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Despite having a fully functional knee and hip in both legs, asymmetries in joint moments of the knee and hip are often seen in gait of persons with a unilateral transtibial amputation (TTA), possibly resulting in excessive joint loading. We hypothesize that persons with a TTA can walk with more symmetric joint moments at the cost of increased effort or abnormal kinematics. The hypothesis was tested using predictive simulations of gait. Open loop controls of one gait cycle were found by solving an optimization problem that minimizes a combination of walking effort and tracking error in joint angles, ground reaction force and gait cycle duration. A second objective was added to penalize joint moment asymmetry, creating a multi-objective optimization problem. A Pareto front was constructed by changing the weights of the objectives and three solutions were analyzed to study the effect of increasing joint moment symmetry. When the optimization placed more weight on moment symmetry, walking effort increased and kinematics became less normal, confirming the hypothesis. TTA gait improved with a moderate increase in joint moment symmetry. At a small cost of effort and abnormal kinematics, the peak hip extension moment in the intact leg was decreased significantly, and so was the joint contact force in the knee and hip. Additional symmetry required a significant increase in walking effort and the joint contact forces in both hips became significantly higher than in able-bodied gait. [ABSTRACT FROM AUTHOR]

Lateral wedge insoles (LWIs) reduce the peak external knee adduction moment (KAM). However, the efficacy of LWIs is limited in certain individuals for whom they fail to decrease KAM. Possible explanations for a lack of desired LWI response are variations in foot alignments. The purpose of this study was to evaluate whether the immediate biomechanical effects of LWIs depend on individual foot alignments during gait. Fifteen healthy adults participated in this study. Their feet were categorized as normal, pronated, and supinated using the foot posture index. All subjects were subsequently requested to perform a normal gait under barefoot and LWI conditions. A three-dimensional motion analysis system was used to record the kinematic and kinetic data, included peak KAM, KAM impulse (KAAI), center of pressure displacement, and knee-ground reaction force lever arm (KLA). Furthermore, lower limb frontal plane kinematic parameters at the rear foot, ankle, knee, and hip were evaluated. Among all feet, there was no significant difference in the peak KAM and KAAI between the conditions. In contrast, the peak KAM was significantly reduced under the LWI condition relative to the barefoot condition in the normal foot group. Reductions in the peak KAM were correlated with a more lateral center of pressure and reduced KLA. In addition, a reduced KLA was correlated with decreased hip adduction. LWIs significantly reduced the peak KAM in normal feet, indicating that biomechanical effects of LWIs vary between individual foot alignments. Our findings suggest that it is helpful to assess individual foot alignment to ensure adequate insole treatment for patients with knee osteoarthritis. [ABSTRACT FROM AUTHOR]

Lateral trunk lean (LTL) is a proposed intervention for knee osteoarthritis but increased muscular demands have not been considered. The objective was to compare lower extremity and trunk muscle activation and joint mechanics between normal and increased LTL gait in healthy adults. Participants (n=20, mean age 22 years) were examined under two gait conditions: normal and increased LTL. A motion capture system and force plates sampled at 100 and 2000Hz respectively were used to determine joint angles and external moments including LTL angle and external knee adduction moment (KAM). Surface electromyography, sampled at 2000Hz, measured activation of six trunk/hip muscles bilaterally. Peak LTL angle, peak KAM, gait speed, and mean values from electromyography waveforms were compared between normal and LTL conditions using paired t-tests or 2-way analysis of variance. There was a significant (p<0.05) increase in peak LTL angle, decrease in first but not second peak KAM, and decrease in gait speed during LTL gait. There were significant (p<0.01) increases in external oblique and iliocostalis muscle activation during LTL gait. There was no change in activation for internal oblique, rectus abdominis, longissimus, and gluteus medius. LTL gait decreased early/mid-stance KAM demonstrating its ability to decrease medial compartment knee loading. Increases in external oblique and iliocostalis activation were present but small to moderate in size and unlikely to lead to short term injury. Longitudinal studies should evaluate the effectiveness of increased LTL for knee osteoarthritis and if the increase in muscular demands leads to negative long term side effects. [ABSTRACT FROM AUTHOR]

Abstract: The extent to which therapeutic, exercise or robotic devices can maximize gait function is a major unresolved issue in neurorehabilitation. Several factors may influence gait outcomes such as similarity of the task to overground walking, degree of coordination within and across limbs, and cycle-to-cycle variability in each device. Our objective was to compare lower extremity kinematics, coordination and variability during four locomotor tasks: overground walking, treadmill walking, elliptical training and stationary cycling in 10 non-disabled adults (6 male; mean age 22.7±2.9 yrs, range 20–29). All first performed four overground walking trials at self-selected speed with mean temporal–spatial data used to pace the other conditions. Joint positions, excursions, and the Gait Deviation Index (GDI) were compared across conditions to evaluate kinematic similarity. Time-series data were correlated within and across limbs to evaluate intralimb and interlimb coordination, respectively. Variability in cadence was quantified to assess how constrained the locomotor rhythm was compared to overground walking. Treadmill walking most closely resembled overground with GDI values nearly overlapping, reinforcing its appropriateness for gait training. Cycling showed the largest GDI difference from overground, with elliptical closer but still a significant distance from all three. Cycling showed greater hip reciprocation Cycling and elliptical showed stronger intralimb synergism at the hip and knee than the other two. Based on kinematics, results suggest that elliptical training may have greater transfer to overground walking than cycling and cycling may be more useful for enhancing reciprocal coordination. Further evaluation of these devices in neurological gait disorders is needed. [Copyright &y& Elsevier]

Abstract: Many patients respond positively to treatments for crouch gait, yet surgical outcomes are inconsistent and unpredictable. In this study, we developed a multivariable regression model to determine if biomechanical variables and other subject characteristics measured during a physical exam and gait analysis can predict which subjects with crouch gait will demonstrate improved knee kinematics on a follow-up gait analysis. We formulated the model and tested its performance by retrospectively analyzing 353 limbs of subjects who walked with crouch gait. The regression model was able to predict which subjects would demonstrate ‘Improved’ and ‘Unimproved’ knee kinematics with over 70% accuracy, and was able to explain approximately 49% of the variance in subjects’ change in knee flexion between gait analyses. We found that improvement in stance phase knee flexion was positively associated with three variables that were drawn from knowledge about the biomechanical contributors to crouch gait: (i) adequate hamstrings lengths and velocities, possibly achieved via hamstrings lengthening surgery, (ii) normal tibial torsion, possibly achieved via tibial derotation osteotomy, and (iii) sufficient muscle strength. [Copyright &y& Elsevier]

Abstract: We have reported that peak hip extension is nearly identical in walking and running, suggesting that anatomical constraints, such as flexor muscle tightness may limit the range of hip extension. To obtain a more mechanistic insight into mobility at the hip and pelvis we examined the lengths of the muscle–tendons units crossing the hip joint. Data defining the three-dimensional kinematics of 26 healthy runners at self-selected walking and running speeds were obtained. These data were used to scale and drive musculoskeletal models using OpenSIM. Muscle–tendon unit (MTU) lengths were calculated for the trailing limb illiacus, rectus femoris, gluteus maximus, and biceps femoris long head and the advancing limb biceps femoris and gluteus maximus. The magnitude and timing of MTU length peaks were each compared between walking and running. The peak length of the right (trailing limb) illiacus MTU, a pure hip flexor, was nearly identical between walking and running, while the maximum length of the rectus femoris MTU, a hip flexor and knee extensor, increased during running. The maximum length of the left (leading limb) biceps femoris was also unchanged between walking and running. Further, the timing of peak illiacus MTU length and peak contralateral biceps femoris MTU length occurred essentially simultaneously during running, at a time during gait when the hamstrings are most vulnerable to stretch injury. This latter finding suggests exploring the role for hip flexor stretching in combination with hamstring stretching to treat and/or prevent running related hamstring injury. [Copyright &y& Elsevier]

Abstract: This study investigated the effect of continual use of augmented low-Dye (ALD) taping on neuromotor control of the lower limb during gait, as well as foot posture and mobility. Twenty-eight females were randomly allocated to wear ALD tape continuously or a no-tape control for a mean 12±2 days. Electromyographic activity from 12 lower limb muscles, three-dimensional motion at the ankle, knee, hip and pelvis (i.e., measures of neuromotor control) and foot posture and mobility was measured before and after the tape or control interventions. For the tape group, arch height ratio (=arch height/distance from heel to first metatarsophalangeal joint line) was greater by 0.006 (95% confidence interval: 0.0002–0.01, p =0.04) following the intervention period, whereas no change was observed for the control group (−0.003 (−0.01–0.004), p =0.36). The difference between groups (0.009 (0.0004–0.02), p =0.04) equated to a 0.16cm increase in arch height for the tape group following continual use of ALD tape. There was no change in neuromotor control of gait following continual use of ALD taping (p >0.05). Continual use of ALD tape for approximately 12 days produced a small change in foot posture, but no alteration in neuromotor control. Previous literature suggests that this increase in arch height is likely to be clinically relevant and may be one factor that contributes to the known efficiency of ALD tape in the treatment of lower extremity pain and injury. [Copyright &y& Elsevier]

Abstract: The contact time (CT) and the ratio between the duration of braking (BP) and propulsion phase (PP) during the support are two mechanical parameters that are relevant for the performance in sprinting. Several different kinematic methods have been used to estimate the BP–PP transition point, with some disagreements among studies. The purpose of this study was to compare three criteria to individuate that point: the maximum knee flexion (KNEEFLEX), the maximum fall of the COM (COMVERT) and the horizontal COM acceleration (COMHORIZ). It was hypothesized that these three events would take place in different instants, representing different moments of the step cycle. The kinematic analysis was performed through stereophotogrammetry on seven male middle-level sprinters (mean±SD height: 180±5 cm; body mass: 75±11 kg; personal best on 100m: 10.96±0.45s). The COMVERT expressed as percentage of CT (mean±SD 31.73±8.29%) was on average strongly anticipated compared to both KNEEFLEX (45.07±3.60%, p <0.01) and COMHORIZ (56.86±8.56%, p <0.01). The ∼12% difference between KNEEFLEX and COMHORIZ was also statistically significant (p <0.01). The 40–60% relative proportion of BP and PP considered to be optimal in the literature, was reflected in this study only by the KNEEFLEX criterion. Given the importance of BP time as a reference parameter to assess the training status and efficacy of training interventions, it looks necessary both from a scientific and applied perspective to consider a standardized criterion to identify the BP–PP transition point. [Copyright &y& Elsevier]

Abstract: Lower limb alignment is important for the internal loading conditions in the knee. In this study, we aimed to evaluate a new imageless, non-invasive method for quantifying frontal plane alignment by direct comparison against CT. To determine the mechanical femoral–tibial angle (mFTA), functional posture analysis was performed in 15 limbs (13 individuals) using previously published methods for the minimisation of skin marker artefact together with the functional identification of joints, and compared against a published regression method. Whilst the average Functional-mFTA (1.3±2.3) was not significantly different (p >0.25) from the CT-mFTA (1.5±2.1), the Regression-mFTA (4.7±5.6) showed a significant error (p <0.01). The Functional-mFTA correlated significantly (R =0.91; p <0.0001), with a small bias (0.3°) and agreed better with the CT-mFTA than the Regression-mFTA (R =0.76; p <0.001), which had a bias of 3.4°. The results demonstrate that the mFTA can be quantified accurately using an imageless, non-invasive functional approach, which also offers greater accuracy over regression methods.These new techniques could provide an accurate, non-invasive approach for quantifying frontal plane alignment, particularly in cases where X-rays may not be available. [Copyright &y& Elsevier]

Abstract: Adapted strategies in rising from a chair occur with muscle weakness. To assess whether muscle weakness caused the strategy change, an experimental simulation was performed that allowed to investigate separately effects of reduced muscle capacity and of strategy change on movement dynamics. It was hypothesized that a sit-to-stand (STS) strategy change spares muscles that become overloaded when muscle weakness develops. Ten healthy females participated; seven of them completed all tests. Muscle weakness causes an increased load-over-capacity ratio. In the present study, this ratio was increased by providing participants with a waist-coat containing 45% of their body mass. Participants performed sit-to-stand manoeuvres with and without added mass; moreover they were instructed to perform two different strategies, the moment-transfer-strategy and the stabilization-strategy. During these STS-tasks sagital 2D-video analysis were made and ground reaction forces (GRF) were measured. Joint moments and powers for ankle, knee and hip joint were calculated. The preferred strategy under the normal condition was the moment-transfer strategy. Increasing the load without adapting the strategy resulted in significantly higher (13%) knee-joint extension moments. Allowing a strategy shift in the loaded condition spared the knee-joint extensors (−6%) and transferred effort to hip-joint extensors (57%) and plantar flexor (67%) muscles. These results suggest that the capacity of knee-joint extensors limits the STS-performance when muscle weakness occurs. [Copyright &y& Elsevier]

Abstract: A cadaver knee simulator has been developed to model surgical transfer of the rectus femoris. The simulator allows knee specimens six degrees of freedom and is capable of modeling both the swing and stance phases of human gait. Experiments were conducted using a mechanical hinge analog of the knee to verify that time, flexion angle, and knee extension force measurements recorded when using the simulator were not influenced by its design or operation. A ballistic double pendulum model was used to model the swing phase of gait, and the contributions of hip and ankle torques and hamstrings cocontraction were included when modeling the stance phase of gait. When modeling swing, range of motion and time to peak knee flexion in swing for the hinge knee were similar to those of in vivo test subjects. Measurements of hinge knee extension force when modeling stance under various biomechanical conditions matched those predicted using an analytical model. Future studies using cadaver knee specimens will apply techniques described in this paper to further our understanding of changes in knee biomechanics caused by rectus femoris transfer surgery. [Copyright &y& Elsevier]

Abstract: Transtibial amputees are at an increased risk of falling compared to age-matched, able-bodied individuals. The aim of this study was to compare the gait patterns of recent amputee fallers vs. non-fallers during level walking by investigating joint kinematics, kinetics and variability of temporal–spatial parameters. Eleven participants (fallers=6; non-fallers=5) walked along a 10-m walkway at their self-selected pace while three-dimensional kinematic and kinetic data were collected. The fallers had a significantly greater first peak vertical GRF (p =0.01) and load rate on the prosthetic limb than the non-fallers (p =0.03). Joint range of motion was similar between the two groups. Joint moment profiles were similar for the ankle and hip, with more noticeable differences at the knee. On the intact limb, the fallers also showed significantly smaller A1 and larger H2 power bursts and greater variability of swing time duration compared to the non-fallers. The non-fallers had a smaller load rate and knee moment that remained extensor suggesting they could make compensatory adjustments to maintain stability on the prosthetic side by modifying muscular demands of the knee extensors. This research suggests that falls prevention and prosthetic rehabilitation programmes should focus on improving knee muscle strength of the prosthetic limb, and eccentric ankle and hip strength of the intact limb, to improve stability and progression, particularly during weight transfer onto single support of the prosthetic limb. [Copyright &y& Elsevier]

Abstract: This study aims to determine optimal locations on the lower limbs for skin-mounted markers representing the tibial segment in three-dimensional (3D) gait analysis. It was predicted that markers located on the anterior tibial crest and malleoli would be least susceptible to soft tissue movement. Ten retro-reflective markers were attached to each tibial segment for 20 participants. Participants performed 10 walking trials and two different range-of-movement tasks (knee flexion/extension and ankle plantarflexion/dorsiflexion). The results showed a subset of four markers with inter-marker pair distances on the tibia have less than 1.6mm variation (standard deviation (S.D.)) during walking. Minimal variation was also found in isolated ROM tasks, where marker pairs showed variability of less than 2.2mm. Other marker locations, the femoral epicondyles and the tibial tuberosity varied up to 4mm during walking and up to 11mm during the isolated ROM tasks. The four marker locations that are optimal for defining the tibia are the proximal anterior tibial crest, the distal anterior tibial crest, the lateral malleolus and the medial malleolus. [Copyright &y& Elsevier]

Abstract: Compensatory mechanisms in below-knee amputee gait are necessary due to the functional loss of the ankle muscles, especially at higher walking speeds when the mechanical energetic demands of walking are greater. The objective of this study was to examine amputee anterior/posterior (A/P) ground reaction force (GRF) impulses and joint kinetics across a wide range of steady-state walking speeds to further understand the compensatory mechanisms used by below-knee amputees. We hypothesized that amputees would rely more on their intact leg to generate greater propulsion relative to the residual leg, which would result in greater GRF asymmetry between legs as walking speed increased. Amputee and control subject kinematic and kinetic data were collected during overground walking at four different speeds. Group (n =14) average amputee data showed no significant differences in braking or propulsive GRF impulse ratios, except the propulsive ratio at 0.9m/s, indicating that the subjects maintained their initial levels of GRF asymmetry when walking faster. Therefore, our hypothesis was not supported (i.e., walking faster does not increase GRF loading asymmetry). The primary compensatory mechanism was greater positive residual leg hip joint power and work in early stance, which led to increased propulsion from the residual leg as walking speed increased. In addition, amputees had reduced residual leg positive knee work in early stance, suggesting increased output from the biarticular hamstrings. Thus, increasing residual leg hip extensor strength and output may be a useful mechanism to reduce GRF loading asymmetry between the intact and residual legs. [Copyright &y& Elsevier]

Abstract: Knee flexion contracture influences the physiological movements in lower extremities and may cause the kinematic changes of the trunk. Our purpose was to investigate static and dynamic changes in trunk kinematics with simulated knee flexion contracture. Ten healthy females averaged 62 years participated in our study. Unilateral knee flexion contractures of 15° and 30° were simulated with a knee brace. Relaxed standing and level walking were measured at our laboratory using a motion analysis system which consisted of five cameras, a force plate, and thirteen retro-reflective markers. Three-dimensional trunk kinematics and vertical knee forces (% Body Weight) with the contractures were compared with those without the contracture. The 15° contracture did not significantly change trunk kinematics. However, the 30° contracture significantly changed the kinematics in each of the following planes. In the coronal plane, the trunk tilted to the contracture side in standing and walking. In the sagittal plane, posterior inclination of the pelvis in standing significantly increased. In addition, anterior inclination of the trunk and pelvis during walking significantly increased. In the axial plane, trunk rotation to the unaffected side significantly decreased during walking. The vertical knee force in the contracture limb decreased, being accompanied by the increase of the force in the unaffected limb during standing and walking. Results of our study suggest that knee flexion contracture significantly influences three-dimensional trunk kinematics during relaxed standing and level walking, and will lead to spinal imbalance. These facts may explain the onset of the “Knee-Spine Syndrome”. [Copyright &y& Elsevier]

Abstract: The importance of knee position for bodily stability is described by some authors, however Biodex Stability System (BSS) trials have not been used to assess the reliability and effects of different knee positions. The purposes of this study were to test the reliability of BSS indices using two knee positions in the measurement protocol (either permitting slight knee flexion or maintaining them locked in total extension) and to compare the BSS indices between these two knee positions. The measurements were taken of the Overall Stability Index (OSI), Anterior–Posterior Stability Index (APSI) and Medial–Lateral Stability Index (MLSI) during a 30s protocol which gradually and automatically increased in difficulty among 21 healthy female subjects (22.8±1.0 years old). The subjects performed four trials which, without visual feedback, permitted knee flexion as well as four trials which did not, in a randomized order. The first two trials in each set were used for familiarization only. Permitting slight flexion yielded better reliability results (OSI Intra-class Correlation Coefficient [ICC]=0.93, APSI ICC=0.90, MLSI ICC=0.89) than maintaining the knee in total extension (OSI ICC=0.88, APSI ICC=0.87, MLSI ICC=0.79), with good agreement in the Bland and Altman test. Moreover, permitted knee flexion in BSS presented better balance stability values for OSI (P =0.001) and APSI (P = 0.024), however the MLSI did not present significant difference between positions (P =0.345). [Copyright &y& Elsevier]

Abstract: Several functional methods to determine joint centers of rotation (CoR) and axes of rotation (AoR) have been reported in the literature. These have previously been compared using noise introduced to marker positions. The current study compares four of these methods under both rigid body and deformable body conditions using a mechanical analog of the lower extremity. In the latter condition, significant inter-marker distance changes were present in patterns directly related to the joint motion. Both hip CoR location and knee AoR location and direction are determined. Results indicate that while all methods produced accurate measures under rigid body conditions (<5mm location and <2° direction), there were many differences between methods in deformable conditions. Under these conditions, the method described by Gamage and Lasenby performed better than the other methods examined. Maximum mean errors for this technique were approximately 1cm for CoR and AoR locations and 1° for AoR direction. [Copyright &y& Elsevier]

Abstract: Introduction: Proprioception is an important mechanism in knee stability and function. After an injury like an anterior cruciate ligament (ACL) rupture changes appear in knee proprioception which play a major role in rehabilitation. There are several methods to measure proprioception; the threshold to detect passive motion (TTDPM) is often used to quantify proprioception. In this study the reliability and validity were tested of an apparatus, which measures the TTDPM based on the Lund technique of Fridén and Roberts (Sweden). Materials and methods: Sixteen healthy participants were tested on both legs, from start position 20° and 40°, towards extension (TE) and flexion (TF). The same measurement was repeated 12 (6–21) days later. Results: An overall mean TTDPM of 0.58° (95% confidence interval CI=0.53–0.62°) was found. Thresholds were different depending on direction of motion and start position. TTDPM in 20° TE (0.51°, CI=0.48–0.56°) and in 40° TF (0.54°, CI=0.50–0.58°) were significantly lower than TTDPM in 40° TE (0.68°, CI=0.63–0.74°) and in 20° TF (0.58°, CI=0.54–0.63°). Thresholds were rising with age. Women had higher thresholds than men. Conclusion: The method is a reliable and valid way to measure proprioception. The next step is to use this method on patients with an ACL-rupture and compare these results with healthy subjects. [Copyright &y& Elsevier]

Abstract: This study examines how lower extremity fatigue of the quadriceps alters gait variables related to slip propensity. Sixteen healthy young adults were recruited to walk across vinyl floor surfaces in states of fatigue and no fatigue. Kinematic and kinetic data were collected using a three-dimensional motion analysis system and force plates. The results indicated a significant increase in both the heel contact velocity and required coefficient of friction and a decrease in the transitional acceleration of the whole body center of mass and peak knee joint moment in the fatigue trials. Thus, suggesting that slip propensity could increase with fatigue. Additionally, there was increased knee flexion and reduced ankle dorsiflexion at the heel contact phase of the gait cycle during fatigue trials. These findings provide new insights into the biomechanical relationship between localized muscle fatigue and gait parameters associated with slip propensity. The present study concluded that localized muscle fatigue affects gait parameters and hence can be considered as a potential risk factor for slip-induced falls. [Copyright &y& Elsevier]

Abstract: Background: Most previous biomechanical studies of Parkinson''s disease (PD) have been restricted to the description of spatiotemporal parameters and certain peak values for angular parameters. The reliability of joint angle curves and comparisons with control data are of major interest in PD, since variability in gait cycle timing is a feature of this pathology. Methods: We used a video motion analysis system to record kinematic, spatiotemporal and angular parameters in 32 ‘off-drug’ PD patients. The reliability of the patients’ lower limb joint angle curves in the sagittal plane were analysed using the intra-class correlation coefficient (ICC), together with fast Fourier transform (FFT) analysis and hierarchical classification for discarding deviant curves. Lastly, we compared average curves (using a mixed model and the bootstrap method) for the less-affected and more-affected sides of PD patients and then compared the patient data with the results from 30 age-matched controls. Results: The ICC-based procedure was easily applicable. Only 9.4% and 12.5% of the patients’ hip and knee curves (respectively) were deemed to be unreliable. However, the PD patients’ very high cycle-to-cycle variability in the sagittal plane ankle curves prevented us from applying to this joint. For the knee joint, the curves for the most disabled patients (who walked at below 0.5m/s) were not reliable. We did not find any differences between the less and more disabled sides. The differences between patient and control curves concerned the double-support time during the stance phase and the time point for maximum knee flexion during the swing phase. Patients and controls differed in terms of the hip extension phase, with lower values in PD. Conclusion: We have developed the use of validated statistic tools for unambiguously comparing PD patients and controls in terms of joint angle curve differences. [Copyright &y& Elsevier]

Abstract: We aimed to determine the repeatability and variation of quantitative gait data in patients with stroke and to compare the subgroups in terms of gait variability. Time–distance and kinematic characteristics of gait were evaluated in 90 inpatients (30 women) with hemiparesis (mean±S.D. age 57.7±12.5 years and time since stroke 5.99±6.46 months). Subgroups were based on “gender”, “side of paresis”, “lesion type”, “motor recovery level”, “sensory status”, “time since stroke” and “walking velocity”. Repeatability was adequate to excellent in all stroke subgroups (ICC range 0.48–0.98). Walking velocity was the most repeatable gait parameter after stroke. Variation in step length was significantly higher in women than in men (CV 16% versus 9%, p <0.05). Slow walkers (walking velocity <0.34m/s) had a higher variation than fast walkers in step length (CV 12.5% versus 7.5%, p <0.01), single support time (CV 11.9% versus 6.3%, p <0.05), peak hip extensions in stance (CV 11.5% versus 3.7%, p <0.01) and knee flexion in swing (CV 11.8% versus 6.5%, p <0.05). In our stroke patients, their age, time since injury, lesion characteristics, impaired proprioception or level of motor recovery had no effect on gait variability. For better interpretation of quantitative gait data, clinicians should consider that variation in step length, single support time, peak hip extension in stance and knee flexion in swing differs according to walking velocity after stroke. [Copyright &y& Elsevier]

Abstract: Hip rotation during gait has traditionally been measured using thigh wand markers. Hip rotation data calculated using thigh wands shows large variability between different laboratories and underestimates the rotation movement. This study investigated effectiveness of a patella marker in tracking hip rotation range of motion in comparison with traditional thigh wands. In controlled trials of isolated hip internal–external rotation, the patella marker detected 98±8% of the actual range of motion, compared with 53±10% for a distal thigh wand and 43±13% for a proximal thigh wand. The patella marker produced the smoothest hip rotation curves and the smallest hip rotation range in walking, and results from the patella marker did not depend on walking speed. These results suggest that the patella marker is less vulnerable to wobbling, inertial effects, and soft tissue movement than traditional thigh wands. The use of patella markers with knee alignment devices may therefore allow for more accurate measurement of hip rotations during clinical gait analysis than is currently possible using traditional thigh wands. [Copyright &y& Elsevier]

Abstract: The greatest population of amputees in developed nations are elderly dysvascular transtibial amputees. Conventional prostheses, e.g. the solid ankle cushioned heel (SACH) foot, create difficulties in walking on inclines. The aim of this study was to analyse the gait characteristics of elderly amputees walking on an incline, through quantitative three-dimensional biomechanical analysis, by comparing them to age-matched controls. Participants walked up and down an inclined (5°) instrumented walkway at a self-selected pace. A Vicon™ System 370 was used to acquire gait data, including temporo-spatial characteristics, ground reaction forces (GRF), electromyography (EMG), kinematics, and kinetics of the lower limb. Compared to the age-matched controls, the amputees demonstrated reduced speed, knee and hip range of motion, hip moments, vertical GRF, along with increased amplitude and periods of muscle activation. The residual limb also had shorter single support stance phase, small stance phase knee moments, and the smallest moments and powers. These differences demonstrate instability in stance of the residual limb. The sources of this instability include the prosthesis’ limited range of ankle motion and ankle power generation, coupled with the residual limb''s limited proprioception and tolerance of force. For these amputees to regain a gait pattern equivalent to their able-bodied counterparts on inclined walkways, they must be equipped with a prosthesis that has a full range of ankle motion and active power generation at the ankle. Prosthesis design and rehabilitation training should also improve the proprioception of their residual limb and increase their tolerance of force through the residual limb. [Copyright &y& Elsevier]

Abstract: Introduction: The adduction moment measured at the knee during gait is important to the study of osteoarthritis. The purpose of this study was to explore the effect of describing the knee adduction moment using three different biomechanical models, and furthermore, how the choice of model affects differences that are identified between asymptomatic and osteoarthritic gait. Methods: Gait was measured for 44 asymptomatic subjects and 44 subjects with moderate osteoarthritis. The adduction moment was calculated and compared using three common biomechanical models: a 2D coordinate system, a 3D tibial coordinate system, and a 3D floating axis coordinate system. Several portions of the gait cycle waveform were compared between the two groups. Results and discussion: It was found that the choice of biomechanical model changes the overall magnitude and shape of the adduction moment waveform (maximum value changed 8–14% and peak value changed 5–17%). Significant differences between the study groups were found for each model applied; but more importantly, the portions of the gait cycle exhibiting the differences depended on the model. Conclusion: These findings support the importance of specifying the knee model and waveform feature used to compare asymptomatic and osteoarthritic groups. The overall magnitude of the adduction moment throughout stance, and the mid-stance adduction moment value were found to differentiate between the two groups regardless of the adduction moment model. [Copyright &y& Elsevier]

Abstract: Abnormal muscle activity in patients with a central neurological disorder is commonly attributed to the underlying condition. This study considered abnormal muscle activity in orthopaedic patients who had no neurological involvement. Thirty-nine patients with a variety of orthopaedic problems underwent gait analysis, which included measurement of passive range of motion at the legs, manual muscle strength testing (MMST), instrumented gait analysis, and surface electromyography (EMG). Abnormal timing and duration of EMG activity was found in 51/77 legs. Muscle weakness was the most important cause of the abnormal EMG activity (p <0.001). However, abnormal muscle activity did not correspond to the joint which was controlled by the weak muscles. The triceps surae muscle, represented by the medial gastrocnemius, was significantly more involved (68.6%). Co-activity of the knee extensors and hamstrings was found in 17% of the affected legs. Three out of the 51 legs showed a continuous activity of the rectus femoris muscle in swing. These findings illustrate mechanisms to compensate for muscle weakness in stance in neurologically intact subjects. [Copyright &y& Elsevier]

Abstract: Axial tibiofemoral joint contact forces were non-invasively determined for two high range of motion (high flexion) squatting activities. An electromagnetic motion tracking system and a non-conductive force platform were used to collect kinematic and kinetic data. An innovative scaling method was used to model subject-specific muscle group moment arms. One subject attained a peak axial tibiofemoral joint contact force of 49.7N/kg during squatting at 149.9° knee flexion. Average joint angles and average axial joint contact forces were calculated for each of the activities in order to facilitate a comparison with stair climbing data. Compared to stair climbing, the maximum average joint contact forces during the squatting activities occurred at significantly higher flexion angles (p <0.05.) The relative simplicity of the method makes it useful for application to large subject groups from diverse regions. The results of this study can be applied to the diagnosis and treatment of pathologies, and to the development of high range of motion (ROM) knee replacements. [Copyright &y& Elsevier]

Abstract: A few investigators have described the movement of the center of pressure (COP) of the ground reaction force and the activation patterns of the lower limb muscles during gait initiation and termination. This study examines the effective rocker (roll-over shape) behavior of the knee–ankle–foot (KAF) system during gait initiation, steady-state walking (i.e. constant speed gait), and gait termination. The KAF roll-over shapes were characterized by transforming COP data of 10 able-bodied subjects from a laboratory-based coordinate system into a leg-based coordinate system. The resulting roll-over shapes (effective rockers) were characterized using a circular arc model. The KAF roll-over shapes exhibit an overall “flexed” orientation during the first step of gait initiation and an “extended” orientation during the last step of gait termination. Understanding the behavior of the anatomical KAF system during gait initiation and termination may aid in the design of prosthetic components, i.e. mechanical devices that replace complete anatomical structures. Prostheses that intend to mimic the overall behavior of physiological KAF systems (biomimetic designs) could be manufactured using approaches that are much simpler than attempting to reconstruct the complexity of the lower limb. [Copyright &y& Elsevier]

Abstract: Background: Most previous work on the use of knee bracing and taping has focussed on sagittal plane movement. However, most bracing and taping techniques aim to modify patellar movement in the coronal and transverse planes. Objective: This study investigated the effect of patellar bracing and taping on the three-dimensional mechanics of the knee during a controlled eccentric step down task. Method: Twelve healthy subjects were asked to conduct a slow step down exercise. The step down was conducted under three randomised conditions: (a) no intervention, (b) neutral patella taping and (c) patellofemoral bracing. A step was constructed to accommodate an AMTI force platform and to produce a step height of 20cm. Kinematic data were collected using a six camera ProReflex motion analysis system. Reflective markers were placed on the foot, shank and thigh using the Calibrated Anatomical Systems Technique (CAST). Results: The patellofemoral brace and taping led to a significant reduction in the maximum coronal and range of torsional knee angles by 5° and 2°, respectively (p =0.030, 0.006). The range of coronal and transverse plane knee moments was also significantly reduced by 0.15Nm/kg and 0.03Nm/kg (p =0.020, 0.0019). The brace was shown to be more effective in the coronal and transverse planes in comparison to taping or no intervention. Conclusion: Bracing and taping appear to offer coronal plane and torsional control of the knee during eccentric step descent. Coronal and transverse plane mechanics should not be overlooked when studying patellofemoral pain. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to investigate the effect of knee pain and total knee replacement (TKR) surgery on the gait stability of knee osteoarthritis (OA) patients compared to controls. Gait spatio-temporal measures, center of mass kinematics and pain levels of 21 TKR subjects and 21 controls (CON) were assessed during level walking and obstacle crossing at two testing periods, pre-surgery (P1) and 6 months post-surgery (P2). The TKR patients reported greater pain and disability than CONs at P1 and P2, walked and negotiated the obstacle more slowly and had a shorter stride length than CONs. After surgery, the TKR center of mass–center of pressure (COM–COP) separation distance and the peak anterior inclination angle were significantly smaller than CONs. Pain was found to be significantly related to sagittal plane measures, but not to similar measures in the frontal plane. The data suggest that total knee replacement surgery and pain affect gait stability predominantly in sagittal plane variables. The TKR subjects used a conservative strategy to manage the COM and COP in the sagittal plane, possibly to reduce the kinetic demands on the involved limb. [Copyright &y& Elsevier]

Abstract: This study quantified the interaction of integrated electromyography (iEMG) obtained from the vastus lateralis and the metabolic energy cost of running (C r), an index to assess running economy, during 90-min prolonged running. The iEMG during running was divided into eccentric (ECC) and concentric (CON) phases using a force platform and a knee-joint goniometer. The ratio of ECC to CON (ECC/CON ratio) significantly decreased during 90-min prolonged running in novice distance runners, which would be explained by an increase in muscle activity during the CON phase of running. The average C r value significantly increased during 90-min prolonged running. The individual''s C r values significantly correlated with the ECC/CON ratio (r =−0.702, P <0.05). These results suggest that changes in the ECC/CON ratio and C r value during prolonged running are associated. [Copyright &y& Elsevier]

Abstract: Objective: To study limitations in function and adjustment strategies in lower limb amputees during obstacle crossing. Design: Observational cohort study. Subjects: Transfemoral and transtibial amputees and able-bodied control subjects. Methods: In a motion analysis laboratory unimpeded and obstacle crossing runs were performed. The subjects stepped over an obstacle of 0.1m height and thickness and 1m width. Outcome measures were gait velocity, hip, knee and ankle joint angles and leading limb preference. Results: Whereas able-bodied and transtibial subjects demonstrated an increase in knee flexion during obstacle crossing compared to unimpeded walking, in transfemoral amputees the opposite was seen, namely a decrease in knee flexion. The lack of knee strategy in transfemoral amputees was compensated by circumduction at the hip on the prosthetic side and plantar flexion of the non-affected ankle. Transtibial amputees preferred to cross the obstacle with the prosthetic limb first, while transfemoral amputees preferred the non-affected limb. Conclusion: The different leading limb strategy in transfemoral and transtibial amputees could be explained by the restricted flexion and propulsion properties of the prosthetic knee. Training of obstacle crossing tasks during rehabilitation and improvement of prosthetic design may contribute to safe obstacle crossing. [Copyright &y& Elsevier]

Abstract: This study investigated the biomechanical strategy adopted by older adults with medial compartment knee osteoarthritis for successful obstacle crossing. Fifteen older adults with bilateral medial compartment knee OA and 15 healthy controls were recruited to walk and cross obstacles of heights of 10%, 20% and 30% of their leg lengths. Kinematic and kinetic data were obtained using a three-dimensional (3D) motion analysis system and forceplates. The groups had comparable walking speeds, toe clearances and horizontal foot–obstacle distances (p >0.05). When the swing toe was above the obstacle, the OA group showed smaller swing knee flexion (p =0.01) and stance hip adduction (p =0.003) and internal rotation (p =0.04). They showed greater swing ankle dorsiflexion (p =0.04) as well as swing-side pelvic listing (p =0.006) and backward rotation (p =0.02). They also exhibited greater peak knee abductor moments (p =0.02) during early stance while adopting similar knee abductor moments (p =0.04) and greater hip abductor moments (p =0.04) when the leading toe was above the obstacle and thereafter. Smaller knee extensor (p <0.004), yet greater hip extensor moments (p <0.04), were found in the OA group throughout the stance phase. People with medial compartment knee OA had acquired different biomechanical strategies to compensate for the compromised function of the diseased knee. [Copyright &y& Elsevier]

Abstract: Human movement analysis still suffers from the weakness of the currently used protocols for data collection and reduction. Reliable data comparisons and precise functional assessment require anatomically based definitions of the reference axes and frames, and therefore careful identification and tracking of the landmarks. When impaired children are analysed, the marker-set and other measurement procedures have to be minimised to reduce the time of the experiment and ensure patient collaboration. A new protocol is proposed for the analysis of pelvis and lower limb motion obtained as a compromise between these two requirements. A marker-set is proposed which involves the attachment of 22 skin markers, the calibration by a pointer of 6 anatomical landmarks, and the identification of the hip joint centre by a prediction approach. Anatomical reference frames and joint rotations are defined according to current recommendations. The protocol was assessed by analysing a single child in several repetitions by different examiners, and a population of 10 healthy children, mean age 9.7-years-old. The entire analysis was repeated after subtraction of the offset by static posture angles. The minimum and maximum means of the standard deviations from five examiners of the same child were respectively 2.1° in pelvic obliquity and 6.8° in knee rotation. The minimum and maximum means of the standard deviations from the 10 healthy children were 2.1° in pelvic obliquity and 9.6° in knee internal–external rotation. The protocol is feasible and allows 3D anatomical-based measurements of segment and joint motion and data sharing according to current standards. [Copyright &y& Elsevier]

Abstract: A new valgus brace was evaluated in 15 patients with medial osteoarthritis of the knee and a varus leg axis. Significant improvement of pain and function were found after 6 weeks of brace treatment. Gait analysis showed that the brace had a tendency of lowering the peak varus moment about the knee. This effect was more profound in the presence of higher initial varus deformity angle of the knee. Furthermore, bracing led to a small decrease of knee extension at the end of the swing phase and an increase of walking velocity. The mechanisms identified by gait analysis in this study may be of clinical importance for future developments in brace treatment. [Copyright &y& Elsevier]

Abstract: Standing balance depends on the effective control of the torques at the ankle, knee, and hip. Stiffness at each joint and feedback proportional to joint angle contributes to these torques and to postural stability. This study examines the interaction of multiple joints on the minimum effective joint stiffnesses needed to maintain quiet standing and determines the inherent patterns of sway motion based on dynamic calculations of a four-link, three-joint, sagittal plane model. The equations of motion for quiet standing are solved to obtain the limits of stability for an individual (75kg, 1.753m tall) considering different combinations of joint stiffness. These calculations demonstrate that the single-link inverted pendulum model provides a less conservative estimate of minimum stiffness. That is, more stiffness is required at each joint to preserve stability when rotation is permitted at the knee and hip joints. Based on these analyses, the well recognized ankle and hip balance strategies appear to correspond to variations of the inherent patterns of motion of the lowest frequency mode. Additional calculations show that the stability decreases with an increase in body mass index. The present results quantify the interaction of the combined active and passive stiffnesses at the ankle, knee, and hip, and identify the minimum conditions needed for quiet standing. These criteria define standing-balance stability thresholds needed to assess the risk of falling and to guide rehabilitation. [Copyright &y& Elsevier]

Abstract: Compared to young adults, older adults exhibit a slower walking speed, smaller step length, shorter swing phase time and decreased range of motion in their lower extremity joints. The underlying mechanisms causing these gait adaptations is not well understood, with various musculoskeletal parameters being put forth as contributing factors, including increased joint stiffness and decreased isometric muscle strength. The objective of this study was to identify the necessary compensatory mechanisms to overcome such musculoskeletal deficits and regain a normal walking pattern. Understanding these mechanisms has important implications for designing effective rehabilitation interventions for older adults that target specific muscle groups and properties (e.g., isometric strength versus joint stiffness) to improve gait performance. Muscle-actuated forward dynamics simulations of normal walking were analyzed to quantify compensatory mechanisms in the presence of muscle weakness in specific muscle groups and increased hip joint stiffness. Of particular importance were the compensatory mechanisms provided by the plantar flexors, which were shown to be able to compensate for many musculoskeletal deficits, including diminished muscle strength in the hip and knee flexors and extensors and increased hip joint stiffness. This importance was further highlighted when a normal walking pattern could not be achieved through compensatory action of other muscle groups when the uniarticular and biarticular plantar flexor strength was decreased as a group. Thus, rehabilitation or preventative exercise programs may consider focusing on increasing or maintaining plantar flexor strength, which appears critical to maintaining normal walking mechanics. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to determine if using similar walking velocities obtained from fractions of the Froude number (N Fr ) and leg length can lead to kinematic and kinetic similarities and lower variability. Fifteen male subjects walked on a treadmill at 0.83 (VS1) and 1.16ms−1 (VS2) and then at two similar velocities (V Sim27 and V Sim37) determined from two fractions of the N Fr (0.27 and 0.37) so that the average group velocity remained unchanged in both conditions (). N Fr can theoretically be used to determine walking velocities proportional to leg lengths and to establish dynamic similarities between subjects. This study represents the first attempt at using this approach to examine plantar pressure. The ankle and knee joint angles were studied in the sagittal plane and the plantar pressure distribution was assessed with an in-shoe measurement device. The similarity ratios were computed from anthropometric parameters and plantar pressure peaks. Dynamically similar conditions caused a 25% reduction in leg joint angles variation and a 10% significant decrease in dimensionless pressure peak variability on average of five footprint locations. It also lead to heel and under-midfoot pressure peaks proportional to body mass and to an increase in the number of under-forefoot plantar pressure peaks proportional to body mass and/or leg length. The use of walking velocities derived from N Fr allows kinematic and plantar pressure similarities between subjects to be observed and leads to a lower inter-subject variability. In-shoe pressure measurements have proven to be valuable for the understanding of lower extremity function. Set walking velocities used for clinical assessment mask the effects of body size and individual gait mechanics. The anthropometric scaling of walking velocities (fraction of N Fr ) should improve identification of unique walking strategies and pathological foot functions. [Copyright &y& Elsevier]

Abstract: Fifty patients with spastic diplegic cerebral palsy were included in this retrospective study which compared visual assessment of gait to three-dimensional (3D) gait analysis. Inter-observer variability was evaluated as well. Inclusion criteria comprehended independent ambulation (i.e. without assistive devices or orthoses). All subjects went through 3D gait analysis at the Gait Analysis Laboratory of the AACD Hospital. Four observers, viewing videotaped gait cycles, evaluated 10 specific points of interest of the cycle: hip flexion at terminal stance; knee flexion at initial contact; knee extension at terminal stance; knee flexion at initial swing; ankle dorsiflexion at initial contact; pelvic obliquity at mid stance; hip adduction at loading response; pelvic rotation; hip rotation at mid stance and foot progression angle, in relation to the lower limb, at mid stance. Their evaluation was then compared to the 3D kinematics data. A statistical analysis of the results was performed using kappa and McNemar''s test in order to determine inter-observer and visual/3D analysis agreement. Results showed that inter-observer agreement was high but on the other hand, only two points of the gait cycle (knee flexion at initial contact and pelvic obliquity) were shown to have been similarly evaluated visually and with the 3D analysis. In conclusion, this study indicates that only knee flexion at initial contact and pelvic obliquity appear to be reliably evaluated on a visual basis alone. Visual observation is therefore inadequate for the evaluation of the other eight selected points of the gait cycle which require some form of quantitative assessment. [Copyright &y& Elsevier]

Abstract: The functionality of movable platforms used in human balance studies is limited as they allow rotations around pre-defined axes, which typically run close to the platform''s surface and so cannot be used to directly investigate control mechanisms of proximal joints. A new six degrees of freedom platform (CAREN, Motek, Amsterdam) is now available which in principle could be programmed to rotate around any axis of rotation. The location of the default axes of rotation for this device are not documented and the algorithm to move the axes has not yet been defined. The purpose of this study was to (1) locate the platform''s default axes of rotation, (2) implement an algorithm for relocating its axes of rotation and (3) evaluate the algorithm. A simplified method was developed to locate the bounding rectangles within which the default axes of rotations were located. The three axes of rotation were found to be at x =1.13±0.69mm, z =−204.22±0.63mm in the roll plane, y =−2.67±0.59mm, z =−211.38±0.63mm in the pitch plane and x =0.43±0.70mm, y =−4.72±0.65mm in the yaw plane (X: left, Y: rear, Z: up), relative to the centre of its surface, with the maximum bounding rectangle of dimensions 2.50mm by 2.42mm. Relocation of the platform''s axes of rotation was achieved by the use of compensatory corrections, which were determined using a translation algorithm. Evaluation of the algorithm involved pitching the platform around three newly defined axes in the sagittal plane, representing the ankle, knee and hip joints. The platform was able to rotate around the new axes while keeping the instantaneous axes of rotation within bounding rectangles of 1.87mm×0.81mm (ankle), 3.04mm×1.23mm (knee), 3.14mm×1.63mm (hip). The ability to overcome the limitation of other moveable platforms makes the CAREN system a valuable tool in research on the role of individual joints in balance. [Copyright &y& Elsevier]

Abstract: Short-leg walking boots offer several advantages over traditional casts. However, their effects on ground reaction forces (GRF) and three-dimensional (3D) biomechanics are not fully understood. The purpose of the study was to examine 3D lower extremity kinematics and joint dynamics during walking in two different short-leg walking boots. Eleven (five females and six males) healthy subjects performed five level walking trials in each of three conditions: two testing boot conditions, Gait Walker (DeRoyal Industries, Inc.) and Equalizer (Royce Medical Co.), and one pair of laboratory shoes (Noveto, Adidas). A force platform and a 6-camera Vicon motion analysis system were used to collect GRFs and 3D kinematic data during the testing session. A one-way repeated measures analysis of variance (ANOVA) was used to evaluate selected kinematic, GRF, and joint kinetic variables (p <0.05). The results revealed that both short-leg walking boots were effective in minimizing ankle eversion and hip adduction. Neither walker increased the bimodal vertical GRF peaks typically observed in normal walking. However, they did impose a small initial peak (<1BW) earlier in the stance phase. The Gait Walker also exhibited a slightly increased vertical GRF during midstance. These characteristics may be related to the sole materials/design, the restriction of ankle movements, and/or the elevated heel heights of the tested walkers. Both walkers appeared to increase the demand on the knee extensors while they decreased the demand of the knee and hip abductors based on the joint kinetic results. [Copyright &y& Elsevier]

Abstract: The goal of the study was to simultaneously obtain accurate kinematic and kinetic data from a total knee arthroplasty (TKA) during level walking, by coupling force plate data with the kinematics of TKA measured by a movable video-fluoroscopic system. Kinematic and kinetic information of a TKA is crucial for the improvement of implant designs and for the increased longevity of the implant components. Instrumented gait analysis, with skin mounted marker tracking and force plates, is a well-established method for the acquisition of kinematic and kinetic data of TKA in vivo and for non-invasive estimation of joint function. However, resultant moments at the knee joint are inaccurate with this method, due to skin movement artifacts. Video-fluoroscopy reduces these inaccuracies by means of the direct tracking of the implant components with X-ray. However this measuring technique carries disadvantages: it provides only kinematic data, and the image intensifier covers a limited field of view. This paper presents a newly developed measuring technique, which enables a more accurate resultant moments calculation for level walking than could be achieved by conventional instrumented gait analysis. [Copyright &y& Elsevier]

Abstract: This investigation utilized a Markov model to investigate the relationship of correlated lower extremity joint fluctuations and the selection of a steady state gait pattern in the young and elderly. Our model simulated the neuromuscular system by predicting the behavior of the joints for the next gait cycle based on the behavior exhibited in the preceding gait cycles. Such dependencies in the joint fluctuations have been noted previously in the literature. We speculated that compared to the young model, the characteristics of the correlated fluctuations in the elderly model would result in the selection of a different steady state gait pattern. The results of our simulation support the notion that correlated fluctuations in the joint kinematics influence the selection of a steady state gait pattern. The steady state gait pattern for the elderly model was dependent the ankle and hip. Conversely, the steady state gait pattern for the young control model was dependent on the behavior of the knee and hip. Based on our model, we suggested that the altered steady state gait patterns observed in the elderly may be due to an altered neuromuscular memory of prior joint behaviors. [Copyright &y& Elsevier]

Abstract: The gait acquisition is an important milestone of motor development. Structural modifications observed during this period add complexity to the process, and the child needs to use appropriate neuromuscular strategies to walk independently. The objective of this study was to document the longitudinal modifications in neuromuscular mechanisms and in functional anthropometric measures during independent gait acquisition in typically developing children. Twelve children were followed for 2 months after gait acquisition, with its initial period documented by the standardized test Alberta Infant Motor Scale. Quantification of the EMG signals of six muscles in the right lower limb allowed the calculation of the co-contraction indexes (CCI) considering pairs of antagonistic muscles, representing the hip, knee and ankle joints. The CCIs were summed up to yield a total index. Anthropometric measures were transformed into gravitational torque (mLg) values for stance and swing phases of gait. Statistical analyses included repeated measures ANOVA models with one factor (week post-acquisition) for the dependent variables mLg and normalized CCI (CCI/mLg). A significant increase was observed in the mLg during the period evaluated both in stance and swing phases (p =0.0001). In addition, there was a decrease in the value of the normalized hip and total CCIs in both phases of gait (p <0.05). The results revealed changes in the neuromuscular mechanisms used by typical children to deal with the demands involved in the process of gait acquisition. [Copyright &y& Elsevier]

Abstract: Knee kinematics after anterior cruciate ligament (ACL) reconstruction is of interest in studies evaluating the effect of training programs. Many studies have addressed knee flexion/extension but not valgus/varus movements. Considering that joint stability is a major concern in ACL reconstruction surgery, movements occurring in the frontal plane of the knee also deserve attention. Knee extensor torque was analyzed by an isokinetic dynamometer and the angular amplitudes and velocities of flexion/extension and valgus/varus movements were analyzed by goniometry during gait 9 months after ACL reconstruction. The analysis was repeated after 3 months of eccentric isokinetic training of the quadriceps in five patients. The gait pattern was also recorded for 10 healthy controls. The knee extensor torque and flexion/extension range of movement during gait increased significantly after training. However, an unexpectedly increased valgus, most pronounced during the swing phase, which may imply adverse effects on the knee, was also observed in the ACL reconstructed knee. The recorded valgus angles may however be overestimated due to crosstalk. Thus, the extent of the increased valgus, as well as the mechanisms involved and the functional and clinical implications, need clarification before eccentric training after ACL reconstruction can be generally recommended. [Copyright &y& Elsevier]

Abstract: Rocker sole shoes are commonly prescribed to diabetic patients with insensate feet. Recent passage of the therapeutic shoe bill has drawn an increased focus to prescription rehabilitative footwear. The purpose of this work is to investigate the dynamics of lower extremity joints (hip, knee and ankle) with the application of a negative heel rocker sole shoe under controlled lab conditions. Forty normal adults volunteered for gait evaluations using controlled baseline and prescription negative heel rocker sole shoes. Three-dimensional motion analysis techniques were used to acquire kinematic and kinetic data using a six-camera Vicon 370 motion system and two AMTI force plates. No significant change in walking speed or stride length was seen with the negative heel rocker shoe, although cadence was increased. The most significant kinematic changes with the application of the negative heel shoe occurred at the ankle in the sagittal plane with increased plantarflexion at terminal stance. Significant hip and knee changes were also noted with increased mid-stance hip extension and knee flexion. The most significant kinetic effects were seen in the transverse plane followed by changes in the sagittal and coronal planes. Changes in power were mostly noted in the sagittal plane. Other statistically significant changes in gait kinematics and kinetics were observed, although the magnitudes and durations were limited and as a result were not considered clinically significant. The study results indicated the negative heel rocker shoe significantly altered proximal joint metrics (hip and knee). The most significant distal joint alterations were seen in sagittal plane ankle kinetics. These kinematic and kinetic changes, along with previously studied effects of pressure relief at the metatarsal heads, should aid medical professionals in prescribing prophylactic footwear. [Copyright &y& Elsevier]

Abstract: Prior knowledge of potentially slippery conditions has been shown to alter normal human gait in slip and fall experiments. Here we quantify the effects of two aspects of prior knowledge – awareness of a possible slip and prior slip experience – on normal gait. Sixty-eight subjects (40F, 28M) each walked over 48 high-friction surfaces (control trials) and 12 low-friction surfaces. Within- and between-subject changes in lower limb muscle activation, gait kinematics and ground reaction forces were analyzed in three non-slip control trials: one before and one after the first unexpected slip exposure, and a third after repeated slip exposures. Subjects knew they might slip in the latter two trials but not the first trial. Twenty subjects slipped during their first low-friction exposure (early slip group), 32 in later low-friction exposures (late slip group), and 16 subjects did not slip at all. Simultaneous changes in awareness and experience between the first two analyzed trials of the early slip group altered the muscle activity in both limbs, reduced the foot and knee angles at heel strike in the slip limb and reduced the ground reaction forces, impulses and utilized friction after heel strike in the slip limb. A change in only awareness between the first two analyzed trials of the late slip group produced the same kinematic changes seen in the early slip group, but only small muscle activity change and no kinetic changes. Subsequent slip experience in the late slip group produced the muscle activation and kinetic changes observed in the early slip group, but no further kinematic changes. These results showed that awareness of a potential slip primarily alters how the slip-limb approaches the floor, whereas prior slip experience primarily alters the anticipatory muscle activation and how the foot interacts with the floor. These muscle, kinematic and kinetic changes were consistent with a more cautious “normal” gait, and can reduce the external validity of slip and fall experiments. [Copyright &y& Elsevier]

Abstract: Soft tissue artefact and anatomical landmark misplacement have been recognized as the most critical sources of error in gait analysis. The double calibration method was recently proposed to compensate for soft tissue artefact in knee kinematics. This compensation method resulted very effective in the absence of anatomical landmark misplacement. The purpose of the present work was to assess the effectiveness of double calibration in reducing the effects of skin motion artefact on knee rotations and translations when anatomical landmark misplacement is present on the thigh and shank. The double calibration method was used to calculate knee kinematics of two subjects while they performed several motor tasks. The results were compared with those from conventional single calibration. The soft tissue artefact propagated to knee kinematics was quantified by simulating different misplacement errors using both single and double calibration. The double calibration method performed much better than the single calibration one in quantifying knee rotations and particularly translations, with misplacement error up to 15mm superimposed on the anatomical coordinates of the epicondyles. If misplacement errors were limited to just 5mm, the double calibration would be effective in providing kinematics accurate enough for orthopaedic biomechanic applications. [Copyright &y& Elsevier]

Abstract: This study compared the effects of a unilateral solid ankle–foot orthosis (AFO), hinged AFO and no AFO (shoe) worn by healthy adults on pelvic angles, lower extremity joint angles, moments and powers, and temporal-spatial gait characteristics during stair locomotion. A convenience sample of 19 healthy adults participated in this repeated measures design with subjects serving as their own controls. Subjects ambulated on stairs wearing a left shoe and either a right solid AFO, hinged AFO or shoe. Kinematic and kinetic data were collected with motion analysis equipment and a force plate for the three conditions. Pelvic angles and right hip, knee and ankle angles, moments and powers during stance were compared to determine differences among the conditions. Subjects wearing either orthosis walked slower during stair locomotion and with a shorter right single limb support time during descent. Sagittal knee and ankle angles, moments and powers were similar in individuals wearing a hinged AFO or shoe during pull-up (PU) in ascent and controlled lowering (CL) in descent. Decreased ankle dorsiflexion angle, plantar flexion power, knee flexion angle and extensor moment were seen in subjects wearing a solid AFO as compared to a hinged AFO during PU in ascent and CL in descent. Findings contributed to understanding how biomechanical changes imposed at the ankle by a unilateral solid AFO resulted in more kinetic and kinematic compensations than the hinged AFO in healthy adults without the confounding effects of neuromuscular impairments. [Copyright &y& Elsevier]

Abstract: To examine the mechanisms underlying return to pre-injury function in individuals with anterior cruciate ligament deficiency (ACL-D), we grouped 15 individuals (18–50 years of age) with ACL-D by functional status and strength (i.e. copers, non-copers and adapters) and compared measures of proprioception, somatosensory evoked potentials and neuromuscular responses to dynamic testing between groups. Seven subjects without ACL-D provided a comparative sample for dynamic balance testing (DBT). DBT consisted of bilateral EMG recordings of anterior tibialis, medial gastrocnemius, medial hamstrings and quadriceps during toes-down platform rotation. Relative latencies and relative amplitudes were calculated. Somatosensory evoked potential (SEPs) testing was based on identifying the presence or absence of the P27 potential. Proprioception was tested using threshold to detection of passive movement (TDPM). Those with the highest level of function, the copers, had a proprioceptive deficit, loss of P27 and altered postural synergies consisting of earlier and larger hamstring activation. Conversely, those with the lowest functional status, the non-copers, had strength and proprioception deficits, intact SEPs and inconsistent postural synergies. These results suggest that changes in central sensory representation may facilitate altered postural synergies that enable return to pre-injury functional status. [Copyright &y& Elsevier]

Abstract: Several studies indicated that walking with an ankle foot orthosis (AFO) impaired third rocker. The purpose of this study was to evaluate the effects of two types of orthoses, with similar goal settings, on gait, in a homogeneous group of children, using both barefoot and shoe walking as control conditions. Fifteen children with hemiplegia, aged between 4 and 10 years, received two types of individually tuned AFOs: common posterior leaf-spring (PLS) and Dual Carbon Fiber Spring AFO (CFO) (with carbon fibre at the dorsal part of the orthosis). Both orthoses were expected to prevent plantar flexion, thus improving first rocker, allowing dorsiflexion to improve second rocker, absorbing energy during second rocker, and returning it during the third rocker. The effect of the AFOs was studied using objective gait analysis, including 3D kinematics, and kinetics in four conditions: barefoot, shoes without AFO, and PLS and CFO combined with shoes. Several gait parameters significantly changed in shoe walking compared to barefoot walking (cadence, ankle ROM and velocity, knee shock absorption, and knee angle in swing). The CFO produced a significantly larger ankle ROM and ankle velocity during push-off, and an increased plantar flexion moment and power generation at pre-swing compared to the PLS (<0.01). The results of this study further support the findings of previous studies indicating that orthoses improve specific gait parameters compared to barefoot walking (velocity, step length, first and second ankle rocker, sagittal knee and hip ROM). However, compared to shoes, not all improvements were statistically significant. [Copyright &y& Elsevier]