The sensitivity of joint kinematics and kinetics to marker placement during a change of direction task

How reliable are femoropelvic kinematics during deep squats? The influence of subject-specific skeletal modelling on measurement variability

BACKGROUND

Biplanar radiography displays promising results in the production of subject-specific (S.specific) biomechanical models. However, the focus has predominantly centred on methodological investigations in gait analysis. Exploring the influence of such models on the analysis of high range of motion tasks linked to hip pathologies is warranted. The aim of this study is to investigate the effect of S.Specific modelling techniques on the reliability of deep squats kinematics in comparison to generic modelling.

METHODS

8 able-bodied male participants attended 5 motion capture sessions conducted by 3 observers and performed 5 deep squats in each. Prior to each session a biplanar scan was acquired with the reflective-markers attached. Inverse kinematics of pelvis and thigh segments were calculated based on S.specific and Generic model definition. Agreement between the two models femoropelvic orientation in standing was assessed with Bland-Altman plots and paired t- tests. Inter-trial, inter-session, inter-observer variability and observer/trial difference and ratio were calculated for squat kinematic data derived from the two modelling approaches.

RESULTS

Compared to the Generic model, the S.Specific model produced a calibration trial that is significantly offset into more posterior pelvis tilt (-2.8±2.7), hip extension (-2.2±3.8), hip abduction (-1.2±3.6) and external rotation (-13.8±11.4). The S.specific model produced significantly different squat kinematics in the sagittal plane of the pelvis (entire squat cycle) and hip (between 40 % and 60 % of the squat cycle). Variability analysis indicated that the error magnitude between the two models was comparable (difference<2°). The S.specific model exhibited a lower variability in the observer/trial ratio in the sagittal pelvis and hip, the frontal hip, but showed a higher variability in the transverse hip.

SIGNIFICANCE

S.specific modelling appears to introduce a calibration offset that primarily translates into an effect in the sagittal plane kinematics. However, the clinical added value of S.specific modelling in terms of reducing experimental sources of kinematic variability was limited.

Marker location and knee joint constraint affect the reporting of overhead squat kinematics in elite youth football players

Motion capture systems are used in the analysis and interpretation of athlete movement patterns for a variety of reasons, but data integrity remains critical regardless. The extent to which marker location or constraining degrees of freedom (DOF) in the biomechanical model impacts on this integrity lacks consensus. Ten elite academy footballers performed bilateral overhead squats using a marker-based motion capture system. Kinematic data were calculated using four different marker sets with 3DOF and 6DOF configurations for the three joint rotations of the right knee. Root mean squared error differences between marker sets ranged in the sagittal plane between 1.02 and 4.19 degrees to larger values in the frontal (1.30-6.39 degrees) and transverse planes (1.33 and 7.97 degrees). The cross-correlation function of the knee kinematic time series for all eight marker-sets ranged from excellent for sagittal plane motion (>0.99) but reduced for both coronal and transverse planes (<0.9). Two-way ANOVA repeated measures calculated at peak knee flexion revealed significant differences between marker sets for frontal and transverse planes (p < 0.05). Pairwise comparisons showed significant differences between some marker sets. Marker location and constraining DOF while measuring relatively large ranges of motion in this population are important considerations for data integrity.

Are inter-limb differences in change of direction velocity and angle associated with inter-limb differences in kinematics and kinetics following anterior cruciate ligament reconstruction?

BACKGROUND

Quantifying inter-limb differences in kinematics and kinetics during change of direction is proposed as a means of monitoring rehabilitation following anterior cruciate ligament reconstruction (ACLR). Velocity and centre of mass (CoM) deflection angle are fundamental task descriptors that influence kinematics and kinetics during change of direction. Inter-limb differences in approach velocity and CoM deflection angle have been identified following ACLR and may contribute to the presence of inter-limb differences in kinematics and kinetics during change of direction.

RESEARCH QUESTION

The aim of this study was to quantify the proportion of variance in kinematic and kinetic inter-limb differences attributable to inter-limb differences in approach velocity and centre of mass deflection angle during a change of direction task.

METHODS

A cohort of 192 patients (male, 23.8 ± 3.6 years, 6.3 ± 0.4 months post primary ACLR) completed a pre-planned 90° change of direction task on both their operated and non-operated limb. Inter-limb differences in approach velocity and CoM deflection angle were calculated alongside lower-extremity kinematic and kinetic variables. The relationship between inter-limb differences in task-level variables and inter-limb differences in kinematic and kinetic variables was examined using linear regression models. Kinematic and kinetic inter-limb differences were adjusted for inter-limb differences in approach velocity and CoM deflection angle. Adjusted and unadjusted inter-limb differences were submitted to one sample t-tests.

RESULTS

Inter-limb differences in approach velocity and centre of mass deflection angle explained 3 - 60% of the variance in kinematic and kinetic inter-limb differences. Statistical inferences remained consistent between adjusted and unadjusted conditions with the exception of hip flexion angle.

SIGNIFICANCE

Inter-limb differences in task-level features explain a large proportion of the variance in inter-limb differences in several kinematic and kinetic variables. Accounting for this variation reduced the magnitude of kinematic and kinetic inter-limb differences comparable to those previously observed in normative cohorts.

Comparison of a single-view image-based system to a multi-camera marker-based system for human static pose estimation

The purpose of this study was to compare human static pose estimation data measured with a single-view image-based system and a multi-camera marker-based system. Thirty participants (20 male/10 female, mean ± standard deviation 29.1 ± 10.0 years old, 1.75 ± 0.10 m tall, 79.1 ± 18.0 kg) performed six repetitions each of static holds of arm-raises and squats, in a different orientation for each repetition. These trials were captured simultaneously with a 120-Hz 12-camera marker-based system and a variable-frequency single-view image-based system. Data for each trial were time-synchronized between the two systems using a near-infrared LED-light that was visible to both systems. Discrete measurements of bilateral shoulder angles during arm-raises and bilateral knee angles during squats were compared between the systems using Bland-Altman plots and descriptive statistics. Pearson correlation coefficients were calculated, comparing the participant trial mean values across systems. Finally, a two-way ANOVA was used to examine whether participant orientation in the capture volume significantly affected either system. Biases for discrete measurements ranged in magnitude from 1.3 to 1.9°, and standard deviations of the differences between systems ranged from 2.4 to 4.7°. Pearson correlation coefficients were all above 0.97, and the ANOVA was unable to find a statistically significant orientation effect for either system. Thus, the marker-based and image-based systems produced similar measurements of static shoulder and knee angles. Future work should examine more complex measurements using volumetric scan-based models and also investigate the ability of single-view image-based systems to measure dynamic movements.

Dynamic segmental kinematics of the lumbar spine during diagnostic movements

Background: In vivo measurements of segmental-level kinematics are a promising avenue for better understanding the relationship between pain and its underlying, multi-factorial basis. To date, the bulk of the reported segmental-level motion has been restricted to single plane motions. Methods: The present work implemented a novel marker set used with an optical motion capture system to non-invasively measure dynamic, 3D in vivo segmental kinematics of the lower spine in a laboratory setting. Lumbar spinal kinematics were measured for 28 subjects during 17 diagnostic movements. Results: Overall regional range of motion data and lumbar angular velocity measurement were consistent with previously published studies. Key findings from the work included measurement of differences in ascending versus descending segmental velocities during functional movements and observations of motion coupling paradigms in the lumbar spinal segments. Conclusion: The work contributes to the task of establishing a baseline of segmental lumbar movement patterns in an asymptomatic cohort, which serves as a necessary pre-requisite for identifying pathological and symptomatic deviations from the baseline.

Examining movement asymmetries during three single leg tasks using interlimb and single subject approaches

PURPOSE

s: To examine whether healthy individuals displayed asymmetric trunk and lower extremity kinematics in the frontal and sagittal planes using both interlimb and single subject models.

METHODS

Trunk, pelvis, and lower extremity kinematic waveforms were analyzed bilaterally during the single leg squat (SLS), forward step down (FSD), and lateral step down (LSD). Participants identified task specific preferred and non-preferred legs based on perceived stability for interlimb analyses. Movement patterns were also analyzed with a single subject approach that included Fisher's exact tests to assess whether asymmetries were related to the task.

RESULTS

Participants were found to have increased pelvic drop on the non-preferred leg during the LSD from 41 to 77% of the movement (p = 0.01). No other bilateral differences were found for interlimb analyses. Single subject analyses indicated that no task had a greater probability of finding or not finding asymmetries. Associations were found between the FSD and SLS for frontal plane hip (p < 0.01) and knee motion (p < 0.01).

CONCLUSIONS

Interlimb analyses can be influenced by intraparticipant movement variability between preferred and non-preferred legs. Movement asymmetries during single leg weightbearing are likely task dependent and a battery of tests is necessary for assessing bilateral differences.

High-demand tasks show that ACL reconstruction is not the only factor in controlling range of tibial rotation: a preliminary investigation

BACKGROUND

Excessive range of tibial rotation (rTR) may be a reason why athletes cannot return to sports after ACL reconstruction (ACLR). After ACLR, rTR is smaller in reconstructed knees compared to contralateral knees when measured during low-to-moderate-demand tasks. This may not be representative of the amount of rotational laxity during sports activities. The purpose of this study is to determine whether rTR is increased after ACL injury compared to the contralateral knee and whether it returns to normal after ACLR when assessed during high-demand hoptests, with the contralateral knee as a reference.

METHODS

Ten ACL injured subjects were tested within three months after injury and one year after reconstruction. Kinematic motion analysis was conducted, analysing both knees. Subjects performed a level-walking task, a single-leg hop for distance and a side jump. A paired t-test was used to detect a difference between mean kinematic variables before and after ACL reconstruction, and between the ACL-affected knees and contralateral knees before and after reconstruction.

RESULTS

RTR was greater during high-demand tasks compared to low-demand tasks. Pre-operative, rTR was smaller in the ACL-deficient knees compared to the contralateral knees during all tests. After ACLR, a greater rTR was seen in ACL-reconstructed knees compared to pre-operative, but a smaller rTR compared to the contralateral knees, even during high-demand tasks.

CONCLUSION

The smaller rTR, compared to the contralateral knee, seen after a subacute ACL tear may be attributed to altered landing technique, neuromuscular adaptation and fear of re-injury. The continued reduction in rTR one year after ACLR may be a combination of this neuromuscular adaptation and the biomechanical impact of the reconstruction.

TRIAL REGISTRATION

The trial was registered in the Dutch Trial Register (NTR: www.trialregister.nl , registration ID NL7686).

Between-day reliability and minimum detectable change of the Conventional Gait Model 2 and Plug-in Gait Model during running

BACKGROUND

The Plug-in Gait model (PiG) is commonly used in 3D motion analysis but has limited reliability. Although an improved version of PiG has been developed, called the Conventional Gait Model 2 (CGM2), there is limited evidence on its between-day reliability for running.

RESEARCH QUESTION

What is the between-day intraclass correlation coefficient (ICC3,k) and minimum detectable change (MDC) of lower limb kinematics and kinetics for CGM2 during running and does reliability differ between CGM2 and PiG.

METHODS

Twenty-three healthy participants performed running at a comfortable speed in two identical test sessions at least 5 days apart. Lower limb kinematic and kinetic data in the three planes of motion were calculated using CGM2 and PiG. The ICC and MDC were calculated for the kinematic and kinetic parameters at initial contact and peak during the stance phase of running.

RESULTS

CGM2 kinematics showed good-to-excellent reliability (ICC: 0.75-0.93), except for hip extension and ankle internal rotation, and less than 5° MDC (1.8°-4.9°) of the coronal and sagittal planes, except for hip extension. PiG showed poor-to-moderate reliability (ICC: -0.15 to 0.72) in the coronal and transverse planes and greater than 5° MDC (5.0°-21.8°), except for knee extension, adduction, and ankle dorsiflexion. CGM2 showed good-to-excellent reliability for peak kinetics (ICC: 0.75-0.97), except for hip internal rotation and knee extension. The ICC and MDC were higher for CGM2 than PiG, with significant differences in the coronal plane of the hip and knee joints and transverse plane of the hip joint in kinematics and in the sagittal and coronal plane of the hip and knee joints in kinetics.

SIGNIFICANCE

The between-day reliability of CGM2 was mostly good to excellent for lower limb kinematics and kinetics during running. We believe that CGM2 can more accurately assess kinematic differences between the coronal and transverse planes than the PiG.

The Conventional Gait Model’s sensitivity to lower-limb marker placement

Clinical gait analysis supports treatment decisions for patients with motor disorders. Measurement reproducibility is affected by extrinsic errors such as marker misplacement—considered the main factor in gait analysis variability. However, how marker placement affects output kinematics is not completely understood. The present study aimed to evaluate the Conventional Gait Model’s sensitivity to marker placement. Using a dataset of kinematics for 20 children, eight lower-limb markers were virtually displaced by 10 mm in all four planes, and all the displacement combinations were recalculated. Root-mean-square deviation angles were calculated for each simulation with respect to the original kinematics. The marker movements with the greatest impact were for the femoral and tibial wands together with the lateral femoral epicondyle marker when displaced in the anterior–posterior axis. When displaced alone, the femoral wand was responsible for a deviation of 7.3° (± 1.8°) in hip rotation. Transversal plane measurements were affected most, with around 40% of simulations resulting in an effect greater than the acceptable limit of 5°. This study also provided insight into which markers need to be placed very carefully to obtain more reliable gait data.

Conclusion or Illusion: Quantifying Uncertainty in Inverse Analyses From Marker-Based Motion Capture due to Errors in Marker Registration and Model Scaling

Estimating kinematics from optical motion capture with skin-mounted markers, referred to as an inverse kinematic (IK) calculation, is the most common experimental technique in human motion analysis. Kinematics are often used to diagnose movement disorders and plan treatment strategies. In many such applications, small differences in joint angles can be clinically significant. Kinematics are also used to estimate joint powers, muscle forces, and other quantities of interest that cannot typically be measured directly. Thus, the accuracy and reproducibility of IK calculations are critical. In this work, we isolate and quantify the uncertainty in joint angles, moments, and powers due to two sources of error during IK analyses: errors in the placement of markers on the model (marker registration) and errors in the dimensions of the model’s body segments (model scaling). We demonstrate that IK solutions are best presented as a distribution of equally probable trajectories when these sources of modeling uncertainty are considered. Notably, a substantial amount of uncertainty exists in the computed kinematics and kinetics even if low marker tracking errors are achieved. For example, considering only 2 cm of marker registration uncertainty, peak ankle plantarflexion angle varied by 15.9°, peak ankle plantarflexion moment varied by 26.6 N⋅m, and peak ankle power at push off varied by 75.9 W during healthy gait. This uncertainty can directly impact the classification of patient movements and the evaluation of training or device effectiveness, such as calculations of push-off power. We provide scripts in OpenSim so that others can reproduce our results and quantify the effect of modeling uncertainty in their own studies.

Comparison of marker-less and marker-based motion capture for baseball pitching kinematics

The purpose of this study was to compare baseball pitching kinematics measured with marker-less and marker-based motion capture. Two hundred and seventy-five fastball pitches were captured at 240 Hz simultaneously with a 9-camera marker-less system and a 12-camera marker system. The pitches were thrown by 30 baseball pitchers (age 17.1 ± 3.1 years). Data for each trial were time-synchronised between the two systems using the instant of ball release. Coefficients of Multiple Correlations (CMC) were computed to assess the similarity of waveforms between the two systems. Discrete measurements at foot contact, during arm cocking, and at ball release were compared between the systems using Bland-Altman plots and descriptive statistics. CMC values for the five time series analysed ranged from 0.88 to 0.97, indicating consistency in movement patterns between systems. Biases for discrete measurements ranged in magnitude from 0 to 16 degrees. Standard deviations of the differences between systems ranged from 0 to 14 degrees, while intraclass correlations ranged from 0.64 to 0.92. Thus, the marker-based and marker-less motion capture systems produced similar patterns for baseball pitching kinematics. However, based on the variations between the systems, it is recommended that a database of normative ranges be established for each system.

Biomechanical asymmetries differ between autograft types during unplanned change of direction after ACL reconstruction

Nine months after anterior cruciate ligament (ACL) reconstruction, athletes who undergo surgery using a bone-patellar-tendon-bone (BPTB) autograft demonstrate higher loading asymmetries during vertical jumping than those with a hamstring tendon (HT) autograft. These asymmetries may transfer into sporting movements with a greater ACL injury risk. The aim of this study was to compare between-limb asymmetries in knee mechanics and task performance during an unplanned 90° change-of-direction (CoD) task in male field sport athletes reconstructed with BPTB or HT autografts. Seventy-eight male multidirectional field sport athletes with either a BPTB (n = 39) or HT (n = 39) autograft completed maximal unplanned CoD trials in a three-dimensional motion capture laboratory at approximately 9 months post-surgery. A mixed-model 2x2 ANOVA (autograft type x limb) was used to compare variables related to ACL injury risk (e.g., internal knee moments) and performance (e.g., completion time) between autografts and limbs. Statistical parametric mapping was used for a waveform comparison throughout stance, supplemented with a discrete point analyses of peak knee moments and performance variables. Interaction effects were found at the knee joint, with BPTB demonstrating greater asymmetries than HT in knee extension moment (p < 0.001); resultant ground reaction force (p < 0.001); peak knee external rotation moment (p = 0.04); and knee adduction (p = 0.05), medial rotation (p < 0.001), and flexion (p < 0.001) angles. No differences were found between autografts for any performance variable. BPTB demonstrated greater lower-limb biomechanical asymmetries than HT during CoD, which may influence knee loading and longer-term outcomes and should thus be targeted during rehabilitation prior to return to play.

Development and validation of FootNet; a new kinematic algorithm to improve foot-strike and toe-off detection in treadmill running

The accurate detection of foot-strike and toe-off is often critical in the assessment of running biomechanics. The gold standard method for step event detection requires force data which are not always available. Although kinematics-based algorithms can also be used, their accuracy and generalisability are limited, often requiring corrections for speed or foot-strike pattern. The purpose of this study was to develop FootNet, a novel kinematics and deep learning-based algorithm for the detection of step events in treadmill running. Five treadmill running datasets were gathered and processed to obtain segment and joint kinematics, and to identify the contact phase within each gait cycle using force data. The proposed algorithm is based on a long short-term memory recurrent neural network and takes the distal tibia anteroposterior velocity, ankle dorsiflexion/plantar flexion angle and the anteroposterior and vertical velocities of the foot centre of mass as input features to predict the contact phase within a given gait cycle. The chosen model architecture underwent 5-fold cross-validation and the final model was tested in a subset of participants from each dataset (30%). Non-parametric Bland-Altman analyses (bias and [95% limits of agreement]) and root mean squared error (RMSE) were used to compare FootNet against the force data step event detection method. The association between detection errors and running speed, foot-strike angle and incline were also investigated. FootNet outperformed previously published algorithms (foot-strike bias = 0 [–10, 7] ms, RMSE = 5 ms; toe-off bias = 0 [–10, 10] ms, RMSE = 6 ms; and contact time bias = 0 [–15, 15] ms, RMSE = 8 ms) and proved robust to different running speeds, foot-strike angles and inclines. We have made FootNet’s source code publicly available for step event detection in treadmill running when force data are not available.

Spinal Palpation Error and Its Impact on Skin Marker-Based Spinal Alignment Measurement in Adult Spinal Deformity

Spinal alignment measurement in spinal deformity research has recently shifted from using mainly two-dimensional static radiography toward skin marker-based motion capture approaches, allowing three-dimensional (3D) assessments during dynamic conditions. The validity and accuracy of such skin marker-based methods is highly depending on correct marker placement. In this study we quantified, for the first time, the 3D spinal palpation error in adult spinal deformity (ASD) and compared it to the error in healthy spines. Secondly, the impact of incorrect marker placement on the accuracy of marker-based spinal alignment measurement was investigated. 3D, mediolateral and inferosuperior palpation errors for thoracolumbar and lumbar vertebral levels were measured on biplanar images by extracting 3D positions of skin-mounted markers and their corresponding anatomical landmarks in 20 ASD and 10 healthy control subjects. Relationships were investigated between palpation error and radiographic spinal alignment (lordosis and scoliosis), as well as body morphology [BMI and soft tissue (ST) thickness]. Marker-based spinal alignment was measured using a previously validated method, in which a polynomial is fit through the marker positions of a motion trial and which allows for radiograph-based marker position correction. To assess the impact of palpation error on spinal alignment measurement, the agreement was investigated between lordosis and scoliosis measured by a polynomial fit through, respectively, (1) the uncorrected marker positions, (2) the palpation error-corrected (optimal) marker positions, and (3) the anatomically corrected marker positions (toward the vertebral body), and their radiographic equivalents expressed as Cobb angles (ground truth), using Spearman correlations and root mean square errors (RMSE). The results of this study showed that, although overall accuracy of spinal level identification was similar across groups, mediolateral palpation was less accurate in the ASD group (ASD_mean: 6.8 mm; Control_mean: 2.5 mm; p = 0.002). Significant correlations with palpation error indicated that determining factors for marker misplacement were spinal malalignment, in particular scoliotic deformity (r = 0.77; p < 0.001), in the ASD group and body morphology [i.e., increased BMI (r _s = 0.78; p = 0.008) and ST thickness (r _s = 0.66; p = 0.038)] in healthy spines. Improved spinal alignment measurements after palpation error correction, shows the need for radiograph-based marker correction methods, and therefore, should be considered when interpreting spinal kinematics.

Centre of pressure error with increasing gait velocity: The clinical impact on predicted inverse dynamics during gait in children with typical development

BACKGROUND

Centre of pressure (CoP) location error is common when predicting inverse dynamic parameters during gait. Tolerance levels of error have been previously reported. However, the clinical impact of gait velocity on CoP error has not been considered.

RESEARCH QUESTION

What is the clinical impact of CoP error with increasing gait velocity on predicted inverse dynamic parameters during gait in children with typical development?

METHODS

Three-dimensional kinematic and kinetic data were recorded at three self-selected velocities on children with typical development (walking, fast instructed walking and running). CoP location error was applied in 3 mm increments up to a maximum of 12 mm in an anteroposterior direction. Differences in maximum kinetic parameters between increments and gait velocities were assessed in conjunction with changes in GDI-kinetic.

RESULTS

Relative error (difference expressed as a % of maximum moment) decreased at all joints as gait velocity increased. The GDI-kinetic was only clinically significant for the self-selected walking condition at 9 mm and 12 mm respectively.

SIGNIFICANCE

The GDI-kinetic difference remained below the threshold for fast walking and running which suggested that CoP error of up to 12 mm in the 3D optoelectric / force plate configuration would be acceptable if subjects were assessed under these conditions.

A New Zn(II) Complex: Fluorescent Detection of Fe3+ Ions in Water and Prevention Effect on DVT By Regulating Platelets Numbers and Activity of Clotting Factor

[Zn(dima)(H₂O)_0.5]·H₂O (1), a three-dimensional metal organic framework (MOF) with high porosity was formed by self-assembly of 4,6-di(1 h-imidazol-1-yl)isophthalic acid (H₂dima) and Zn²⁺ ion. Owning to its excellent luminescence and excellent water stability, complex 1 can be used as a super sensitive sensor to detect Fe³⁺ ions via the behaviors of fluorescence quenching. At the same time, the mechanism for the fluorescence quenching is also further discussed. Furthermore, the prevention effect of the compound on the deep vein thrombosis of the lower extremities (DVT) after lower venous CHIVA surgery was evaluated in vivo. Firstly, the DVT animal models was constructed and the number of platelets was measured with flow cytometry and content of clotting factor IX and anticoagulant factor III was also detected with Lowry method after compound treatment. The molecular docking simulation results indicate that the Zn(II) complex has activity to protein docking pocket with different sizes.

The effect of ankle Kinesio™ taping on ankle joint biomechanics during unilateral balance status among collegiate athletes with chronic ankle sprain

OBJECTIVES

To determine the effects of ankle Kinesio-taping (KT) on postural sway, lower limb ROM, and muscle activity during a unilateral balance tasks.

DESIGN

Case control study design.

SETTING

Data were collected at the human movement analysis laboratory.

PARTICIPANTS

30 collegiate athletes with chronic ankle sprain (11 females and 19 males, 23.91 ± 2.58 years).

MAIN OUTCOME MEASURE

Hip, knee and ankle joints ranges of motion (ROMs); postural sway area and velocities in both anteroposterior and mediolateral directions; and muscular activity amplitudes (% peak) of lateral and medial gastrocnemius, tibialis anterior and peroneus longus in a 20s single leg balance test in two non-taped (control) and KT (intervention) conditions.

RESULTS

Significant decrease observed in ankle lateral ROM (p = 0.048, d = 0.52), mediolateral postural sway velocity (p = 0.029, d = 1.25), and peroneus longus activity amplitudes (p = 0.042, d = 0.55) after KT application.

CONCLUSION

Acute application of KT among athletes with chronic ankle instability could provide lateral mechanical support to the ankle, potentially decreasing the velocity of frontal plane sway, and decreasing the magnitude of muscle activation. These data suggest that KT may be beneficial for improving static joint stability among individuals with chronic ankle sprain, and thus could be considered an option to allow safe return-to-activity.

Agreement between An Inertia and Optical Based Motion Capture during the VU-Return-to-Play- Field-Test

The validity of an inertial sensor-based motion capture system (IMC) has not been examined within the demands of a sports-specific field movement test. This study examined the validity of an IMC during a field test (VU®) by comparing it to an optical marker-based motion capture system (MMC). Expected accuracy and precision benchmarks were computed by comparing the outcomes of a linear and functional joint fitting model within the MMC. The kinematics from the IMC in sagittal plane demonstrated correlations (r²) between 0.76 and 0.98 with root mean square differences (RMSD) < 5°, only the knee bias was within the benchmark. In the frontal plane, r² ranged between 0.13 and 0.80 with RMSD < 10°, while the knee and hip bias was within the benchmark. For the transversal plane, r² ranged 0.11 to 0.93 with RMSD < 7°, while the ankle, knee and hip bias remained within the benchmark. The findings indicate that ankle kinematics are not interchangeable with MMC, that hip flexion and pelvis tilt higher in IMC than MMC, while other measures are comparable to MMC. Higher pelvis tilt/hip flexion in the IMC can be explained by a one sensor tilt estimation, while ankle kinematics demonstrated a considerable level of disagreement, which is likely due to four reasons: A one sensor estimation, sensor/marker attachment, movement artefacts of shoe sole and the ankle model used.