Segment Kinematics Research Articles

Distribution of segmental foot kinematics in patients with degenerative joint disease of the ankle.

Degenerative joint disease (DJD) of the ankle is a debilitating chronic disease associated with severe pain and dysfunction resulting in antalgic gait alteration. Little information is available about segmental foot and ankle motion distribution during gait in ankle osteoarthritis. The aim of the current study was to dynamically characterize segmental foot and ankle kinematics of patients with severe ankle arthrosis requiring total ankle replacement. This was a prospective study involving 36 (19 M, 17 F) adult patients with a clinical diagnosis of ankle arthrosis ("DJD" group) and 36 (23 M, 13 F) healthy subjects ("Control" group). Motion data were collected at 120 Hz using a 3-D motion camera system at self-selected speed along a 6-m walkway and processed using the Milwaukee Foot Model (MFM). The SF-36 Health Survey and Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale were administered to evaluate functional levels. Findings include decreases in walking speed, cadence, stride length and swing phase, and reduced outcomes scores (SF-36 and AOFAS). Multisegemental motion in patients with ankle DJD demonstrates significant changes in foot mechanics characterized by altered segment kinematics and significant reduction in dynamic ROM at the tibia, hindfoot, forefoot, and hallux when compared to controls. The results demonstrate decreased temporal-spatial parameters and low outcomes scores indicative of functional limitations. Statement of clinical significance: Altered segment kinematics and reduced overall range of motion demonstrate how a single joint pathology affects kinematic distribution in the other segments of the foot and ankle and alters patients' overall gait. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1739-1746, 2018.

Is L5-S1 motion segment different from the rest? A radiographic kinematic assessment of 72 patients with chronic low back pain.

The relationship between biomechanical instability and degenerative changes in the lumbar spine in chronic low back pain (CLBP) patients remains controversial. The main objective of this retrospective radiographical study was to evaluate changes in kinematics at different lumbar levels (in particular the L5-S1 level) with progressive grades of disc degeneration and facet joint osteoarthritis in CLBP patients. Using standing neutral and dynamic flexion/extension (Fx/Ex) radiographs of the lumbar spine, in vivo segmental kinematics at L1-L2 through L5-S1 were evaluated in 72 consecutive CLBP patients. Disc degeneration was quantified using changes in signal intensity and central disc height on mid-sagittal T2-weighted magnetic resonance (MR) scans. Additionally, the presence or absence of facet joint osteoarthritis was noted on T2-weighted axial MR scans. Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level (p=0.188), but an association was observed between the two at L4-L5 (p<0.001) and L3-L4 (p<0.05) levels. In the absence of facet joint osteoarthritis, the L5-S1 segment showed a greater range of motion (ROM) in Ex (3.3°±3.6°) and a smaller ROM in Fx (0.6°±4.2°) compared with the upper lumbar levels (p<0.05), but the differences diminished in the presence of it. In the absence of facet joint osteoarthritis, no change in L5-S1 kinematics was observed with progressive disc degeneration, but in its presence, restabilisation of the L5-S1 segment was observed between mild and severe disc degeneration states. The L5-S1 motion segment exhibited unique degenerative and kinematic characteristics compared with the upper lumbar motion segments. Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level, but not at the other lumbar levels. Severe disc degeneration in the presence of facet joint osteoarthritis biomechanically restabilised the L5-S1 motion segment.

Effect of global postural alignment on gait: A study on 145 asymptomatic subjects with a large age range

Introduction Global postural alignment parameters have been shown to be major determinants of quality of life [1] . Gait is an essential task of functionality during daily living activities. It is still unknown how global postural alignment can influence gait. The aim was to investigate how global postural alignment can influence gait in asymptomatic subjects. Materiel et methodes Overall, 145 asymptomatic subjects (age: 29.2 ± 11 years [18–59], 70F) underwent 3D gait analysis followed by full body biplanar X-rays. Kinematics of lower limb segments (pelvis, hip, knee, ankle and foot) were extracted in the 3 planes during the gait cycle. Full body 3D reconstructions were obtained from the biplanar X-rays and global postural alignment was evaluated by calculating: sagittal vertical axis (SVA), center of the auditory meatus plumbline to the hip axis, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic parameters (PI, PT, SS). Agglomerative hierarchical clustering (AHC) was performed on each postural parameter to classify subjects into homogeneous groups. Differences in gait parameters between groups were evaluated using ANCOVA while adjusting for demographic confounding factors (age, weight, height and sex). Resultats The most discriminant postural parameter in gait kinematics was the SVA. AHC differentiated 3 groups of SVA: Gr1: 10 mm, n = 55. Weight, height and sex were statistically different between groups (Gr1 vs. Gr3: 68 ± 16 vs. 77 ± 13 kg, 167, n 10 vs. 173 ± 10 cm, 39F/23 M vs. 6F/22 M, p Discussion This is the first study demonstrating the influence of postural alignment parameters on gait. While interindividual variations of TK and LL were not shown to impact gait, subjects with elevated SVA had their general gait modified even after correcting for confounding factors: higher duration with larger knee flexion during shock absorption phase at the beginning of gait cycle. While these results were shown in asymptomatic subjects with high SVA (> 10 cm), higher SVA in subjects with spinal deformities could be a cause for more altered gait kinematics.

A model-based approach for estimation of changes in lumbar segmental kinematics associated with alterations in trunk muscle forces

The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental kinematics of lumbar spine was estimated for a single static trunk flexed posture involving, respectively, 40° and 10° of thoracic and pelvic rotations. Minimum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 0° to 0.7° and 0 mm to 0.04 mm, respectively. Maximum changes in the angular and translational deformations of a motion segment with alterations in TMFs ranged from 2.4° to 7.6° and 0.11 mm to 0.39 mm, respectively. The differences in kinematics of lumbar segments between each combination of two sets of TMFs in 97% of cases for angular deformation and 55% of cases for translational deformation were within the reported accuracy of current imaging techniques. Therefore, it might be possible to use image-based kinematics of lumbar segments along with computational modeling for personalized assessment of TMFs.

Spine kinematics exhibited during the stop-jump by physically active individuals with adolescent idiopathic scoliosis and spinal fusion

Background ContextIndividuals with adolescent idiopathic scoliosis post spinal fusion often return to exercise and sport. However, the movements that individuals with spinal fusion for adolescent idiopathic scoliosis (SF-AIS) use to compensate for the loss of spinal flexibility during high-effort tasks are not known. PurposeThe objective of this study was to compare the spinal kinematics of the trunk segments displayed during the stop-jump, a maximal effort task, between SF-AIS and healthy control groups. Study DesignThe study used a case-controlled design. Materials and MethodsTen SF-AIS (physically active, posterior-approach spinal fusion: 11.2±1.9 fused segments, postop time: 2±.6 years) and nine control individuals, pair matched for gender, age (17.4±1.3 years and 20.6±1.5 years, respectively), mass (63.50±12.2 kg and 66. 40±10.9 kg), height (1.69±.09 m and 1.72±.08 m), and level of physical activity, participated in the study. Individuals with spinal fusion for adolescent idiopathic scoliosis and controls (CON) performed five acceptable trials of the stop-jump task. Spatial locations of 21 retroreflective trunk and pelvis markers were recorded via high-speed motion capture methodology. Mean differences and analysis of covariance (jump height=covariate, p<.05) were used to compare the groups' relative angle (RelAng) and segmental angle (SegAng) of the three trunk segments (trunk segments=upper trunk [C7–T8], middle trunk [MT: T9–T12], lower trunk [LT: L1–L5]) for each rotation plane in the three phases of interest (flight, stance, and the vertical flight phases). ResultsNo significant group differences for jump height and RelAng were detected in the three phases of stop-jump. Individuals with spinal fusion for adolescent idiopathic scoliosis displayed 3.2° greater transverse plane RelAng of LT compared with CON (p=.059) in the stance phase. Group differences for RelAng ranged from 0° to 15.3°. For SegAng in the stance phase, LT demonstrated greater SegAng in the sagittal and frontal planes (mean difference: 3.2°–6.2°), whereas SegAng for MT was 5.1° greater in the sagittal plane and had a tendency of 2° greater displacement in the frontal plane (p=.070). In the vertical flight phase, greater LT displacement in the frontal plane was observed for SF-AIS than CON. In the flight phase, LT had a tendency for greater SegAng for SF-AIS than for CON in the transverse plane (p=.089). ConclusionsOverall, SF-AIS who participate in physical activity on a regular basis are able to demonstrate similar trunk kinematics during a high-intensity stop-jump task as their matched healthy peers. Fewer group differences for relative angular displacements of the spine were observed than anticipated. This finding suggests that the fused MT appeared to be moving synchronously with the LT, thereby suggesting a compensatory adaptation of SF-AIS to achieve sufficient trunk movements during this high-effort movement.

The Effects of Prosthesis Inertial Parameters on Inverse Dynamics: A Probabilistic Analysis.

Joint kinetic measurement is a fundamental tool used to quantify compensatory movement patterns in participants with transtibial amputation (TTA). Joint kinetics are calculated through inverse dynamics (ID) and depend on segment kinematics, external forces, and both segment and prosthetic inertial parameters (PIPS); yet the individual influence of PIPs on ID is unknown. The objective of this investigation was to assess the importance of parameterizing PIPs when calculating ID using a probabilistic analysis. A series of Monte Carlo simulations were performed to assess the influence of uncertainty in PIPs on ID. Multivariate input distributions were generated from experimentally measured PIPs (foot/shank: mass, center of mass (COM), moment of inertia) of ten prostheses and output distributions were hip and knee joint kinetics. Confidence bounds (2.5-97.5%) and sensitivity of outputs to model input parameters were calculated throughout one gait cycle. Results demonstrated that PIPs had a larger influence on joint kinetics during the swing period than the stance period (e.g., maximum hip flexion/extension moment confidence bound size: stance = 5.6 N·m, swing: 11.4 N·m). Joint kinetics were most sensitive to shank mass during both the stance and swing periods. Accurate measurement of prosthesis shank mass is necessary to calculate joint kinetics with ID in participants with TTA with passive prostheses consisting of total contact carbon fiber sockets and dynamic elastic response feet during walking.

Validation of simplified centre of mass models during gait in individuals with chronic stroke

BackgroundThe feasibility of using a multiple segment (full-body) kinematic model in clinical gait assessment is difficult when considering obstacles such as time and cost constraints. While simplified gait models have been explored in healthy individuals, no such work to date has been conducted in a stroke population. The aim of this study was to quantify the errors of simplified kinematic models for chronic stroke gait assessment. MethodsSixteen individuals with chronic stroke (>6months), outfitted with full body kinematic markers, performed a series of gait trials. Three centre of mass models were computed: (i) 13-segment whole-body model, (ii) 3 segment head-trunk-pelvis model, and (iii) 1 segment pelvis model. Root mean squared error differences were compared between models, along with correlations to measures of stroke severity. FindingsError differences revealed that, while both models were similar in the mediolateral direction, the head-trunk-pelvis model had less error in the anteroposterior direction and the pelvis model had less error in the vertical direction. There was some evidence that the head-trunk-pelvis model error is influenced in the mediolateral direction for individuals with more severe strokes, as a few significant correlations were observed between the head-trunk-pelvis model and measures of stroke severity. InterpretationThese findings demonstrate the utility and robustness of the pelvis model for clinical gait assessment in individuals with chronic stroke. Low error in the mediolateral and vertical directions is especially important when considering potential stability analyses during gait for this population, as lateral stability has been previously linked to fall risk.

The relationship between segmental kinematics and ball spin in Type-2 cricket spin bowling

ABSTRACTThe techniques of spin bowling in cricket have been largely formulated from the collective intuitions of past players. A standard model of bowling technique has been generally prescribed for both off-spin and leg-spin bowlers, but there has been no biomechanics research to validate this approach. This study measured 20 Type-2 off-spin and 15 Type-2 leg-spin bowlers using a 3D Cortex motion analysis system. Correlation coefficients between segmental kinematic variables and spin rate in the off-spin and leg-spin bowlers revealed that off-spin bowling was associated with an earlier movement time of the thorax, whereas leg-spin bowling was associated with a greater magnitude and earlier movement time of pelvis rotation, as well as a greater magnitude of pelvis-shoulder separation movement. The maximum velocity of rear hip flexion differentiated between both groups of bowlers. The GLM suggested that for off-spinners, rear hip flexion velocity significantly explained the variance in spin rate (subject to sequential timing constraints), while for leg-spinners, the time of maximum rear hip flexion and maximum arm circumduction velocity significantly explained variance in spin rate. This study supports the notion that off-spinners and leg-spinners have significant differences in their joint kinematics, and should not be coached under a one-size-fits-all technical model.

Contribution of upper limb muscles to two different gripping styles in elite indoor tug of war athletes

To investigate characteristic upper limb muscle use between two common tug of war (TOW) gripping styles, 20 elite athletes from two high school TOW teams were recruited. Under conditioned attack pulling (with 90% maximal force) on a tug machine, participants used their own habitual gripping style to pull for five 15-s trials. Force and kinematic measurements showed a significantly better force performance and higher centre-of-gravity tilting angle with the gripping style one than with the gripping style two (GS2) (both p < 0.05). However, an overall higher and more symmetrical muscle activation detected by normalised surface electromyography signal amplitude was found in the GS2 group (both p < 0.05). In both groups, the distal and flexor muscles were more activated than the proximal and extensor muscles, respectively (p < 0.05). Higher co-contraction ratio was found in the wrist joints of the latter arm in both groups (p < 0.05). As higher muscle activation level and co-contraction indicate higher muscle and joint injury incidences, we suggest that gripping style factors should be considered in training to prevent muscle and joint injury. Future study concerning segmental kinematics, ground reaction force, moment arm and muscle endurance during the defence phase are warranted.

Effects of knee sleeves on coordination of lower-limb segments in healthy adults during level walking and one-leg hopping.

The evaluation of multisegment coordination is important in gaining a better understanding of the gait and physical activities in humans. Therefore, this study aims to verify whether the use of knee sleeves affects the coordination of lower-limb segments during level walking and one-leg hopping. Eleven healthy male adults participated in this study. They were asked to walk 10 m on a level ground and perform one-leg hops with and without a knee sleeve. The segment angles and the response velocities of the thigh, shank, and foot were measured and calculated by using a motion analysis system. The phases between the segment angle and the velocity were then calculated. Moreover, the continuous relative phase (CRP) was calculated as the phase of the distal segment subtracted from the phase of the proximal segment and denoted as CRPTS (thigh–shank), CRPSF (shank–foot), and CRPTF (thigh–foot). The root mean square (RMS) values were used to evaluate the in-phase or out-of-phase states, while the standard deviation (SD) values were utilized to evaluate the variability in the stance and swing phases during level walking and in the preflight, flight, and landing phases during one-leg hopping. The walking velocity and the flight time improved when the knee sleeve was worn (p < 0.05). The segment angles of the thigh and shank also changed when the knee sleeve was worn during level walking and one-leg hopping. The RMS values of CRPTS and CRPSF in the stance phase and the RMS values of CRPSF in the preflight and landing phases changed (p < 0.05 in all cases). Moreover, the SD values of CRPTS in the landing phase and the SD values of CRPSF in the preflight and landing phases increased (p < 0.05 in all cases). These results indicated that wearing a knee sleeve caused changes in segment kinematics and coordination.

Driving cycle prediction model based on bus route features

Bus fuel economy is deeply influenced by the driving cycles, which vary for different route conditions. Buses optimized for a standard driving cycle are not necessarily suitable for actual driving conditions, and, therefore, it is critical to predict the driving cycles based on the route conditions. To conveniently predict representative driving cycles of special bus routes, this paper proposed a prediction model based on bus route features, which supports bus optimization. The relations between 27 inter-station characteristics and bus fuel economy were analyzed. According to the analysis, five inter-station route characteristics were abstracted to represent the bus route features, and four inter-station driving characteristics were abstracted to represent the driving cycle features between bus stations. Inter-station driving characteristic equations were established based on the multiple linear regression, reflecting the linear relationships between the five inter-station route characteristics and the four inter-station driving characteristics. Using kinematic segment classification, a basic driving cycle database was established, including 4704 different transmission matrices. Based on the inter-station driving characteristic equations and the basic driving cycle database, the driving cycle prediction model was developed, generating drive cycles by the iterative Markov chain for the assigned bus lines. The model was finally validated by more than 2years of acquired data. The experimental results show that the predicted driving cycle is consistent with the historical average velocity profile, and the prediction similarity is 78.69%. The proposed model can be an effective way for the driving cycle prediction of bus routes.

Inertial measurement systems for segments and joints kinematics assessment: towards an understanding of the variations in sensors accuracy

BackgroundJoints kinematics assessment based on inertial measurement systems, which include attitude and heading reference system (AHRS), are quickly gaining in popularity for research and clinical applications. The variety of the tasks and contexts they are used in require a deep understanding of the AHRS accuracy for optimal data interpretation. However, published accuracy studies on AHRS are mostly limited to a single task measured on a limited number of segments and participants. This study assessed AHRS sensors kinematics accuracy at multiple segments and joints through a variety of tasks not only to characterize the system’s accuracy in these specific conditions, but also to extrapolate the accuracy results to a broader range of conditions using the characteristics of the movements (i.e. velocity and type of motion). Twenty asymptomatic adults (overline{age} = 49.9) performed multiple 5 m timed up and go. Participants’ head, upper trunk, pelvis, thigh, shank and foot were simultaneously tracked using AHRS and an optical motion capture system (gold standard). Each trial was segmented into basic tasks (sit-to-stand, walk, turn).ResultsAt segment level, results revealed a mean root-mean-squared-difference overline{(RMSD)} varying between 1.1° and 5.5° according to the segment tracked and the task performed, with a good to excellent agreement between the systems. Relative sensor kinematics accuracy (i.e. joint) varied between 1.6° and 13.6° over the same tasks. On a global scheme, analysis of the effect of velocity on sensor kinematics accuracy showed that AHRS are better adapted to motions performed between 50°/s and 75°/s (roughly thigh and shank while walking).ConclusionResults confirmed that pairing of modules to obtain joint kinematics affects the accuracy compared to segment kinematics. Overall, AHRS are a suitable solution for clinical evaluation of biomechanics under the multi-segment tasks performed although the variation in accuracy should be taken into consideration when judging the clinical meaningfulness of the observed changes.

Kinematics of cervical segments C5/C6 in axial rotation before and after total disc arthroplasty.

The kinematical properties of C5/C6 segments in axial rotation are evaluated before and after total disc arthroplasty (TDA) with PRESTIGE®-and BRYAN® Cervical Disc (Medtronic) under flexion/extension as parameters and compared with those of C3/C4. Eight human segments were stimulated by triangularly varying, axially directed torque (T z(t)) under compressing static axial preloads. Using a 6D-measuring device with high resolution, the response of segmental motion was characterized by the instantaneous helical axis (IHA). The position, direction, and migration path length of the IHA were measured before and after TDA (parameter: position of the axially directed preload). The periodic torque T z(t) generated IHA migrations whereupon the IHA direction was constantly rotated to the dorsal by ≈15.5°. After TDA, the IHA0 (neutral positions) were significantly shifted to the dorsal (PRESTIGE®: 4.3mm, BRYAN®: 7.0mm) just as the points of balance of the entire IHA migration paths. Due to the configuration of the vertebral joints and their interaction with the intervertebral disc, the IHA migrates during the axial rotation within a distinct domain of each C5/C6-segment. Implantation of the PRESTIGE® and BRYAN® prostheses significantly alters these kinematical properties by dorsal displacements of the domains. Statistically TDA of C3/C4 and of C5/C6 are not correlated. Under axial rotation of the cervical spine, additional lateral and/or ventral/dorsal displacements are produced by TDA. Consequently, adjacent level disease (ALD) may be mechanically stimulated.

Linearity in force – length Relation and Determination of Muscle Forces

This paper examines the force–length relations of skeletal muscle actuators during normal human gait based on gait data analysis. Instead of time or gait cycle, the joint coordinates were taken as independent parameters in the study of force–length relations. Force–length relations are nonlinear and non-analytic functions in the domain of each gait cycle. We propose to carry out kinematic segmentation of each joint coordinate function into four kinematic states depending on its displacement, velocity and acceleration for studying the force–length relations. When considered segment-wise, linear fit to force–length curves were found statistically significant. Thus it was seen that the skeletal muscles behaved linearly when evaluated in terms of the kinematic segments in the gait cycle. Hence a method to evaluate muscle force distribution was proposed using linear equivalent static formulation based on strain energy minimization as a rapid procedure in comparison with static optimization algorithm. The method resulted in simplified modeling and analysis of musculo-skeletal system to draw interim conclusions before the fully fledged musculo-skeletal analysis is carried out. The proposed method was applied on a single degree of freedom case and was verified with established analysis procedure, namely static optimization using OpenSim, an open-source software system.

Lower extremity control during turns initiated with and without hip external rotation

The pirouette turn is often initiated in neutral and externally rotated hip positions by dancers. This provides an opportunity to investigate how dancers satisfy the same mechanical objectives at the whole-body level when using different leg kinematics. The purpose of this study was to compare lower extremity control strategies during the turn initiation phase of pirouettes performed with and without hip external rotation. Skilled dancers (n=5) performed pirouette turns with and without hip external rotation. Joint kinetics during turn initiation were determined for both legs using ground reaction forces (GRFs) and segment kinematics. Hip muscle activations were monitored using electromyography. Using probability-based statistical methods, variables were compared across turn conditions as a group and within-dancer. Despite differences in GRFs and impulse generation between turn conditions, at least 90% of each GRF was aligned with the respective leg plane. A majority of the net joint moments at the ankle, knee, and hip acted about an axis perpendicular to the leg plane. However, differences in shank alignment relative to the leg plane affected the distribution of the knee net joint moment when represented with respect to the shank versus the thigh. During the initiation of both turns, most participants used ankle plantar flexor moments, knee extensor moments, flexor and abductor moments at the push leg׳s hip, and extensor and abductor moments at the turn leg׳s hip. Representation of joint kinetics using multiple reference systems assisted in understanding control priorities.

Learning to Ride a Unicycle: Coordinating Balance and Propulsion

We investigated the coordination of balance and propulsion processes in learning to ride a unicycle through a principal component analysis (PCA) of the nature and number of functional degrees of freedom (DOF) in the movement coordination patterns. Six participants practiced unicycle riding on an indoor track for 28 sessions over separate days. The movement time and performance outcomes were recorded for each trial and body segment kinematics were collected from the first and every succeeding 4th session. The first appearance of no-hand-support performance varied across participants from the 5th practice session to the 22nd session. The PCA showed that initially in practice the 39 kinematic time series could be represented by 6–9 components that were reduced over practice to 4–7 components. The loadings of the PCA that reflected balance and propulsion processes became more coupled as a function of successfully riding the unicycle. The findings support the proposition that learning to ride the unicycle is a process of making the system more controllable by coordinating balance and propulsion while mastering the redundant DOF.

The acute effects of ankle mobilisations on lower extremity joint kinematics

IntroductionPrevious investigations have identified compensatory movement strategies (CMS) within the lower extremity or lumbopelvic complex during closed chain exercises may be associated with a loss of ankle dorsiflexion range of motion (ROM). The aim of this study was to investigate the acute effects of ankle mobilisations on proximal joint kinematics during a movement task that demands a high amount of ankle dorsiflexion ROM. MethodsEight healthy males (mean (SD) age 25 (4) years) demonstrating side-to-side asymmetry during the weight-bearing lunge test (WBLT) and CMS during the single-leg step-down exercise were accepted for this study. Participants completed five repetitions of a single-leg step-down, both before and after an ankle mobilisation intervention aimed at improving joint athrokinematics. A Vicon motion capture system recorded 3D joint and segment kinematics of the ankle, knee, hip and pelvis. A paired samples t-test was used to identify significant changes of lower extremity joint kinematics during the single-leg step-down, before and after mobilisation. ResultsFollowing the mobilisation intervention, statistically significant gains in ankle dorsiflexion ROM were identified during the WBLT [mean difference 2.425 (0.9377) centimeters, t = −7.315, p < 0.01]. No evidence was found of altered joint kinematics during the single-leg step-down. ConclusionThese findings indicate that increases in ankle dorsiflexion ROM do not automatically integrate into functional movement tasks.

The dorsal skinfold chamber: A versatile tool for preclinical research in tissue engineering and regenerative medicine.

Previous human study suggested that fresh-frozen intervertebral disc allograft transplantation can relieve neurological symptoms and restore segmental kinematics. Before wide clinical application, research into the pathophysiology of the postoperative disc allograft is needed. One important question that remains to be answered in disc allografting is the healing process of the host-graft interface and the subsequent change of the endplates. With the goat model for lumbar disc allografting, histology, micro-computed tomography analysis, scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping were applied to evaluate the healing of the host-graft interfaces, the remodelling of subchondral bone, and the changes of the bony and cartilaginous endplates after transplantation. It was found that healing of the host-graft interfaces started at 1.5 months and was completed at 6 months by natural remodelling. This bony remodelling was also noted in the subchondral bone area after 6 months. The bony endplate was well preserved initially, but was gradually replaced by trabecular bone afterwards; on the other hand, the cartilaginous endplate became atrophic at 6 months and nearly disappeared at the final follow-up. Collectively, after intervertebral disc allograft transplantation, bony healing and remodelling were seen which ensured the stability and mobility of the disc-transplanted segment, but the integrity of bony and cartilaginous endplates was gradually lost and nearly disappeared finally.

Scaling approach in predicting the seatbelt loading and kinematics of vulnerable occupants: How far can we go?

ABSTRACTObjective: Occupants with extreme body size and shape, such as the small female or the obese, were reported to sustain high risk of injury in motor vehicle crashes (MVCs). Dimensional scaling approaches are widely used in injury biomechanics research based on the assumption of geometrical similarity. However, its application scope has not been quantified ever since. The objective of this study is to demonstrate the valid range of scaling approaches in predicting the impact response of the occupants with focus on the vulnerable populations.Methods: The present analysis was based on a data set consisting of 60 previously reported frontal crash tests in the same sled buck representing a typical mid-size passenger car. The tests included two categories of human surrogates: 9 postmortem human surrogates (PMHS) of different anthropometries (stature range: 147–189 cm; weight range: 27–151 kg) and 5 anthropomorphic test devices (ATDs). The impact response was considered including the restraint loads and the kinematics of multiple body segments. For each category of the human surrogates, a mid-size occupant was selected as a baseline and the impact response was scaled specifically to another subject based on either the body mass (body shape) or stature (the overall body size). To identify the valid range of the scaling approach, the scaled response was compared to the experimental results using assessment scores on the peak value, peak timing (the time when the peak value occurred), and the overall curve shape ranging from 0 (extremely poor) to 1 (perfect match). Scores of 0.7 to 0.8 and 0.8 to 1.0 indicate fair and acceptable prediction.Results: For both ATDs and PMHS, the scaling factor derived from body mass proved an overall good predictor of the peak timing for the shoulder belt (0.868, 0.829) and the lap belt (0.858, 0.774) and for the peak value of the lap belt force (0.796, 0.869). Scaled kinematics based on body stature provided fair or acceptable prediction on the overall head/shoulder kinematics (0.741, 0.822 for the head; 0.817, 0.728 for the shoulder) regardless of the anthropometry. The scaling approach exhibited poor prediction capability on the curve shape for the restraint force (0.494 and 0.546 for the shoulder belt; 0.585 and 0.530 for the lap belt). It also cannot well predict the excursion of the pelvis and the knee.Conclusions: The results revealed that for the peak lap belt force and the forward motion of the head and shoulder, the underlying linear relationship with body size and shape is valid over a wide anthropometric range. The chaotic nature of the dynamic response cannot be fully recovered by the assumption of the whole-body geometrical similarity, especially for the curve shape. The valid range of the scaling approach established in this study can be reasonably referenced in predicting the impact response of a given specific population with expected deviation. Application of this knowledge also includes proposing strategies for restraint configuration and providing reference for ATD and/or human body model (HBM) development for vulnerable occupants.

The Effect of Intensity on 3-Dimensional Kinematics and Coordination in Front-Crawl Swimming.

Coaches are often challenged to optimize swimmers' technique at different training and competition intensities, but 3-dimensional (3D) analysis has not been conducted for a wide range of training zones. To analyze front-crawl 3D kinematics and interlimb coordination from low to severe swimming intensities. Ten male swimmers performed a 200-m front crawl at 7 incrementally increasing paces until exhaustion (0.05-m/s increments and 30-s intervals), with images from 2 cycles in each step (at the 25- and 175-m laps) being recorded by 2 surface and 4 underwater video cameras. Metabolic anaerobic threshold (AnT) was also assessed using the lactate-concentration-velocity curve-modeling method. Stroke frequency increased, stroke length decreased, hand and foot speed increased, and the index of interlimb coordination increased (within a catch-up mode) from low to severe intensities (P ≤ .05) and within the 200-m steps performed above the AnT (at or closer to the 4th step; P ≤ .05). Concurrently, intracyclic velocity variations and propelling efficiency remained similar between and within swimming intensities (P > .05). Swimming intensity has a significant impact on swimmers' segmental kinematics and interlimb coordination, with modifications being more evident after the point when AnT is reached. As competitive swimming events are conducted at high intensities (in which anaerobic metabolism becomes more prevalent), coaches should implement specific training series that lead swimmers to adapt their technique to the task constraints that exist in nonhomeostatic race conditions.