Since the European Society of Biomechanics was founded in 1976, we are celebrating its 50th anniversary this year. As part of the celebrations, the Council decided to establish an archive of historical documents to preserve the society's legacy properly. While we collected photos and documents, we took the opportunity to write a brief history of this scientific society. Under the conviction that this little narrative might be of interest to many readers of the Journal of Biomechanics, we proposed to the Editorial Board to publish it as a Letter to the Editor. We begin with a brief history of biomechanics, culminating in the creation of the International Council of Sport and Physical Education Working Group on Biomechanics, from which the International Society of Biomechanics was born in 1973. The scope of this society, focused on the biomechanics of movement, was narrower than the breadth of this emerging scientific domain, as documented by the papers published in the Journal of Biomechanics since 1968. We believe this was the main reason for the establishment of the European Society of Biomechanics (1976) and the American Society of Biomechanics (1977). In the following 50 years, this niche research topic has experienced an explosive growth, and the European Society of Biomechanics has grown from a group of 20 scientists in a room to a modern scientific society with over 1600 members.
We performed a prospective study to assess the repeatability and reproducibility of the novel Brillouin Optical Scanning System (BOSS®) in measuring the biomechanical properties of the cornea and crystalline lens in vivo, to determine device utility in a clinical setting. Adult study participants underwent standard ophthalmic exams to confirm eligibility. At two separate visits to the clinic, monocular lens scans and corneal scans (one point and seven points, respectively) were performed three times on each of three BOSS devices, operated by different technicians. The measured Brillouin parameters per person included the lens stiffness and the stiffnesses (e.g., "Mean", "Minimum") across the seven corneal points. Results were combined across participants to calculate the coefficients of variation (CVs) for repeatability (within each device) and reproducibility (across devices), along with the repeatability and reproducibility limits (2.8 times the respective standard deviations). Eleven of the 33 participants (ages 24-72 years; 15 females) had keratoconus (5 with prior crosslinking, 3 without crosslinking, and 3 post-keratoplasty); the other 22 participants were visually normal. There were no adverse events. The average lens stiffness was 3.33 ± 0.052 GPa (mean ± SD), with an overall repeatability CV of 1.6%, with values ranging from 3.35 ± 0.037 GPa with a CV of 1.1% to 3.30 ± 0.071 with a CV of 2.1% across the separate devices. The mean corneal stiffness was 2.83 ± 0.031 GPa, with an overall repeatability CV of 1.1%, ranging from 2.85 ± 0.015 with a CV of 0.5% to 2.81 ± 0.036 with a CV of 1.3% across devices. The reproducibility CVs were 2.1% and 1.6% for lenses and corneal Means, respectively. The study results demonstrated consistent stiffness values for both lenses and corneas within and between the three BOSS devices tested. The study shows that this device could be a useful new biomechanics-measuring tool for applications in ophthalmology.
A recent definition of clinical obesity emphasises the presence of age-adjusted limitations in activities of daily living (ADLs). Early identification of ADL limitations and factors negatively influencing the development of disability is needed to enhance the effectiveness of rehabilitation programs. To investigate the relationship between functional limitations in ADLs, body composition parameters, and comorbid conditions in a large cohort of adults with different degrees of obesity. Retrospective observational cross-sectional study. Hospital-based rehabilitation setting. Adult inpatients with different degree of obesity, from mild to severe obesity. Patients were enrolled at hospital admission. Collected data included demographic/anthropometric measures, functional status (by modified Katz ADL Index), comorbidities, body composition, and muscle strength. Out of 3229 enrolled patients, 193 (6.0%) resulted fully dependent, while 2115 (65.5%) were fully independent. The most frequently observed disabilities were in urine/fecal continence (24.7%) and toileting (15.5%). ADL impairments were significantly associated with older age, higher BMI, higher waist circumference, excess of fat mass, reduced fat-free mass and lower values of HGS. The logistic model identified 5 variables statistically associated with the probability to be a fully dependent patient: age, weight and waist circumference increased this probability, while Muscle Mass and Hand Grip strength lowered it. Osteoarthritis was present in 52% of patient with severe limitations. The severity in ADLs is influenced by both body composition and comorbid conditions. Rehabilitation should focus on functional limitations and presence of comorbidities and risk factors in patients with obesity, and particularly on preventing muscle mass loss during weight management.
Joint moments derived from inverse dynamics are widely used to infer muscular demand during walking. While low-pass filtering of kinematic and kinetic data is essential, the choice of cutoff frequency combinations varies substantially and can influence joint moment estimates. Although these effects are well documented in dynamic sports movements, their impact during walking remains unclear. Therefore, the purpose of this study was to examine how different kinematic-kinetic low-pass filter cutoff combinations affect lower limb joint moments during level walking. Kinematic and kinetic data were filtered with a fourth-order Butterworth filter using four cutoff frequency pairings: 6-50, 6-6, 10-10 and 15-15 Hz. Peak hip extensor, hip abductor, knee extensor, and ankle extensor moments were compared, with waveform differences further assessed using one-dimensional statistical parametric mapping. Results showed that filter selection substantially affected peak hip extensor moments, which were reduced as the matched cutoff frequencies were lowered, differing up to two-fold between 15 and 15 and 6-6 Hz. Hip abductor and knee extensor moments showed smaller but significant differences, whereas the ankle extensor moment was unaffected. Filtering also altered hip extensor moment waveforms, particularly during early stance, with mismatched and higher cutoffs producing sharp, physiologically implausible moment spikes. Even during walking, joint moment estimates are highly sensitive to filtering choices, especially at the hip. Matched cutoff frequencies as low as 6-6 Hz may yield more physiologically reasonable hip extensor moment profiles. Transparent reporting of filtering practices is essential for interpretation and comparability of walking biomechanics studies.
Femoral version (FV) affects hip biomechanics and postoperative outcomes in developmental dysplasia of the hip (DDH) as well as femoroacetabular impingement (FAI). However, its assessment depends on advanced imaging modalities such as CT and MRI with limited clinical utility for cost-effective screening of FV. This study aimed to implement and test the diagnostic accuracy of the lesser trochanter index (LTI) as an indicator for increased femoral FV on pelvic radiographs in patients with symptomatic DDH and FAI. This prospective, diagnostic cohort study included symptomatic patients with DDH (n = 194 patients) and FAI (n = 22 patients) undergoing hip preservation surgery. Patients underwent a standardized protocol of anteroposterior pelvic radiographs and magnetic resonance imaging (MRI) of the pelvis, hip and lower extremity. FV was measured in accordance to the Murphy method. The lesser trochanter morphology on pelvic radiographs was used to calculate the lesser trochanter index (LTI). It was predefined as positive to detect increased FV (>25/30° Murphy) with a cut-off value of > 1.5. A total of 409 hips in 216 patients were included. Patients with DDH were significant older (30.7 vs. 25.5, p = 0.008), were more frequently female (77.3% vs. 34.8, p < 0.001) and had a significant higher femoral version compared to FAI (28 vs. 21.8, p = 0.013). The LTI > 1.5 showed a high sensitivity (25°/30° FV - 90.9/93.1%), but a low specifity (25°/30° FV - 20.3/18.9%) to detect increased FV. The negative predictive value remained moderate (25°/30° FV - 65.5/81%), while the LTI has only a weak positive predictive value (25°/30° FV - 57.5/42.7%). The LTI represents a clinical useful and widely available indicator of increased FV and can optimize the use of subsequent MRI and CT assessment. However, due to its moderate diagnostic accuracy, the LTI is more a rule- out test, than a diagnostic marker of increased FV and cannot replace advanced imaging modalities.
This study aimed to investigate the biomechanical effect of external trunk perturbations on the plant leg during a football instep kick. Fifteen healthy male national level division-II football athletes were recruited as participants. A Vicon three-dimensional motion capture system synchronized with Kistler force plates was utilized to collect kinematic and kinetic data during standardized instep kicking. Joint angles, moments, and stiffness of the plant leg under four perturbation conditions. Two-way repeated measures ANOVA were employed for statistical analysis. Significant main effects of perturbation anticipation and direction on the biomechanical variables of the plant leg were found. UN perturbation increased hip flexion-extension (F = 21.94, p < 0.01) and abduction-adduction (F = 30.64, p < 0.01) and knee abduction-adduction (F = 20.13, p < 0.01) range of motion. Reduced knee extension angles, increased ankle inversion angles, and abnormal changes in knee flexion-extension moments and ankle plantarflexion moments were observed, indicating compromised joint stability. Regarding directional effects, contralateral perturbations (right side) produced more pronounced alterations with increased hip adduction angles (F = 20.75, p < 0.01) and moments, higher peak knee adduction angles (F = 8.8, p = 0.01), and enhanced ankle inversion-eversion stiffness (F = 9.11, p < 0.01). As the key findings suggested, the dynamic stability under UN perturbation should be enhanced to improve the resistance of perturbations and movement control, thereby providing reference for injury prevention and training optimization.
The authors analyze effectiveness of functional alignment in robot-assisted knee arthroplasty in patients with valgus deformity. The study demonstrates a significant improvement in clinical indicators: KSS score increase from 69.5 to 95 in the knee and from 65 to 94 in functional components, median OKS score 45 and high FJS score (93). Radiological assessment confirmed effective correction of valgus deformity: the HKA angle was corrected from 187° to 181.1°, valgus deformity decreased from 3° to 1°. Functional alignment demonstrated significant advantages compared to mechanical and modified kinematic approaches: significant less need for additional soft tissue release (15.7% versus 35.7-38.6%), better joint balance in extension (99.0% versus 86.0%) and flexion (98.0% versus 43.0%). Range of motions improved (flexion contracture decrease from preoperative 0-15° to postoperative 0-5° while maintaining flexion range at 130°). Technological advantages of robot-assisted technique include better control of implantation parameters: valgus angle of femoral component (on average 1.5°), external rotation of femoral component (0°) and tilt of tibial component (0.1°). The CPAK classification provided a personalized approach to deformity correction, taking into account individual anatomical features. Long-term analysis revealed low complication rate (1.7% of aseptic loosening cases) and efficacy of functional approach in robotic-assisted knee arthroplasty for valgus deformity. Представлен комплексный анализ эффективности применения функционального выравнивания при робот-ассистированном эндопротезировании коленного сустава у пациентов с вальгусной деформацией. Исследование демонстрирует значительное улучшение клинических показателей: повышение оценки по шкале KSS с 69,5 до 95 баллов в коленном и с 65 до 94 баллов в функциональном компонентах, достижение медианы оценки по OKS 45 баллов и высоких оценок по шкале FJS (93 балла). Радиологическая оценка подтвердила эффективную коррекцию вальгусной деформации: угол бедренно-большеберцовой оси (HKA) скорректирован с 187 до 181,1°, вальгусная деформация уменьшилась с 3 до 1°. Функциональное выравнивание продемонстрировало существенные преимущества по сравнению с механическим и модифицированным кинематическим подходами: значительное снижение необходимости дополнительного релиза мягких тканей (15,7% против 35,7—38,6%), лучшее достижение баланса в разгибании (99,0% против 86,0%) и сгибании (98,0% против 43,0%). Отмечено улучшение амплитуды движений: снижение контрактуры сгибания с предоперационных 0—15° до послеоперационных 0—5° при сохранении амплитуды сгибания на уровне 130°. Технологические преимущества робот-ассистированной техники включают улучшенный контроль параметров имплантации: вальгусного угла бедренного компонента (в среднем 1,5°), наружной ротации бедренного компонента (0°) и наклона большеберцового компонента (0,1°). Применение классификационной системы CPAK обеспечило персонализированный подход к коррекции деформации с учетом индивидуальных анатомических особенностей пациентов. Долгосрочный анализ выявил низкую частоту развития осложнений (1,7% случаев асептического расшатывания), подтверждая надежность функционального подхода при робот-ассистированном эндопротезировании коленного сустава с вальгусной деформацией.
Due to shared ß-hexosamindase A deficiencies and significant clinical overlap, the predominating subtypes of late-onset GM2 gangliosidosis, late-onset Tay-Sachs (LOTS) and late-onset Sandhoff disease (LOSD) have been considered essentially indistinguishable. However, growing evidence supports several distinctions between the two entities. We highlight these distinctions through the cross-sectional evaluation of 27 (21 LOTS and 6 LOSD) late-onset GM2 gangliosidosis participants. Study protocol included physical examinations, assessments of gait, balance, muscle strength, ataxia, and nerve conduction velocities, and brain magnetic resonance imaging. Lower limb weakness and later development of upper limb weakness was highly prevalent in both diseases. Accompanying gait disturbances, balance issues, and dysmetria were also prevalent in both cohorts. Strength evaluations showed weakness in both the LOTS and LOSD cohorts compared to controls primarily impacting extensor muscles. In contrast, BARS scores for dysarthria and oculomotor dysfunction were present and heterogenous in LOTS participants and absent in LOSD participants. Twenty-four percent of LOTS participants and none of the LOSD participants had a history of neuropsychiatric symptoms. Cerebellar volume including lobules V and VI were lower in LOTS compared to LOSD and normative data. However, severe length-dependent sensory neuropathy was present in all LOSD participants but not in LOTS participants. The finding of lower cerebellar volume in LOTS suggests the distinctive features of the LOTS phenotype are related to cerebellar dysfunction. However, the cause of the phenotypic differences between LOTS and LOSD remains a mystery, and the molecular and biochemical basis for the dichotomy requires further investigation.
New wearable circuited fabric biomechanic technology that can be used in a more ecological context to measure elbow-varus torque and throw count is now available but needs to be validated compared with markerless biomechanics. To examine the construct validity of the Nextiles Arm Sleeve by assessing its agreement and convergence with markerless 3-dimensional (3D) biomechanics used as a reference for (1) peak elbow-varus torque and (2) pitches thrown with separate analyses for fastballs, breaking balls, and changeups. Cross-sectional study. Laboratory. A total of 29 collegiate pitchers (age = 19.5 ± 1.3 years, height = 1.88 ± 0.06 m, mass = 91.7 ± 9.5 kg, body mass index = 26.2 ± 1.9 kg/m2) participated. Pitchers were assessed simultaneously via the Nextiles sleeve and markerless 3D motion capture (KinaTrax) as they threw fastballs, breaking balls, and changeups to a catcher at regulation distance. Nested Bland-Altman limits of agreement (LoA) for construct validity, mixed-effects linear regressions for convergence validity, and intraclass correlation coefficients (ICCs) for test-retest reliability were calculated between the Nextiles sleeve and 3D biomechanics for elbow-varus torque. We determined that an a priori acceptable threshold for LoA and convergence was a 95% CI width of 0.15 and 95% CI lower limit of 0.50. Pitchers threw 200 pitches (fastball: 72%, n = 143; breaking ball: 14%, n = 27; changeup: 15%, n = 30), with 182 pitches recorded by the Nextiles sleeve and 18 pitches (n = 3 pitchers) not recorded due to technical errors. Agreement and validity for pitch measures (mean difference [lower, upper] LoA = 6.7 N·m [-26.2, 39.6 N·m]; β = 0.31 [0.12, 0.52]; Nextiles sleeve ICC [95% CI] = 0.96 [0.93, 0.98]; KinaTrax ICC [95% CI] = 0.97 [0.94, 0.98]) were higher compared with agreement for body weight × height (BW×H; mean difference [lower, upper] LoA = 0.37 BW×H [-1.41, 2.45 BW×H]; β = 0.37 [-1.41, 2.15]; Nextiles sleeve ICC [95% CI] = 0.93 [0.88, 0.96]; KinaTrax ICC [95% CI] = 0.95 [0.92, 0.98]). We found no interaction per pitch type (P = .47) or pitch thrown (P = .58). The Nextiles sleeve collected pitch counts accurately except for 3 pitchers for whom it did not collect any pitches thrown due to technical errors. However, the demonstrated LoA and convergence were beyond the a priori acceptability threshold and lower than the a priori defined acceptable lower bound of the 95% CI. These results suggest that the Nextiles sleeve does not measure the same construct as KinaTrax.
Troodon formosus (T. formosus) is a theropod dinosaur from the Late Cretaceous of North America. T. formosus, like many theropods, are speculated to have used their forelimbs to hunt, and the complexity of their preserved egg clutches suggests T. formosus may have also used its forelimbs to move its eggs. Understanding the morphology and range of movement of T. formosus's forelimb could help shed light onto these hypotheses. However, no complete forelimb material has yet been found for T. formosus, and a 3D reconstruction and range of motion (ROM) estimate has not been attempted. This study aims to address this gap by leveraging digital modelling technology to create the first forelimb reconstruction and ROM for T. formosus. Surface scans from multiple T. formosus fossils housed in the Museum of the Rockies (Bozeman, Montana) were digitally combined to reconstruct a nearly complete forelimb. Digital articulations based on this assembled model were compared with physical ROM using 3D printed copies. Results show higher ranges of flexion than extension in T. formosus's joints, consistent with closely related species. However, T. formosus shows higher manual extension than close relatives. The humerus also shows anatomy convergent with more basal theropod species. These differences may imply a divergent morphology and function of the manus, as well as a deviation from avian ancestor forelimb morphology. ROM results cannot confirm whether T. formosus was able to grasp objects single-handed, but two-handed apprehension of objects, including eggs, remains feasible.
Femoral neck anteversion (FNA) may lead to compensatory mechanisms during gait but the isolated influence of abnormal FNA on patellofemoral joint (PFJ) mechanics is not yet well understood. We used a detailed musculoskeletal model of the knee with 12 degrees of freedom. Seven models with different FNA, ranging from -8° to 52°, were developed by rotating the proximal part of the femur and the corresponding muscle attachment points along the mechanical axis of the femur, in the transverse plane. OpenSim COMAK and Monte Carlo simulations were used to estimate muscle force and patellar kinematics while accounting for ligament force and PFJ cartilage contact force. Our analyses revealed that increasing FNA led to increased patellar lateral tilt and shift, lower PFJ cartilage pressure during the loading response, but higher cartilage pressure during mid and late stance. Also, the abduction moment arm of the gluteus minimus and medius decreased, while their extension moment arm increased with increasing FNA. Therefore, during the early and late stance phases, the hip abductor muscles in the models with increased FNA generated not only a hip abductor moment, but also a hip extensor moment. Consequently, the contribution of hip flexor muscles, including the rectus femoris, increased in these phases to counteract the increased hip extensor moment. Our findings explain why individuals with increased FNA may reduce their hip abductor moment during the second part of the stance phase, but not the first part. These findings may have clinical implications for patellar instability and joint stress.
The central nervous system (CNS) organizes movements through a modular activation of functionally related muscle groups, called muscle synergies. These synergies have been mainly used to describe the contribution of muscles to the focal component of human movements, while their role in ensuring postural control during voluntary tasks has been poorly explored. This study aimed at investigating and characterizing the spatial and temporal organization of whole-body muscle synergies during upper limb tasks in healthy subjects and describing their variability between the dominant and non-dominant upper limb. Fifteen right-handed volunteers performed upper limb elevation movements along three different planes with the dominant and non-dominant arms and surface electromyographic signals were collected from 20 trunk and upper limbs muscles. Non-negative matrix factorization was used to decompose electromyographic signal envelopes and extract spatial and temporal profile of muscle synergies. Inter-subject variability was assessed using cosine similarity. Based on spatial and temporal profile of 4 extracted synergies, M1 explained arm acceleration during elevation movements, M2 was assumed to ensure postural control during arm acceleration, M3 included muscles responsible for arm deceleration, while M4 contributed to ensuring postural control during arm deceleration. Inter-subject similarity was higher for the dominant (median: 0.70, interquartile range: 0.07) compared to non-dominant arm (median: 0.63, interquartile range: 0.09) (p < 0.001). The organization of muscle synergies follows a biomechanical rationale, reflecting CNS ability to manage the focal and postural movement components during upper limb elevation. Higher variability during movements performed with the non-dominant upper limb may depend on lower neuromuscular control.
Monitoring gymnasts in their training environments, using markerless motion capture, could enhance our understanding of their injuries and facilitate the implementation and evaluation of injury prevention measures. This study compared a smartphone-based markerless motion capture system (OpenCap) to a gold standard marker-based system (Vicon) to see how well it could track basic gymnastics. Ten participants were recorded simultaneously using both systems whilst performing: walk, squat, sit-to-stand, drop jump, handstand, cartwheel, handstand walk, handstand hop. Comparisons were made between gymnastics and non-gymnastics movements, and the effects of musculoskeletal range of motion (ROM) constraints and body region (upper vs lower body) were evaluated. System performance was assessed using complimentary metrics: magnitude of error between systems, waveform similarity, agreement and bias, and the relative magnitude of inter-system error compared to inter-subject variability. For gymnastics movements, using a musculoskeletal model with ROM constraints adapted to ranges typically utilised significantly reduced root mean square error (RMSE) between Vicon and OpenCap. However, the mean RMSE across all joints for gymnastics movements (40.14° ± 14.48°) was still significantly higher than non-gymnastics movements (11.57° ± 6.66°). Kinematic errors were lower for lower- than upper- limb joints, with the greatest discrepancies observed at the pelvis and shoulder during gymnastics movements. Although movement-specific modelling approaches can improve performance, OpenCap currently tracks complex gymnastics movements less accurately than simpler functional tasks. Further developments, including training on a wider range of activities and implementation of appropriate movement-specific constraints, are required before markerless motion capture can be applied with confidence to gymnastics.
Effective weapon control in fencing requires precise coordination of forces across the fingers, yet the organization of digit-level grip forces during dynamic fencing actions remains largely unknown. We aimed to quantify finger-force distribution during fencing thrusts and determine whether it is influenced by spatial accuracy demands and temporal constraints. Thirty-four elite foil and épée fencers performed thrusts toward small and large targets under self-paced and reaction-time conditions. Digit contact forces applied by the thumb, index, middle, ring, and little fingers were recorded using an instrumented fencing handle, while muscle activity was assessed using surface electromyography. Relative finger contributions, percentage of individual maximum force, and the effective number of fingers were used to characterize finger-force organization. Finger-forces were distributed asymmetrically across the digits, with the index finger producing the largest share of total force. The thumb-index unit contributed more than half of total digit contact force. Despite this asymmetry, forces remained distributed across all digits. Temporal constraints influenced grip organization: reaction-time thrusts increased the contribution of the middle finger and shifted force distribution away from the thumb-index unit, accompanied by greater muscle activation; this pattern was absent when forces were normalized to individual digit maxima. In contrast, spatial accuracy demands had little effect on force distribution, though this conclusion is limited by the lack of trial-level accuracy measures. Present findings demonstrate that finger-force organization during fencing relies on a stable yet adaptable multi-digit strategy in which temporal constraints primarily influence how forces are redistributed across the hand.
Biomechanical models of myocardial growth and remodelling (G&R) are often modelled as responses to deviations from a preferred biomechanical homeostatic state, triggered by stretch or stress. Yet how these critical values of stretch and stress should be defined remains unresolved. This study examines how different homeostatic threshold definitions influence predicted left ventricular G&R. Myocardial growth was implemented using an updated-reference constrained mixture framework, with eccentric growth driven by diastolic myofibre stretch and concentric growth driven by systolic active stress. Homeostatic thresholds were derived from the baseline LV dynamics. Our results demonstrate that the choice of critical homeostatic thresholds plays an important role in triggering cardiac G&R. For volume overload, the mean and 50th percentile end-diastolic myofibre stretch show the potential to approach a preferred mechanical state with preserved cardiac pump function. For pressure overload, a 90th percentile threshold of peak active stress appears to normalise systolic stress to baseline levels with sufficient cardiac output. Localised thresholds generally lead to more heterogeneous growth patterns and potentially high stretch/stress concentrations. These findings highlight the importance of defining homeostatic targets as tissue-level quantities and provide practical guidance to improve cardiac G&R modelling.
In sit-skiing, propulsion is generated by the upper-extremities and trunk. We examined if terrain incline and class affected the speed, trunk range of motion, and cycle kinematics of sit-skiers during competitive distance events. Thirty-six elite Para-Nordic sit-skiers were equipped with integrated IMU- and GNSS-sensors at the 2022 and 2023 World Championships, and five individual races were analysed at each event. Relationships between speed, trunk range of motion, cycle length and cycle rate and "incline" and "class" were modelled using mixed-effects models. The classes showed similar adaptations to changing incline, with decreased speed and cycle length and relatively constant range of motion and cycle rate. Compared to the LW12 class, the LW10.5 class had a lower speed (p = 0.004), trunk range of motion (p = 0.005) and cycle length (p = 0.049) at the 2022 event and lower range of motion (p = 0.017) and higher cycle rate (p = 0.020) at the 2023 event. There were considerable overlaps between the classes in all variables, which highlights that despite a relatively large number of measurements, this study was likely statistically underpowered for the between-class comparisons. Overall, this study suggests that while some differences exist between the LW12 and LW10.5 classes, between-class differences may be smaller than the differences between individual athletes.
This study investigated the influence of pacer body size on the aerodynamic drag experienced by elite marathon runners. Using 3D numerical simulations, various drafting configurations were analyzed at a running speed of 21  km/h with 1.2 m spacings between runners. The modeled runner groups comprised one elite protected marathoner (1.80 m) and one or two pacers of different heights (1.70  m, 1.80  m, and 1.90  m). Isosurfaces of total pressure and pressure coefficient maps revealed that taller pacers generate a wider wake and a more favorable pressure field for downstream runners. Specifically, compared to running solo, a 1.80 m runner positioned between two 1.90  m pacers benefits from a maximum drag reduction of 61.6%, resulting in a 6.48% improvement in running economy and a time gain of 5 min 02 s over the marathon distance. The relationship between projected frontal area, group configuration, and pressure field variations underscores the critical role of fluid-structure interactions on running performance. This study demonstrates that drag reduction depends not only on positioning but also on runner morphology, and opens promising avenues for fine-tuning drafting strategies in elite pack running.
Fibrous dysplasia (FD) affecting the upper cervical spine is exceptionally rare and results in severe cervico-occipital pain and limited neck mobility due to altered biomechanics and irritation of the third occipital nerve (TON). Surgical management is challenging because of the proximity to critical neurovascular structures. In the absence of neurological deficits, targeted TON blocks have shown promise as part of conservative management. A 33-year-old woman presented with a 7-year history of neck and suboccipital pain. Imaging revealed expansile FD at C1-C2 with partial fusion and no neurovascular compromise. An ultrasound-guided right-sided TON therapeutic block was administered, which resulted in immediate and substantial pain relief (Numeric Rating Scale 8/10 reduced to 3/10) and sustained functional improvement for 3 months. Ultrasound-guided TON block provided meaningful long-term pain relief and avoided high-risk surgical intervention in this rare case of C1-C2 FD.
Individuals with incomplete spinal cord injury (iSCI) exhibit diverse walking capabilities due to partial sensory and/or motor impairment below the injury level. This study examined how neuromuscular weakness patterns influence compensatory gait strategies, dynamic balance (margins of stability, MoS), and joint-level mechanics across iSCI subgroups compared to non-disabled controls. We analyzed gait data from 21 iSCI participants previously classified into four subgroups through dynamic time warping and hierarchical clustering. Temporospatial parameters, anterior-posterior (AP) and mediolateral (ML) MoS, and joint kinetics were analyzed using linear mixed-effects models with walking speed as a covariate to isolate group differences beyond speed. The most functional individuals, with mild plantarflexor weakness, walked comparably to controls but exhibited elevated peak hip flexion moments, suggesting a possible long-term hip joint health concern. The individuals with moderate plantarflexor weakness adopted slower walking speed as their primary compensation, with no residual differences from controls once speed was accounted for. The two most impaired groups of individuals, with combined plantarflexor and hip muscle weakness, additionally compromised frontal-plane balance - adopting wider step widths and higher ML MoS - and showed a redistribution of mechanical demand during stance, with the hips contributing a larger proportion of total positive joint work than the ankles. The individuals with most impairment further showed elevated AP MoS persisting beyond speed reduction, lower peak plantarflexion moment, and a shift of mechanical work toward the knee. These findings indicate that gait adaptations in iSCI depend on the muscle weakness profile rather than severity alone, supporting tailored rehabilitation strategies.
Running mechanical power can be estimated using formulations that quantify different components of mechanical work, including external center-of-mass dynamics and internal segmental work. Several algorithms have been proposed to estimate running power from kinematic data or theoretical analytical formulations, yet most have been evaluated in small samples of healthy runners, limiting generalizability. This study aimed to compare four mechanical power algorithms (Minetti; Theoretical Power Work 1 (TPw1); Theoretical Power Work 2 (TPw2); and Jenny & Jenny (JJ)) in a large and heterogeneous cohort of recreationally active adults, and to determine whether algorithm-velocity relationships were consistent in men and women. Three-dimensional kinematic data from 1,550 participants (39.9 ± 10.6 years; 725 women, 825 men) were collected during treadmill running using a motion capture system. Running power was computed for each model in both absolute (W) and relative (W·kg⁻1) terms. Correlations with treadmill velocity were assessed using Spearman's rank test, and between-model differences were evaluated through one-way ANOVA and effect sizes (Cohen's d). Normalized power values exhibited near-perfect correlations with velocity for Minetti, TPw1, and TPw2 (r = 0.964-0.968, r2 = 0.929-0.938), whereas JJ showed slightly lower but still high correlations (r = 0.914, r2 = 0.835). All between-model differences were significant (p < 0.001), with large effects (d > 0.8) observed mainly between Minetti and TPw2. These findings demonstrated that Minetti, TPw1, and TPw2 yield consistent estimates of running power, with mass-normalized outputs showing robust power-velocity relationships across a heterogeneous sample of recreationally active adults from both sexes, while model selection should consider the analytical goal and data availability.