensional motion capture analysis

PurposeTo quantify the vertical translation between the first metatarsal and medial cuneiform during the stance phase of gait in young individuals with and without hallux valgus.DesignThis cross-sectional observational study included 34 young adults (male, n = 4; female, n = 30) who were divided into three groups according to the hallux valgus angle: control (< 20°, n = 13), mild hallux valgus (≥ 20° to < 30°, n = 12), and moderate hallux valgus (≥ 30°, n = 9). The mobility of the first tarsometatarsal joint was evaluated during the stance phase using B-mode ultrasound synchronized with a motion analysis system.ResultsThe medial cuneiform shifted more plantar during the early phase in mild hallux valgus and during the middle and terminal phases in moderate hallux valgus than in control. The severity of the hallux valgus was correlated with a trend toward plantar shift of the medial cuneiform. The first metatarsal was located more dorsal than the medial cuneiform; however, there was no significant variation. No significant differences in the peak ankle plantarflexion angle and moment were noted between the groups.ConclusionThe hypermobility of the first tarsometatarsal joint, especially plantar displacement of the medial cuneiform in the sagittal plane, was found in young individuals with hallux valgus during the stance phase of gait, and the mobility increased with the severity of hallux valgus. Our findings suggest the significance of preventing hallux valgus deformity early in life.

Mechanical loading of bone-anchored implants during functional performance tests in service members with transfemoral limb loss.

For individuals with limb loss, bone-anchored implants create a direct structural and functional connection to a terminal prosthesis. Here, we characterized the mechanical loads distal to the abutment during several functional performance tests in Service members with transfemoral (TF) limb loss, to expand on prior work evaluating more steady-state ambulation on level ground or slopes/stairs. Two males with unilateral TF limb loss and two males with bilateral TF limb loss participated after two-stage osseointegration (24 and 12 months, respectively). Tri-directional forces and moments were wirelessly recorded through a sensor, fit distal to the abutment, during six functional tests: Timed Up and Go (TUG), Four Square Step Test (FSST), Six Minute Walk Test (6MWT), Edgren Side-Step Test (SST), T-Test (TTEST), and Illinois Agility Test (IAT). Additionally, participants performed a straight-line gait evaluation on a 15 m level walkway at a self-selected speed (0.93-1.24 m/s). Peak values for each component of force and moment were extracted from all six functional tests; percent differences compared each peak with respect to the corresponding mean peak in straight-line walking. Peak mechanical loads were largest during non-steady state components of the functional tests (e.g., side-stepping during SST or TTEST, standing up from the ground during IAT). Relative to walking, peak forces during functional tests were larger by up to 143% (anterior-posterior), 181% (medial-lateral), and 110% (axial); peak moments were larger by up to 108% (flexion-extension), 50% (ab/adduction), and 211% (internal/external rotation). A more comprehensive understanding of the mechanical loads applied to bone-anchored implants during a variety of activities is critical to maximize implant survivability and long-term outcomes, particularly for Service members who are generally young at time of injury and return to active lifestyles.

Optimal energy dissipation ratio of base-rocking walls

Base-rocking walls (BRWs) were excellent in maintaining enhanced post-earthquake serviceability and decreasing repair costs and downtime. However, little research has been aimed at finding the optimal range of energy dissipation ratio for designing BRWs. In this study, an approach was developed first for designing BRWs to obtain an intended level of energy dissipation capacity. Using the proposed approach, fifteen BRWs with different heights (i.e., 16, 25.6, and 38.4 m) and energy dissipation ratios (i.e., 0, 0.25, 0.50, 0.75, and 1.00) were designed and modeled using experimentally validated numerical models. Conducting nonlinear time history analyses using far-field (FF), near-field no-pulse (NFnP), and pulse-like (NFP) ground motions, the walls’ response features (RFs), including residual and transient lateral drifts, story acceleration, energy dissipation capacity, post-tensioning (PT) tendons strain, and structural demand were estimated and compared to the existing criteria. Proposing a desirability index (DI), the extent of criteria exceedance for the walls RFs was investigated to find the optimal range of energy dissipation ratio. The results showed that the walls designed by the developed approach could achieve the pre-assumed energy dissipation capacity. Increasing the energy dissipation ratio increases the lateral residual drift while decreasing the transient lateral drift, PT tendon strain, and wall demand. Increasing the wall height increases dissipated energy, exacerbating the adverse effects of higher modes while decreasing PT tendon strain. The obtained residual and transient drifts and PT tendon strain for NFP records are higher than those for FF and NFnP records. Moreover, the peak moment occurred at the lower wall height for NFP records. The adverse effects of higher modes are more evident in FF records. In general, for designing BRWs, the optimal energy dissipation ratio range was 0.50–0.75.

A study of the effect of local scour on the flow field near the spur dike

The flow field near a spur dike such as down flow and horseshoe vortex system (HVS) are susceptible to the topographic changes in the local scouring process, resulting in variation of the sediment transport with time. In this study, large eddy simulations with fixed-bed at different scouring stages were conducted to investigate the changes in flow field. The results imply that the bed deformation leads to an increase in flow rate per unit area, which represent the capability of sediment transportation by water, in the scour hole. Moreover, the intensity of turbulent kinetic energy and bimodal motion near the sand bed induced by the HVS were also varied. However, the peak moments between the two sediment transport mechanisms were different. Hence, understanding the complex feedback mechanism between topography and flow field is essential for the local scour problem.

Effects of external loads-induced inclination damage on the seismic performance of traditional straight M-T joints

Under the earthquakes, wind, and other external loads, ancient timber structures have experienced various degrees of damages, in which the inclination damage of mortise and tenon (M-T) joints, induced by the external loads, has an adverse effect on the safety of the whole structure. To study the effect of various degrees of inclination damage on the seismic behavior of straight M-T joints, we fabricated four 1/3.2-scaled ancient straight M-T joint specimens, one without inclination and three with different degrees of inclination, and subjected them to the cyclic loading tests. The inclination of the joint was simulated artificially, i.e., pushing the intact joint to the predetermined inclination rotation and holding the loads, then unloading when the part of tenon entered a nonrecoverable plastic state. The failure modes, initial elastic stiffness, moment-resisting capacity, strength and stiffness degradation laws as well as energy dissipation and deformation capacities of the joints were investigated. The results showed that the plastic deformation of the tenon and mortise edge, tenon pull-out, and longitudinal splitting of the tenon were exhibited in the inclined joint specimens. Compared to the intact joint, the plastic deformation of the tenon and tenon pull-out for the inclined M-T joints were more apparent during the positive loading. The hysteretic curve of each joint exhibited an anti- "Z" shaped, and the greater the inclination degree, the more apparent the negative initial slipping and pinching effect. With an increase in the damage degree, the initial stiffness, ultimate moment-resisting capacity, and hysteretic energy dissipation behavior of the inclined M-T joint gradually degraded. When the damage degree was 3.89%, the positive yielding moment, peak moment, and initial stiffness of the inclined M-T joint degraded to 52.41%, 86.09%, and 67.19% of that of the intact joint. Based on the hysteretic characteristics and test results of the inclined M-T joints, the degradation formulas of the key parameters of seismic behavior for the inclined M-T joints were established, and an improved degraded hysteretic model, which can reflect the hysteretic behaviors of inclined M-T joint, was proposed. Good agreements between the model predictions and the test results were observed.

Lower limb squat biomechanics and select clinical measures in chronic ankle instability

BackgroundIndividuals with chronic ankle instability often present with clinical and biomechanical abnormalities, however squat biomechanics have not been investigated. The purpose of this study was to compare select clinical assessments and squat biomechanics between individuals with and without chronic ankle instability. MethodsFifteen individuals with chronic ankle instability and a matched control group were studied. A weight-bearing dorsiflexion lunge test, foot posture, and an in-line half-kneeling motor control test for core stability were assessed. Lower limb 3D bilateral and unilateral squat biomechanics were captured. Groups, limbs and squat tasks were compared using an alpha of 0.05. FindingsIndividuals with chronic ankle instability had less static weight-bearing dorsiflexion and failed the core stability test more frequently, but did not differ in foot morphology compared to the controls. When squatting, those with chronic ankle instability demonstrated reduced peak ankle dorsiflexion angles and moments in the involved limb (p < 0.04) during single limb squats and had interlimb differences in ankle dorsiflexion angle as well as hip and knee kinetics (p < 0.04) during double limb squats. In those with chronic ankle instability, there was less overall motion, but higher kinetic demands in single limb versus double leg squatting (p < 0.03). InterpretationIndividuals with chronic ankle instability had impaired weight-bearing dorsiflexion and showed impaired core stability more often, which accompanied altered squatting mechanics in both variations. Within the limbs with chronic ankle instability, single limb squats showed lesser kinematic demands but higher kinetic demands than double limb squatting.

Children with bilateral cerebral palsy use their hip joint to complete a step-up task.

Performance in stair-climbing is largely associated with disruptions to mobility and community participation in children with cerebral palsy (CP). It is important to understand the nature of motor impairments responsible for making stairs a challenge in children with bilateral CP to clarify underlying causes of impaired mobility. In pediatric clinical populations, sensitive measurements of movement quality can be captured during the initial step of stair ascent. Thus, the purpose of this study was to quantify the lower limb joint moments of children with bilateral CP during the stance phases of a step-up task. Participants performed multiple stepping trials in a university gait laboratory. Outcome measures included extensor support moments (the sum of hip, knee, and ankle sagittal plane moments), hip abduction moments, and their timing. We recruited seven participants per group. We found that peak support and hip abduction moments were similar in the bilateral CP group compared to the typical development (TD) group. We also found that children with bilateral CP timed their peak moments closer together and increasingly depended on the hip joint to complete the task, especially in their more affected (MA) lower limb. Our investigation highlights some underlying causes that may make stair climbing a challenge for the CP population, including a loss of selective voluntary motor control (SVMC), and provides a possible treatment approach to strengthen lower limb muscles.

Determining whether biomechanical variables that describe common ‘safe lifting’ cues are associated with low back loads

Lift technique training programs have been implemented to help reduce injury risk, but the underlying content validity of cues used within these programs is not clear. The objective of this study was to determine whether biomechanical variables, that commonly used lifting cues aim to elicit, are associated with resultant low back extensor moment exposures. A sample of 72 participants were recruited to perform 10 repetitions of a floor-to-waist height barbell lift while whole-body kinematics and ground reaction forces were collected. Kinematic, kinetic, and energetic variables representative of characteristics commonly targeted by lifting cues were calculated as predictor variables, while peak and cumulative low back moments were calculated as dependent measures. Multiple regression revealed that 56.6–59.2% of variance in low back moments was explained by predictor variables. From these regression models, generating motion with the legs (both greater hip and knee work), minimizing the horizontal distance of the body to the load, maintaining a stable body position, and minimizing lift time were associated with lower magnitudes of low back moments. These data support that using cues targeting these identified variables may be more effective at reducing peak low back moment exposures via lift training.

Applying the BeiDou Navigation Satellite System in the acquisition of the coseismic deformation and the high-frequency dynamic displacement of the 2021 MW 7.4 Maduo earthquake

SUMMARY This study acquires the coseismic deformation field and the high-frequency dynamic displacement of the MW 7.4 earthquake that occurred in Maduo, China, on 2021 May 22, based on the BeiDou Navigation Satellite System (BDS), and the comparison with the results obtained by the Global Positioning System (GPS) reveals that the two systems are certain differences in their ability to acquire the coseismic deformation field. The maximum difference in the horizontal coseismic deformation is &amp;lt;5 mm, and the maximum difference in the vertical coseismic deformation is 8.7 mm. The dynamic displacement waveforms of the 2021 MW 7.4 Maduo earthquake acquired by BDS and GPS are very similar, which confirms that BDS can acquire ground-shaking images with an accuracy comparable to that of GPS. Based on the empirical relationship equation of the peak ground displacement (PGD) and moment magnitude (MW), this study verifies and calculates both the MW of the 2021 MW 7.4 Maduo earthquake and the error and finds that the MW can be quickly and accurately obtained by using the empirical PGD and MW equations, and this MW value can be used as a supplementary means of calibrating the MW of the large earthquake early warning systems, which can be quickly determined by seismic wave data. Finally, by comparing the slip distributions inverted from the BDS and GPS coseismic deformation fields, this study finds that BDS is equally effective as GPS.

Lower limb strength and training experience in elite and sub-elite female footballers

BACKGROUND: Strength differences between performance levels remain unclear in female football. Furthermore, the relationship between fulltime training and strength has been unexplored despite increased professionalisation in the sport. OBJECTIVE: The aims of this research were to examine knee flexor/extensor and hip adductor/abductor strength differences between elite and sub-elite female footballers, and then determine the relationship of strength performance to age, years of football experience (FE), and years of fulltime training (FTT). METHODS: 15 elite and 15 sub-elite professional female footballers were tested. The main outcomes were concentric isokinetic knee flexor and extensor peak moment at 60, 180, and 300∘/s, and isometric hip adductor (ADD) and abductor (ABD) force. RESULTS: The elite team had higher absolute (300∘/s: 47.13–49.33 Nm vs 37.33–38.93 Nm, p&lt; 0.05) and normalised (300∘/s: 0.76–0.80 Nm/kg vs 0.59–0.62 Nm/kg, p&lt; 0.05) knee flexor values, and higher normalised ADD (5.64–5.66 N/kg vs 4.98–5.05 N/kg, p&lt; 0.05) and ABD force (5.80–6.00 N/kg vs 5.26–5.39 N/kg, p&lt; 0.05), compared to the sub-elite team. Age, FE, and FTT were correlated to knee flexor values (r= 0.381–0.559, p&lt; 0.05). Additionally, FTT was correlated with normalised ADD and ABD force (r= 0.362–0.546, p&lt; 0.05). CONCLUSION: Sub-elite female footballers may require additional knee flexor and hip strengthening in order to make the step up to the elite level. Those who are younger or have low FTT may also be recommended additional lower limb strengthening ahead of joining a fulltime training environment.

Optimization model of battery electric vehicle charging facility layout towards embedded system and data mining algorithm

Abstract Battery electric vehicles have been developing rapidly in recent years due to their advantages of energy saving and emission reduction. However, the development of battery electric vehicles is still in its infancy due to the relatively immature charging technology and the lack of infrastructure development. In many researches, there have been many solutions to adopt remote monitoring systems in battery electric vehicles to monitor and collect them in real time for statistical analysis and fault diagnosis. However, the current monitoring systems are carried out statistically and it is difficult to extract much valuable information from the data. In this paper, after analyzing the construction mode of battery electric vehicle charging facilities, the battery electric vehicle charging facility system platform using embedded system was analyzed. Several functions were simulated to meet the problems encountered by users in using it, studying the battery electric vehicle charging facility layout optimization model based on data mining algorithm. Focusing on the coverage problem in the siting problem, the State-of-Charge (SOC) of the battery charge state was analyzed. Taking residential areas as an example and 4 weeks as a cycle, it was found that during the first to fourth weeks, the negative power at 1:00, 20:00 and 24:00 was higher. At the same type of time point, different charging thresholds had a significant impact on the charging load demand of users. The larger the charging threshold of battery electric vehicles appeared, the earlier the peak moment and the higher the peak load. The battery state of the battery electric vehicle in the work area is 60 % at 1:00, and it reaches a relatively full state of 90 % at 8:00. In different regions, the allocation of charging thresholds for battery electric vehicles was different, and the Markov theory was derived from the analysis of the coverage problem to enable fast and effective siting of charging piles while satisfying charging convenience and high utilization of charging facilities to complement the research on the optimization model of battery electric vehicle charging facility layout.

The relationship between knee flexion excursion and mechanical stress during gait in medial knee osteoarthritis

BackgroundA decrease in knee flexion excursion during the loading response may affect not only quadriceps muscle weakness, pain, and inflammatory symptoms, but also lead to physical function decline and activity limitation. The aim of this investigation was to clarify the relationship between knee flexion excursion during the loading response and mechanical stress on the knee joint, muscle strength, pain, and physical function in patients with knee osteoarthritis. MethodsTwenty patients diagnosed with medial knee osteoarthritis. The participants walked along a 10 m corridor in the laboratory at a comfortable pace. The kinematic and kinetic data were collected using a 3D motion analysis system. We employed to control for gait speed and age while examining the relationship between knee flexion excursion during the loading response and mechanical stress on the knee joint, muscle strength, pain, and physical function. FindingsKnee flexion excursion showed a significant positive correlation with the peak and angular impulse of knee flexion moment. In the partial correlation coefficients controlling for age and gait speed, significant negative correlations were found between knee flexion excursion and knee adduction moment angular impulse. InterpretationIt can be inferred that gait with reduced knee flexion movement during the loading response in patients with knee osteoarthritis may result in increased mechanical stress on the knee joint in the frontal plane. Exercise interventions aimed at increasing knee flexion excursion may result in a reduction in disease progression.

Quasi-Static Model Test of Pile-Supported Wharf under Cyclic Lateral Loading

The pile-supported wharf (PSW) is one of the most common structures in harbor engineering. To investigate the dynamic response characteristics of the PSW, a quasi-static model test of a PSW–ground system under cyclic lateral loading is conducted. The deformation and damage processes of piles and the sand stratum are observed and obtained. The hysteresis characteristics of the PSW–ground system and the response characteristics of piles are systematically explored. The strain energy of the pile group on the sloping ground is calculated and analyzed. The results show that there are two peak bending moments on the pile, and the maximum one occurs at the pile top. The pile embedded depth and the loading direction strongly affect the strain energy distribution of the pile group. Under downslope direction loading, the center piles have the largest strain energy percentage. The strain energy extends from the center piles to the outside piles with the increase in loading displacement amplitude. The test results indicate that the landside pile and center pile should be strengthened during seismic design.

Comparison of biomechanical parameters in lower limb joints of stroke patients according to conventional evaluation scores during level walking.

Objective: Patients with chronic stroke capable of independent gait were classified into functional ambulation category (FAC) 4 or 5, and the kinetic and kinematic data on their lower limb joints on the affected and unaffected sides were compared with that of healthy individuals. Finally, the qualitative changes in the gait of patients with stroke were investigated based on the differences in FAC scores. Methods: Twelve healthy participants and 19 patients with stroke capable of independent gait were included. The three-dimensional (3D) motion analysis and conventional assessment were conducted for all patients with stroke. Results: The FAC 5 group exhibited a larger range of motion (ROM) than the FAC 4 group in knee and hip joints on the affected side and only in the hip on the unaffected side. In the FAC 5 group, ROM differences in the healthy group on either the affected or unaffected side were absent. The peak of the hip flexion moment on the affected side in both the FAC 4 and 5 groups was smaller than that in the healthy group and in the FAC 4 group on the unaffected side. The absorption power minimum on the affected side was smaller only in the FAC 4 group than that in the healthy group and was larger in the FAC 5 group than that in the FAC 4 group. On the unaffected side, the absorption power minimum was smaller only in the FAC 4 group than that in the healthy group. Conclusion: Functional differences in gait were found in patients classified based on conventional evaluation capable of independent gait after post-stroke rehabilitation. Patients may not exhibit complete recovery in the kinetic indices even if they are judged to be normal in the conventional evaluation, and the kinematic gait indices indicate recovery. Evaluating kinetic indices in addition to kinematic indices is necessary, and joint power may be an especially useful index.

Chronic Adaptions in Quadriceps Fascicle Mechanics Are Related to Altered Knee Biomechanics After Anterior Cruciate Ligament Reconstruction.

Following anterior cruciate ligament reconstruction (ACLR), patients exhibit abnormal walking mechanics and quadriceps dysfunction. Quadriceps dysfunction has been largely attributed to muscle atrophy and weakness. While important, these factors do not capture intrinsic properties of muscle that govern its ability to generate force and withstand load. While fascicle abnormalities after ACLR have been documented in early stages of recovery (<12mo), long-term effects of ACLR on fascicle mechanics remain unexplored. We evaluated quadriceps fascicle mechanics during walking 3years post-ACLR and examined the relationship with knee mechanics. Participants included 24 individuals with ACLR and 24 Controls. Linear mixed models compared the ACLR, Contralateral, and Controls limbs for (1)quadriceps strength, (2)fascicle architecture and mechanics, and (3)knee mechanics. No difference in strength or overall fascicle length excursions was found between limbs. The ACLR limb exhibited longer fascicles at heel strike and peak knee extension moment (P < .001-.004), and smaller fascicle angles at heel strike, peak knee extension moment, and overall suppressed fascicle angle excursions (P < .001-.049) relative to the Contralateral and/or Control limb. This indicates an abnormality in fascicle architecture and mechanics following ACLR and suggests abnormalities in contractile function that cannot be explained by muscle weakness and may contribute to long-term gait irregularities.

Effects of ankle exoskeleton assistance and plantar pressure biofeedback on incline walking mechanics and muscle activity in cerebral palsy

Ankle dysfunction affects more than 50 % of people with cerebral palsy, resulting in atypical gait patterns that impede lifelong mobility. Incline walking requires increased lower limb effort and is a promising intervention that targets lower-limb extensor muscles. A concern when prescribing incline walking to people with gait deficits is that this exercise may be too challenging or reinforce unfavorable gait patterns. This study aims to investigate how ankle exoskeleton assistance and plantar pressure biofeedback would affect gait mechanics and muscle activity during incline walking in CP. We recruited twelve children and young adults with CP. Participants walked with ankle assistance alone, biofeedback alone, and the combination while we assessed ankle, knee, and hip mechanics, and plantar flexor and knee extensor activity. Compared to incline walking without assistance or biofeedback, ankle assistance alone reduced the peak biological ankle moment by 12 % (p < 0.001) and peak soleus activity by 8 % (p = 0.013); biofeedback alone increased the biological ankle moment (4 %, p = 0.037) and power (19 %, p = 0.012), and plantar flexor activities by 9 – 27 % (p ≤ 0.026); assistance-plus-biofeedback increased biological ankle and knee power by 34 % and 17 %, respectively (p ≤ 0.05). The results indicate that both ankle exoskeleton assistance and plantar pressure biofeedback can effectively modify lower limb mechanics and muscular effort during incline walking in CP. These techniques may help in establishing personalized gait training interventions by providing the ability to adjust intensity and biomechanical focus over time.

Experimental and Parametric Study on Rotational Performance of Through-Tenon Joints in Traditional Timber Structures

ABSTRACT The rotational capacity of mortise-tenon joints is crucial for stability in traditional timber structures. However, these joints are influenced by various factors such as environmental conditions and internal features, impacting their rotational performance over time. To assess these influences, four groups of through-tenon joints with different small and large tenon lengths were constructed and tested. Deformation characteristics, hysteresis, bearing capacity, stiffness, and energy consumption of the joints were investigated. Finite element models were created and verified through testing. An orthogonal design scheme analyzed the effects of parameters and their interactions on rotational performance. The results indicated that increasing the length of the smaller tenon improved tenon pull-out length and ductility, while simultaneously reducing bearing capacity, stiffness, and energy dissipation. Tenon dimensions and the ratio of small tenon length to total tenon length were found to significantly impact peak moment. Critical parameters affecting rotational performance included tenon length, elastic modulus perpendicular to the grain, and the gap between the tenon and mortise.

Reproducibility of peak moment for isometric and isokinetic knee extension exercise

BackgroundAccurate measurements of muscular performance are important for diagnostics, for example during rehabilitation after traumatic injuries but also in competitive sports. For these purposes, dynamometric devices are widely used and considered the gold standard for muscle strength testing. However, few previous studies have tested the reproducibility of peak moment (PM) at velocities close to the maximum device capability, and in general, reproducibility results cannot be transferred to other devices or test protocols. The purpose of this study was to evaluate the reproducibility of PM for different isometric and isokinetic knee extension exercises using the IsoMed 2000.MethodsThirty subjects volunteered in three repeated test sessions, including isometric knee extension (100° and 140° knee angle) and isokinetic knee extension (30°/s and 400°/s). Statistical analysis for comparison of sessions two and three included paired sample t-test, calculation of intraclass correlation coefficient (ICC) and standard error of measurement (SEM). Additionally, Bland Altman statistics and corresponding plots were created.ResultsA significant difference between sessions in PM was found for isometric knee extension in one leg (140° left). Reproducibility was high for all conditions with ICC ranging from 0.964 to 0.988 and SEM in the range of 7.6 to 10.5 Nm. Bland Altman statistics revealed a bias between − 7.3 and 0.7 Nm.ConclusionsReproducibility of PM using the IsoMed 2000 was good after an initial familiarization trial with high values of relative reproducibility. Absolute reproducibility can be interpreted as appropriate for most common practical applications.

Differential effects of sex on upper body kinematics and kinetics during fatiguing, Asymmetric lifting

This study quantified sex-specific biomechanical adaptations to fatigue in asymmetric lifting. Twenty-one females and fifteen males performed a prolonged asymmetric lifting protocol while upper body, trunk and pelvis kinematics were collected. Features of movement identified with principal component analysis, and peak joint angular velocities and moments were calculated. Sex-specific kinematic adaptations to fatigue included females adopting a ‘stoop-like’ lifting strategy to a greater extent than males. Additionally, females exhibited higher vertical elbow positions during load rotation, moved their body toward the destination for load deposit, and did not reduce peak right shoulder flexion velocities, in contrast to male participants. Females also had greater low back and shoulder peak normalized joint moments. When fatigued, females adopted an asymmetric lifting strategy that minimized metabolic demand as supported by smaller decreases in maximum voluntary contractions. However, females' fatigue-related adaptations increased biomechanical exposures associated with injury risk.

Improving the ecological validity of isokinetic knee tests at different hip angles: reciprocal concentric-eccentric movements as a suitable alternative for discrete tests

ABSTRACT Isokinetic knee tests mostly evaluate reciprocal concentric-concentric flexor-extensor movements in a seated position. Discrete tests generate higher moments, but time requirements impede their widespread implementation. This study examined if hip angle (flexed vs. extended) and test modality (discrete vs. reciprocal) affect camera-based data (100 fps). Sixteen healthy males performed concentric (con) and eccentric (ecc) isokinetic knee flexor (H) and extensor (Q) movements (60°/s). Peak moments and contractional work of discrete and reciprocal tests (QconQecc, HconHecc) strongly correlated for extended (Q:91%≥R2≥71%; H:95%≥R2≥87%) and flexed hip (Q:88%≥R2≥70%; H:81%≥R2≥75%) without significant differences (p>0.05) between test modalities. Discrete and “traditional” seated QconHcon-tests revealed substantially lower correlations for extended (Q:44%≥R2≥43%; H:55%≥R2≥54%) and flexed hip (Q:81%≥R2≥77%; H:48%≥R2≥47%). Although most mean values did not significantly differ, moderate correlations were predominant and the respective limits of agreement demonstrated considerable effects of hip angle and test modality. These insights assist practitioners in interpreting isokinetic data of different test procedures. If time constraints prevent discrete knee tests (gold standard), concentric-eccentric movements provide highly correlated outcomes, independent of the hip angle.