Journal of biomechanics最新文献

Most often, gait biomechanics is studied during straight-ahead walking. However, real-life walking imposes various lateral maneuvers people must navigate. Such maneuvers challenge people's lateral balance and can induce falls. Determining how people regulate their stepping movements during such complex walking tasks is therefore essential. Here, 24 adults (12F/12M; Age 25.8±3.5yrs) walked on wide or narrow virtual paths that were either straight, slowly-winding, or quickly-winding. From each trial, we computed time series of participants' step widths and their lateral body positions relative to their path. We applied our Goal Equivalent Manifold framework - an analysis of how task-level redundancy impacts motor regulation - to quantify how participants adjusted their step width and lateral position from step to step as they walked on these paths. On the narrower paths, participants walked with narrower steps and less lateral position and step width variability. They did so by correcting step-to-step deviations in lateral position more, while correcting step-to-step deviations in step width less. On the winding paths, participants took both narrower and more variable steps. Interestingly, on slowly-winding paths, participants corrected step-to-step deviations in step width more by correcting step-to-step deviations in lateral position less: i.e., they prioritized maintaining step width over position. Conversely, on quickly-winding paths, participants strongly corrected step-to-step deviations in both step width and lateral position: i.e., they prioritized maintaining both approximately equally, consistent with trying to maximize their maneuverability. These findings have important implications for persons who have elevated fall risk.

Changes to the variability within biomechanical signals may reflect a change in the health of the human system. However, for running gait variability measures calculated from wearable device data, it is unknown whether a between-day difference reflects a shift in system dynamics reflective of a change in human health or is a result of poor between-day reliability of the measurement device or the biomechanical signal. This study investigated the reliability of stride time and sacral acceleration variability measures calculated from inertial measurement units (IMUs). Nineteen runners completed six treadmill running trials on two occasions seven days apart. Stride time and sacral acceleration signals were obtained using IMUs. Stride time variability and complexity were calculated using the coefficient of variation (CV) and detrended fluctuation analysis (DFA), respectively. Sacral acceleration regularity was quantified using sample entropy with a range of input parameters m (vector length) and r (similarity threshold). Between-day reliability was assessed using the intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimum detectable change. Stride time CV displayed moderate relative reliability (ICC = 0.672), but with a large absolute minimum detectable change = 0.525 %, whilst stride time DFA-α displayed poor relative reliability (ICC = 0.457) and yielded large minimum detectable changes (≥ 0.208). Sample entropy displayed good relative reliability in mediolateral and resultant sacral acceleration signals for certain combinations of the parameters m and r, although again with large minimum detectable changes. Researchers should be cognisant of these reliability metrics when interpreting changes in running gait variability measures in clinical contexts.

This study explored how systematic changes in running shoe degradation and foot inversion alter the distribution and peak value of heel pressure and calcaneus stress, as well as the total stress-concentration exposure (TSCE) within the calcaneal bone. A foot-shoe finite element model was employed and three shoe wear conditions (new shoe (CON), moderate worn shoe (MWSC), excessive worn shoe (EWSC)) coupled with three foot inversion angles (0°, 10°, 20°) were further modulated. Simulations were conducted at the impact peak instant during running. Compared to CON0, heel pressure during neutral landings shifted medially and increased with progressive shoe wear, peaking under EWSC0. This shift expanded the high-pressure area by 1.333 cm² and raised peak pressure by 24.42 %. Foot inversion landings exhibited an opposite trend: increased shoe wear promoted balanced pressure distribution, centralizing the load and eliminating high-pressure areas under EWSC10, where peak pressure was 11.36 % lower than CON10. Calcaneus stress during neutral landings, initially concentrated on the medial calcaneal surface and inferior tuberosity, intensified with wear, expanding high-stress area by 5.276 cm² and increasing peak stress by 22.79 % under EWSC0. For foot inversion, the high-stress region shifted to the inferior tuberosity, with wear reducing peak stress by 10.41 % and eliminating high-stress area in EWSC10 compared to CON10. TSCE analysis revealed that EWSC10 had the lowest stress exposure (0 %kPa) across all conditions. Worn-out shoes would exacerbate heel internal biomechanics, while these effects may be mitigated by foot inversion, likely due to the formation of a relatively flat and larger contact area between the lateral sole and the ground.

Understanding intrinsic muscular adaptations more deeply can help clarify their relationships with sports performance. Therefore, the aim of this study was to determine if vastus lateralis muscle architecture, quality and stiffness can explain knee extensor maximal torque and countermovement and squat jump performance of athletes. One hundred and two athletes were evaluated based on the architecture, quality and stiffness of the vastus lateralis at rest. Furthermore, the knee extensor maximal voluntary isometric contraction and maximal concentric contraction at 60°/s and vertical jumps countermovement and squat jump performance were measured. Stepwise linear regression showed vastus lateralis echo intensity and muscle thickness determine knee extensor maximal voluntary isometric contraction (r² = 0.435) and knee extensor maximal concentric contraction at 60°/s (r² = 0.400) in athletes. Moreover, vastus lateralis echo intensity, muscle thickness and pennation angle can determine athletes' performance during countermovement (r² = 0.439-0.578) and squat-jump (r² = 0.459-0.570). The findings emphasize that vastus lateralis muscle architecture and quality is an important determinant of maximal knee extensor torque (40-44 %) and countermovement (44-58 %) and squat-jump (46-57 %) performance. Our results demonstrate that the muscle architecture and quality of the vastus lateralis are important determinants of torque and power output performance across various sports disciplines.

Increased energy demands during walking is a recurrent issue for children with cerebral palsy (CP). Given the high incidence of spasticity in these children, several authors have analyzed the impact of selective dorsal rhizotomy (SDR) on energy consumption during walking, typically showing minimal changes post-SDR. To further investigate muscle behavior after SDR, our recent study identified alterations in individual muscle force production without changes in muscle activation during walking. This suggests that children with CP may experience a more favorable dynamic scenario for developing sub-maximal muscle forces after SDR, due to reduced spasticity unlocking joint movement. Thus, this raises questions about whether these changes in muscle force production could lead to increased muscle energy expenditure, which may not be fully reflected in overall energy consumption. The aim of this study was to build upon our previous research on muscle behavior after SDR by evaluating the surgery's impact on individual muscle energy expenditure during walking, using neuro-musculoskeletal simulations. Our research compared two matched groups comprising 81 children with CP: those who underwent SDR and those who did not. Our results showed no significant changes in overall energy consumption or total muscle energy expenditure in either group post-surgery. However, we observed alterations in individual muscle energy expenditure during walking in the SDR group compared to children with CP who received other treatments. Compared to the findings from our first study, we observed a significant decrease in spasticity of the plantarflexor muscles, an improvement in ankle joint angle, an increase in individual muscle force during walking, and no statistically significant changes in energy expenditure of the gastrocnemius and soleus muscles post-SDR. These findings, along with the absence of changes in muscle activity post-SDR, support the hypothesis that muscle tissue alterations contribute to energy deficits observed in children with CP during walking.

The present study aims to determine if morphological differences of the scaphoid, trapezoid, and second metacarpal are associated with thumb osteoarthritis by comparing three-dimensional bone models of healthy controls and osteoarthritis patients. Fifty-eight patients with moderate to severe thumb osteoarthritis (modified Eaton ≥ II) and 35 healthy controls from a larger completed investigation were examined. To quantify morphological variations, a statistical shape model was created that classified binary with respect to the Eaton grading system: non-osteoarthritis or moderate/severe osteoarthritis (II-IV). Three-dimensional surface models based on computed tomography images from the scaphoid, trapezoid, and second metacarpal were used to "train" the statistical shape model and yielded features that best explain variation within the three bones: the principal components These principal components were tested for significant differences between patient and control group. Additionally, a statistical shape model entailing all three bones was created. For the second metacarpal, only a single principal component was significantly associated with osteoarthritis (p = 0.035). The combined model utilizing all three bones, however, showed that with using one principal component of each of the bones, we could classify a sample as moderate/severe trapeziometacarpal osteoarthritis with an accuracy of 0.77. No individual shape components of the scaphoid or trapezoid significantly correlated to osteoarthritis. This study affirms that basilar thumb osteoarthritis is not limited to the trapeziometacarpal joint. Future studies investigating surrounding bones and joints as contributors to disease occurrence or progression will provide a more holistic insight into the prevention, diagnostic, and treatment of thumb osteoarthritis.

In order to improve the understanding foot function in the presence of planovalgus foot deformity, functional joint center determination is applied to the ankle and midfoot for application in 3D-gait analysis. Gait data of 36 patients with planovalgus (PV) foot deformity as well as of 33 typically developing (TD) subjects were collected using foot markers according to the Heidelberg Foot Measurement method. During single-limb stance subjects performed a circular movement of the foot and ankle (CIR) by drawing a circle with the hallux in the air. Midfoot joint center location as well as kinematics was calculated based (a) on functional calibration, (b) via a simple midpoint approach, and (c) via linear regression. All typically developing participants were able to perform the CIR movement with sufficient ROM for calibration whereas 10 % of the participants with idiopathic PV foot deformity and 72 % of the participants with a neurogenic PV foot were not able to perform this movement adequately. Nevertheless, the regression approach led to almost the same location of the midfoot joint center compared to the functional method with similar kinematics. PV feet show substantially larger Forefoot/Hindfoot flexion and Forefoot/Hindfoot adduction in gait compared to TD feet. On top, feet with neurologic background show reduced ROM of these angles in gait. The CIR movement task may prove useful in future studies monitoring active ranges of ankle and midfoot motion since the kinematics of this task may also be directly assessed via the proposed regression approach.

Investigating muscle architecture in static and dynamic conditions is essential to understand muscle function and muscle adaptations. Muscle architecture analysis, primarily through extended field-of-view ultrasound imaging, offers high reliability at rest but faces limitations during dynamic conditions. Traditional methods often involve "best fitting" straight lines to track muscle fascicles, leading to possible errors, especially with longer fascicles or those with nonlinear paths. Moreover, muscle architecture varies along the same muscle, with potential differences in curvature. This study aimed to develop and test a new software for muscle architecture characterization considering fascicle curvature during dynamic conditions. Muscle architecture data from different muscle regions using various digitalization methods were compared. Ten healthy young adults (24.1 ± 1.6 years; 177.7 ± 7.4 cm; 72.7 ± 7.7 kg; 9M/1F) performed maximal knee extension at 75°.s^-1 while B-mode ultrasound images of vastus lateralis muscle were captured in two muscle sites (at 50 % and 83 % of femur length). The analysis involved automated straight-line (ST) methods and custom manual linear extrapolation (MLE) software with segmented fascicle tracking using 2 (MLE2) and 4 (MLE4) segments inside the field of view. Results indicated significant overestimations of fascicle length, muscle belly length and thickness and underestimation of pennation angle using ST compared to MLE methods, especially in the distal region. Intra-rater repeatability for MLE4 was excellent (ICC = 0.93; 0.90; 0.93; 0.88, respectively; P < 0.001), while inter-rater reliability varied. This study confirms the need to consider fascicle curvature for accurate resting muscle architecture characterization, even in the middle region of the muscle, and extends these considerations to dynamic conditions.

Spine kinematics are commonly measured by external sensors such as motion capture and accelerometers. However, these skin-based measures cannot directly capture intervertebral motion of the lumbar spine. To date, research in this area has focused on the estimation of intervertebral kinematics using static trials but no study has analyzed agreement throughout the dynamic range of motion. This study investigated the agreement between skin-based sensors (accelerometers and motion capture) and quantitative fluoroscopy (QF) in measuring lumbar spine kinematics for the duration of complete flexion and extension motion in a healthy female population. Twenty female participants (age 30-57, BMI < 30) were guided through a standing flexion and extension bending protocol while spine kinematics were concurrently measured by QF (L2, L3, L4, L5, and S1) and motion capture sensors and accelerometers positioned over the spinous processes of L2, L4, and S1. Intervertebral angles (L2-L4, L4-S1, L2-S1) and individual vertebrae levels were compared between measures. Non-parametric limits of agreement between QF and skin-based markers were greatest at the end-range of motion for both flexion and extension, but differences increased variably between participants, sometimes over-and sometimes underestimating angles, thus, disproving the common assumption that it increases linearly. The two skin-based marker systems showed good agreement with one another showing that they can be used interchangeably but they can only be used to estimate lumbar spine kinematics. Normalizing angles to a change in angle and considering the posture of instrumentation would be beneficial to reduce potential sources of errors.

In large animal models of bone fracture repair, postmortem torsional testing is commonly used to assess healing biomechanics. Bending and axial tests are physiologically relevant, but much less commonly performed. Virtual torsional testing using image-based finite element models has been validated to postmortem bench tests, but its predictive value for capturing whole-bone mechanics and fracture healing quality under other physiologically relevant loading modes has not yet been established. Accordingly, the purpose of this study was to evaluate the association between mechanical biomarkers derived from virtual torsion, axial, and bending tests under strict alignment and malalignment conditions. Computed tomography (CT) scans from 24 intact and operated sheep tibiae and 29 human tibial fractures were used to create digital twins that were subjected to torsion, axial, and bending tests. The results indicated that torsional rigidity is a strong surrogate for bending flexural rigidity in both ovine and human bones. Torsional rigidity and axial stiffness were strongly correlated in the ovine data, but only moderately in human fractures due to the complex fracture patterns. Axial testing was highly prone to stiffness estimation errors as high as 50% if the applied load and anatomic axis were not perfectly aligned. In contrast, torsional rigidity had errors <1.3% for all malalignment scenarios. Based on this study, virtual torsional rigidity is the recommended summary mechanical biomarker of bone healing because it captures variations in healing biomechanics that are present in other loading modes with a simple setup that is insensitive to alignment error.