Biomechanical Phenomena Research Papers - Academia.edu (original) (raw)

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- Psychology, Pediatrics, Medicine, Prospective studies

Since connective tissue pulleys implement Listing's law by systematically changing rectus extraocular muscle (EOM) pulling directions, non-Listing's law gaze-dependence of the vestibuloocular reflex is currently inexplicable. Differential activation of compartments within rectus EOMs may endow the ocular motor system with more behavioral diversity than previously supposed. Innervation to horizontal, but not vertical, rectus EOMs of mammals is segregated into superior and inferior compartments. Magnetic resonance imaging in normal subjects demonstrates contractile changes in the lateral rectus (LR) inferior, but not superior, compartment during ocular counter-rolling (OCR) induced by head tilt. In human orbits ipsilesional to unilateral superior oblique palsy, neither LR compartment exhibits contractile change during head tilt, although the inferior compartment contracts normally in contralesional orbits. This suggests that differential compartmental LR contraction assists normal OCR. Computational simulation suggests that differential compartmental action in horizontal rectus EOMs could achieve more force than required by vertical fusional vergence.

- by Joseph Demer
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- Magnetic Resonance Imaging, Multidisciplinary, Connective tissue, Eye Movements

For musculoskeletal tissues that transmit loads during movement, the interfaces between tissues are essential to minimizing injury. Therefore, the reproduction of functional interfaces within engineered musculoskeletal tissues is critical to the successful transfer of the technology to the clinic. The goal of this work was to rapidly engineer ligament equivalents in vitro that contained both the soft tissue sinew and a hard tissue bone mimetic. This goal was achieved using cast brushite (CaHPO 4 Á2H 2 O) anchors to mimic bone and a fibrin gel embedded with fibroblasts to create the sinew. The constructs formed within 7 days. Fourteen days after seeding, the interface between the brushite and sinew could withstand a stress of 9.51 AE 1.7 kPa before failure and the sinew reached a Young's modulus value of 0.16 AE 0.03 MPa. Treatment with ascorbic acid and proline increased the collagen content of the sinew (from 1.34% AE 0.2% to 8.34% AE 0.37%), strength of the interface (29.24 AE 6 kPa), and modulus of the sinew (2.69 AE 0.25 MPa). Adding transforming growth factor-b resulted in a further increase in collagen (11.25% AE 0.39%), interface strength (42 AE 8 kPa), and sinew modulus (5.46 AE 0.68 MPa). Both scanning electron and Raman microscopy suggested that the interface between the brushite and sinew mimics the in vivo tidemark at the enthesis. This work describes a major step toward the development of tissue-engineered ligaments for the repair of ligament ruptures in humans.

- by Jennifer Paxton
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- Biomedical Engineering, Tissue Engineering, Collagen, Calcium Phosphates

There are several pathologies related to the patellofemoral joint, in which the patellofemoral syndrome is one af the most common and challenging to treat. The patellofemoral syndrome results from a malalignment of the knee extenso r mechanism. The purpose af our study was to describe and compare EMG responses of the vastus medialis and vastus lateralis muscles while walking up and down stairs and other clinical and functional responses in PFS subjects before and afier a physical therapy intervention. Eleven subjects were studied and divided in two groups: six subjects with clinically diagnosed patellofemoral syndrome and five healthy control subjects. Subjects were evaluated by a functional and biomechanical evaluation protocol: postural evaluation, pain and knee function evaluation, and electromyographic activity of vastus medialis and lateralis muscles while walking up and down a staircase. Results showed higher efficiency of the vastus medialis muscle in carrying out eccentric exercises and increased musc1e activity in both the vastus medialis and vastus lateralis muscles while c1imbing stairs after physical therapy treatment. We were able to identify an improvement in postural alignment of lower Ihl1b muscles and knee functionality among patellofemoral syndrome group subjects afier treatment.

- by arnon guilherme
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- Biomechanics, Skeletal muscle biology, Adolescent, Physical Therapy

Ankle Foot Orthoses (AFOs) to promote walking ability are a common treatment in patients with neurological or muscular diseases. However, guidelines on the prescription of AFOs are currently based on a low level of evidence regarding their efficacy. Recent studies aiming to demonstrate the efficacy of wearing an AFO in respect to walking ability are not always conclusive. In this paper it is argued to recognize two levels of evidence related to the ICF levels. Activity level evidence expresses the gain in walking ability for the patient, while mechanical evidence expresses the correct functioning of the AFO. Used in combination for the purpose of evaluating the efficacy of orthotic treatment, a conjunct improvement at both levels reinforces the treatment algorithm that is used. Conversely, conflicting outcomes will challenge current treatment algorithms and the supposed working mechanism of the AFO. A treatment algorithm must use relevant information as an input, derived from measur...

- by fred holtkamp
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- Algorithms, Biomedical Engineering, Evidence Based Medicine, Treatment Outcome

10. DC cultures were generated as described (5, 22). Immature I-A kϩ DCs grown from C3H/HeN, C3H/HeJ, and CBA/J (Jackson Labs, Bar Harbor, ME) marrow suspensions were pulsed with HEL (1 to 3 mg/ml) with or without LPS (1 to 10 ng/ml, E. coli 0111.B4) for 1 to 3 hours, washed, and chased in HEL-and LPS-free media. Similar results were obtained with DCs from each strain. DC cultures contained supernatant from mGM-CSFexpressing J558L cells (from A. Lanzavecchia, Basel Institute, Basel, Switzerland). LPS was removed from HEL (Sigma) with Kuttsuclean adsorbent (Maruha Corporation, Ibaraki, Japan). Maturation stimuli included LPS, CD40L, tumor necrosis factor-␣, or replating (22). 11. DCs were fixed with 4% (wt/vol) paraformaldehyde and washed in phosphate-buffered saline. Cells were incubated with monoclonal antibodies (mAbs) on ice as described (23). The rat mAb C4H3 was provided by R. Germain (NIH, Bethesda, MD). C4H3 was purified on protein A-Sepharose and biotinylated. Cells were labeled with biotin-conjugated mAbs (Pharmingen) to I-E k (14-4-4S) or I-A k (10-2.16) and fluorescein

- by Barbara Davis
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- Psychology, Phonetics, Science, Language Development
- by Constance Lebrun
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- Mechanical Engineering, Sports Medicine, Canada, Curriculum and Pedagogy
- by J. Koolstra
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- Dentistry, Temporomandibular Joint, Finite Element Analysis, Dental

Plantar pressure assessment is a tool useful for study of the gait cycle. In this study, we present a means of assessing the gait cycle using a temporal analysis of plantar pressures and lower-leg muscle activities. Plantar pressures and surface electromyography (EMG) of the tibialis anterior (TA) and medial gastrocnemius (MG) muscles were recorded as 19 men walked on a treadmill at seven speeds between 0.45 and 1.79 m/s. A typical 'heel strike to toe off' gait pattern was observed. Speed had minimal effects on the shapes of the muscle EMG root-mean-square-and plantar pressure-time curves except for the pressure-time curves in the heel and midfoot. A linear relationship was found between speed and peak pressures in the heel, medial forefoot, and toes; pressures in these regions increased by 91-289% going from 0.45 to 1.79 m/s. The temporal pressure changes in the forefoot and toes were paralleled by changes in MG muscle activity (i.e., cross-correlations of 0.90); TA muscle activity was not cross-correlated with the temporal pressure patterns in any region. However, the peak values of TA muscle activity were found to be highly correlated across speeds with peak pressures in the heel and toes (i.e., r 0.98); similar high correlations were found between peak values of MG muscle activity and heel pressure. In summary, these data collected on able-bodied persons during motorized treadmill walking can be useful for comparison to those of patients undergoing treadmill evaluations for atypical gait cycle patterns and for tracking the progress of patients during gait rehabilitation.

- by Gordon Warren
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- Mechanical Engineering, Biomechanics, Skeletal muscle biology, Cross Correlation
- by Elena Diaconescu
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- Sports Medicine, Ergonomics, Evidence Based Medicine, Human Factors

Determining the epithelium's contribution to corneal biomechanics is important for the predictive numerical simulation of corneal biomechanical behaviour in which the cornea's five main layers are represented separately. Twenty-four corneal buttons were tested under posterior inflation conditions while monitoring their behaviour using non-contact methods. The corneas were divided into two groups of 12; one with and one without the epithelium. Control of specimen hydration, temperature and pressure application rate, and limiting the programme to specimens within a small age range resulted in a narrow scatter of test results. On average, intact specimens were able to carry slightly more pressure at the same deformation, and experienced less average stress for the same strain, compared with specimens without the epithelium. These results indicated that the stiffness of the epithelium was considerably lower than that of the stroma, and might therefore be ignored in numerical simulation studies.

- by Ahmed Elsheikh
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- Biomechanics, Cornea, Elasticity, Numerical Simulation

Objective. This investigation aims to determine (1) whether shockwave treatment helps fracture healing and (2) whether the effect of shockwave treatment on fracture healing is dose dependent. Design. Shockwave was applied over tibial osteotomy in an animal model to assess its effect on the healing of the fracture. Methodology. Bilateral tibial diaphyseal transverse osteotomy was conducted on 42 rabbits, dividing into experimental and control group, immobilized using an external skeletal fixator, with one leg tested with shockwave therapy and the contralateral leg acting as the control without therapy. Serial radiography and measurement of bone mineral density via dual-energy X-ray absorptiometry were performed to assess the fracture healing. The experimental animals had two or three sessions of shockwave therapy (5000 impulses, 0.32 mJ/mm 2 , Orthopedice) over the osteotomy sites on day 7, 21 and 35; while the control group did not receive any treatment. The animals were sacrificed on day 42 or 56. Then, bilateral tibias were harvested and sent for mechanical tests as well as the histological examination. The pertinent statistic methods were applied to analyze the results. Background. Shockwave therapy has become a useful alternative approach in treating various orthopedic conditions, but the mechanism which it works remains unclear. Thus far, shockwave therapy has been found effective in treating long bone pseudoarthrosis, but whether it can benefit fresh fracture healing continues to be debated. Results. Higher union rates occurred during the early but not the late stages in the experimental group, while mechanical strength was higher in the experimental group than in the control group. No significant dose-dependent response occurred between the second and third applications of shockwave treatment. No significant difference in mechanical strength occurred between the experimental groups at 4 weeks and the control group at 6 weeks, or between the experimental groups at 6 and 8 weeks. Furthermore, no significant correlation occurred between the absolute values of maximum torque and bone mineral density. Conclusion. Based on this investigation, shockwave treatment has a positive effect on early fracture healing while its long term effects require further investigation. Relevance Shockwave therapy can be a useful alternative adjunct modality in the treatment of fresh long bone fracture.

- by Swei Hsueh
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- Mechanical Engineering, Biomedical Engineering, Animal Studies, Medicine

Reconstruction after pan-plexus root avulsions often includes gracilis free functioning muscle transfer. For elbow flexion reconstruction, the free functioning muscle transfer distal tendon is inserted into the biceps tendon or more distally (i.e., flexor digitorum profundus/flexor pollicis longus tendons) for combined elbow and finger flexion; the theoretical drawback of the latter approach is weaker elbow flexion. The authors compared elbow flexion strength with a biceps tendon versus a flexor digitorum profundus/flexor pollicis longus tendon attachment to determine which insertion point resulted in better elbow flexion. Thirty-nine patients underwent free functioning muscle transfer with either a biceps tendon or a distal attachment. Groups were compared on postoperative elbow flexion strength, preoperative and postoperative Disabilities of the Arm, Shoulder, and Hand questionnaire scores, range of motion, and other surgical and demographic characteristics. A biomechanical analys...

The purpose of this study was to investigate systematically if complementary knowledge could be obtained from the recordings of electromyography (EMG) and mechanomyography (MMG) signals. EMG and MMG activities were recorded from the first dorsal interosseous muscle during slow concentric, isometric, and eccentric contraction at 0, 25, 50, 75 and 100% of the maximal voluntary contraction (MVC). The combination of the EMG and MMG recordings during voluntary concentric-isometric-eccentric contraction showed significant different non-linear EMG/force and MMG/force relationships (PϽ0.001). The EMG root mean square (rms) values increased significantly from 0 to 50% MVC during concentric and isometric contraction and up to 75% MVC during eccentric contraction (PϽ0.05). The MMG rms values increased significantly from 0 to 50% MVC during concentric contraction (PϽ0.05). The non-linear relationships depended mainly on the type and the level of contraction together with the angular velocity. Furthermore, the type of contraction, the contraction level, and the angular velocity influenced the electromechanical efficiency evaluated as the MMG to EMG ratio (PϽ0.05). These results highlight that EMG and MMG provide complementary information about the electrical and mechanical activity of the muscle. Different activation strategies seem to be used during graded isometric and anisometric contraction.

- by Prem Bajaj
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- Sports Medicine, Skeletal muscle biology, Electromyography, Root-Mean Square Error
- by Richard Kay
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- Biomechanics, Biology, Locomotion, Medicine

The inertial loading thresholds for infant head injury are of profound medico-legal and safety-engineering significance. Injurious experimentation with infants is impossible, and physical and computational biomechanical modelling has been frustrated by a paucity of paediatric biomechanical data. This study describes the development of a computational infant model (MD Adams®) by combining radiological, kinematic, mechanical modelling and literature-based data. Previous studies have suggested the neck as critical in determining inertial head loading. The biomechanical effects of varying neck stiffness parameters during simulated shakes were investigated, measuring peak translational and rotational accelerations and rotational velocities at the vertex. A neck quasi-static stiffness of 0.6 Nm/deg and lowest rate-dependent stiffness predisposed the model infant head to the highest accelerations. Plotted against scaled infant injury tolerance curves, simulations produced head acceleration...

- by Alison Kemp
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- Engineering, Law, Medicine, Computer Simulation
- by Stephen Prentice
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- Kinetics, Control system, Gait, Walking

The purpose of this study was to analyze, in an animal model, the histologic and biomechanical phenomena at the bone-implant interface of implants inserted with high torque (HT) as compared to low torque (LT) during the first 6 weeks of healing. Forty tapered-screw-form implants were placed in five hybrid sheep. The implant sites were placed in the mandible, using an extraoral approach; four were placed with HT (test: mean 110 Ncm) on one side and four were placed with LT (control: mean 10 Ncm) on the contralateral side. After 1, 2, 3, 4, and 6 weeks of healing, removal torque testing and resonance frequency analysis were performed and the animals were sacrificed for histologic examination. Implants from the HT group showed significantly higher bone apposition than implants from the LT group at all examined healing times. Similarly, removal torque was consistently higher for the HT as compared to the LT group. A significant loss of primary stability in the HT group was evident 7 day...

- by Ugo Consolo
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- Dentistry, Biomedical Engineering, Wound Healing, Osseointegration

Interested readers are encouraged to engage in an exchange of information through this Section. Letters should relate specifically to material published in the Journal of Rehabilitation Research and Development. We request that the following information be supplied: full name of the author of the article, title of the article, Volume and Issue number, the page number on which the article appeared. In addition, we request that the letter contain the full name and academic degree of the letter writer, along with the facility that the writer represents. We hope to open up an ongoing dialogue between professionals as a means of exchanging information and sharing diverse opinions among disciplines.

- by Ivan Baiges
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- Algorithms, Skeletal muscle biology, Tremor, Energy Dissipation

To biomechanically compare anterior cruciate ligament (ACL) tibial bony avulsion fixation by suture anchors, EndoButtons (Smith & Nephew, Andover, MA), and high-strength sutures subjected to cyclic loading. Methods: Type III tibial eminence fractures were created in 49 ovine knees, and 7 different types of repairs were performed. Each repair group contained 7 specimens. The repair groups were as follows: No.

- by serkan davul
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- Orthopedic Surgery, Fracture, Treatment, Treatment Outcome
- by Shane C Burgess
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- Flow Cytometry, Confocal Microscopy, Endothelial Cells, Cell Death

The purpose of this study was to examine the effect of mineralization on the mechanical properties of embryonic bone rudiments. For this purpose, four-point bending experiments were performed on unmineralized and mineralized embryonic mouse ribs at 16 and 17 days of gestational age. Young's modulus was calculated using force -displacement data from the experiment in combination with finite element analysis (FEA). For the unmineralized specimens, a calculated average for the Young's modulus of 1.11 ( F 0.62) MPa was established after corrections for sticking to the four-point bending device and aspect ratio, which is the ratio between the length of the bone and its diameter. For the mineralized specimens, the value was 117 ( F 62) MPa after corrections. Hence, Young's moduli of embryonic bone rudiments increase by two orders of magnitude within 1 day, during endochondral ossification. As an effect, the hypertrophic chondrocytes in the calcifying cartilage experience a significant change in their mechanical environment. The chondrocytes are effectively stress shielded, which means that they do not carry stresses since stresses are supported by the stiffest parts of the tissue, which are in this case the diaphyseal cortex and the calcified matrix. The deformability of the hypertrophic chondrocytes is, therefore, severely reduced. Since the transition is so sudden and enormous, it can be seen as a process of 'catastrophic' proportion for the hypertrophic chondrocytes. The subsequent resorption of calcified cartilage and the expansion of the marrow cavity could be consequential to stress shielding. D 2004 Elsevier Inc. All rights reserved.

Objective: Human body finite element models (FE-HBMs) are available in standard occupant or pedestrian postures. There is a need to have FE-HBMs in the same posture as a crash victim or to be configured in varying postures. Developing FE models for all possible positions is not practically viable. The current work aims at obtaining a posture-specific human lower extremity model by reconfiguring an existing one. Methodology: A graphics-based technique was developed to reposition the lower extremity of an FE-HBM by specifying the flexion–extension angle. Elements of the model were segregated into rigid (bones) and deformable components (soft tissues). The bones were rotated about the flexion–extension axis followed by rotation about the longitudinal axis to capture the twisting of the tibia. The desired knee joint movement was thus achieved. Geometric heuristics were then used to reposition the skin. A mapping defined over the space between bones and the skin was used to regenerate the soft tissues. Mesh smoothing was then done to augment mesh quality. Results: The developed method permits control over the kinematics of the joint and maintains the initial mesh quality of the model. For some critical areas (in the joint vicinity) where element distortion is large, mesh smoothing is done to improve mesh quality. Conclusions: A method to reposition the knee joint of a human body FE model was developed. Repositions of a model from 9 degrees of flexion to 90 degrees of flexion in just a few seconds without subjective interventions was demonstrated. Because the mesh quality of the repositioned model was maintained to a predefined level (typically to the level of a well-made model in the initial configuration), the model was suitable for subsequent simulations.

- by Dhaval Jani
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- Psychology, Computer Graphics, Mesh quality, Automotive Engineering

This study proposes a simple estimate of hamstring length at initial contact (LEST) for use when musculoskeletal modelling is not available. The estimate is calculated by using the kinematic curves to measure the excessive flexion (above normal) at the hip and knee at initial contact. The excessive hip flexion is then multiplied by a scaling factor (k) and the excessive knee flexion subtracted from the result. Validation of this estimate was carried out using kinematic gait data from 25 children with cerebral palsy (50 limbs) by comparing the results of the estimate with an equivalent measure derived from musculoskeletal modelling (LTRUE). Very high agreement was found when LTRUE and LEST were compared for the three biarticular hamstring muscles, demonstrated by correlation coefficients of over 0.9. Different k values were tested with a value of 3 giving the best results overall. The estimate is acceptable as a simple ‘rule of thumb’ for use in clinical practice. It can provide useful additional information to complement the clinical examination and gait assessment results.

- by ILse Jonkers
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- Mechanical Engineering, Skeletal muscle biology, Cerebral Palsy, Adolescent

Current studies on pole-vaulting focus mostly on energy transfer data [Ekevad, M., Lundberg, B., 1995. Simulation of ''smart'' pole .] and often fail to take into account the actions exerted on the pole [Arampatzis, . Effect of the pole-human body interaction on pole-vaulting performance. Journal of Biomechanics 37, 1353-1360]. The present study integrates the 3D kinematics data of the athlete but also the actions measured at the end of the pole in the planting box and on the track during the last stride before take-off. It proposes a mechanical model allowing determination of the pole-vaulter's actions on the pole. The model is based on a global mechanical approach. The pole-vaulter's action on his upper and lower hand is concentrated on one middle point to solve the dynamics problem. The model was applied to seven experienced pole-vaulters. The force and the moment exerted on the pole by the pole-vaulter during the last stride before take off and during jump stage, were calculated. This analysis of the compressive force and bending moment for seven pole-vaulters helps to highlight the impact of the moment in the performance. The conclusion is confirmed by an additional comparative study carried out on two polevaulters, with comparable morphologies and performing with the same pole. r

- by Michel Mesnard
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- Mechanical Engineering, Biomedical Engineering, Biomechanics, Energy Conversion
- by Kenneth Meijer and +2
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- Mechanical Engineering, Running, Fatigue, Shoes
- by Guido Westhoff
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- Target Tracking, Biological Sciences, Movement, Elapidae

Biological debris between modular components using Morse tapers in hip arthroplasty can lead to weakening of the implant construct. We conducted a study to determine the effect of blood and fat within the taper interface. Tapers were divided into groups 1 (clean), 2 (surface covered with blood and fat), and 3 (blood and fat wiped off). Each taper was impacted and disassembled 5 times. There was a difference in mean disassembly force between pulls within group 2. Thus, blood and fat contamination can have a significant effect on the potential for disassembly.

- by Luis Baerga
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- Titanium, Adipose tissue, Blood, prosthesis Design

Study Design: A biomechanical study using human cadaveric thoracic spine specimens.

- by William Hutton
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- Clinical Sciences, Aged, Thoracic Vertebrae, Spinal Fusion

Grazing is a complex process involving the simultaneous occurrence of both trampling and defoliation. Clonal plants are a common feature of heavily grazed ecosystems where large herbivores inflict the simultaneous pressures of trampling and defoliation on the vegetation. We test the hypothesis that physiological integration (resource sharing between interconnected ramets) may help plants to deal with the interactive effects of trampling and defoliation. In a field study, small and large ramets of the root-suckering clonal tree Populus simonii were subjected to two levels of trampling and defoliation, while connected or disconnected to other ramets. Plant responses were quantified via survival, growth, morphological and stem mechanical traits. Disconnection and trampling increased mortality, especially in small ramets. Trampling increased stem length, basal diameter, fibrous root mass, stem stiffness and resistance to deflection in connected ramets, but decreased them in disconnected...

- by Niels Anten and +1
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- Biomass, Plant Biology, Ecology, Resource sharing

The purpose of this study was to investigate the effect of tissue hydration on the structural properties of human patellar tendon. Specimens were subjected to a load relaxation experiment prior to being stretched to failure. The experiments indicated that tendons relaxed faster in hypotonic solutions when compared to hypertonic solutions. At a strain rate of 50% s-r the structural stiffness was significantly higher while immersed in a hypotonic versus hypertonic solution. No difference in tensile stiffness was documented between baths for 0.5% s-l. Tendons immersed in the hypotonic solution were significantly stiffer for 50% s-r against 0.5% s-r. The results indicate that the structural properties of human patellar tendon are more sensitive to time when the tissues are fully hydrated.

- by Roger Haut
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- Mechanical Engineering, Biomedical Engineering, Viscoelasticity, Biomechanics

Spatial and temporal parameters of gait are of recognised clinical relevance in the assessment of motor pathologies, because they normally occur in established combinations which can be altered by pathologies. The data collected from 596 healthy subjects have been used to establish relationships among these parameters and a procedure to estimate deviation from normality based on the comparison between measured values and values estimated by exploiting these relationships. The applied multiple linear regression method (MLRM) was preliminarily validated by comparing its outputs with those of corresponding equations found in the literature, and by applying it to a control group of 12 healthy subjects.

- by R. Saggini
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- Mechanical Engineering, Mathematics, Medicine, Gait

Biomechanical studies suggest that one determinant of abdominal aortic aneurysm (AAA) rupture is related to the stress in the wall. In this regard, a reliable and accurate stress analysis of an in vivo AAA requires a suitable 3D constitutive model. To date, stress analysis conducted on AAA is mainly driven by isotropic tissue models. However, recent biaxial tensile tests performed on AAA tissue samples demonstrate the anisotropic nature of this tissue. The purpose of this work is to study the influence of geometry and material anisotropy on the magnitude and distribution of the peak wall stress in AAAs. Three-dimensional computer models of symmetric and asymmetric AAAs were generated in which the maximum diameter and length of the aneurysm were individually controlled. A five parameter exponential type structural strain-energy function was used to model the anisotropic behavior of the AAA tissue. The anisotropy is determined by the orientation of the collagen fibers (one parameter o...

Mechanical sit-to-stand devices assist patient transfers and help protect against work-related injuries in rehabilitation environments. However, observational differences between patient's movements within devices compared to normal sit-to-stand transfers deter clinician use. This study compared kinematics and muscle demands during sit-to-stand transfers with no device (ND), and device-assisted during which participants exerted no effort (DA-NE) and best effort (DA-BE). Coefficient of multiple correlations (CMCs) compared kinematic profiles during each device-assisted condition to ND. Compared to DA-NE, CMCs were higher during DA-BE at the hip, knee, and ankle. However, DA-BE values were lower than DA-NE at the trunk and pelvis due to the device's mechanical constraints. In general, all joints' final DA-NE postures were more flexed than other conditions. Electromyographic was significantly lower during DA-NE compared to ND for all muscles except lateral hamstring, and during DA-BE compared to ND for gluteus maximus, gastrocnemius, and soleus. Verbal encouragement (DA-BE) significantly increased medial hamstring, vastus lateralis, gastrocnemius, soleus and tibialis anterior activation compared to DA-NE. In conclusion, device-assisted sit-to-stand movements differed from normal sit-to-stand patterns. Verbally encouraging best effort during device-assisted transfers elevated select lower extremity muscle activation and led to greater similarity in hip, knee and ankle movement profiles. However, trunk and pelvis profiles declined.

- by Thad Buster
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- Mechanical Engineering, Skeletal muscle biology, Medicine, Physical Therapy
- by Kate Webster
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- Cognitive Science, Biomechanics, Gait, Walking
- by Wu Jesse
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- Adolescent, Medicine, Cancellous bone, Clinical Sciences

Children with many types of motor dysfunction have problems maintaining postural stability. Because maintenance of postural stability is an integral part of all movements, therapists evaluate and treat to improve postural stability in these children. This article reviews current pediatric assessment tools for postural stability and issues affecting testing this construct in children. The tests and measurements are classified according to their testing purpose and the National Center for Medical Rehabilitation Research disablement framework, focusing on the impairment and functional limitation dimensions. Postural stability is defined from a systems perspective with tests related to the sensory, motor, and biomechanical systems described. Reliability and validity information on the measurements is discussed. Relatively few measurements of postural stability in children are available that have acceptable reliability and validity documentation. Suggestions for research on test development in this area are discussed. [Westcott SL, Lowes LP, Richardson PK. Evaluation of postural stability in children: current theories and assessment tools.

- by Linda Lowes
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- Psychology, Adolescent, Medicine, Physical Therapy

The rear-facing Infant Car Seat (ICS) is designed to meet federal requirements for transporting children less than 1 year old. Typical use includes transfer in and out of a vehicle, which is shown to be a difficult lift. Despite the frequency of this lift, manufacturers provide little guidance for users. Review of relevant literature suggested an ICS featuring an angled handle, promoting a neutral wrist posture, would increase grip stability and decrease lifting effort. Popular press suggested a foot-in-car stance for the ICS lift would do the same. An experiment was conducted in which wrist deviations from neutral posture were recorded along with lifting muscle activation levels (multiple flexor muscles and biceps brachii) and overall perceived exertion for straight versus a new bent handle design and conventional stance versus foot-in-car. Foot position was examined to test the recommendations in the popular press. Surprisingly, wrist deviation was not significantly affected by the new bent handle design (due to compensatory behavior with the straight handle) but was related to foot placement (p ¼ 0.04). Results revealed the bent handle to significantly reduce flexor activation compared with the straight handle (p ¼ 0.0003); however, the level of biceps activation increased. Biceps activation also significantly increased for foot-in-car stance (p ¼ 0.035) but not flexor activation. In general, the bent handle enabled the user to lift the ICS with a steadier grip and less effort.

- by David B . Kaber and +1
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- Engineering, Medicine, Automobiles, Applied Ergonomics

An important question in alpine skiing is how to determine characteristics of well-performed ski turns, an issue that has become more crucial with the arrival of new carving skis. This article introduces a new method for estimating the quality of skiing at each point of observation based on mechanical energy behavior that can be measured using established motion analysis techniques. It can be used for single or multiple-skier analyses for evaluation of skiing technique as well as racing tactics. An illustration of its use is shown by analyzing 16 top-level racers using a 3-D kinematical system and video recorded during an alpine ski world cup race. Based on energy behavior of several racers, it is demonstrated that the most direct line with shortest radius of turn is not necessarily the most effective strategy in contrast to what some coaches believe.

- by Matej Supej
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- Mechanical Engineering, Biomedical Engineering, Kinetics, Skiing

Calcium-alginate hydrogel has been widely studied as a material for cell encapsulation for tissue engineering. At present, the effect that cells have on the degradation of alginate hydrogel is largely unknown. We have shown that fibroblasts encapsulated at a density of 7.5 Â 10 5 cells ml À1 in both 2% and 5% w/v alginate remain viable for at least 60 days. Rheological analysis was used to study how the mechanical properties exhibited by alginate hydrogel changed during 28 days in vitro culture. Alginate degradation was shown to occur throughout the study but was greatest within the first 7 days of culture for all samples, which correlated with a sharp release of calcium ions from the construct. Fibroblasts were shown to increase the rate of degradation during the first 7 days when compared with acellular samples in both 2% and 5% w/v gels, but after 28 days both acellular and cell-encapsulating samples retained disc-shaped morphologies and gel-like spectra. The results demonstrate that although at an early stage cells influence the mechanical properties of encapsulating alginate, over a longer period of culture, the hydrogels retain sufficient mechanical integrity to exhibit gel-like properties. This allows sustained immobilization of the cells at the desired location in vivo where they can produce extracellular matrix and growth factors to expedite the healing process.

- by Nicola Hunt
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- Tissue Engineering, Rheology, Calcium, Multidisciplinary
- by Iain Fletcher
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- Skeletal muscle biology, Anthropometry, Knee, Movement

 Tibial torsion, twisting of the tibia about its longitudinal axis, varies during development and early childhood. Knowledge of the normal range of tibial torsion at various ages and its accurate clinical measurement is important in the assessment of the extent of a torsional deformity. To evaluate tibial torsion a reliable technique for its measurement in vivo is therefore required. The aim of this study was to determine which of 4 existing in vivo methods of measuring tibial torsion was the most accurate and had the highest repeatability, by comparing them with direct measurement of the tibia. A wide range of mean values for tibial torsion was observed, using the various techniques, with none of the indirect techniques employed having a strong correlation with direct measurement of tibial torsion. The repeatability of the indirect techniques was observed to be low both in cadavers (n l 4) and the living (n l 3). Since none of the in vivo techniques appear to measure true tibial torsion or be of a reasonable repeatability, alternative easy to use and inexpensive methods need to be developed. Accurate clinical measurement of tibial torsion is important in the assessment of the extent of a torsional deformity. It is recommended that data gained using the methods reviewed here are interpreted with caution.

- by Roger Soames
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- Biomedical Engineering, Anthropometry, Anatomy, Tibia

Background Scene supervision is a major tool to make medical robots safer and more intuitive. The paper shows an approach to efficiently use 3D cameras within the surgical operating room to enable for safe human robot interaction and action perception. Additionally the presented approach aims to make 3D camera-based scene supervision more reliable and accurate. Methods A camera system composed of multiple Kinect and time-of-flight cameras has been designed, implemented and calibrated. Calibration and object detection as well as people tracking methods have been designed and evaluated. Results The camera system shows a good registration accuracy of 0.05 m. The tracking of humans is reliable and accurate and has been evaluated in an experimental setup using operating clothing. The robot detection shows an error of around 0.04 m. Conclusions The robustness and accuracy of the approach allow for an integration into modern operating room. The data output can be used directly for situation and workflow detection as well as collision avoidance.

- by Tim Beyl and +1
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- Robotics, Intuition, Calibration, Clinical Sciences

Background: Quick procedures with proper psychometric properties that can capture the combined alignment of the foot-ankle complex in a position that may be more representative of the status of the lower limb during ground contact are... more

- by Sergio Teixeira da Fonseca
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- Psychometrics, Gait, Young Adult, Athletes
- by Aizhan Aimbetova
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- Animal Welfare, Swimming, Dolphins, Health Services

Background: Understanding the acute response of healthy knee cartilage to running may provide valuable insight into functional properties. In recent years, quantitative magnetic resonance (MR) imaging techniques (T1 r and T2 relaxation measurement) have shown tremendous potential and unique ability to noninvasively and quantitatively determine cartilage response to physiologic levels of loading occurring with physiologic levels of exercise.

- by Deepak Kumar
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- Mechanical Engineering, Biomedical Engineering, Magnetic Resonance Imaging, Running
- by Tron Krosshaug
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- Engineering, Education, Epidemiology, Prevention

Background This study evaluated the effects of a combination of three ergonomic measures designed to reduce the risk of low back complaints among gypsum bricklayers. The measures focused on optimizing working height and reducing carrying distances. Methods A within-subjects (N ¼ 10) controlled field study was used to compare the effects of working with the ergonomic measures with those of working with conventional working methods at the worksite during the course of a full working day. Productivity, work demands, and workload were assessed.

- by Bart Visser
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- Health Promotion, Construction Materials, Health Education, Risk