Performance analyses in cross-country skiing often focus on lap or terrain-level splits. However, few studies have explored micro-pacing strategies-particularly in Skiathlon, an Olympic event requiring athletes to complete both classical and freestyle techniques on the same course. Thirteen national-level male skiers were tracked during an International Ski Federation-certified Skiathlon using GNSS and trunk-mounted sensors. Instantaneous speed profiles were analysed using one-dimensional statistical parametric mapping (SPM) to identify "race-critical clusters": contiguous intervals where speed significantly predicted section time (α = 0.05) across all eight laps (four classical, four freestyle). Freestyle laps were 4% faster than classical, with greater terrain-specific speed differences and pacing variability in classical, especially downhills. Seven race-critical clusters were identified: two uphill, four downhill, and one flat. These accounted for 11.3s (classic) and 10.9s (freestyle) of the time gap between the fast and slow group. In these segments, faster skiers used higher-gear sub-techniques and exhibited longer cycle lengths and/or higher frequencies (p < 0.05). Within race-critical clusters, the faster skiers gained substantial time advantages. Secondary analyses showed clear differences in sub-technique selection and kinematic profiles, suggesting that technical execution plays a critical role in these performance gains. Athletes and coaches may consider integrating GNSS-based tracking, SPM, and wearable-derived technique analysis into race evaluation to move beyond traditional split times and focus training on the most decisive segments of the course.

ABSTRACTBackgroundAccurate knowledge about biomechanical alterations in chronic ankle instability (CAI) during dynamic movements may inform rehabilitation strategies.ObjectiveTo identify movement patterns associated with CAI injury during a step‐down task.MethodSeventeen participants with CAI and 17 healthy controls performed a step‐down task from heights of 20 and 40 cm. Lower limb joint angles, range of motion (ROM), moments, and power were measured. The one‐dimensional statistical parametric mapping (SPM) test compared groups across the entire task (0%–100%).ResultsAt 20 cm height, the CAI group exhibited greater hip abduction angles (0%–2%, p = 0.024 and 21%–77%, p = 0.014) but smaller hip abduction (7%–13%, 19%–20%, and 47%–64% (p < 0.05)), hip external rotation (8%–12% and p = 0.04), knee abduction (7%–30%, p = 0.001 and 49%–53%, p = 0.024), and ankle external rotation moments (7%–42% and p = 0.001). At 40 cm height, the CAI group showed greater hip abduction (44%–100% and p = 0.005), reduced ankle eversion (4%–12% and p = 0.012) angles, and smaller hip abduction, hip external rotation, knee abduction, ankle plantarflexion, and external rotation moments (all p < 0.05). No between‐group differences were observed for the ROMs and power (p > 0.05).ConclusionCAI individuals exhibited greater hip abduction, less ankle eversion, and smaller muscle moments, which are associated with an increased risk of injury. Rehabilitation should emphasize strengthening the hip muscles to mitigate the risk of injury.

Functional imaging reveals cerebral microvascular dysfunction in primary antiphospholipid syndrome: Pathophysiologic insights and translational implications.

3D printed pediatric head phantom for assessing deep epileptic sources localization.

BackgroundWe evaluated the predictive performance of 18F‐flortaucipir (FTP) tau imaging within the NIA‐AA multilevel tau staging framework with respect to tau accumulation and cognitive decline in non‐demented individuals. We also tested the relationships of cognitive measures with baseline tau and tau accumulation.MethodsFTP scans from 213 non‐demented participants were processed and sampled in Statistical Parametric Mapping software (SPM), version 8, using CenTauR masks. Tau accumulation and cognitive decline associations were assessed longitudinally, with respect to two timepoints, their baseline and most recent evaluations, via survival analysis. Individuals were categorized into 4 groups reflecting the NIA‐AA imaging stages: Initial, with only b‐amyloid (Ab) pathology was present in PET; Early, with Ab pathology and tau pathology in the mesial temporal region; Intermediate, with moderate tau pathology in the meta temporal region; and Advanced, with high levels of tau in the meta temporal region. A “None” group reflecting no pathology was included as a control. Linear regressions were used to compare the longitudinal effects of either baseline tau (SUVR) or tau accumulation (SUVR/year) on cognitive decline.ResultsWhile the two sets of thresholds yielded slightly different trajectories, both showed that when applying multiple levels of tau positivity, increasing stages of tau predicted both earlier tau accumulation and earlier cognitive decline. Linear regressions revealed that change in global measures of cognition (MMSE, CDR‐SB) were significantly associated with baseline tau, while decline in Delayed Recall (DR) was significantly associated with both baseline tau and tau accumulation, where tau accumulation had a greater influence in the model, and Immediate Recall (LM) decline was significantly only associated with tau accumulation.ConclusionsImplementing the multiple tau stages from the new NIA‐AA biological staging framework clearly predicts distinct patterns of tau accumulation and cognitive decline. While baseline tau is predictive of global cognitive decline, tau accumulation is a better predictor of memory decline. Future work is needed to determine how the thresholds utilized here compare to visual reads and to determine the suitability of these thresholds in differentiating trajectories of individuals with cognitive impairment.

Joint kinematics and inter-segmental coordination during underwater undulatory swimming: Comparing swimmers of different performance levels.

Shoe companies produce running shoes that feature either reinforced (e.g., maximalist) or diminished (e.g., minimalist) midsole thicknesses, claiming potential benefits for injury prevention and enhanced running performance. Previous research has examined various footwear models available on the market, specifically investigating the effects of different midsole thicknesses. However, no studies have specifically focused on the biomechanical factors associated with carbon plate minimalist shoes. Therefore, the current study aims to investigate the effects of midsole thicknesses of 0mm, 6mm, and 8mm on the kinematic and kinetic parameters observed in elite runners, utilizing a standardized test shoe prototype. Method: Thirteen male participants, all habitual rearfoot strikers, were recruited from local social running clubs. A three-dimensional motion capture system (Vicon, Oxford, UK) consisting of ten cameras was employed to collect and analyze running kinematic data at a sampling frequency of 200 Hz. Ground reaction forces were recorded using a Kistler Type 9281 B force plate (Kistler Instrument AG, Winterthur, Switzerland) with a sampling frequency of 1000 Hz. One-way repeated-measures ANOVA was conducted to compare the biomechanical variables using SPSS version 25.0. We observed a significant interaction between heel drop and peak vertical ground reaction force (vGRF), foot strike angle (FSA), and propulsion force. Runners exhibited a reduced FSA when wearing DF6 and DF0 shoes compared to DF8 shoes. However, we did not observe a shift in running strike patterns. The results indicate that shoes with a higher heel drop (DF8) lead to a decrease in peak vGRF, ankle dorsiflexion moment, and knee flexion moment. Furthermore, shoes with a lower drop significantly increased peak propulsion force, ankle plantarflexion, dorsiflexion angle, knee flexion angle, and hip extension angle when compared to thicker shoes (DF8). This study primarily investigates the immediate effects of three different heel-drop running shoes on strike patterns, vertical ground reaction force (vGRF) peak force, joint angles, and joint moments during the running stance phase. The results offer insights into the mechanisms by which newly developed running shoes can enhance elite runners' performance. Furthermore, the statistical parametric mapping (SPM) findings from this study assess the differences throughout the entire stance phase, thereby improving our understanding of how variations in heel height influence running performance.

With the increase in life expectancy and the health benefits of exercise, running has become a popular physical activity. Nonetheless, the incidence of running-related injuries remains high. Knee mechanics during running, particularly excessive movements and angles in the frontal and transverse planes, have been identified as potential biomechanical risk factors for the development of injuries. Variations in the frontal and transverse plane measurements across studies may result from differences in static standing postures, such as toe-in or toe-out positions, which might influence knee mechanics during running. This study aimed to identify the effects of different static standing postures on knee mechanics during running. Twenty healthy participants (10 males and 10 females; age: 24.7±1.3 years; height: 1.73±0.08 m; weight: 66.5±10.7 kg) completed three different static calibration trials: (1) 30° toe-in, (2) 0° neutral position, and (3) 30° toe-out, prior to running at their self-selected speeds. A twelve-camera three-dimensional VICON motion analysis system, integrated with two AMTI force platforms, was utilized to capture knee mechanics data during running. Repeated-measures ANOVA with statistical parametric mapping (SPM) was applied to assess differences across static calibration posture trials. Significant differences were observed in knee flexion angle (29.7%-33.8%, F=5.55, p=0.048), adduction/abduction angle (0-100%, F=129.01, p &lt; 0.001), and internal/external rotation angle (0-100%, F=58.58, P &lt; 0.001). Post hoc analyses revealed that, compared to 0°, knee flexion angle decreased with greater toe-in angles during the early stance phase (p=0.006). Knee flexion angle increased progressively (p &lt; 0.001), while internal rotation angle decreased progressively during most of the stance phase (p &lt; 0.001), with greater toe-out angles. Significant differences were found in knee extension moments (0-1.8%, F=16.34, p &lt; 0.045;9.9%-10.1%, F=6.16, p &lt; 0.05; 11.7%-13.7%, F=7.26, p &lt; 0.045; 14.2%-21.9%, F=9.32, p &lt; 0.008) and knee adduction moments (9.3%-55.3%, F=63.16, p &lt; 0.001; 64.8%-86.4%, F=39.06, p &lt; 0.001). Post hoc analyses revealed that knee internal moment decreased with greater toe-out angles (p &lt; 0.001); however, knee extension moment increased with greater toe-out angles only in the early stance phase (p &lt; 0.05). No significant differences in knee internal rotation moment were observed across conditions (p &gt; 0.05). This study represents the first attempt to utilize SPM to analyze the effects of different static postures on knee mechanics during running. Alterations in static standing postures significantly influenced knee mechanics measurements. Consequently, this study underscores the critical need to standardize foot positioning in static trials to minimize potential misinterpretations of intervention efficacy and intergroup differences in clinical research.

ABSTRACTCeramic‐on‐ceramic hip resurfacing arthroplasty (CoC‐HRA) has been developed to eliminate metal ion concerns which have been associated with metal‐on‐metal hip resurfacing arthroplasty (MoM‐HRA) while maintaining similar functionality. The aim of the study was to examine gait function pre‐ and postoperatively between CoC‐HRA, MoM‐HRA, and THA using subjective and objective measures with comparison to a healthy control group. Nineteen unilateral CoC‐HRA, 19 unilateral MoM‐HRA, and 18 unilateral THA gender, age, and BMI matched participants completed patient‐reported outcome measures (PROMs) (Oxford hip score [OHS] and metabolic equivalence of task score [MET]) and underwent gait analysis on an instrumented treadmill, preoperatively (2–8 weeks) and then postoperatively (40–52 weeks). Spatiotemporal measures and vertical ground reaction forces (GRF) were recorded. Statistical parametric mapping was used to detect differences in GRF between affected and nonaffected leg and to healthy controls. Preoperatively, there were no differences between groups in PROMs or objective measures. All groups showed an improved OHS postoperatively with only CoC‐HRA and MoM‐HRA demonstrating significant increase in MET. Postoperatively, TWS in both HRA groups improved with no difference to CON while THA was unable to demonstrate improvements. Postoperatively, at 6.5 km/h, THA demonstrated an asymmetric GRF profile, whereas CoC‐HRA and MoM‐HRA showed no differences between legs. In comparison of the affected leg GRF, THA demonstrated a weaker push off when compared to both resurfacing groups and CON. CoC‐HRA and MoM‐HRA showed no significant differences to CON. CoC‐HRA emerges as a potential alternative to MoM‐HRA, effectively addressing metal ion release concerns while retaining similar functional benefits.

Shoulder elevation and arm extension influence elbow joint loading during door-opening in total elbow arthroplasty: a musculoskeletal modelling study.

Iliopsoas strengthening increases hip joint forces during gait: A simulation study.

Effects of custom-made foot orthoses on lower limb kinematics and kinetics during step-up and step-down tasks in individuals with progressive collapsing foot deformity.

Rocker shoe apex settings do not induce anticipatory changes in foot progression angle before the onset of the second rocker.

This study applies one-dimensional statistical parametric mapping (SPM1d) to analyze the effects of exercise-induced fatigue on lower limb biomechanics during the landing phase of two high-risk backhand smash movements in female badminton players. It aims to reveal fatigue-induced changes in movement patterns and differences between the two actions, providing scientific insights for performance optimization, injury prevention, and training interventions. Thirteen female elite badminton players were recruited. A fatigue protocol based on a badminton-specific speed test was applied, and SPM1d was used to analyze kinematic and kinetic data before and after fatigue. After fatigue, significant increases were observed in hip coronal range of motion (ROM) (P = 0.024), knee valgus angle (P = 0.037), and trunk lateral tilt (P = 0.012), with significant decreases in hip abduction angle (P = 0.024) and trunk forward flexion (P = 0.048). When comparing the backward jump smash (BRJS) to the lateral jump smash (BLJS), significant differences were found in ankle (sagittal P = 0.006, horizontal P = 0.006) and hip (sagittal P &lt; 0.001, horizontal P &lt; 0.001) ROM, ankle external rotation angle (P = 0.047), knee flexion angle (P = 0.049), hip abduction angle (P = 0.002), trunk forward flexion angle (P = 0.042), ankle inversion torque (P = 0.048), internal rotation torque (P &lt; 0.001), knee inversion torque (P = 0.003), external rotation torque (P = 0.019), hip adduction torque (P = 0.003), and forward ground reaction force (GRF) (P = 0.05), all of which were significantly greater in BRJS. However, BRJS showed significantly smaller hip flexion angle (P = 0.014), hip extension torque (P = 0.019), hip internal rotation torque (P = 0.046), knee extension torque (P = 0.024), trunk lateral tilt (P = 0.004), lateral GRF (P &lt; 0.001), and vertical GRF (P = 0.003) compared to BLJS (1) The increase in knee valgus angle, trunk flexion angle, and lateral tilt angle, as well as the decrease in hip abduction angle caused by exercise-induced fatigue, increases the risk of ACL injuries in the lower limbs. (2) Both high-risk smash landings pose injury risks. In BRJS, increased ankle inversion/internal rotation torques heighten ankle sprain risk, while higher forward GRF and knee valgus torque raise ACL injury risk. In BLJS, greater medial GRF increases ankle sprain risk, whereas higher knee extension torque, trunk lateral tilt, and reduced knee/trunk flexion elevate ACL injury risk.

The effects of cognitive demand on distributions of medial and lateral plantar loads while walking in anxiety-inducing virtual settings.

This study sought to identify spatial patterns of elevated fat infiltration (FI) in the multifidus associated with chronic low back pain (cLBP) chronicity (duration) and physical activity levels. On 223 cLBP patients, we mapped the FI distribution in the multifidus at L4L5 and L5S1 using 3T MRI and advanced sequences (IDEAL). Using statistical parametric mapping, we identified FI patterns independently associated with increased cLBP chronicity and decreased physical activity levels. Then, we used linear mixed-effects modeling to identify associations between cLBP chronicity, physical activity level and two FI measures, the FI% of the entire muscle cross-sectional area (overall FI%) and the FI% in the deepest 15% of the MF (deep15 FI%). Increased cLBP chronicity associated with elevated FI in the deepest 24% of the MF at L4L5 (p < .01) and in the superficial region of the MF at L4L5 (p < .05) and L5S1 (p < .05). Lower levels of physical activity associated with higher MF FI in the deepest 10% of the MF at L4L5 (p < .05). We also find that increased cLBP chronicity (p < .01) and lower physical activity levels (p < .05) associated with elevated deep15 FI%, independent of age, disc degeneration, and pain severity. Increased cLBP chronicity and lower physical activity levels independently associate with elevated MF FI. Further, these associations are independent of age, disc degeneration, and pain severity. Lastly, physical activity may have an independent association with MF FI specific to the deep MF, where fat infiltration has been shown to associate with cLBP symptoms and adjacent disc degeneration.

BackgroundMicroglia can take on proinflammatory or anti‐inflammatory phenotypes, but it is unclear how these phenotypes play out along the Alzheimer's disease (AD) continuum. The purpose was to assess regional variances of microglial activation in distinct stages of the disease, and the role of microglial responses on grey matter volume and mean diffusivity in different brain areas and on cognition across the course of AD.Method48 subjects (23 AD patients, 14 mild cognitive impairment [MCI], and 11 healthy controls [HC]) underwent TSPO‐PET, diffusion tensor imaging (DTI) and extensive neuropsychometric assessment. SPM (Statistical parametric mapping) analysis was conducted for single subject analysis. GM volume for each subject was derived from T1 volumetric MRI using the FreeSurfer pipeline, mean diffusivity (DTI), alongside voxel‐based morphometric analysis. Using postmortem brain tissue from 26 AD subjects, we evaluated CD32a and CD163 anti‐bodies, markers of proinflammatory and anti‐inflammatory microglia, respectively.ResultVoxel‐wise analyses identified positive and negative clusters of associations for IRF90 with GM volume and mean diffusivity. The presence of pro‐ and anti‐inflammatory phenotypes was confirmed in human postmortem brain, in the frontal, parietal and entorhinal cortices. In addition, higher TSPO, signal in temporal lobes associated with lower hippocampal volume and mean diffusivity, and higher TSPO, signal across the cortex, correlated with poorer performance on neuropsychometric tests.ConclusionThere may be protective and deleterious microglial phenotypes in an individual, region specific and disease stage dependent. Therapeutic modulation of microglia is warranted to promote anti‐inflammatory functions while suppressing pro‐inflammatory functions.

Background/Objectives: Marker-based motion capture remains widely used for lower limb kinematics due to its high precision, although its application is often constrained by elevated operational costs and the requirement for controlled laboratory environments. Markerless methods, such as MediaPipe offer a promising alternative for extending biomechanical analyses beyond traditional laboratory settings, but evidence supporting their validity in controlled tasks is still limited. This study aimed to validate a pixel-based markerless pipeline for two-dimensional kinematic analysis of hip and knee motion during squatting. Methods: Ten healthy volunteers performed three squats with a maximum depth of 90°. Kinematic data were collected simultaneously using marker-based and markerless systems. For the marker-based method, hip and knee joint angles were calculated from marker trajectories within a fixed coordinate system. For the markerless approach, a custom pixel-based pipeline was developed in MediaPipe 0.10.26 to compute bidimensional joint angles from screen coordinates. A paired t-test was conducted using Statistical Parametric Mapping, and maximum flexion values were compared between systems with Bland–Altman analysis. Total range of motion was also analyzed. Results: The markerless pipeline provided valid estimates of hip and knee motion, despite a systematic tendency to overestimate joint angles compared to the marker-based system, with a mean bias of −17.49° for the right hip (95% LoA: −51.89° to 16.91°). Conclusions: These findings support the use of markerless tools in clinical contexts where cost and accessibility are priorities, provided that systematic biases are taken into account during interpretation. Overall, despite the systematic differences, the 2D MediaPipe-based markerless system demonstrated sufficient consistency to assist clinical decision-making in settings where traditional motion capture is not available.

BackgroundSacroiliac joint (SIJ) allows limited motion essential for load transfer from the spine to the pelvis. Identifying structures that adapt to this motion may lead to the establishment of an imaging-based diagnosis of SIJ dysfunction. The interosseous sacroiliac ligament (ISIL) is a major bond between the sacrum and ilium; however, it remains unclear whether the ligament adapts to mechanical stress on the SIJ. This study aimed to investigate ISIL based on macroscopic appearance, fiber orientation characteristics, and histological analysis.MethodsEleven hemipelves from eight donors were analyzed. Six hemipelves were analyzed macroscopically, and the other five were analyzed histologically. For the six hemipelves in the macroscopic analysis, phosphotungstic acid-enhanced micro-computed tomography images were obtained, and fiber orientation analysis was performed. During fiber orientation analysis, the angles of the horizontal and vertical fibers were defined as 0° and +90°, respectively. Fiber angle distribution was compared between superior and inferior ISIL regions from +90° (vertical) to -90° using paired t-tests of the statistical parametric mapping. The significance level was set at p < 0.05.ResultsMacroscopic analysis revealed that the ISIL had a fibrous regularity, the inferior area of the ISIL was relatively vertical, and the superior area was horizontal. Fiber orientation analysis showed that the relative vertical ones (+70° to +80°) were of higher frequency in the inferior area than in the superior area, and relative horizontal ones (-40° to -20°) were of higher frequency in the superior area than in the inferior area (p<0.05). Histological analysis confirmed fiber regularity was similar to the macroscopic findings and identified a synovial bursa-like structure between the ISIL and the posteroinferior region of the sacrum.ConclusionsISIL was characterized by vertical and horizontal fibrous orientations in its inferior and superior areas, respectively, and a synovial bursa-like structure between the inferior area and sacrum. These fiber orientation characteristics in the ISIL likely reflect mechanical adaptation to SIJ motion and may support imaging-based evaluation of SIJ dysfunction, which is recognized as a factor that may influence the outcome of hip arthroscopy.

Hip dysplasia reduces femoral head coverage and elevates joint pressure, accelerating cartilage wear and risk of early osteoarthritis. Periacetabular osteotomy (PAO) aims to correct this anatomical defect and improve joint function. Despite clinical benefits, many patients ultimately require total hip arthroplasty. To better understand joint loading in dysplastic hips, this study assesses the effect of PAO on hip reaction forces during walking and squatting.Ten participants (4♂, 6♀; age 18–43) with unilateral acetabular dysplasia were assessed preoperatively and ~10 months post-PAO. Lateral center-edge angle (LCEA) and Tönnis were extracted from clinical imaging data. Three-dimensional kinematics of the pelvis and lower limbs during walking and squatting were captured using an optoelectronic motion analysis system (Vicon). Ground reaction forces were concurrently recorded via force platforms (AMTI). Joint kinematics and hip reaction forces were estimated via musculoskeletal modeling in OpenSim. Radiographic parameters were analyzed with paired t-tests. Time series data were evaluated using repeated-measures ANOVA through statistical parametric mapping to assess effects of side (healthy vs. affected) and surgery (pre vs. post; p < 0.05).Postoperatively, radiographic angles normalized (LCEA: 16±10 → 28±6°, Tönnis: 13±10 → 4±6°; p<0.001). In squatting, hip abduction during the descent decreased on the affected side (6.3±6.0 → 4.5±5.5°) and increased on the healthy side (4.2±4.1 → 5.8±3.7°; interaction: p<0.05). Peak posterior hip reaction force became more symmetric (interaction: p<0.05), reflecting increased loading on the healthy side (2.3±0.3 → 2.6±0.5 N/kg) and decreased loading on the affected side (2.8±0.3 → 2.7±0.4 N/kg). Walking showed a bilateral reduction in posterior reaction forces (1.0±0.1 → 0.7±0.2 N/kg; p<0.05) at toe-off, and in adduction angle (0.6±1.1 → -0.9±0.6°; p<0.05) during the loading phase.Both squatting and walking exhibited reduced posteriorly directed hip reaction forces following surgery. This change is likely attributable to the reorientation of the acetabulum, which increased anterior coverage. Prior to correction, patients may have compensated for deficient anterior coverage by anteriorly rotating the pelvis, thereby relying more heavily on the available posterior coverage. These biomechanical changes may help delay osteoarthritis progression by reducing joint loading in patients with acetabular dysplasia.