Joint Excursion Research Articles

Dynamic knee joint stiffness in subjects with a progressive increase in severity of knee osteoarthritis

Background Persons with knee osteoarthritis demonstrate a reduction in knee joint excursion during loading response which is often coupled with a reduction in the moment acting to flex the knee. While these individual kinetic and kinematic changes are well documented, the interaction between changes in joint moment and changes in joint angle (dynamic joint stiffness) is not well understood in persons with knee osteoarthritis. Methods Twelve persons with severe knee osteoarthritis (Kellgren–Lawrence score 4) and 22 persons with moderate knee osteoarthritis (Kellgren–Lawrence scores 2–3) were compared to a healthy control group ( n = 22). Dynamic knee joint stiffness was calculated during loading response and was defined as the slope of the linear regression when joint moment is plotted against joint angle. Group differences were compared at 1.0 m/s, self-selected and fast walking speeds using a one-way ANOVA, as well as a one-way ANCOVA to account for differences in freely chosen walking speed. Differences between speeds were compared using an ANOVA with one repeated measure (walking speed). Findings At all walking speeds, the severe group had significantly higher stiffness, even when accounting for differences in walking speed ( P ⩽ 0.038). A significant increase in dynamic joint stiffness was found for all groups when speed was increased ( P = 0.001). Interpretation Persons with advanced stages of knee osteoarthritis develop higher joint stiffness irrespective of walking speed. While this may be a strategy to overcome knee instability often reported in this population during walking, the potential detrimental effects of higher dynamic joint stiffness should be explored in future research.

Influence of Gravity Compensation on Muscle Activation Patterns During Different Temporal Phases of Arm Movements of Stroke Patients

Background. Arm support to help compensate for the effects of gravity may improve functional use of the shoulder and elbow during therapy after stroke, but gravity compensation may alter motor control. Objective. To obtain quantitative information on how gravity compensation influences muscle activation patterns during functional, 3-dimensional reaching movements. Methods. Eight patients with mild hemiparesis performed 2 sets of repeated reach and retrieval movements, with and without unloading the arm, using a device that acted at the elbow and forearm to compensate for gravity. Electromyographic (EMG) patterns of 6 upper extremity muscles were compared during elbow and shoulder joint excursions with and without gravity compensation. Results. Movement performance was similar with and without gravity compensation. Smooth rectified EMG (SRE) values were decreased from 25% to 50% during movements with gravity compensation in 5 out of 6 muscles. The variation of SRE values across movement phases did not differ across conditions. Conclusions. Gravity compensation did not affect general patterns of muscle activation in this sample of stroke patients, probably since they had adequate function to complete the task without arm support. Gravity compensation did facilitate active arm movement excursions without impairing motor control. Gravity compensation may be a valuable modality in conventional or robot-aided therapy to increase the intensity of training for mildly impaired patients.

Robot Assisted Gait Training With Active Leg Exoskeleton (ALEX)

Gait training of stroke survivors is crucial to facilitate neuromuscular plasticity needed for improvements in functional walking ability. Robot assisted gait training (RAGT) was developed for stroke survivors using active leg exoskeleton (ALEX) and a force-field controller, which uses assist-as-needed paradigm for rehabilitation. In this paradigm undesirable gait motion is resisted and assistance is provided towards desired motion. The force-field controller achieves this paradigm by effectively applying forces at the ankle of the subject through actuators on the hip and knee joints. Two stroke survivors participated in a 15-session gait training study each with ALEX. The results show that by the end of the training the gait pattern of the patients improved and became closer to a healthy subject's gait pattern. Improvement is seen as an increase in the size of the patients' gait pattern, increased knee and ankle joint excursions and increase in their walking speeds on the treadmill.

Gait Training After Stroke: A Pilot Study Combining a Gravity-Balanced Orthosis, Functional Electrical Stimulation, and Visual Feedback

This case report describes the application of a novel gait retraining approach to an individual with poststroke hemiparesis. The rehabilitation protocol combined a specially designed leg orthosis (the gravity-balanced orthosis), treadmill walking, and functional electrical stimulation to the ankle muscles with the application of motor learning principles. The participant was a 58-year-old man who had a stroke more than three years before the intervention. He underwent gait retraining over a period of five weeks for a total of 15 sessions during which the gravity compensation provided by the gravity-balanced orthosis and visual feedback about walking performance was gradually reduced. At the end of five weeks, he decreased the time required to complete the Timed Up and Go test; his gait speed increased during overground walking; gait was more symmetrical; stride length, hip and knee joint excursions on the affected side increased. Except for gait symmetry, all other improvements were maintained one month post-intervention. This case report describes possible advantages of judiciously combining different treatment techniques in improving the gait of chronic stroke survivors. Further studies are planned to evaluate the effectiveness of different components of this training in both the subacute and chronic stages of stroke recovery.

The Effect of Exercise Training in Improving Motor Performance and Corticomotor Excitability in People With Early Parkinson's Disease

Fisher BE, Wu AD, Salem GJ, Song J, Lin C-H, Yip J, Cen S, Gordon J, Jakowec M, Petzinger G. The effect of exercise training in improving motor performance and corticomotor excitability in people with early Parkinson's disease. Objectives To obtain preliminary data on the effects of high-intensity exercise on functional performance in people with Parkinson's disease (PD) relative to exercise at low and no intensity and to determine whether improved performance is accompanied by alterations in corticomotor excitability as measured through transcranial magnetic stimulation (TMS). Design Cohort (prospective), randomized controlled trial. Setting University-based clinical and research facilities. Participants Thirty people with PD, within 3 years of diagnosis with Hoehn and Yahr stage 1 or 2. Interventions Subjects were randomized to high-intensity exercise using body weight–supported treadmill training, low-intensity exercise, or a zero-intensity education group. Subjects in the 2 exercise groups completed 24 exercise sessions over 8 weeks. Subjects in the zero-intensity group completed 6 education classes over 8 weeks. Main Outcome Measures Unified Parkinson's Disease Rating Scales (UPDRS), biomechanic analysis of self-selected and fast walking and sit-to-stand tasks; corticomotor excitability was assessed with cortical silent period (CSP) durations in response to single-pulse TMS. Results A small improvement in total and motor UPDRS was observed in all groups. High-intensity group subjects showed postexercise increases in gait speed, step and stride length, and hip and ankle joint excursion during self-selected and fast gait and improved weight distribution during sit-to-stand tasks. Improvements in gait and sit-to-stand measures were not consistently observed in low- and zero-intensity groups. The high-intensity group showed lengthening in CSP. Conclusions The findings suggest the dose-dependent benefits of exercise and that high-intensity exercise can normalize corticomotor excitability in early PD.

The Effects of Cool Pool Exercise on Gait and Balance in Individuals with Multiple Sclerosis

The altered conduction of impulses from demyelinated neurons can disturb motor functions of people with Multiple Sclerosis (MS). Individuals with MS also experience heat sensitivity, which may exacerbate the neurological symptoms. PURPOSE: The purpose of this study was to examine the effects of a 12-week cool pool exercise program on gait and balance outcomes in individuals with MS. METHODS: 24 individuals with MS were recruited and randomly assigned to two groups. The aquatic group (n=13) participated in a 50-minute cool pool exercise program (82-84° F) 3 times a week for 12 weeks. The control was recommended to exercise at home. Gait variables included spatiotemporal, peak joint angles and joint excursions in the lower extremities. Balance was measured based on the time of a sit-to-stand performance and Biodex balance test scores. All participants walked on a 10-meter walkway at their maximum speed for three trails with 30-second rest in between. The Vicon Motion Analysis system was used to capture and process gait data, applying the Plug-in-Gait model. RESULTS:. A multivariate analysis of variance showed the aquatic group increased cadence, stride length and walking velocity after the 12-week intervention (Ps<.05). Significantly increased peak angles of hip flexion and extension, knee flexion, and ankle dorsi-flexion were found while decreases in hip abduction and external rotation were noted (Ps<.05). Significant improvements were found in the joint excursions in the hip, knee and ankle (Ps<.05). The aquatic group also showed significant reduction in the sit-to-stand time, but no changes in the Biodex balance test scores. No significant improvements were found in the control group. CONCLUSIONS:The study findings suggest that a structured exercise program in the cool pool can help people with MS improve gait and balance. These findings will also assist clinicians to develop evidence-based interventions for individuals with MS or similar neurological disorders.

Effect of Decreases in Joint Excursion on the Torque-Length Relationship and Velocity after Shortening Contractions.

PURPOSE: To compare changes in joint excursion (ROM) with maximum isometric voluntary torque (MVC) and contractile properties at various joint angles, as well as peak shortening velocity following an isotonic dorsiflexion fatiguing task. METHODS: Using a Biodex System 3 dynamometer, seven young men performed fatiguing isotonic (30% MVC through 40° of ROM) dorsiflexion contractions at maximum effort, until ROM was reduced to 60% of baseline (PRE). Fatigue and recovery of ROM, MVC and evoked isometric contractile properties of doublet and 50-Hz tetanus [at long, optimal and short muscle lengths: 30° and 10° plantar flexion (PF), and 10° dorsiflexion (DF), respectively], and velocity were measured at task failure (POST), 0.5, 2, 5, and 10 minutes of recovery (R). RESULTS: ROM at POST decreased to ~55% of the value at PRE (40°), but recovered by R5. At POST, velocity decreased to ~35% of the value at PRE (165 ± 23 deg/s) and recovered at R5, whereas, the decrease in MVC (~70%) relative to PRE (49 ± 9 Nm at 30° PF) was similarly reduced at all joint angles and remained depressed up to R10. Voluntary activation at all angles at PRE (~ 99%) remained high (>92%) at POST and throughout recovery. Doublet torque was depressed at POST for all angles, however the decrease at 10DF (~20% relative to PRE (6 ± 3 Nm)) was greater than the decrease (~60% relative to PRE) for 30PF and 10PF. At POST, 50Hz torque declined similarly for all angles to ~75% of PRE (23 ± 5 Nm) but showed different rates of recovery. That is, at R10, 50-Hz torque for 10DF recovered to ~78% of PRE, whereas 10PF and 30PF recovered to ~88% of PRE. Normalized maximum rates of rise and relaxation of the 50-Hz response declined similarly at POST for all angles (~70% relative to PRE) and recovered by R5. CONCLUSION: The decrease in ROM and shortening velocity following dynamic fatigue recovered quickly, but this was not related to the decrease and incomplete recovery of MVC assessed at short, optimal, and long muscle lengths. Furthermore, 50-Hz tetanus maximum rates of rise and relaxation appeared closely related to the recovery in ROM. Results indicate that peripheral mechanisms impairing dynamic crossbridge function were related to failures in ROM and velocity with dynamic fatigue. Supported by NSERC and OGS.

Effects of Fear of Movement on Spine Velocity and Acceleration After Recovery From Low Back Pain

A cross-sectional assessment of the association between pain-related fear and joint motions and their higher order derivatives in 88 participants recently recovered from an episode of low back pain. To determine how the psychological construct of pain-related fear maps to motor behavior in standardized reaching tasks. Pain-related fear is a significant predictor of avoidance behavior and occupational disability in individuals with low back pain. However, it is not currently known how pain-related fear maps to motor behavior. Participants were tested at 4 weeks (+/-2 weeks) after resolution of a recent episode of back pain. Participants performed reaching tasks at comfortable and fast-paced movement speeds to 3 targets (high, middle, low) located in a midsagittal plane. Three-dimensional joint motions of the thoracic spine, lumbar spine, and hip were recorded using an electromagnetic tracking device. Group differences in joint excursions, peak velocities, and accelerations were assessed using 2-group (high pain-related fear, low pain-related fear) x 2-hand (left, right) x 2-movement speed (comfortable-pace, fast-pace) x 3-target height (high, middle, low) multivariate analyses of variances. Individuals with high pain-related fear had smaller peak velocities and accelerations of the lumbar spine and hip joints for the fast-pace reaching trials. The present study provides important evidence that pain-related fear is a robust construct that clearly maps on to differences in peak velocity and acceleration of the lumbar spine even after resolution of back pain.

The relationship between pain-related fear and lumbar flexion during natural recovery from low back pain

Pain-related fear has been associated with avoidance behavior and increased risk for chronic low back pain; however, few studies have examined how pain-related fear relates specifically to motion of the spine following an acute episode of back pain. Thirty-six participants with a recent episode of low back pain were recruited from the general population using a combination of fliers and radio advertisements. To explore the natural recovery from low back pain we recruited individuals who were not seeking medical care. Participants performed a forward bending task at 3, 6, and 12 weeks following onset of low back pain. Three-dimensional joint motions of the spine and hip were recorded using an electromagnetic tracking device. Initial assessments of low back pain and pain-related fear were then correlated with joint excursions observed during each forward bending. Lumbar motion was inversely related to pain-related fear, but not low back pain, at all three testing sessions. In contrast, hip motion was inversely related to pain at all three testing sessions but was not related to fear. These findings suggest that pain-related fear results in avoidance behavior that specifically limits or restricts motion of the lumbar spine.

Kinematics and muscle activity of individuals with incomplete spinal cord injury during treadmill stepping with and without manual assistance

BackgroundTreadmill training with bodyweight support and manual assistance improves walking ability of patients with neurological injury. The purpose of this study was to determine how manual assistance changes muscle activation and kinematic patterns during treadmill training in individuals with incomplete spinal cord injury.MethodsWe tested six volunteers with incomplete spinal cord injury and six volunteers with intact nervous systems. Subjects with spinal cord injury walked on a treadmill at six speeds (0.18–1.07 m/s) with body weight support with and without manual assistance. Healthy subjects walked at the same speeds only with body weight support. We measured electromyographic (EMG) and kinematics in the lower extremities and calculated EMG root mean square (RMS) amplitudes and joint excursions. We performed cross-correlation analyses to compare EMG and kinematic profiles.ResultsNormalized muscle activation amplitudes and profiles in subjects with spinal cord injury were similar for stepping with and without manual assistance (ANOVA, p > 0.05). Muscle activation amplitudes increased with increasing speed (ANOVA, p < 0.05). When comparing spinal cord injury subject EMG data to control subject EMG data, neither the condition with manual assistance nor the condition without manual assistance showed a greater similarity to the control subject data, except for vastus lateralis. The shape and timing of EMG patterns in subjects with spinal cord injury became less similar to controls at faster speeds, especially when walking without manual assistance (ANOVA, p < 0.05). There were no consistent changes in kinematic profiles across spinal cord injury subjects when they were given manual assistance. Knee joint excursion was ~5 degrees greater with manual assistance during swing (ANOVA, p < 0.05). Hip and ankle joint excursions were both ~3 degrees lower with manual assistance during stance (ANOVA, p < 0.05).ConclusionProviding manual assistance does not lower EMG amplitudes or alter muscle activation profiles in relatively higher functioning spinal cord injury subjects. One advantage of manual assistance is that it allows spinal cord injury subjects to walk at faster speeds than they could without assistance. Concerns that manual assistance will promote passivity in subjects are unsupported by our findings.

Digital goniometric measurement of knee joint motion. Evaluation of usefulness for research settings and clinical practice

An accurate and reproducible measurement method for joint motion is essential for classification of success or failure in therapeutic intervention. Digital goniometry is increasingly used as a method of classification for knee joint excursion. The reliability of goniometry however remains debatable. Aim of the study was to determine both intra- and inter-rater reproducibility in degrees, with an electronic digital inclinometer (EDI 320) for active and passive maximum flexion and active maximum extension of the knee joint and to determine the reproducibility of active and passive range of motion. A classical crossover design, with strict measurement protocol was used. Two raters measured 72 knee motions each, in 42 healthy subjects in four sessions. The smallest detectable difference (SDD) was calculated by using adjusted Bland and Altman plots for each knee excursion. No differences in joint excursions between the sexes were found. Passive maximum flexion showed larger excursions than active maximum flexion with additional higher levels of reproducibility. SDDs for inter-rater comparisons yielded: 0 ± 3.9° for active maximum extension, 0 ± 7.4° for active maximum flexion, 0 ± 6.4° for passive maximum flexion, 0 ± 7.6° for AROM and 0 ± 5.4° for PROM. Intra-rater SDDs showed increased reproducibility by 0.4–1.9°. We conclude that interpretation of knee joint excursions in clinical settings is with these SDDs. Clinical and statistical differences in research settings within these SDDs are not a true difference but should be attributed to measurement error.

Pain-Related Fear Is Associated With Avoidance of Spinal Motion During Recovery From Low Back Pain

A longitudinal assessment of the association between pain-related fear and joint motions in 36 participants with subacute low back pain. To determine how the psychologic construct of pain-related fear maps to motor behavior in standardized reaching tasks. Pain-related fear is a significant predictor of avoidance behavior and occupational disability in individuals with low back pain. However, it is not currently known how pain-related fear maps to motor behavior. Participants with an episode of subacute LBP were tested at 3, 6, and 12 weeks following pain onset. Participants performed reaching tasks at comfortable and fast-paced movement speeds to 3 targets (high, middle, low) located in a midsagittal plane. Three-dimensional joint motions of the thoracic spine, lumbar spine, and hip were recorded using an electromagnetic tracking device. Group differences in joint excursions were assessed using 2 groups (high pain-related fear, low pain-related fear) x 3 times (3, 6, 12 weeks) x 2 movement speeds (comfortable, fast paced) x 3 target heights (high, middle, low) MANOVAs. Individuals with high pain-related fear had smaller excursions of the lumbar spine for reaches to all targets at 3 and 6 weeks, but not at 12 weeks following pain onset. Individuals with high pain-related fear adopt alternative movement strategies and avoid motion of the lumbar spine when performing a common reaching movement. Identifying how pain-related fear maps to actual motor behavior (i.e., alternative movement strategies) is a crucial first step in determining how pain-related fear and motor behavior interact to promote or delay recovery from acute low back pain.

Differences in Knee Kinematics during Single and Both Limb Athletic Tasks

Anterior cruciate ligament (ACL) injuries often occur during single limb landing or cutting. However, research studies investigating ACL biomechanics often analyze tasks involving both limbs. There are few studies that have examined the differences between knee kinematics during single and both limb tasks. PURPOSE: To identify screening tests as well as the mechanism of ACL injury estimated by single and both limb athletic tasks. METHODS: Twenty four female collegiate basketball and lacrosse athletes participated in this study. IRB approved informed consent was obtained from all subjects. The subjects performed both limb jump-landing, single limb landing and single limb plant-cutting tasks. The tasks were recorded using a high speed (200Hz) motion analysis system. Three dimensional knee motion analysis was used to calculate the differences in peak joint angle and angular joint excursion. ANOVA with repeated measures was performed to compare the differences between the tasks. RESULTS: At the time of foot contact, the position of the knee was in varus rotation during all tasks and in external tibial rotation during single limb tasks. After foot contact, knee valgus and internal tibial rotation increased with time. The peak knee valgus angle was significantly larger in both limb jump-landing compared to single limb landing and plant-cutting (7.1±5.5, −1.2±5.3, −2.6±6.1, respectively; p<0.01). Excursion for internal tibial rotation was significantly larger in single limb landing and plant-cutting compared to both limb jump-landing (21.4±6.4, 26.8±6.8, 12.1±4.8, respectively; p<0.01). CONCLUSION: The most likely mechanism of non-contact ACL injury is internal tibial rotation and valgus rotation of the knee. Both limb jump-landing is an appropriate screening test for knee valgus, however single limb tasks should be used for examining internal tibial rotation.

Asymmetrical shoulder kinematics in children with brachial plexus birth palsy

Shoulder movement patterns differ between limbs of children with unilateral brachial plexus birth palsy. To better understand the interlimb differences we examined the glenohumeral and scapulothoracic joint contributions to arm elevation. Sixteen children with brachial plexus birth palsy, 4-12 years of age participated. Shoulder 3D kinematic data were collected using a magnetic tracking device during arm elevation with the involved and non-involved limbs for three trials each at a fixed rate. Based on maximum arm elevation in the involved limb the children were divided into two groups: group one <or=75 degrees ; and group two >75 degrees . During arm elevation from 15 to 75 degrees the involved limb of group one displayed lower glenohumeral joint excursion than the non-involved and both limbs of group two. Scapular upward rotation was higher in the involved limb of both groups. For group one, the glenohumeral:scapulothoracic ratio for 15-75 degrees arm elevation was lower in the involved (0.6:1) than the non-involved (2.2:1) limb and both limbs of group two: involved (1.7:1); non-involved (1.9:1). During 15-135 degrees arm elevation for group two, the glenohumeral:scapulothoracic ratio was more similar between limbs: involved (1.5:1) and non-involved (2:1). The scapulothoracic joint made a greater contribution to arm elevation than the glenohumeral joint only in the involved limb of group one, altering the scapulohumeral rhythm. Musculoskeletal and neural factors may account for the group and limb differences. Routine 3D kinematic analysis of shoulder joint rotation may aid treatment planning and better quantify outcomes in this group.

Myofascial force transmission and tendon transfer for patients suffering from spastic paresis: A review and some new observations

The current rationale of clinical practice in spastic tendon transfer surgery is based on four assumptions: (1) changes in muscle fiber length (serial number of sarcomeres) determine the available length range and joint excursion, (2) muscle cross-sectional area determines the maximal force output, (3) fiber length and muscle force are invariable functions of muscle length, (4) there is an invariable relation between the elastic force and the active force exerted by the sarcomeres. The validity of these assumptions is discussed. Additionally, some new perspectives in muscle research are discussed and myofascial force transmission is introduced as a co-determinant for the outcome of tendon transfer by presenting some exploratory observations.

Toy-oriented changes in early arm movements III: Constraints on joint kinematics

The purpose of this study was to identify invariant features of shoulder and elbow kinematics during prereaching arm movements with and without a toy present. Invariant movement features may reflect the presence of constraints that reduce the complexity of learning to reach and provide a link between early arm movements and reaching. Joint excursion and smoothness were consistently greater at the shoulder than the elbow suggesting strong organismal constraints on prereaching movements. Speed became greater in the shoulder than the elbow only with a toy present during the 4 weeks leading up to reach onset suggesting the introduction of task related constraints. We propose that organismal constraints on joint coordination throughout the prereaching period provide a foundation for the overlay of task related constraints closer to reach onset. We also suggest that the coordinative structures of early arm movements and later reaching may be much more similar than currently thought. This similarity would significantly reduce the elements needing to be actively controlled, and simplify the learning process.

The effects of prior exposure, warning, and initial standing posture on muscular and kinematic responses to sudden loading of a hand-held box

Twelve percent of work-related low back injuries have been attributed to sudden loading events. When a sudden load is applied to an object that is held in front of the body, postural responses are rapid, yet it is not clear whether these responses differ with respect to initial posture at the time of loading, or by providing prior exposure to, or warning of a sudden loading event. Thirty male subjects in either an upright or stooped standing posture held a pre-weighted box that was suddenly pulled downwards. Surface electromyography techniques were used to detect onset latencies of seven muscles of the right lower limb and trunk, and two-dimensional motion data in the sagittal plane were simultaneously collected. The first trial involved sudden unexpected loading in the upright standing posture, without any prior experience or warning of the loading event. This was followed by a series of randomised loading trials in the upright and stooped standing posture, with and without prior warning of the loading event. Prior exposure and warning was found to influence postural responses in the upright standing posture, decreasing muscle and joint onset latencies, and resultant maximal angular displacement of the trunk and lower limb. Perturbation in the stooped posture was less reliant on abdominal muscle activation and produced an overall different joint movement initiation pattern, with less joint displacement than in the upright standing position. These findings indicate that prior exposure to, and warning of a sudden loading event lead to changes in postural responses and decreased joint excursion. These changes may contribute to increased stability and decreased risk of musculoskeletal injury.

CHARACTERIZATION AND VALIDATION OF VIRTUAL REALITY WALKING SIMULATOR

Purpose/Hypothesis: Virtual Reality (VR) has been proposed as a strategy for rehabilitation. To measure the potential of new VR devices they need to be characterized and compared to their real world counterparts. The primary purpose of this study was to characterize and validate the gait of individuals who walked on a VR walking simulator (WS) by comparing it to the kinematics and velocity of overground walking. The secondary purpose was to determine if the presence of the virtual environment (VE) modified walking characteristics. We hypothesized that walking velocity would be greater overground and slowest without the VE. Number of Subjects: Ten healthy subjects (2 male and 8 female) ages 24–53 without musculoskeletal injuries or neuromuscular pathology participated. Materials/Methods: Gait step length and velocity were collected (three trials) as participants walked at their self selected speed on a Gait Rite mat. Participants wore a harness and refective markers on the foot, ankle, knee, hip and trunk. They stood on the WS with each foot secured on a robotic platform, a harness attached to an unweighing frame, facing a screen. Unweighed 40% of their body weight they practiced walking on the WS (2–8 min.) until achieving the criterion gait pattern. Data were collected for four street crossing trials, walk without VE (2), walk with VE (2). An auditory tone or the VE green light prompted participants to begin walking. Kinematics were acquired using a 6 camera Peak system at 60 Hz. Joint angles were calculated for push of and initial contact by averaging the peak angle of three steps. Velocity data were averaged from the x-translation plots of the ffth metatarsal. Joint excursions from push of to initial contact-loading response were compared to normative data. Differences between overgound walking velocity and step length relative to the mobility simulator with and without the VE were assessed using a repeated measures ANOVA (alpha level= .05). Results: Walking velocity and step length were significantly greater for overground walking (1.5 m/sec; .79 m) compared with the mobility simulator with (.22 m/sec; .17 m) and without (.21 m/s; .18 m) the VE. The average joint excursions on the mobility simulator for push of to initial contact-loading response were 34 (knee) and 18 (ankle) degrees; compared to a range from push of to initial contact-loading response of 22–40 (knee) and 10–20 (ankle) degrees in normal gait. Conclusions: Walking in the VE resulted in pronounced decreases in temporal distance measures of gait however joint excursions were comparable to normal gait. There were no differences in gait velocity, step length or joint excursions when walking on the mobility simulator with and without the VE. The mechanics of the robot limit step length however, changing street crossing time in the VE may increase walking velocity. Clinical Relevance: Selected aspects of gait were preserved in the WS while others were not. Transfer of training from the walking simulator to real world walking still needs to be determined.

Modular Organization of Finger Movements by the Human Central Nervous System

The motor system may generate automated movements, such as walking, by combining modular spinal motor synergies. However, it remains unknown whether a modular neuronal architecture is sufficient to generate the unique flexibility of human finger movements, which rely on cortical structures. Here we show that finger movements evoked by transcranial magnetic stimulation (TMS) of the primary motor cortex reproduced distinctive features of the spatial representation of voluntary movements as identified in previous neuroimaging studies, consistent with naturalistic activation of neuronal elements. Principal component analysis revealed that the dimensionality of TMS-evoked movements was low. Principal components extracted from TMS-induced finger movements resembled those derived from end-postures of voluntary movements performed to grasp imagined objects, and a small subset of them was sufficient to reconstruct these movements with remarkable fidelity. The motor system may coordinate even the most dexterous movements by using a modular architecture involving cortical components.

Coordination and timing of spine and hip joints during full body reaching tasks

Coupling of spine and hip joints during full body reaching tasks was investigated in 16 participants (8 male and 8 female) who performed reaching tasks at comfortable and fast-paced movement speeds to three targets located in a para-sagittal plane. The participants paused at target contact for 500ms and then returned to an upright posture. Three-dimensional joint motions of the spine and hip were recorded using an electromagnetic tracking device. We found an effect of movement phase (i.e., reach and return) on the onset timing of the spine and hip joints. For most target locations and movement speeds, spine motion onset preceded hip motion onset during the reaching phase of the movement task. In the reach phase, when averaged across all movement conditions, spine joint motion preceded hip joint motion by an average of 48.9ms. In contrast, in the return phase, hip joint motion preceded spine joint motion by an average of 63.0ms. Additionally, when participants were instructed to use either a knee flexion or knee extension strategy to perform the reaching tasks there was no effect of movement strategy on timing of the spine and hip. There was also no effect of target height on the spine–hip ratio, but as movement speed increased, the spine/hip ratio decreased for all target locations due primarily to an increase in hip joint excursion. The findings indicate clear differences in onset timing of the spine and hip joints during reaching tasks that necessitate some forward bending of the trunk and that onset timing is reversed for the return to an upright posture.