Gait analysis using a shoe-integrated wireless sensor system.

We describe a wireless wearable system that was developed to provide quantitative gait analysis outside the confines of the traditional motion laboratory. The sensor suite includes three orthogonal accelerometers, three orthogonal gyroscopes, four force sensors, two bidirectional bend sensors, two dynamic pressure sensors, as well as electric field height sensors. The "GaitShoe" was built to be worn in any shoe, without interfering with gait and was designed to collect data unobtrusively, in any environment, and over long periods. The calibrated sensor outputs were analyzed and validated with results obtained simultaneously from the Massachusetts General Hospital, Biomotion Laboratory. The GaitShoe proved highly capable of detecting heel-strike and toe-off, as well as estimating foot orientation and position, inter alia.

Correlated change in upper limb function and motor cortex activation after verum and sham acupuncture in patients with chronic stroke.

BACKGROUND: Acupuncture may improve motor function in patients with chronic hemiparetic stroke, yet the neural mechanisms underlying such an effect are unknown. As part of a sham-controlled, randomized clinical trial testing the efficacy of a 10-week acupuncture protocol in patients with chronic hemiparetic stroke, we examined the relationship between changes in function of the affected upper limb and brain activation using functional magnetic resonance imaging (fMRI). METHODS: Seven (7) chronic hemiparetic stroke patients underwent fMRI and testing of function of the affected upper limb (spasticity and range-of-motion) before and after a 10-week period of verum (N=4) or sham (N=3) acupuncture. The correlation between changes in function of the affected upper limb and brain activation after treatment was tested across patients. RESULTS: We found a significant positive correlation between changes in function of the affected upper limb (spasticity and range of motion) and activation in a region of the ipsilesional motor cortex. Patients treated with verum acupuncture showed a trend toward a greater maximum activation change in this motor cortical area as compared to those treated with sham acupuncture. CONCLUSIONS: Acupuncture may improve function of the affected upper limb in chronic hemiparetic stroke patients by increasing activity in the ipsilesional motor cortex.

Chair rise strategies in older adults with functional limitations.

Studies investigating chair rise (CR) strategies in older adults, including the identification of CR strategies in the clinical setting, are limited. We identified biomechanical differences between CR strategies performed by older adults. The "healthy" momentum transfer (MT), the exaggerated trunk flexion (ETF), and the dominant vertical rise (DVR) CR strategies were observed in 29 women and 17 men (64-88 yr) with functional limitations. The DVR strategy required the greatest knee torque (mean = 12.76 moment-% body weight). Maximum knee torque occurred significantly earlier for the ETF strategy (mean = 47% CR time). Lift-off time was earliest for the ETF strategy (mean = 32% CR time). Peak trunk flexion was the primary distinguishing biomechanical measure for classifying CR strategy. This finding may offer clinicians an easy method of identifying CR strategies during evaluation. Because of DVR and ETF movement timing and torque demands, we conclude that MT is the safest and most preferable CR strategy.

The effects of Tai Chi on bone mineral density in postmenopausal women: a systematic review.

OBJECTIVE: To evaluate the evidence for Tai Chi as an intervention to reduce rate of bone loss in postmenopausal women. DATA SOURCES: Literature search using Medline, Science Citation Index, Cochrane databases, China Biological Medicine Database, and additional manual reference searches of retrieved articles and personal libraries. STUDY SELECTION: Randomized controlled trials (RCTs), prospective cohort studies, and cross-sectional studies that included Tai Chi as an intervention, and had at least 1 outcome related to measurement of bone mineral density (BMD). DATA EXTRACTION: Authors critically reviewed studies, evaluated methodologic quality, and synthesized study results in a summary table. DATA SYNTHESIS: Six controlled studies were identified by our search. There were 2 RCTs, 2 nonrandomized prospective parallel cohort studies, and 2 cross-sectional studies. The 2 RCTs and 1 of the prospective cohort studies suggested that Tai Chi-naive women who participated in Tai Chi training exhibited reduced rates of postmenopausal declines in BMD. Cross-sectional studies suggested that long-term Tai Chi practitioners had higher BMD than age-matched sedentary controls, and had slower rates of postmenopausal BMD decline. No adverse effects related to Tai Chi were reported in any trial. CONCLUSIONS: Conclusions on the impact of Tai Chi on BMD are limited by the quantity and quality of research to date. This limited evidence suggests Tai Chi may be an effective, safe, and practical intervention for maintaining BMD in postmenopausal women. In combination with research that indicates Tai Chi can positively impact other risk factors associated with low BMD (eg, reduced fall frequency, increased musculoskeletal strength), further methodologically sound research is warranted to better evaluate the impact of Tai Chi practice on BMD and fracture risk in postmenopausal women.

Functional vs. strength training in disabled elderly outpatients.

OBJECTIVE: To determine whether high-intensity functional training (FT) or strength training (ST) better enables impairment, disability, and functional gains among disabled community-dwelling elders. DESIGN: Randomized, blinded, prospective clinical trial in a large, tertiary care outpatient rehabilitation department. Fifteen elders (62-85 yrs old) referred for physical therapy with one or more impairments, including lower-limb arthritis, participated in 6 wks of FT (weekly outpatient and three to five times per week of home practice in rapid and correct execution of locomotor activities of daily living, including gait, stepping, and sit to stand) or progressive resistive ST using elastic bands with intensity, therapist contact, and home practice similar to those of FT. RESULTS: Both groups significantly improved their combined lower-extremity strength (hip abduction, ankle dorsiflexion, knee flexion, ankle plantarflexion, and knee extension) (P = 0.003), but no statistical difference between the ST and FT group gains (P = 0.203) was found. Subjects in both interventions improved their gait speed, but the FT group improved more than the ST group (P = 0.001). During chair rise, the FT group improved their maximum knee torque more than the ST group (P = 0.033), indicating that they employed a more controlled and efficient movement strategy. CONCLUSIONS: These data suggest that an intensive FT intervention results in strength improvements of comparable magnitude as those attained from ST and that FT also confers greater improvements in dynamic balance control and coordination while performing daily life tasks.

Acupuncture for upper-extremity rehabilitation in chronic stroke: a randomized sham-controlled study.

OBJECTIVE: To compare the effects of traditional Chinese acupuncture with sham acupuncture on upper-extremity (UE) function and quality of life (QOL) in patients with chronic hemiparesis from stroke. DESIGN: A prospective, sham-controlled, randomized controlled trial (RCT). SETTING: Patients recruited through a hospital stroke rehabilitation program. PARTICIPANTS: Thirty-three subjects who incurred a stroke 0.8 to 24 years previously and had moderate to severe UE functional impairment. INTERVENTIONS: Active acupuncture tailored to traditional Chinese medicine diagnoses, including electroacupuncture, or sham acupuncture. Up to 20 treatment sessions (mean, 16.9) over a mean of 10.5 weeks. MAIN OUTCOME MEASURES: UE motor function, spasticity, grip strength, range of motion (ROM), activities of daily living, QOL, and mood. All outcomes were measured at baseline and after treatment. RESULTS: Intention-to-treat (ITT) analyses found no statistically significant differences in outcomes between active and sham acupuncture groups. Analyses of protocol-compliant subjects revealed significant improvement in wrist spasticity (P<.01) and both wrist (P<.01) and shoulder (P<.01) ROM in the active acupuncture group, and improvement trends in UE motor function (P=.09) and digit ROM (P=.06). CONCLUSIONS: Based on ITT analyses, we conclude that acupuncture does not improve UE function or QOL in patients with chronic stroke symptoms. However, gains in UE function observed in protocol-compliant subjects suggest traditional Chinese acupuncture may help patients with chronic stroke symptoms. These results must be interpreted cautiously because of small sample sizes and multiple, unadjusted, post hoc comparisons. A larger, more definitive RCT using a similar design is feasible and warranted.

Corroboration of in vivo cartilage pressures with implications for synovial joint tribology and osteoarthritis causation.

Pressures on normal human acetabular cartilage have been collected from two implanted instrumented femoral head hemiprostheses. Despite significant differences in subjects' gender, morphology, mobility, and coordination, in vivo pressure measurements from both subjects covered similar ranges, with maximums of 5-6 MPa in gait, and as high as 18 MPa in other movements. Normalized for subject weight and height (nMPa), for free-speed walking the maximum pressure values were 25.2 for the female subject and 24.5 for the male subject. The overall maximum nMPa values were 76.2 for the female subject during rising from a chair at 11 months postoperative and 82.3 for the male subject while descending steps at 9 months postoperative. These unique in vivo data are consistent with corresponding cadaver experiments and model analyses. The collective results, in vitro data, model studies, and now corroborating in vivo data support the self-pressurizing "weeping" theory of synovial joint lubrication and provide unique information to evaluate the influence of in vivo pressure regimes on osteoarthritis causation and the efficacy of augmentations to, and substitutions for, natural cartilage.

Stepping stability: effects of sensory perturbation.

BACKGROUND: Few tools exist for quantifying locomotor stability in balance impaired populations. The objective of this study was to develop and evaluate a technique for quantifying stability of stepping in healthy people and people with peripheral (vestibular hypofunction, VH) and central (cerebellar pathology, CB) balance dysfunction by means a sensory (auditory) perturbation test. METHODS: Balance impaired and healthy subjects performed a repeated bench stepping task. The perturbation was applied by suddenly changing the cadence of the metronome (100 beat/min to 80 beat/min) at a predetermined time (but unpredictable by the subject) during the trial. Perturbation response was quantified by computing the Euclidian distance, expressed as a fractional error, between the anterior-posterior center of gravity attractor trajectory before and after the perturbation was applied. The error immediately after the perturbation (Emax), error after recovery (Emin) and the recovery response (Edif) were documented for each participant, and groups were compared with ANOVA. RESULTS: Both balance impaired groups exhibited significantly higher Emax (p = .019) and Emin (p = .028) fractional errors compared to the healthy (HE) subjects, but there were no significant differences between CB and VH groups. Although response recovery was slower for CB and VH groups compared to the HE group, the difference was not significant (p = .051). CONCLUSION: The findings suggest that individuals with balance impairment have reduced ability to stabilize locomotor patterns following perturbation, revealing the fragility of their impairment adaptations and compensations. These data suggest that auditory perturbations applied during a challenging stepping task may be useful for measuring rehabilitation outcomes.

Comparison of head- and body-velocity trajectories during locomotion among healthy and vestibulopathic subjects.

The optimal strategies for improving locomotor stability in people with vestibulopathy remain unclear. To help identify likely targets for intervention, we sought to determine whether vestibulopathic postural control impairment during locomotor activity was more localized to either the head or the whole body. We used high curvature analysis (HCA) to quantify the smoothness of head- and body-velocity trajectories during repeated stepping in 18 vestibulopathic and 17 healthy subjects. We employed a mixed-model repeated measures analysis of variance to compare differences in head- and body-trajectory HCA scores. Pearson coefficients were used to describe relationships between head- and body-trajectory HCA scores within each group. The results revealed that neither head- nor body-velocity trajectories were relatively more impaired in subjects with vestibulopathy. Importantly, however, the smoothness of head and body trajectories was more strongly related in subjects with vestibulopathy compared with healthy subjects, suggesting that the fundamental motor control impairment produced by vestibulopathy may be related to an abnormal coupling of head and body motion. We discuss implications for locomotor training in patients with vestibulopathy.

Tai Chi and vestibular rehabilitation improve vestibulopathic gait via different neuromuscular mechanisms: preliminary report.

BACKGROUND: Vestibular rehabilitation (VR) is a well-accepted exercise program intended to remedy balance impairment caused by damage to the peripheral vestibular system. Alternative therapies, such as Tai Chi (TC), have recently gained popularity as a treatment for balance impairment. Although VR and TC can benefit people with vestibulopathy, the degree to which gait improvements may be related to neuromuscular adaptations of the lower extremities for the two different therapies are unknown. METHODS: We examined the relationship between lower extremity neuromuscular function and trunk control in 36 older adults with vestibulopathy, randomized to 10 weeks of either VR or TC exercise. Time-distance measures (gait speed, step length, stance duration and step width), lower extremity sagittal plane mechanical energy expenditures (MEE), and trunk sagittal and frontal plane kinematics (peak and range of linear and angular velocity), were measured. RESULTS: Although gait time-distance measures were improved in both groups following treatment, no significant between-groups differences were observed for the MEE and trunk kinematic measures. Significant within groups changes, however, were observed. The TC group significantly increased ankle MEE contribution and decreased hip MEE contribution to total leg MEE, while no significant changes were found within the VR group. The TC group exhibited a positive relationship between change in leg MEE and change in trunk velocity peak and range, while the VR group exhibited a negative relationship. CONCLUSION: Gait function improved in both groups consistent with expectations of the interventions. Differences in each group's response to therapy appear to suggest that improved gait function may be due to different neuromuscular adaptations resulting from the different interventions. The TC group's improvements were associated with reorganized lower extremity neuromuscular patterns, which appear to promote a faster gait and reduced excessive hip compensation. The VR group's improvements, however, were not the result of lower extremity neuromuscular pattern changes. Lower-extremity MEE increases corresponded to attenuated forward trunk linear and angular movement in the VR group, suggesting better control of upper body motion to minimize loss of balance. These data support a growing body of evidence that Tai Chi may be a valuable complementary treatment for vestibular disorders.

Instant of chair-rise lift-off can be predicted by foot-floor reaction forces.

OBJECTIVE: To develop a predictive model of the lift-off event during chair rise in healthy subjects, using foot-floor reaction forces. BACKGROUND: An important event during chair rise is lift-off from the seat: the transition from the inherently stable three-point contact to the unstable two-point contact. There is no consistent or generally agreed upon method for estimating the time of lift-off when an instrumented seat is unavailable. METHODS: Twenty healthy volunteers were divided into a testing set and training set. Each subject performed repeated chair rise trials at different speeds. Seat-floor and foot-floor forces, recorded with two force platforms, were used to develop a model of the lift-off event. RESULTS: The magnitude of the vertical foot-floor reaction at lift-off (F0VF) was linearly related (R2 = 0.71, P < 0.001) to the peak vertical foot-floor reaction force (FMVF). A linear model was developed for the training group, which enabled prediction of lift-off time for the testing group with an absolute average error of 6 ms (about 1 data frame at 150 Hz). The linear model derived for the entire sample was: F0VF = 28.14 + FMVF * (0.6434). CONCLUSIONS: The lift-off event for healthy subjects performing chair rise can be accurately predicted from foot-floor reaction forces, without requiring an instrumented seat.

Knee adduction moment and development of chronic knee pain in elders.

OBJECTIVE: To determine whether the adduction moment at the knee during locomotor activity contributes to the development of future chronic knee pain. METHODS: We studied 132 community-dwelling elders who had undergone a full kinetic and kinematic motion analysis while performing 4 different activities: standing, walking, rising from a chair, and descending stairs. We contacted the participants 3-4 years after their baseline locomotion analysis and identified those who reported no knee pain at the time of motion analysis but who subsequently developed new chronic knee pain at followup. We examined whether the development of new chronic knee pain was associated with higher peak adduction moment at the knee during activities, measured at baseline. RESULTS: Of the 132 elders evaluated in 1995-1996, 118 (89%) were contacted in 1999. Of the 118 contacted, 80 (mean age 75 years; 78% women) had no lower extremity prosthetic joints at baseline, no known underlying inflammatory arthritis at baseline nor followup, and no baseline knee pain. At followup, 7 had developed new chronic knee pain defined as pain or stiffness on most days of the month and with walking 2 blocks or using stairs. Compared with those who did not develop knee pain, those who did develop new chronic knee pain had higher baseline adduction moments for all activities (P = 0.01), ranging from 8% higher during chair rise to 39% higher during stair descent. CONCLUSION: We found that greater adduction moment at the knee during activities contributes to the development of future chronic knee pain. Our results suggest that biomechanical factors may play an important role in the pathogenesis of knee pain and should be studied further.

Can Tai Chi improve vestibulopathic postural control?

OBJECTIVES: To evaluate the rationale and scientific support for Tai Chi as an intervention for vestibulopathy and to offer recommendations for future studies. DATA SOURCES: A computer-aided search, including MEDLINE and Science Citation Index, to identify original Tai Chi studies published in English; relevant references cited in the retrieved articles were also included. STUDY SELECTION: A preliminary screening selected all randomized controlled trials (RCTs), non-RCTs, case-control studies, and case series that included Tai Chi as an intervention and had at least 1 outcome variable relevant to postural stability. DATA EXTRACTION: Authors critically reviewed studies and summarized study designs and outcomes in a summary table. DATA SYNTHESIS: Twenty-four Tai Chi studies met screening criteria. No studies specifically studying Tai Chi for vestibulopathy were found. Collectively, the 24 studies provide sometimes contradictory but generally supportive evidence that Tai Chi may have beneficial effects for balance and postural impairments, especially those associated with aging. Ten RCTs were found, of which 8 provide support that Tai Chi practiced alone, or in combination with other therapies, can reduce risk of falls, and/or impact factors associated with postural control, including improved balance and dynamic stability, increased musculoskeletal strength and flexibility, improved performance of activities of daily living (ADLs), reduced fear of falling, and general improvement in psychologic well-being. Studies using other designs support the results observed in RCTs. CONCLUSIONS: At present, few data exist to support the contention that Tai Chi specifically targets the impairments, functional limitations, disability, and quality of life associated with peripheral vestibulopathy. There are, however, compelling reasons to further investigate Tai Chi for vestibulopathy, in part because Tai Chi appears useful for a variety of nonvestibulopathy etiologic balance disorders, and is safe. Especially needed are studies that integrate measures of balance relevant to ADLs with other psychologic and cognitive measures; these might help identify specific mechanisms whereby Tai Chi can remedy balance disorders.

Recovery from perturbations during paced walking.

The aim of the current study was to develop a safe, standardized, stability test and to explore a set of metrics to characterize the recovery of gait stability in healthy individuals following a single mechanical perturbation during steady locomotion. Balance perturbations were mechanically applied to the right foot of 12 healthy subjects during paced walking by translating a platform embedded in a 12 m walkway diagonally (+45/-135 degrees ) relative to the direction of travel approximately 200 ms after heel strike. We examined the medio-lateral (ML) displacement of the sternum before, during and after the platform translation. Measurements of ML position of the right and left shanks in relation to the position of the sternum were used as step-by-step estimates of the moment arm controlling ML motion of the body. We hypothesized that when gait is perturbed in the single stance phase of the step cycle via a translation of the support surface, a series of steps after the perturbation input will be altered reflecting an effort by the CNS to maintain the center of mass (COM) within the base of support and to stabilize the upper body for continued gait. Specifically, if the foot is perturbed laterally during mid-stance a widening of the upcoming step will occur and if the foot is perturbed medially a narrowing of the upcoming step will occur. This behavior was frequent for most subjects. Recovery of non-perturbation behavior was achieved on the third step after the platform translation. An additional strategy was seen for some subjects during lateral perturbation inputs. Instead of widening the upcoming step, these subjects acquired the support to stabilize the body by putting their left foot down very quickly with minimal change in stance width. The recovery profiles of the sternum, though directionally asymmetric, were similar in shape among subjects and roughly proportional to the magnitude of the platform translation. Five to six steps were required for complete recovery in the subjects tested in this study.

Tai Chi and vestibular rehabilitation effects on gaze and whole-body stability.

Tai Chi (TC) is a comparatively new intervention for peripheral vestibular hypofunction, which is often treated with vestibular rehabilitation (VR). We compared gaze stability (GZS), whole-body stability (WBS) and footfall stability (FFS) during locomotion among 26 people with vestibulopathy (VSP), randomized into two treatment arms (13 TC and 13 VR). Each intervention program was offered for 10 weeks. GZS improved more for VR than for TC, but WBS (and FFS) improved more for TC than for VR. There was a significant relationship between changes in GZS and WBS for the VR subjects (r=0.60, p=0.01), but not for TC subjects. There was a significant relationship between changes in WBS and FFS for both VR (r=0.65, p <0.01) and TC (r=0.58, p=0.02) groups; the relationship disappeared in the VR but not the TC group when controlling for GZS. These findings suggest that VR and TC both benefit patients with VSP but via differing mechanisms. Moreover, these data are the first to test the assumption that improving gaze control among patients with VSP perforce improves postural stability: it does not. We conclude that GZS is most improved in those who receive VR, but that TC improves WBS and FFS without improving GZS, suggesting patients with VSP can rely on non-gaze related mechanisms to improve postural control.

Discriminating age and disability effects in locomotion: neuromuscular adaptations in musculoskeletal pathology.

We identified biomechanical variables indicative of lower extremity dysfunction, distinct from age-related gait adaptations, and examined interrelationships among these variables to better understand the neuromuscular adaptations in gait. Sagittal plane ankle, knee, and hip peak angles, moments, and powers and spatiotemporal parameters were acquired during preferred-speed gait in 120 subjects: 45 healthy young, 37 healthy elders, and 38 elders with functional limitations due to lower extremity musculoskeletal pathology, primarily arthritis. Multiple analysis of covariance with discriminate analysis, adjusted for gait speed, was used to identify the variables discriminating groups. Correlation analysis was used to explore interrelationships among these variables within each group. Healthy elders were discriminated (sensitivity 76%, specificity 82%) from young adults via decreased late-stance ankle plantar flexion angle, increased late-stance knee power absorption, and early-stance hip extensor power generation. Disabled elders were discriminated (sensitivity 74%, specificity 73%) from healthy elders via decreased late-stance ankle plantar flexor moment and power generation, increased early-stance ankle dorsiflexor moment, and late-stance hip flexor moment and power absorption. Relationships among variables showed a higher degree of coupling for the disabled elders compared with the healthy groups, suggesting a reduced ability to alter motor strategies. Our data suggest that, beyond age-related changes, elders with lower extremity dysfunction rely excessively on passive action of hip flexors to provide propulsion in late stance and contralateral ankle dorsiflexors to enhance stability. These findings support a growing body of evidence that gait changes with age and disablement have a neuromuscular basis, which may be informative in a motor control framework for physical therapy interventions.