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Publications in this journal

• Gender differences in trunk, pelvis and lower limb kinematics during a single leg squat.

  Authors: Valentina Graci, Linda R Van Dillen, Gretchen B Salsich

  Gait & posture.

  The relationship between trunk and lower limb kinematics in healthy females versus males is unclear since trunk kinematics in the frontal and transverse planes have not been systematically examinedThe relationship between trunk and lower limb kinematics in healthy females versus males is unclear since trunk kinematics in the frontal and transverse planes have not been systematically examined with lower limb kinematics. The aim of this study was to investigate the existence of different multi-joints movement strategies between genders during a single leg squat. We expected that compared to males, females would have greater trunk and pelvis displacement due to less trunk control and display hip and knee movement consistent with medial-collapse (i.e. greater hip adduction, hip medial rotation, knee abduction, and knee lateral rotation) on the weight-bearing limb. Nine females and 10 males participated in the study. Kinematic data were collected using an 8-camera, 3D-motion-capture-system. Trunk relative to pelvis, pelvis relative to the laboratory, hip and knee angles in three planes (sagittal, frontal and transverse) were examined at two time events relevant to knee joint mechanics: 45° of knee flexion and peak knee flexion. Females flexed their trunk less than males and rotated their trunk and pelvis toward the weight-bearing limb more than males. Females also displayed greater hip adduction and knee abduction than males. Taken together these results suggest that females and males used different movement strategies during a single leg squat. Females displayed a trunk and pelvic movement pattern that may put them at risk of knee injury and pain.

• Repeatability of a 3D multi-segment foot model protocol in presence of foot deformities.

  Authors: Kevin Deschamps, Filip Staes, Herman Bruyninckx, Ellen Busschots, Giovanni A Matricali, Pieter Spaepen, Christophe Meyer, Kaat Desloovere

  Gait & posture.

  Repeatability studies on 3D multi-segment foot models (3DMFMs) have mainly considered healthy participants which contrasts with the widespread application of these models to evaluate footRepeatability studies on 3D multi-segment foot models (3DMFMs) have mainly considered healthy participants which contrasts with the widespread application of these models to evaluate foot pathologies. The current study aimed at establishing the repeatability of the 3DMFM described by Leardini et al. [3] in presence of foot deformities. Foot kinematics of eight adult participants were analyzed using a repeated-measures design including two therapists with different levels of experience. The inter-trial variability was higher compared to the kinematics of healthy subjects. Consideration of relative angles resulted in the lowest inter-session variability. The absolute 3D rotations between the Sha-Cal and Cal-Met seem to have the lowest variability in both therapists. A general trend towards higher σ(sess)/σ(trial) ratios was observed when the midfoot was involved. The current study indicates that not only relative 3D rotations and planar angles can be measured consistently in patients, also a number of absolute parameters can be consistently measured serving as basis for the decision making process.

• Foot kinematics and loading of professional athletes in American football-specific tasks.

  Authors: Patrick O Riley, Richard W Kent, Tracy A Dierks, W Brent Lievers, Rebecca E Frimenko, Jeff R Crandall

  Gait & posture.

  The purpose of this study was to describe stance foot and ankle kinematics and the associated ground reaction forces at the upper end of human performance in professional football players duringThe purpose of this study was to describe stance foot and ankle kinematics and the associated ground reaction forces at the upper end of human performance in professional football players during commonly performed football-specific tasks. Nine participants were recruited from the spring training squad of a professional football team. In a motion analysis laboratory setting, participants performed three activities used at the NFL Scouting Combine to assess player speed and agility: the 3-cone drill, the shuttle run, and the standing high jump. The talocrural and first metatarsophalangial joint dorsiflexion, subtalar joint inversion, and the ground reaction forces were determined for the load bearing portions of each activity. We documented load-bearing foot and ankle kinematics of elite football players performing competition-simulating activities, and confirmed our hypothesis that the talocrural, subtalar, and metatarsophalangeal joint ranges of motion for the activities studied approached or exceeded reported physiological limits.

• Stair ascent kinematics and kinetics with a powered lower leg system following transtibial amputation.

  Authors: Jennifer M Aldridge, Jordan T Sturdy, Jason M Wilken

  Gait & posture.

  During stair ascent (STA) persons with transtibial amputation (TTA) typically adopt a hip strategy to compensate for the limited ankle motion and joint power that is characteristic of conventionalDuring stair ascent (STA) persons with transtibial amputation (TTA) typically adopt a hip strategy to compensate for the limited ankle motion and joint power that is characteristic of conventional energy storing and returning (ESR) prosthetic feet. The purpose of this investigation was to determine if providing ankle power via a powered prosthetic device (BiOM) normalized STA kinematics and kinetics. Eleven individuals with TTA participated in two STA gait analysis sessions: (1) using an ESR foot, and (2) using the BiOM. Eleven height and weight matched able-bodied controls (CONT) were also assessed. Lower extremity peak kinematic and kinetic values were calculated at a self-selected and controlled cadence (80steps/min). Increased prosthetic limb peak ankle plantarflexion and push-up power were observed while using the BiOM as compared to ESR. Peak ankle power was not significantly different between BiOM and CONT indicating normalization of ankle power generation. However, peak ankle plantarflexion was significantly lower than CONT. Limb asymmetries including greater prosthetic limb hip flexion and power during stance, and decreased prosthetic limb knee power during stance were observed in the BiOM and ESR conditions. The results suggest that the BiOM successfully increased ankle motion and restored ankle power during STA. These differences did not, however, reduce the use of a hip strategy while ascending stairs. Additional device specific training may be necessary to utilize the full benefits of the device.

• Testing single and double limb standing balance performance: Comparison of COP path length evaluation between two devices.

  Authors: Lars Donath, Ralf Roth, Lukas Zahner, Oliver Faude

  Gait & posture.

  Center of pressure (COP) path length evaluation was commonly applied to measure postural sway and usually obtained from gold standard force plates. Thus, we comparatively investigated the feasibleCenter of pressure (COP) path length evaluation was commonly applied to measure postural sway and usually obtained from gold standard force plates. Thus, we comparatively investigated the feasible and less-expensive GKS® balance system (GKS) with the Kistler® force platform (KIS). 34 non-specifically trained but active adults (14 males, 20 females, age: 25.4±4.8 years; weight: 69.3±12.3kg; height: 1.75±0.09m, sports activity: 5.8±3.6hours per week) were randomly tested on both devices during double and single limb stance with opened and closed eyes. Irrespective of the analysed time frame, repeated measures analyses of variances revealed higher path length readings for GKS compared to KIS for 30s (F=6.8, p=0.01) and 10s (F=21.2, p=0.001). Large effect sizes of the COP path length differences between GKS and KIS decreased from easy tasks (double limb, eyes open; d(30-s)=2.55, d(10-s)=2.04) to the most severe task (single limb, eyes closed; d(30-s)=0.02, d(10-s)=0.23). According to Bland and Altman, the limits of agreements indicated a high random variability component (between 29%, double limb, eyes open and 67%, single limb, eyes closed). The overall intraclass correlation coefficients (ICC) across all four standing balance tasks were moderate for the 30 s- (0.57) as well as the 10 s-analysis (0.65). In conclusion, the COP path length displacements obtained from the GKS balance system seem to differ with a considerable random variability from Kistler force platform data. Thus, measurements of the evaluated devices should not be used interchangeably. Further methodological investigations regarding balance measures seem warranted.

• Dual-tasking interferes with obstacle avoidance reactions in healthy seniors.

  Authors: Judith Hegeman, Vivian Weerdesteyn, Bart van den Bemt, Bart Nienhuis, Jacques van Limbeek, Jacques Duysens

  Gait & posture.

  Dual-tasking can lead to falls, as does a deterioration of obstacle avoidance (OA) skills. Hence, it is expected that a combination of both would be even more detrimental, especially when OA isDual-tasking can lead to falls, as does a deterioration of obstacle avoidance (OA) skills. Hence, it is expected that a combination of both would be even more detrimental, especially when OA is time-critical. Previous studies confirmed this expectation, however, due to several limitations in their design it is yet too early to draw any definitive conclusions on the allocation of attentional resources in OA under dual-task conditions. Therefore, attentionally demanding primary and secondary tasks were used with the instruction to perform as well as possible on both tasks. Nineteen healthy senior individuals (60±4.7 years, 8 females) performed an OA task on a treadmill while walking at 3km/h as a single task and combined with an auditory Stroop task. Biceps femoris (BF) muscle response times, OA failure rates and composite scores were used to evaluate the data. Increased OA failure rates (3%, p=0.03) and delayed BF response times (21ms, p<0.001) were found under dual-task conditions. Composite scores were reduced during (p<0.001) and just after obstacle crossing (p=0.003). In conclusion, dual-tasking during time-critical OA affects the motor as well as the cognitive task when subjects are instructed to keep up performance on both tasks. This adds to the evidence indicating an increased risk of tripping or falling when attention is divided during walking in the presence of unexpected obstacles.

• Biomechanical characteristics of stepping in older Tai Chi practitioners.

  Authors: Ge Wu

  Gait & posture.

  This study compared the biomechanical characteristics of stepping in 10 older (aged 55+ years) Tai Chi (TC) practitioners and 10 age-matched non-TC (NTC) controls. Subjects were asked to take a stepThis study compared the biomechanical characteristics of stepping in 10 older (aged 55+ years) Tai Chi (TC) practitioners and 10 age-matched non-TC (NTC) controls. Subjects were asked to take a step on an auditory cue as fast as possible, in the forward and backward directions, and with and without mental distractions, respectively. Stepping characteristics included step initiation time, preparation time for foot off, foot contact time, and step length and width. The results showed that both groups had similar step initiation time, step length and forward step width (p>0.466). Although mental distraction significantly delayed step initiation time and foot contact time, and shortened step length in both groups (p<0.003), TC practitioners had significantly shorter preparation and foot contact time, and wider backward step width than controls regardless of mental distraction (p<0.024). These group differences are in favor of TC practitioners in situations of postural recovery from potential falls, even with mental distractions, and may explain the positive effect of TC practice on fall reduction in older adults.

• Minimal predicted distance: A common metric for collision avoidance during pairwise interactions between walkers.

  Authors: Anne-Hélène Olivier, Antoine Marin, Armel Crétual, Julien Pettré

  Gait & posture.

  This study investigated collision avoidance between two walkers by focusing on the conditions that lead to avoidance manoeuvres in locomotor trajectories. Following the hypothesis of a reciprocalThis study investigated collision avoidance between two walkers by focusing on the conditions that lead to avoidance manoeuvres in locomotor trajectories. Following the hypothesis of a reciprocal interaction, we suggested a mutual variable as a continuous function of the two walkers' states, denoted minimum predicted distance (MPD). This function predicts the risk of collision, and its evolution over time captures the motion adaptations performed by the walkers. By groups of two, 30 walkers were assigned locomotion tasks which lead to potential collisions. Results showed that walkers adapted their motions only when required, i.e., when MPD is too low (<1m). We concluded that walkers are able (i) to accurately estimate their reciprocal distance at the time the crossing will occur, and (ii) to mutually adapt this distance. Furthermore, the study of MPD evolution showed three successive phases in the avoidance interaction: observation where MPD(t) is constant, reaction where MPD(t) increases to acceptable values by adapting locomotion and regulation where MPD(t) reaches a plateau and slightly decreases. This final phase demonstrates that collision avoidance is actually performed with anticipation. Future work would consist in inspecting individual motion adaptations and relating them with the variations of MPD.

• A comparison of hip joint centre localisation techniques with 3-DUS for clinical gait analysis in children with cerebral palsy.

  Authors: Alana Peters, Richard Baker, M E Morris, Morgan Sangeux

  Gait & posture.

  Functional calibration techniques have been proposed as an alternative to regression equations for estimating the position of the hip within the pelvic co-ordinate system for clinical gait analysis.Functional calibration techniques have been proposed as an alternative to regression equations for estimating the position of the hip within the pelvic co-ordinate system for clinical gait analysis. So far validation of such techniques has focussed on healthy adults. This study evaluated a range of techniques based on regression equations or functional calibration procedures techniques in 46 children representative of those attending a major clinical gait analysis service against previously validated 3-D ultrasound techniques for determining the hip joint centre. Best agreement with ultrasound for the position of the hip within the pelvic coordinate system was found for the Harrington equations (mean 14mm, sd 8mm). Sphere fitting (mean≈22mm, sd 11mm) performed better than transformational techniques applied locally (mean≈33mm, sd 12mm) or globally (mean=30mm, sd 14mm). The participants with cerebral palsy showed reduced range of movement compared with healthy adults. Differences between these results and studies modelling the effects of simulated noise on functional techniques can probably be attributed to differences between that noise and the soft tissue displacements that are actually occurring.

• The reasons why stroke patients expend so much energy to walk slowly.

  Authors: G Stoquart, C Detrembleur, T M Lejeune

  Gait & posture.

  BACKGROUND: The energy consumed per covered distance (C) is increased in hemiparetic stroke adults during walking. OBJECTIVE: To ascertain if increased C in stroke patients is a result of increasedBACKGROUND: The energy consumed per covered distance (C) is increased in hemiparetic stroke adults during walking. OBJECTIVE: To ascertain if increased C in stroke patients is a result of increased mechanical work, of decreased efficiency of work production by muscles or of slow walking speed. METHODS: C and mechanical work were computed in 20 patients walking on a force measuring treadmill at speeds ranging from 1kmh(-1) to their own maximum speed (WS(MAX)). Works done by healthy and pathological limbs were computed separately. RESULTS: For hemiparetic patients, C was around 1.7 times greater than normal. When these patients had a slower WS(MAX), they had greater C and mechanical work (r=-0.44 and -0.57, respectively). The increased C was related to the external work performed to lift the center of body mass when the healthy limb was supporting the body weight (r=0.77). CONCLUSIONS: The increase of C in stroke patients is more pronounced when WS(MAX) is slow. Moreover, this increase is related to increased mechanical work done by muscles and is not related to slow walking speed or decreased efficiency. As in healthy subjects, C and external work presented optimum speeds, indicating a preserved pendular mechanism of walking.

• Integrated assessment techniques for linking kinematics, kinetics and muscle activation to early migration: A pilot study.

  Authors: Nienke Wolterbeek, Eric H Garling, Henrica M J van der Linden, Rob G H H Nelissen, Edward R Valstar

  Gait & posture.

  The goal of this pilot study was to develop and test an integrated method to assess kinematics, kinetics and muscle activation of total knee prostheses during dynamic activities, by integratingThe goal of this pilot study was to develop and test an integrated method to assess kinematics, kinetics and muscle activation of total knee prostheses during dynamic activities, by integrating fluoroscopic measurements with force plate, electromyography and external motion registration measurements. Subsequently, this multi-instrumental analysis was then used to assess the relationship between kinematics, kinetics and muscle activation and early migration of the tibial component of total knee prostheses. This pilot study showed that it is feasible to integrate fluoroscopic, kinematic and kinetic measurements and relate findings to early migration data. Results showed that there might be an association between deviant kinematics and early migration in patients with a highly congruent mobile-bearing total knee prosthesis. Patients that showed high levels of coactivation, diverging axial rotations of the insert and a deviant pivot point showed increased migration and might be at higher risk for tibial component loosening. In the future, to confirm our findings, the same integrated measurements have to be performed in larger patient groups and different prosthesis designs.

• Lower limb joints kinematics in essential tremor and the effect of thalamic stimulation.

  Authors: Alfonso Fasano, Jan Herzog, Jan Raethjen, Franziska E M Rose, Jens Volkmann, Daniela Falk, Günther Deuschl

  Gait & posture.

  Following the hypothesis that thalamic deep brain stimulation improves ataxia in patients with essential tremor by modulating the cerebello-thalamo-cortical pathway, we examined the joint kinematicsFollowing the hypothesis that thalamic deep brain stimulation improves ataxia in patients with essential tremor by modulating the cerebello-thalamo-cortical pathway, we examined the joint kinematics of lower limbs during uninterrupted gait in eleven patients who have been treated with bilateral thalamic stimulation for 24.7±20.3 months. Patients were assessed under routine chronic stimulation, supra-therapeutic amplitude, and off stimulation by means of an infrared movement analysis system while walking on a treadmill. Chronic thalamic DBS normalized the highly variable excursion throughout the gait cycle that characterized the subgroup of patients with longest disease duration. Supratherapeutic thalamic DBS amplitude did not reproduce such improvements while, more importantly, it induced ataxic changes of joint excursion. The normalization of kinematic abnormalities argues against the hypothesis of a cerebellar neurodegeneration in ET. Moreover, these results suggest that the beneficial effect of thalamic DBS on ataxic symptoms is limited to a narrow therapeutic window.

• Reliability of gait parameters during treadmill walking in community-dwelling healthy seniors.

  Authors: Oliver Faude, Lars Donath, Ralf Roth, Livia Fricker, Lukas Zahner

  Gait & posture.

  The present study aimed at assessing the between- and within-day-variability of temporal and spatial gait characteristics during treadmill walking in community-dwelling seniors. In 20 active, healthyThe present study aimed at assessing the between- and within-day-variability of temporal and spatial gait characteristics during treadmill walking in community-dwelling seniors. In 20 active, healthy seniors (10 women, 10 men, age: 64.8 (SD 3.2) years, height: 1.70 (0.10)m, weight: 69.7 (10.9)kg, physical activity: 11 (6)hweek(-1)) gait characteristics were assessed on three days in weekly intervals (between-day variability). Either on days two or three, testing was repeated 30min after the initial trial (within-day variability). We determined routine spatio-temporal gait parameters as well as gait variability during 400 steps at a normal walking speed (5.0 (0.4)kmh(-1)) on a one-dimensional ground reaction force measuring treadmill. No significant mean differences occurred in any parameter for between- and within-day comparisons. Between-day ICC were high (ICC≥0.86) for most parameters except for temporal (ICC=0.44) and spatial (ICC=0.22) gait variability. Coefficients of variation (CoV) were also high in the latter parameters (CoV=30.2-36.1%), whereas all other variables showed clearly lower values (CoV<7%). CoV were still lower between days 2 and 3 (CoV<5%). Compared to between-day comparisons, within-day variability was comparable in spatio-temporal gait parameters (CoV<5%, ICC≥0.97) and lower in gait variability parameters (CoV<18%, ICC≥0.72-0.74). In conclusion, most gait parameters were highly reliable during treadmill walking. Changes of less than 10% can be detected with sufficient confidence. Gait variability parameters were less reliable and, thus, should be carefully interpreted.

• Adaptive changes of foot pressure in hallux valgus patients.

  Authors: Jianmin Wen, Qicheng Ding, Zhiyong Yu, Weidong Sun, Qining Wang, Kunlin Wei

  Gait & posture.

  BACKGROUND: Hallux valgus (HV) is one of the most common deformities in podiatric and orthopedic practice. Plantar pressure technology has been widely used in studying the pressure distribution in HVBACKGROUND: Hallux valgus (HV) is one of the most common deformities in podiatric and orthopedic practice. Plantar pressure technology has been widely used in studying the pressure distribution in HV patients for better assessment to plan interventions. However, previous studies produced an array of controversial findings and most of them only focused on the forefoot. METHODS: We examined the dynamic changes of foot pressure of the whole foot with a large-sample investigation (229 patients and 35 controls). Foot pain, which has been largely neglected previously, was used to group the participants. RESULTS: Compared to healthy controls, patients had significantly higher loading of the first and second metatarsals, where the transverse arch usually collapses, and significantly less loading of the hallux. Moreover, forces in most regions reached their maximum late, indicating a slow build-up of loading. Patients shortened the loading duration on their forefoot, loaded more on the medial foot starting from early foot contact, and delayed the medial-to-lateral load transition. Notably, nearly all these changes were more pronounced in patients with pain. CONCLUSIONS: Biomechanical changes in HV patients are not only caused by physical deformity but also by modified neural control strategies, possibly to alleviate discomfort and to accommodate the foot deformity. Our results suggest that dynamic evaluation of the whole foot and consideration of foot pain are necessary for the functional assessment of foot pressure in HV patients. The foot balance changes have important clinical implications.

• The development, preliminary validation and clinical utility of a shoe model to quantify foot and footwear kinematics in 3-D.

  Authors: Emma J Pratt, Mark L Reeves, Jill M van der Meulen, Ben W Heller, Tim R Good

  Gait & posture.

  Functional electrical stimulation (FES) applied to the common peroneal nerve is commonly prescribed to correct both equinus and excessive foot inversion in swing and initial contact. This paperFunctional electrical stimulation (FES) applied to the common peroneal nerve is commonly prescribed to correct both equinus and excessive foot inversion in swing and initial contact. This paper presents the development of a simple shoe model, to allow quantification of 3-D shoe (foot and footwear) kinematics in clinical situations when footwear is required, e.g. with FES systems requiring footswitches. To preliminarily validate the shoe model, barefoot 'normal' adult data (n=11) processed using validated 3-D foot models, were reprocessed with the shoe model. Outputs were compared through calculation of waveform similarity and correlation. Clinical utility of the shoe model is demonstrated through the presentation of 3-D shoe kinematics, calculated from a cohort of existing unilateral common peroneal FES users (n=16), both with and without FES. A trend of reduced inversion at mid-swing and initial contact was seen, although this was not found to be statistically significant (p≤0.0125). The shoe model was found to be practical to use in a clinical environment, and has potential to contribute to the evidence base for interventions such as common peroneal FES.

• Walking velocity and lower limb coordination in hemiparesis.

  Authors: Emilie Hutin, Didier Pradon, Franck Barbier, Bernard Bussel, Jean-Michel Gracies, Nicolas Roche

  Gait & posture.

  BACKGROUND/OBJECTIVE: Gait training at fast speed has been suggested as an efficient rehabilitation method in hemiparesis. We investigated whether maximal speed walking might positively impactBACKGROUND/OBJECTIVE: Gait training at fast speed has been suggested as an efficient rehabilitation method in hemiparesis. We investigated whether maximal speed walking might positively impact inter-segmental coordination in hemiparetic subjects. METHODS: We measured thigh-shank and shank-foot coordination in the sagittal plane during gait at preferred (P) and maximal (M) speed using the continuous relative phase (CRP), in 20 healthy and 27 hemiparetic subjects. We calculated the root-mean square (CRP(RMS)) and its variability (CRP(SD)) over each phase of the gait cycle. A small CRP(RMS) indicates in-phasing, i.e. high level of synchronization between two segments along the gait cycle. A small CRP(SD) indicates high stability of the inter-segmental coordination across gait cycles. RESULTS: Increase from preferred to maximal speed was 57% in healthy and 49% in hemiparetic subjects (difference NS). In healthy subjects, the main change was shank-foot in-phasing at stance (CRP(Shank-Foot/RMS), P, 98±10; M, 67±12, p<0.001). In hemiparetic subjects, we also found shank-foot in-phasing at late stance bilaterally (non-paretic CRP(Shank-Foot/RMS), P, 37±9; M, 29±8, p<0.001; paretic CRP(Shank-Foot/RMS), P, 38±13; M, 32±12, p<0.001), and thigh-shank in-phasing at mid-stance in the non-paretic limb (CRP(Thigh-Shank/RMS), P, 57±9; M, 49±9, p<0.001). CRP(Thigh-Shank) variability diminished in the paretic limb (CRP(Thigh-Shank/SD), P, 18.3±6.3; M, 16.1±5.2, p<0.001). CONCLUSION: During gait velocity increase in hemiparesis, there is improvement of thigh-shank coordination stability in the paretic limb and of shank-foot synchronization at late stance bilaterally, which optimizes the propulsive phase similarly to healthy subjects. These findings may add incentive for rehabilitation clinicians to explore maximal velocity gait training in hemiparesis.

• Spatiotemporal variability during gait initiation in Parkinson's disease.

  Authors: Ryan T Roemmich, Joe R Nocera, Srikant Vallabhajosula, Shinichi Amano, Kelly M Naugle, Elizabeth L Stegemöller, Chris J Hass

  Gait & posture.

  During gait initiation (GI), consistency of foot placement while stepping is important in making successful transitions from a state of stable static posture to an unstable state of dynamicDuring gait initiation (GI), consistency of foot placement while stepping is important in making successful transitions from a state of stable static posture to an unstable state of dynamic locomotion. In populations characterized by gait dysfunction and postural instability, such as persons with Parkinson's disease (PD), the ability to generate a consistent stepping pattern during GI may be essential in the prevention of falls. However, little is known about GI variability in persons with PD as compared to their healthy elderly peers. Therefore, this study investigated spatiotemporal variability during the first two steps of GI in 46 persons with idiopathic PD and 49 healthy age-matched adults. Stepping characteristics, including the length, width, and time of the first two steps of GI as well as their coefficients of variation (CV) were compared between groups. Persons with PD initiated gait with significantly shorter steps (swing step length=.463 vs. .537m, stance step length=.970 vs. 1.10m) and higher variability in step length (swing step CV=8.82 vs. 5.45, stance step CV=6.76 vs. 3.61). Persons with PD also showed significantly higher variability in the time of the swing step (swing step CV=10.0 vs. 7.4). GI variability did not differ significantly between disease stages in persons with PD. Because greater variability in these measures during gait is related to an increased risk of falls, we propose that higher GI variability may play a considerable role in falls frequently observed during transitions from quiet standing in PD.

• Crouched posture maximizes ground reaction forces generated by muscles.

  Authors: Hoa X Hoang, Jeffrey A Reinbolt

  Gait & posture.

  Crouch gait decreases walking efficiency due to the increased knee and hip flexion during the stance phase of gait. Crouch gait is generally considered to be disadvantageous for children withCrouch gait decreases walking efficiency due to the increased knee and hip flexion during the stance phase of gait. Crouch gait is generally considered to be disadvantageous for children with cerebral palsy; however, a crouched posture may allow biomechanical advantages that lead some children to adopt a crouch gait. To investigate one possible advantage of crouch gait, a musculoskeletal model created in OpenSim was placed in 15 different postures from upright to severe crouch during initial, middle, and final stance of the gait cycle for a total of 45 different postures. A series of optimizations was performed for each posture to maximize transverse plane ground reaction forces in the eight compass directions by modifying muscle forces acting on the model. We compared the force profile areas across all postures. Larger force profile areas were allowed by postures from mild crouch (for initial stance) to crouch (for final stance). The overall ability to generate larger ground reaction force profiles represents a mechanical advantage of a crouched posture. This increase in muscle capacity while in a crouched posture may allow a patient to generate new movements to compensate for impairments associated with cerebral palsy, such as motor control deficits.

• Correlation between anatomic foot and ankle movement measured with MRI and with a motion analysis system.

  Authors: C Marquez-Barrientos, X C Liu, R Lyon, C Tassone, J Thometz, S Tarima

  Gait & posture.

  Several studies have attempted to measure how well external markers track internal bone movement using pins drilled into the foot, but this is too invasive for the pediatric population. This studySeveral studies have attempted to measure how well external markers track internal bone movement using pins drilled into the foot, but this is too invasive for the pediatric population. This study investigated how well a six segment foot model (6SFM) using external markers was able to measure bone movement in the foot compared to MRI measurements. The foot was moved into different positions using a plastic foot jig and measurements were taken with both systems. The aims were to: (1) Look at the correlation between movement tracked with an Electronic Motion Tracking System (EMTS) and by measurements derived from MRI images, specifically the principal intercept angles (PIAs) which are the angles of intersection between principal axes of inertia of bone volumes. (2) To see how well external motion measured by the 6SFM could predict PIAs. Four bone pairs had their movement tracked: Tibia-Calcaneus, Calcaneus-Cuboid, Navicular-1st Metatarsal, and 1st Metatarsal-Hallux. The results showed moderate correlation between measured PIAs and those predicted at the Tibia-Calcaneus, Navicular-1st Metatarsal, and 1st Metatarsal-Hallux joints. Moderate to high correlation was found between the PIA and movement in a single anatomic plane for all four joints at several positions. The 6SFM using the EMTS allows reliable tracking of 3D rotations in the pediatric foot, except at the Calcaneus-Cuboid joint.

• Regional plantar pressure during walking, stair ascent and descent.

  Authors: Smita Rao, Sylvester Carter

  Gait & posture.

  Regional plantar pressures during stair walking may be injurious in at risk populations. However, limited data are available examining the reliability of plantar pressure data collected during stairRegional plantar pressures during stair walking may be injurious in at risk populations. However, limited data are available examining the reliability of plantar pressure data collected during stair walking. The aims of this study were three fold; to assess the reliability of the plantar pressure data recorded during stair walking, to assess the effects of level ground and stair walking on plantar loading, and to develop regression equations to predict regional plantar pressures in stair walking from those collected on level ground. Fifteen subjects without conditions affecting their ability to walk on level surfaces or stairs were recruited. Each participant performed at least 10 steps in level ground and stair walking while plantar pressure data were recorded in six foot regions. Reliability was assessed using Intraclass Correlation Coefficient. A repeated measures ANOVA was used to assess the effect of activity on plantar pressure, and a linear regression was used to predict forefoot loading during stair walking. A reliability of 0.9 was achieved within 10 steps in all foot regions, with the forefoot requiring fewer steps. Plantar pressures were influenced by both, foot region and activity, with the heel and forefoot regions generally experiencing lower peak pressures and maximal forces during stair walking than level ground walking. The regression equations predicting peak pressure during stair walking accounted for between 37% and 70% of the variance of the stair walking data. These findings establish the reliability of plantar pressure data collected during stair walking. Future studies should investigate these parameters in clinical populations.

• WiiFit™ Plus balance test scores for the assessment of balance and mobility in older adults.

  Authors: Rebecca J Reed-Jones, Sandor Dorgo, Maija K Hitchings, Julia O Bader

  Gait & posture.

  The Nintendo Wii™ is becoming an increasingly popular technology for the training and assessment of balance in older adults. Recent studies have shown promising results for its use in fallThe Nintendo Wii™ is becoming an increasingly popular technology for the training and assessment of balance in older adults. Recent studies have shown promising results for its use in fall prevention. However, it is not clear how scores on the WiiFit™ balance games relate to current standardized tests of balance and mobility. The purpose of this study was to evaluate the relationship between WiiFit™ Plus balance tests, and standardized tests of older adult fitness, balance, mobility, self-reported balance confidence, and visual attention and processing. Results from 34 older adult participants indicate that WiiFit™ balance tests do not correlate well with standardized functional balance, mobility and fitness tests. However, the Wii balance score, as measured by the Basic Balance Test of the WiiFit™, does correlate with visual processing speed as measured by the Useful Field of View (UFOV(®)) test. These results indicate that WiiFit™ balance tests may provide advantageous information supplementary to information obtained through standard functional mobility and balance tests; however, caution should be used when using the WiiFit™ balance tests in isolation. Further research is necessary as these technologies become widely used in clinical and home settings for balance training and assessment.

• The relative contributions of the prosthetic and sound limb to balance control in unilateral transtibial amputees.

  Authors: Carolin Curtze, At L Hof, Klaas Postema, Bert Otten

  Gait & posture.

  In unilateral transtibial amputees maintenance of standing balance is compromised due to the lack of active ankle control in the prosthetic limb. The purpose of this study is to disentangle theIn unilateral transtibial amputees maintenance of standing balance is compromised due to the lack of active ankle control in the prosthetic limb. The purpose of this study is to disentangle the contribution of the prosthetic and sound limb to balance control following waist-pull perturbations. We compared the contribution of the hip and ankle joints to balance control of 15 unilateral transtibial amputees and 13 able-bodied controls after been externally perturbed through release of a pulling force. Perturbations were applied in four different directions. Outcome measure was the proportion of joint moment integrated over time generated by the hip and ankle joints in order to restore static stability after perturbation. Analyses revealed that perturbations in backward/forward direction were recovered mainly by the ankle strategy. The amputees compensated for the absence of active ankle control in the prosthetic limb by increasing the ankle moment in the sound limb. Interestingly, the passive properties of the prosthetic foot contributed to balance control, which has important implications for prosthetic fitting and standing stability in lower limb amputees. Amputees and controls resisted perturbations in medio-lateral direction by generating the necessary hip moments. Finally, these findings are discussed with respect to prosthetic design and rehabilitation processes.

• Balance impairment in people with multiple sclerosis: Preliminary evidence for the Balance Evaluation Systems Test.

  Authors: Jesse V Jacobs, Susan L Kasser

  Gait & posture.

  This study examined the validity of the Balance Evaluation Systems Test (BESTest) to identify balance impairments in people with multiple sclerosis (MS) by evaluating differences in BESTestThis study examined the validity of the Balance Evaluation Systems Test (BESTest) to identify balance impairments in people with multiple sclerosis (MS) by evaluating differences in BESTest performance between people with and without MS. We also assessed the BESTest's validity by correlation with objective measures of postural performance as well as with disease severity and fall status. Thirteen subjects with MS (Expanded Disability Status Scale; EDSS: 0-4.5) and 13 matched subjects without MS were evaluated on the BESTest, asked about fall history, and assessed by force plates and motion capture as they performed laboratory tasks of step initiation, forward leaning to the limits of stability, and postural responses to rotations of the support surface. Compared to subjects without MS, subjects with MS exhibited lower total BESTest scores (mean (95%) score for subjects with MS=91 (83-99); subjects without MS=105 (104-107)) as well as section scores pertaining to mechanical constraints, limits of stability, anticipatory postural adjustments, and gait. BESTest scores significantly correlated with objective laboratory measures of step velocity during step initiation (Pearson r(2)=0.48, P<0.01) as well as center-of-pressure displacements during both the leaning (Pearson r(2)=0.55, P<0.005) and postural-response tasks (Pearson r(2)=0.76, P<0.0001). BESTest total scores were 92% accurate to identify fallers and non-fallers, and BESTest scores significantly correlated with EDSS scores (Spearman's rho=0.85, P<0.0005). Thus, the BESTest provides a valid clinical assessment of balance impairments in people with MS.

• Correlation of radiographic and pedobarograph measurements in planovalgus foot deformity.

  Authors: Muayad Kadhim, Laurens Holmes, Freeman Miller

  Gait & posture.

  Planovalgus foot deformity is common in children with cerebral palsy. Several pathologies contribute to the deformity. It begins with the lateral displacement of the navicular and the talar headPlanovalgus foot deformity is common in children with cerebral palsy. Several pathologies contribute to the deformity. It begins with the lateral displacement of the navicular and the talar head becomes uncovered and prominent in the medial side of the midfoot. The purpose of this study was to assess the correlation between the radiographic and the pedobarographic measurements and the ability to predict foot pressure components using radiographic measurement. The patient sample included 43 patients with cerebral palsy who were ambulatory and had planovalgus foot deformity (76 feet). Medial midfoot pressure showed correlation with talonavicular uncoverage index, talonavicular angle, medial arch angle, Meary angle, and lateral talocalcaneal angle. Heel impulse showed negative correlation with talonavicular uncoverage index and talonavicular angle. Simple linear regression was used to assess the relationship between radiographic and foot pressure component measurements. For every unit change in talonavicular uncoverage index, the predicted value of medial midfoot pressure was [9.9+27 (talonavicular uncoverage index)]. This equation accounted for 17.9% of the changes in the medial midfoot pressure. Tibial foot angle and maximum knee extension also contributed to the heel impulse. The radiographic indices of the planovalgus foot can explain the changes in some foot pressure components.

• Arm training in standing also improves postural control in participants with chronic stroke.

  Authors: Sandy McCombe Waller, Michelle G Prettyman

  Gait & posture.

  PURPOSE: To prove the concept that postural control will improve without specific balance control training during arm training in standing with individuals with chronic stroke. METHODS: NinePURPOSE: To prove the concept that postural control will improve without specific balance control training during arm training in standing with individuals with chronic stroke. METHODS: Nine participants (mean age 64±7) received training involving hand orthotic assisted grasp, reach and release in standing 1h, 3×'s/week for 6weeks. Training focused on task completion with no explicit instructions provided for postural alignment, weight shift or balance strategy. Testing consisted of quantified measures using NeuroCom™ Balance Master, Berg Balance Scale (BBS) and Activities-specific Balance Confidence Scale (ABC). RESULTS: Post training participants demonstrate increased (p<.05) composite stability scores for sensory organization testing (mean 71.55±12.7-75.55±11). Velocity and directional control of COP weight shift improved for all 9 subjects with 6/9 achieving 100% target acquisition. Directional control improved (p<.05) for medial/lateral movements for all speeds and composite score. Anterior/posterior rhythmic weight shifting increased significantly in COP velocity control at moderate and fast velocities and composite score. Increases in mean BBS (p<.01) from 41.33±10.1-46.88±8.03 exceeded the clinically important cutoff for the scale. Balance confidence improved with ABC mean scores 70.22±14.5-79.55±12.86 (p<.05). Seven participants demonstrated changes above the minimally important difference for this scale. CONCLUSIONS: Postural control improved following task oriented arm training in standing without explicit postural control goals, instruction or feedback challenging current training paradigms of isolated postural control training with conscious attention directed to center of pressure location and movement.

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