Lower trunk motion and speed-dependence during walking

Highlighting Unseen Activity Through 48-Hour Continuous Measurement in Subacute Stroke Rehabilitation: Preliminary Cohort Study

BACKGROUND

Motor impairments not only lead to a significant reduction in patient activity levels but also trigger a further deterioration in motor function due to deconditioning, which is an issue that is particularly pronounced during hospitalization. This deconditioning can be countered by sustaining appropriate activity levels. Activities that occur outside of scheduled programs, often overlooked, are critical in this context. Wearable technology, such as smart clothing, provides a means to monitor these activities.

OBJECTIVE

This study aimed to observe activity levels in patients who had strokes during the subacute phase, focusing on both scheduled training sessions and other nontraining times in an inpatient rehabilitation environment. A smart clothing system is used to simultaneously measure heart rate and acceleration, offering insights into both the amount and intensity of the physical activity.

METHODS

In this preliminary cohort study, 11 individuals undergoing subacute stroke rehabilitation were enrolled. The 48-hour continuous measurement system, deployed at admission and reassessed 4 weeks later, monitored accelerometry data for physical activity (quantified with a moving SD of acceleration [MSDA]) and heart rate for intensity (quantified with percent heart rate reserve). The measurements were performed using a wearable activity monitoring system, the hitoe (NTT Corporation and Toray Industries, Inc) system comprising a measuring garment (wear or strap) with integrated electrodes, a data transmitter, and a smartphone. The Functional Independence Measure was used to assess the patients' daily activity levels. This study explored factors such as differences in activity during training and nontraining periods, correlations with activities of daily living (ADLs) and age, and changes observed after 4 weeks.

RESULTS

A significant increase was found in the daily total MSDA after the 4-week program, with the average percent heart rate reserve remaining consistent. Physical activity during training positively correlated with ADL levels both at admission (ρ=0.86, P<.001) and 4 weeks post admission (ρ=0.96, P<.001), whereas the correlation between age and MSDA was not significant during training periods at admission (ρ=-0.41, P=.21) or 4 weeks post admission (ρ=-0.25, P=.45). Conversely, nontraining activity showed a negative correlation with age, with significant negative correlations with age at admission (ρ=-0.82, P=.002) and 4 weeks post admission (ρ=-0.73, P=.01).

CONCLUSIONS

Inpatient rehabilitation activity levels were positively correlated with ADL levels. Further analysis revealed a strong positive correlation between scheduled training activities and ADL levels, whereas nontraining activities showed no such correlation. Instead, a negative correlation between nontraining activities and age was observed. These observations suggest the importance of providing activity opportunities for older patients, while it may also suggest the need for adjusting the activity amount to accommodate the potentially limited fitness levels of this demographic. Future studies with larger patient groups are warranted to validate and further elucidate these findings.

Clinical study on low-frequency repetitive transcranial magnetic stimulation for the treatment of walking dysfunction following stroke through three-dimensional gait analysis

BACKGROUND

The recovery of walking capacity is of great significance in stroke rehabilitation. We evaluated changes in post-stroke gait function after low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) treatment.

METHODS

Stroke patients were randomly assigned to control (conventional treatment)/LF-rTMS (LF-rTMS treatment based on conventional treatment) groups. Gait spatiotemporal parameters/affected side joint motion angle/affected side dynamic parameters were analyzed by 3D gait analyses. Motor evoked potential (MEP)/central motor conduction time (CMCT) changes were detected. Correlations between MEP latency/CMCT and gait parameters after LF-rTMS were analyzed by Pearson analysis.

RESULTS

The two groups exhibited boosted stride speed/frequency/length, affected side stride length/swing phase percentage/hip/knee/ankle joint plantar flexion angle, and affected side ahead ground reaction force/ upward ground reaction force (AGRF/UGRF)/ankle joint plantar flexion moment, along with reduced affected side gait period/stance phase percentage after treatment, and the LF-rTMS group manifested better efficacy. MEP latency/CMCT of stroke patients treated with LF-rTMS was adversely linked to stride speed, affected side stride length/swing phase percentage/knee flexion angle, AGRF and UGRF, and positively correlated with affected side stance phase percentage.

CONCLUSION

LF-rTMS significantly improved gait spatiotemporal parameters/affected joint motion angles/neurophysiologic parameters (MEP latency/CMCT) in patients with post-stroke walking dysfunction. MEP latency/CMCT after LF-rTMS treatment were prominently correlated with gait parameters. Relative to the traditional scale assessment, we provided a more accurate, objective and reliable evaluation of the effects of LF-rTMS on lower limb mobility and functional recovery effects in stroke patients from the perspective of 3D gait analysis and neurophysiology, which provided more evidence to support the clinical application of LF-rTMS in post-stroke walking dysfunction treatment.

Smartphone Technology to Remotely Measure Postural Sway during Double- and Single-Leg Squats in Adults with Femoroacetabular Impingement and Those with No Hip Pain

BACKGROUND

The COVID-19 pandemic has accelerated the demand for utilising telehealth as a major mode of healthcare delivery, with increasing interest in the use of tele-platforms for remote patient assessment. In this context, the use of smartphone technology to measure squat performance in people with and without femoroacetabular impingement (FAI) syndrome has not been reported yet. We developed a novel smartphone application, the TelePhysio app, which allows the clinician to remotely connect to the patient's device and measure their squat performance in real time using the smartphone inertial sensors. The aim of this study was to investigate the association and test-retest reliability of the TelePhysio app in measuring postural sway performance during a double-leg (DLS) and single-leg (SLS) squat task. In addition, the study investigated the ability of TelePhysio to detect differences in DLS and SLS performance between people with FAI and without hip pain.

METHODS

A total of 30 healthy (nfemales = 12) young adults and 10 adults (nfemales = 2) with diagnosed FAI syndrome participated in the study. Healthy participants performed DLS and SLS on force plates in our laboratory, and remotely in their homes using the TelePhysio smartphone application. Sway measurements were compared using the centre of pressure (CoP) and smartphone inertial sensor data. A total of 10 participants with FAI (nfemales = 2) performed the squat assessments remotely. Four sway measurements in each axis (x, y, and z) were computed from the TelePhysio inertial sensors: (1) average acceleration magnitude from the mean (aam), (2) root-mean-square acceleration (rms), (3) range acceleration (r), and (4) approximate entropy (apen), with lower values indicating that the movement is more regular, repetitive, and predictable. Differences in TelePhysio squat sway data were compared between DLS and SLS, and between healthy and FAI adults, using analysis of variance with significance set at 0.05.

RESULTS

The TelePhysio aam measurements on the x- and y-axes had significant large correlations with the CoP measurements (r = 0.56 and r = 0.71, respectively). The TelePhysio aam measurements demonstrated moderate to substantial between-session reliability values of 0.73 (95% CI 0.62-0.81), 0.85 (95% CI 0.79-0.91), and 0.73 (95% CI 0.62-0.82) for aamx, aamy, and aamz, respectively. The DLS of the FAI participants showed significantly lower aam and apen values in the medio-lateral direction compared to the healthy DLS, healthy SLS, and FAI SLS groups (aam = 0.13, 0.19, 0.29, and 0.29, respectively; and apen = 0.33, 0.45, 0.52, and 0.48, respectively). In the anterior-posterior direction, healthy DLS showed significantly greater aam values compared to the healthy SLS, FAI DLS, and FAI SLS groups (1.26, 0.61, 0.68, and 0.35, respectively).

CONCLUSIONS

The TelePhysio app is a valid and reliable method of measuring postural control during DLS and SLS tasks. The application is capable of distinguishing performance levels between DLS and SLS tasks, and between healthy and FAI young adults. The DLS task is sufficient to distinguish the level of performance between healthy and FAI adults. This study validates the use of smartphone technology as a tele-assessment clinical tool for remote squat assessment.

Age and walking conditions differently affect domains of gait

INTRODUCTION

Analysing gait in controlled conditions that resemble daily life walking could overcome the limitations associated with gait analysis in uncontrolled real-world conditions. Such analyses could potentially aid the identification of a walking condition that magnifies age-differences in gait. Therefore, the aim of the current study was to determine the effects of age and walking conditions on gait performance.

METHODS

Trunk accelerations of young (n = 27, age: 21.6) and older adults (n = 26, age: 68.9) were recorded for 3 min in four conditions: walking up and down a university hallway on a track of 10 m; walking on a specified path, including turns, in a university hallway; walking outside on a specified path on a pavement including turns; and walking on a treadmill. Factor analysis was used to reduce 27 computed gait measures to five independent gait domains. A multivariate analysis of variance was used to examine the effects of age and walking condition on these gait domains.

RESULTS

Factor analysis yielded 5 gait domains: variability, pace, stability, time & frequency, complexity, explaining 64% of the variance in 27 gait outcomes. Walking conditions affected all gait domains (p < 0.01) but age only affected the time & frequency domain (p < 0.05). Age and walking conditions differently affected the domains variability, stability, time & frequency. The largest age-differences occurred mainly during straight walking in a hallway (variability: 31% higher in older adults), or during treadmill walking (stability: 224% higher, time&frequency: 120% lower in older adults).

CONCLUSION

Walking conditions affect all domains of gait independent of age. Treadmill walking and walking on a straight path in a hallway, were the most constrained walking conditions in terms of limited possibilities to adjust step characteristics. The age by condition interaction suggests that for the gait domains variability, stability, and time & frequency, the most constrained walking conditions seem to magnify the age-differences in gait.

Trunk Velocity Changes in Response to Physical Perturbations Are Potential Indicators of Gait Stability

Response to challenging situations is important to avoid falls, especially after medial perturbations, which require active control. There is a lack of evidence on the relationship between the trunk's motion in response to perturbations and gait stability. Eighteen healthy adults walked on a treadmill at three speeds while receiving perturbations of three magnitudes. Medial perturbations were applied by translating the walking platform to the right at left heel contact. Trunk velocity changes in response to the perturbation were calculated and divided into the initial and the recovery phases. Gait stability after a perturbation was assessed using the margin of stability (MOS) at the first heel contact, MOS mean, and standard deviation for the first five strides after the perturbation onset. Faster speed and smaller perturbations led to a lower deviation of trunk velocity from the steady state, which can be interpreted as an improvement in response to the perturbation. Recovery was quicker after small perturbations. The MOS mean was associated with the trunk's motion in response to perturbations during the initial phase. Increasing walking speed may increase resistance to perturbations, while increasing the magnitude of perturbation leads to greater trunk motions. MOS is a useful marker of resistance to perturbations.

The Physical Activity Level of Ophthalmologists at Work: A Pedometer-Based Study

BACKGROUND

Ophthalmology practice entails many hours of physical inactivity, a potential long-term health hazard. This study aims to perform a pedometer-based evaluation of the physical activity (PA) levels of ophthalmologists at work.

METHODS

This is a prospective observational study. Ophthalmologists from a single tertiary medical center were monitored with electronic pedometers during six morning sessions in the ophthalmology clinics. Working hours and the number of patients seen per clinic session were retrieved. The age and body mass index (BMI) of participants were documented. Step number per working hour (SPH) was calculated for all participants. Comparisons between males and females, practicing ophthalmologists (attendings) and ophthalmology residents (residents), and sub-specialties were performed. Correlations between SPH and age, BMI, and patients seen per clinic session were computed.

FINDINGS

Pedometer readings for a total of 673 working hours were analyzed for 24 ophthalmologists, 17% female, 17 attendings, mean age 44.2 years (standard deviation (SD = 9.8). The average number of SPH for all participants was 359.7 (SD = 166.7). The mean PA level of residents was significantly higher than that of attendings (410.17 SPH vs. 338.95 SPH, respectively, p = .019). Oculoplastic surgeons demonstrated significantly higher step counts per hour than cornea specialists (439.90 SPH vs. 245.55 SPH, respectively, p = .002). A negative correlation was observed between SPH and the number of patients seen per clinic session (ρ = -0.274, p = .001).

CONCLUSIONS/APPLICATIONS TO PRACTICE

Low number of SPH for ophthalmologists in this study indicates ophthalmology to be a highly sedentary medical occupation. PA levels of ophthalmologists in the workplace may indicate a personal health care challenge.

Sex differences in the regularity and symmetry of gait in older adults with and without knee osteoarthritis

BACKGROUND

Three-dimensional (3D) motion measured at the lower back during walking can describe the regularity and symmetry of gait that may be related to osteoarthritis (OA) and functional status. However, gait speed and inherent sex differences, regardless of the presence of OA, may confound these measures. Therefore, there is a need to understand the effect of OA separately among males and females, without the confounding influence of gait speed.

OBJECTIVE

To investigate the difference in 3D gait regularity and symmetry measures between gait speed-matched males and females with and without knee OA.

METHOD

Gait regularity and symmetry were computed as autocorrelations of pelvic accelerations during treadmill walking in four groups of older adults: healthy asymptomatic females (AsymF; n = 44), healthy asymptomatic males (AsymM; n = 45), females diagnosed with knee OA (OAF; n = 44), and males diagnosed with knee OA (OAM; n = 45). Data were obtained from a larger research database, allowing for the matching of gait speed between groups. The main effect of OA, sex, and interaction effect between them was examined for the 3D gait regularity and symmetry measures at an alpha level of 0.05.

RESULTS

There was no main effect of OA on any variable, but there was a significant main effect of sex on mediolateral and anteroposterior gait regularity measures. Specifically, females demonstrated significantly greater gait regularity, most notably in the mediolateral directions compared to males.

CONCLUSION

Older adult females were found to display significantly greater mediolateral gait regularity as compared to males, regardless of the presence of OA. Further, this difference exists among matched gait speeds, suggesting it is not the result of gait speed. Overall, these results highlight the importance of sex-specific analyses and considering gait speed when examining gait acceleration patterns near the center of mass for both cross sectional and longitudinal gait assessments.

Increased Speed Elicited More Automatized but Less Predictable Control in Cyclical Arm and Leg Movements

The present study explores variations in the degree of automaticity and predictability of cyclical arm and leg movements. Twenty healthy adults were asked to walk on a treadmill at a lower-than-preferred speed, their preferred speed, and at a higher-than-preferred speed. In a separate, repetitive punching task, the three walking frequencies were used to cue the target pace of the cyclical arm movements. Movements of the arms, legs, and trunk were digitized with inertial sensors. Whereas absolute slope values (|β|) of the linear fit to the power spectrum of the digitized movements (p < .001, η2 = .676) were systematically smaller in treadmill walking than in repetitive punching, sample entropy measures (p < .001, η2 = .570) were larger reflecting the former task being more automated but also less predictable than the latter task. In both tasks, increased speeds enhanced automatized control (p < .001, η2 = .475) but reduced movement predictability (p = .008, η2 = .225). The latter findings are potentially relevant when evaluating effects of task demand changes in clinical contexts.

Relationship of the sacral slope with early gait derangements in robust older women

BACKGROUND

Trunk pelvic dissociation is fundamental to the compensatory mechanism for muscle weakness during body bending. We carried out an early investigation of gait changes in a sample of community-dwelling women ≥60 years without gait complaints. The primary objective was to correlate spine and pelvic angles with performance tests and accelerometry parameters. The secondary objective was to correlate performance tests with accelerometry.

METHODS

In this cross-sectional study, 54 community-dwelling women ≥60 years were subjected to Falls Efficacy Scale-International (FES-I), performance tests (Berg Balance Scale, Timed Up and Go, and Gait analysis), and radiographic analysis of sagittal alignment (Thoracic and Lumbar Cobb, Pelvic Incidence, Sacral Slope, and Pelvic Tilt angles). Gait speed was assessed in a 10-m comfortable walk, and accelerometry parameters were obtained in a 30-m walk distance.

RESULTS

The sample, aged 72 ± 6 years, exhibited moderate correlation between Sacral Slope and Step Length (+ 0.615). Sacral Slope weakly correlated with FES-I (- 0.339), Berg Balance Scale (+ 0.367), and with further accelerometry data in the AP plane: RMS, (+ 0.439) and Stride Regularity (+ 0.475), p < 0.05, all. Lumbar Cobb weakly correlated with the following accelerometry data in the AP plane: Step Length (+ 0.405), RMS, (+ 0.392), and Stride Regularity (+ 0.345), p < 0.05, all. Additionally, Stride Regularity in AP moderately correlated with FES-I (0,561, p < 0.05), among other weak correlations between performance tests and accelerometry data in AP.

CONCLUSIONS

Early alterations in Sacral Slope and gait abnormalities in the AP plane may provide understanding of the early gait changes in robust older women.

Validation of smoothness evaluation during standing and sitting motions using an accelerometer

[Purpose] To quantitatively evaluate smoothness during standing and sitting motion analysis using an accelerometer and to clarify the relationship between indices. [Participants and Methods] Seventeen healthy males participated in this study. We attached a 9-axis motion sensor to the spinous process of the third lumbar spine and measured the acceleration of standing and sitting motions under normal and unstable conditions. We estimated and compared the root mean square and entropy in the lateral, vertical, longitudinal, and triaxial composite directions. [Results] On comparing both conditions, the unstable condition indices were significantly high, except for the lateral direction of entropy. The root mean square was significantly negatively correlated with entropy under normal conditions. [Conclusion] The study results suggested that the acceleration index quantitatively evaluates motion smoothness. Since each index had different characteristics, the motion-specific index was observed to be significant.

Regularity of kinematic data between single and dual-task treadmill walking in people with Parkinson's disease

BACKGROUND

Regularity, quantified by sample entropy (SampEn), has been extensively used as a gait stability measure. Yet, there is no consensus on the calculation process and variant approaches, e.g. single-scale SampEn with and without incorporating a time delay greater than one, multiscale SampEn, and complexity index, have been used to calculate the regularity of kinematic or kinetic signals. The aim of the present study was to test the discriminatory performance of the abovementioned approaches during single and dual-task walking in people with Parkinson's disease (PD).

METHODS

Seventeen individuals with PD were included in this study. Participants completed two walking trials that included single and dual-task conditions. The secondary task was word searching with twelve words randomly appearing in the participants' visual field. Trunk linear acceleration at sternum level, linear acceleration of the center of gravity, and angular velocity of feet, shanks, and thighs, each in three planes of motion were collected. The regularity of signals was computed using approaches mentioned above for single and dual-task conditions.

RESULTS

Incorporating a time delay greater than one and considering multiple scales helped better distinguish between single and dual-task walking. For all signals, the complexity index, defined as the summary of multiscale SampEn analysis, was the most efficient discriminatory index between single-task walking and dual-tasking in people with Parkinson's disease. Specifically, the complexity index of the trunk linear acceleration of the center of gravity distinguished between the two walking conditions in all three planes of motion.

CONCLUSIONS

The significant results observed across the 24 signals studied in this study are illustrative examples of the complexity index's potential as a gait feature for classifying different walking conditions.

Percentiles and Reference Values for Accelerometric Gait Assessment in Women Aged 50-80 Years

Background: The identification of factors that alter postural stability is fundamental in the design of interventions to maintain independence and mobility. This is especially important for women because of their longer life expectancy and higher incidence of falls than in men. We constructed the percentile box charts and determined the values of reference for the accelerometric assessment of the gait in women. Methods: We used a cross-sectional study with 1096 healthy adult women, who were asked to walk a distance of 20 m three times. Results: In all of the variables, a reduction in the magnitude of accelerations was detected as the age of the group advanced. The box charts show the amplitude of the interquartile ranges, which increases as the age of the participants advances. In addition, the interquartile ranges were greater in the variables that refer to the maximum values of the accelerations. Conclusions: The values obtained can be used to assess changes in gait due to aging, trauma and orthopaedic alterations that may alter postural stability and neurodegenerative processes that increase the risk of falling.

Walking characteristics including mild motor paralysis and slow walking speed in post-stroke patients

Walking speed is strongly influenced by the severity of motor paralysis in post-stroke patients. Nevertheless, some patients with mild motor paralysis still walk slowly. Factors associated with this difference in walking speed have not been elucidated. To confirm walking characteristics of patients with mild motor paralysis and slow walking speed, this study identified patient subgroups based on the association between the severity of motor paralysis and walking speed. Fugl-Meyer assessment synergy score (FMS) and the walking speed were measured (n = 42), and cluster analysis was performed based on the association between FMS and walking speed to identify the subgroups. FMS and walking speed were associated (ρ = 0.50); however, some patients walked slowly despite only mild motor paralysis. Cluster analysis using FMS and walking speed as the main variables classified patients into subgroups. Patients with mild motor paralysis (FMS: 18.4 ± 2.09 points) and slow walking speed (0.28 ± 0.14 m/s) exhibited poorer trunk stability, increased co-contraction of the shank muscle, and increased intramuscular coherence in walking compared to other clusters. This group was identified by their inability to fully utilize the residual potential of motor function. In walking training, intervention in instability and excessive cortical control may be effective.

Evaluation of gait transitional phases using neuromechanical outputs and somatosensory inputs in an overground walk

In a bipedal walk, the human body experiences continuous changes in stability especially during weight loading and unloading transitions which are reported crucial to avoid fall. Prior stability assessment methods are unclear to quantify stabilities during these gait transitions due to methodological and/or measurement limitations. This study introduces Nyquist and Bode methods to quantify stability gait transitional stabilities using the neuromechanical output (CoP) and somatosensory input (GRF) responses. These methods are implemented for five different walking conditions grouped into walking speed and imitated rotational impairments. The trials were recorded with eleven healthy subjects using motion cameras and force platforms. The time rate of change in O/Is illustrated impulsive responses and modelled in the frequency domain. Nyquist and Bode stability methods are applied to quantify stability margins. Stability margins from outputs illustrated loading phases as stable and unloading phases as unstable in all walking conditions. There was a strong intralimb compensatory interaction (p < .001, Spearman correlation) found between opposite limbs. Overall, both walking groups illustrated a decrease (p < .05, Wilcoxon signed-rank test) in stability margins compared with normal/preferred speed walk. Further, stabilities quantified from outputs were found greater in magnitudes than the instability quantified from inputs illustrating the neuromotor balance control ability. These stability outcomes were also compared by applying extrapolated-CoM method. These methods of investigating gait dynamic stability are considered as having important implications for the assessment of ankle-foot impairments, rehabilitation effectiveness, and wearable orthoses.

Quantitative Assessment of Ataxic Gait using Inertial Sensing at Different Walking Speeds

In this study, we employed wearable sensor technology to identify the kinematic features that are associated with the gait abnormalities seen in cerebellar ataxia. Measurements were made at self-selected slow, preferred and fast walking speeds with three sensors attached to the participant's body. Velocity irregularity and resonant frequency characteristics were identified as key features of interest concerning truncal and lower limb movements. Using the principal component analysis, differentiating features of both trunk and lower limb movements were combined to produce an enhanced distinction between the patients and the normal subjects, in addition to obtaining a better correlation with the expert clinician's assessments. The different speed of walking contributed to separation and correlation with medical severity rating scales such as SARA to varying degrees The results of truncal movement in the medio-lateral plane (at the slow gait speed) and antero-posterior movement (at all 3 gait speeds) provided the effective metrics in the diagnosis and severity rating of ataxic gait of CA patients. Furthermore, from the selected dominant features of the trunk and lower limb, principal component description suggested that overall clinical assessments are predominantly influenced by the lower body peripheral movements particularly at higher walking speeds.

Assessment of the gait-related acceleration patterns in adults with autism spectrum disorder

Individuals with autism spectrum disorder (ASD) can exhibit a range of movement issues, which are often characterized by a general slowing of movement responses that can extend to walking speed. The current study was designed to examine the spatio-temporal features and pattern of acceleration for the trunk, neck and head during walking for a cohort of adults with ASD compared to neurotypical individuals. Twenty young adults with ASD and 20 age-matched neurotypical adults participated in this study. Participants performed five walking trials across a 20ft Protokinetics pressure sensitive surface at their preferred walking speed. Accelerations were collected using three triaxial accelerometers affixed to the head, neck, and lower trunk. Comparisons of acceleration amplitude (i.e., RMS), frequency, segmental gain and regularity (i.e., SampEn) during the walking tasks were performed. Results revealed that the adults with ASD walked slower than the neurotypical persons with a greater proportion of time spent in double stance. Despite walking at a slower pace overall, the adults with ASD exhibited a decreased ability to attenuate gait-related oscillations from the trunk to the head. Overall, these findings suggest that adults with ASD exhibited a decreased ability to accommodate and dampen those accelerations related to walking. As declines in gait speed are often linked with loss of head control, one suggestion is that the inability to appropriately compensate for gait-related oscillations may, in part, explain why persons with ASD walk slower.

Coordination of trunk and foot acceleration during gait is affected by walking velocity and fall history in elderly adults

BACKGROUND

Falling is a significant concern for many elderly adults but identifying individuals at risk of falling is difficult, and it is not clear how elderly adults adapt to challenging walking.

AIMS

The aim of the current study was to determine the effects of walking at non-preferred speeds on the coordination between foot and trunk acceleration variability in healthy elderly adults with and without fall history compared to healthy young adults.

METHODS

Subjects walked on a treadmill at 80%-120% of their preferred walking speed while trunk and foot accelerations were recorded with wireless inertial sensors. Variability of accelerations was measured by root mean square, range, sample entropy, and Lyapunov exponent. The gait stability index was calculated using each variability metric in the frontal and sagittal plane by taking the ratio of trunk acceleration variability divided by foot acceleration variability.

RESULTS

Healthy young adults demonstrated larger trunk accelerations relative to foot accelerations at faster walking speeds compared to elderly adults, but both young and elderly adults show similar adaption to their acceleration regularity. Between group differences showed that elderly adult fallers coordinate acceleration variability between the trunk and feet differently compared to elderly non-fallers and young adults.

DISCUSSION

The current results indicate that during gait, elderly fallers demonstrate more constrained, less adaptable trunk movement relative to their foot movement and this pattern is different compared to elderly non-fallers and healthy young.

CONCLUSIONS

Coordination between trunk and foot acceleration variability plays an important role in maintaining stability during gait.

Altered visual and somatosensory feedback affects gait stability in persons with multiple sclerosis

Persons with multiple sclerosis (PwMS) often report problems due to sensory loss and have an inability to appropriately reweight sensory information. Both of these issues can affect individual's ability to maintain stability when walking under challenging conditions. The purpose of the current study was to determine how gait stability is adapted when walking under challenging sensory conditions where vision and somatosensation at the feet is manipulated. 25 healthy adults and 40 PwMS (15 fallers, 25 non-fallers) walked on a treadmill at their preferred normal walking speed under 3 conditions: normal walking, altered vision using goggles that shifted visual field laterally, and altered somatosensation using shoes with compliant foam soles. Inertial measurement united recorded acceleration at the lumbar and right ankle, and acceleration variability measures were calculated including root mean square (RMS), range, sample entropy (SaEn), and Lyapunov exponents (LyE). A gait stability index (GSI) was calculated using each of the four variability measures as the ratio of lumbar acceleration variability divided by foot acceleration variability in the frontal and sagittal planes. The sagittal and frontal GSI_RMS were larger in the somatosensory condition compared to the normal and visual conditions (p < 0.001). The frontal GSI_SaEn was greater in the visual condition compared to the somatosensory condition (p = 0.021). The frontal and sagittal GSI_LyE was greater in the somatosensory condition compared to the normal and visual conditions (p < 0.002). The current study showed that HC, MS non-fallers and MS fallers largely adapted to altered sensory feedback during walking in a similar manner. However, MS faller subjects may be more reliant on visual feedback compared to MS non-fallers and HC subjects.

Mobility related physical and functional losses due to aging and disease - a motivation for lower limb exoskeletons

BACKGROUND

Physical and functional losses due to aging and diseases decrease human mobility, independence, and quality of life. This study is aimed at summarizing and quantifying these losses in order to motivate solutions to overcome them with a special focus on the possibilities by using lower limb exoskeletons.

METHODS

A narrative literature review was performed to determine a broad range of mobility-related physical and functional measures that are affected by aging and selected cardiovascular, respiratory, musculoskeletal, and neurological diseases.

RESULTS

The study identified that decreases in limb maximum muscle force and power (33% and 49%, respectively, 25-75 yrs) and in maximum oxygen consumption (40%, 20-80 yrs) occur for older adults compared to young adults. Reaction times more than double (18-90 yrs) and losses in the visual, vestibular, and somatosensory systems were reported. Additionally, we found decreases in steps per day (75%, 60-85 yrs), maximum walking speed (24% 25-75 yrs), and maximum six-minute and self-selected walking speed (38% and 21%, respectively, 20-85 yrs), while we found increases in the number of falls relative to the number of steps per day (800%), injuries due to falls (472%, 30-90 yrs) and deaths caused by fall (4000%, 65-90 yrs). Measures were identified to be worse for individuals with impaired mobility. Additional detrimental effects identified for them were the loss of upright standing and locomotion, freezing in movement, joint stress, pain, and changes in gait patterns.

DISCUSSION

This review shows that aging and chronic conditions result in wide-ranging losses in physical and sensory capabilities. While the impact of these losses are relatively modest for level walking, they become limiting during more demanding tasks such as walking on inclined ground, climbing stairs, or walking over longer periods, and especially when coupled with a debilitating disease. As the physical and functional parameters are closely related, we believe that lost functional capabilities can be indirectly improved by training of the physical capabilities. However, assistive devices can supplement the lost functional capabilities directly by compensating for losses with propulsion, weight support, and balance support.

CONCLUSIONS

Exoskeletons are a new generation of assistive devices that have the potential to provide both, training capabilities and functional compensation, to enhance human mobility.

Visually fixating or tracking another person decreases balance control in young and older females walking in a real-world scenario

Balance control during overground walking was assessed in 10 young (23.6 ± 3.4) and 10 older (71.0 ± 5.5 years) healthy females during free gaze, and when fixating or tracking another person in an everyday use waiting room. Balance control was characterised by medial/lateral sacrum acceleration dispersion, and gaze fixations were simultaneously assessed with eye tracking equipment. The results showed decreased balance control when fixating a stationary (p = 0.003, g_av = 0.19) and tracking a walking (p = 0.027, g_av = 0.16) person compared to free gaze. The older adults exhibited reduced baseline stability throughout, but the decrease caused by the visual tasks was not more profound than the younger adults. The decreased balance control when fixating on or tracking the observed person was likely due to more challenging conditions for interpreting retinal flow, which facilitated less reliable estimates of self-motion through vision. The older adults either processed retinal flow during the tasks as effectively as the young adults, or they adopted a more rigid posture to facilitate visual stability, which masked any ageing effect of the visual tasks. The decrease in balance control, the first to be shown in this context, may warrant further investigation in those with ocular or vestibular dysfunction.

The Effects of Aging and Dual Tasking on Human Gait Complexity During Treadmill Walking: A Comparative Study Using Quantized Dynamical Entropy and Sample Entropy

Quantized dynamical entropy (QDE) has recently been proposed as a new measure to quantify the complexity of dynamical systems with the purpose of offering a better computational efficiency. This paper further investigates the viability of this method using five different human gait signals. These signals are recorded while normal walking and while performing secondary tasks among two age groups (young and older age groups). The results are compared with the outcomes of previously established sample entropy (SampEn) measure for the same signals. We also study how analyzing segmented and spatially and temporally normalized signal differs from analyzing whole data. Our findings show that human gait signals become more complex as people age and while they are cognitively loaded. Center of pressure (COP) displacement in mediolateral direction is the best signal for showing the gait changes. Moreover, the results suggest that by segmenting data, more information about intrastride dynamical features are obtained. Most importantly, QDE is shown to be a reliable measure for human gait complexity analysis.

Walking speed differentially alters spinal loads in persons with traumatic lower limb amputation

Persons with lower limb amputation (LLA) perceive altered motions of the trunk/pelvis during activities of daily living as contributing factors for low back pain. When walking (at a singular speed), larger trunk motions among persons with vs. without LLA are associated with larger spinal loads; however, modulating walking speed is necessary in daily life and thus understanding the influences of walking speed on spinal loads in persons with LLA is of particular interest here. Three-dimensional trunk-pelvic kinematics, collected during level-ground walking at self-selected (SSW) and two controlled speeds (∼1.0 and ∼1.4 m/s), were obtained for seventy-eight participants: 26 with transfemoral and 26 with transtibial amputation, and 26 uninjured controls (CTR). Using a kinematics-driven, non-linear finite element model of the lower back, the resultant compressive and mediolateral/anteroposterior shear loads at the L5/S1 spinal level were estimated. Peak values were extracted and compiled. Despite walking slower at SSW speeds (∼0.21 m/s), spinal loads were 8-14% larger among persons with transfemoral amputation vs. CTR. Across all participants, peak compressive, mediolateral, and anteroposterior shear loads increased with increasing walking speed. At the fastest (vs. slowest) controlled speed, these increases were respectively 24-84% and 29-77% larger among persons with LLA relative to CTR. Over time, repeated exposures to these increased spinal loads, particularly at faster walking speeds, may contribute to the elevated risk for low back pain among persons with LLA. Future work should more completely characterize relative risk in daily life between persons with vs. without LLA by analyzing additional activities and tissue-level responses.

Inertial sensing of the motion speed effect on the sit-to-walk activity

The STW execution at motion speed faster than normal most possibly enhances the risk for balance loss due to the increase in body segment accelerations. The purpose of the study was to use inertial sensing to examine the effect of motion speed on the STW segmental kinematics and its temporal events. Eighteen young men (20.7 ± 2.0 years) performed STW trials at preferred (PS) and fast (FS) motion speed. Data were collected with Xsens inertial sensors positioned at the trunk, thigh, shank, and foot segments. The maximum segmental values of angular displacement, angular velocity and linear acceleration, the duration of total STW (ttotal), the absolute and relative (% ttotal) phase duration (Flexion, Transition, Extension, Walking) and, the absolute and relative time taken to reach each maximum value were determined. In FS, ttotal and the absolute phase duration (except for Transition), were all significantly shorter (p = 0.000). The relative phase duration was not altered (p > 0.05), except for the Extension shortening (p = 0.001). The maximum angular displacement was altered only for the thigh (decreased, p = 0.038) and shank (increased, p = 0.004). Maximum angular velocities and linear accelerations were all significantly increased (p = 0.000 for all). The absolute time to reach the maximum values shortened in FS (p ≤ 0.05), while, the relative times were not altered (p > 0.05), except for the delayed trunk maximum angular displacement (p = 0.039). Inertial sensing appears to identify the motion speed effect on STW segmental kinematics and their temporal events in healthy young men. The results of the study may contribute improving the preventive or rehabilitation interventions in persons with impaired postural control.

An Automatic Gait Feature Extraction Method for Identifying Gait Asymmetry Using Wearable Sensors

This paper aims to assess the use of Inertial Measurement Unit (IMU) sensors to identify gait asymmetry by extracting automatic gait features. We design and develop an android app to collect real time synchronous IMU data from legs. The results from our method are validated using a Qualisys Motion Capture System. The data are collected from 10 young and 10 older subjects. Each performed a trial in a straight corridor comprising 15 strides of normal walking, a turn around and another 15 strides. We analyse the data for total distance, total time, total velocity, stride, step, cadence, step ratio, stance, and swing. The accuracy of detecting the stride number using the proposed method is 100% for young and 92.67% for older subjects. The accuracy of estimating travelled distance using the proposed method for young subjects is 97.73% and 98.82% for right and left legs; and for the older, is 88.71% and 89.88% for right and left legs. The average travelled distance is 37.77 (95% CI ± 3.57) meters for young subjects and is 22.50 (95% CI ± 2.34) meters for older subjects. The average travelled time for young subjects is 51.85 (95% CI ± 3.08) seconds and for older subjects is 84.02 (95% CI ± 9.98) seconds. The results show that wearable sensors can be used for identifying gait asymmetry without the requirement and expense of an elaborate laboratory setup. This can serve as a tool in diagnosing gait abnormalities in individuals and opens the possibilities for home based self-gait asymmetry assessment.

Estimation of Gait Independence Using a Tri-Axial Accelerometer in Stroke Patients

The purpose of this study was to clarify whether a gait analysis using an accelerometer could estimate gait independence. Eighty-six stroke patients and 21 healthy control subjects participated in this study. Stroke patients were identified as dependent or independent based on their gait ability. The acceleration of the trunk and bilateral thigh was measured using three wireless sensors during walking. The root mean square, gait regularity, and symmetry were calculated from the acceleration to estimate gait quality. ANCOVA showed that gait regularity of the trunk and bilateral thigh were significantly lowest in the dependent group, regardless of gait velocity. A logistic regression analysis showed that the regularity and root mean square of the anteroposterior acceleration of the unaffected thigh were the key factors for estimating gait independence. This study suggests that an acceleration-based gait analysis facilities gait independence estimation, and is a useful tool during the rehabilitation of stroke patients.

Gait characteristics and their discriminative power in geriatric patients with and without cognitive impairment

BACKGROUND

A detailed gait analysis (e.g., measures related to speed, self-affinity, stability, and variability) can help to unravel the underlying causes of gait dysfunction, and identify cognitive impairment. However, because geriatric patients present with multiple conditions that also affect gait, results from healthy old adults cannot easily be extrapolated to geriatric patients. Hence, we (1) quantified gait outcomes based on dynamical systems theory, and (2) determined their discriminative power in three groups: healthy old adults, geriatric patients with- and geriatric patients without cognitive impairment.

METHODS

For the present cross-sectional study, 25 healthy old adults recruited from community (65 ± 5.5 years), and 70 geriatric patients with (n = 39) and without (n = 31) cognitive impairment from the geriatric dayclinic of the MC Slotervaart hospital in Amsterdam (80 ± 6.6 years) were included. Participants walked for 3 min during single- and dual-tasking at self-selected speed while 3D trunk accelerations were registered with an IPod touch G4. We quantified 23 gait outcomes that reflect multiple gait aspects. A multivariate model was built using Partial Least Square- Discriminant Analysis (PLS-DA) that best modelled participant group from gait outcomes.

RESULTS

For single-task walking, the PLS-DA model consisted of 4 Latent Variables that explained 63 and 41% of the variance in gait outcomes and group, respectively. Outcomes related to speed, regularity, predictability, and stability of trunk accelerations revealed with the highest discriminative power (VIP > 1). A high proportion of healthy old adults (96 and 93% for single- and dual-task, respectively) was correctly classified based on the gait outcomes. The discrimination of geriatric patients with and without cognitive impairment was poor, with 57% (single-task) and 64% (dual-task) of the patients misclassified.

CONCLUSIONS

While geriatric patients vs. healthy old adults walked slower, and less regular, predictable, and stable, we found no differences in gait between geriatric patients with and without cognitive impairment. The effects of multiple comorbidities on geriatric patients' gait possibly causes a 'floor-effect', with no room for further deterioration when patients develop cognitive impairment. An accurate identification of cognitive status thus necessitates a multifactorial approach.

Inclined Weight-Loaded Walking at Different Speeds: Pelvis-Shoulder Coordination, Trunk Movements and Cost of Transport

Although studied at level surface, the trunk kinematics and pelvis-shoulder coordination of incline walking are unknown. The aim of this study was to evaluate the speed effects on pelvis-shoulder coordination and trunk movement and the cost of transport (C) during unloaded and loaded (25% of body mass) 15% incline walking. We collected 3-dimensional kinematic and oxygen consumption data from 10 physically active young men. The movements were analyzed in the sagittal plane (inclination and range of trunk motion) and the transverse plane (range of shoulder and pelvic girdle motion and phase difference). The rotational amplitude of the shoulder girdle decreased with load at all speeds, and it was lower at the highest speeds. The rotational amplitude of the pelvic girdle did not change with the different speeds. The phase difference was greater at optimal speed (3 km.hr^-1, at the lowest C) in the loaded and the unloaded conditions. The trunk inclination was greater with load and increased with speed, whereas the range of trunk motion was lower in the loaded condition and decreased with increasing speed. In conclusion, the load decreased the range of girdles and trunk motion, and the pelvis-shoulder coordination seemed to be critical for the incline walking performance.

Monitoring gait in multiple sclerosis with novel wearable motion sensors

BACKGROUND

Mobility impairment is common in people with multiple sclerosis (PwMS) and there is a need to assess mobility in remote settings. Here, we apply a novel wireless, skin-mounted, and conformal inertial sensor (BioStampRC, MC10 Inc.) to examine gait characteristics of PwMS under controlled conditions. We determine the accuracy and precision of BioStampRC in measuring gait kinematics by comparing to contemporary research-grade measurement devices.

METHODS

A total of 45 PwMS, who presented with diverse walking impairment (Mild MS = 15, Moderate MS = 15, Severe MS = 15), and 15 healthy control subjects participated in the study. Participants completed a series of clinical walking tests. During the tests participants were instrumented with BioStampRC and MTx (Xsens, Inc.) sensors on their shanks, as well as an activity monitor GT3X (Actigraph, Inc.) on their non-dominant hip. Shank angular velocity was simultaneously measured with the inertial sensors. Step number and temporal gait parameters were calculated from the data recorded by each sensor. Visual inspection and the MTx served as the reference standards for computing the step number and temporal parameters, respectively. Accuracy (error) and precision (variance of error) was assessed based on absolute and relative metrics. Temporal parameters were compared across groups using ANOVA.

RESULTS

Mean accuracy±precision for the BioStampRC was 2±2 steps error for step number, 6±9ms error for stride time and 6±7ms error for step time (0.6-2.6% relative error). Swing time had the least accuracy±precision (25±19ms error, 5±4% relative error) among the parameters. GT3X had the least accuracy±precision (8±14% relative error) in step number estimate among the devices. Both MTx and BioStampRC detected significantly distinct gait characteristics between PwMS with different disability levels (p<0.01).

CONCLUSION

BioStampRC sensors accurately and precisely measure gait parameters in PwMS across diverse walking impairment levels and detected differences in gait characteristics by disability level in PwMS. This technology has the potential to provide granular monitoring of gait both inside and outside the clinic.

Human runners exhibit a least variable gait speed

This study characterises the relationship between gait variability and speed in runners using data from trunk accelerations in each axis. Twelve participants of varying fitness ran on the treadmill with three sessions of six randomly ordered self-selected speeds. A VO_2max test was conducted on the fourth session. Running gait was tracked with inertial sensors. The occurrence of a mid-range speed was analysed for the anterior-posterior, vertical and lateral directional coefficient of variation (CV) of root mean square (RMS) acceleration data. One participant with noisy gait signals was omitted. The results show all remaining participants consistently showed significant quadratic U-shaped relationships between vertical RMS CV acceleration and speed. Neither anterior-posterior nor lateral RMS CV acceleration were clearly related to speed. These least variable gait speeds were similar to estimates of optimal speed derived from minimum cost of transport with speed. In conclusion, there exists a mid-range speed for each runner with the least variable gait in the vertical direction, and this occurred significantly more often than would be expected by chance (P < 0.05). However, there are no prominent patterns for the anterior-posterior and lateral directions. This finding supports anecdotal evidence from runners and coaches concerning gait consistency.

Relationship between trunk and foot accelerations during walking in healthy adults

Understanding upper body and lower body segment relationships may be an important step in assessing stability during gait. This study explored the relationship between acceleration patterns at the trunk and at the foot during treadmill walking at self-selected pace in healthy adults. Forty healthy subjects walked on a treadmill for 3 minutes at self-selected speed. Root mean square (RMS) and approximate entropy (ApEn) were derived from the acceleration time series at the trunk and at the foot in the frontal and sagittal plane. RMS of accelerations at the trunk were strongly correlated with RMS values at the foot in the sagittal plane (r=0.883, p<0.01) and in the frontal plane (r=0.811, p<0.01). ApEn values at the trunk were moderately correlated with ApEn values at the foot in the sagittal plane (r=0.603, p<0.01) only. These results show that acceleration variability at the foot is related to acceleration variability at the trunk, specifically that increased variability at the foot is tied to increased variability at the trunk in healthy adults. Portable inertial sensors can potentially be used in any environment including a laboratory, clinic, or at home to measure lower and upper body segment motion, and assessing relationships between upper and lower body motion may provide a more comprehensive evaluation of overall stability.

Wearable inertial sensors for human movement analysis

INTRODUCTION

The present review aims to provide an overview of the most common uses of wearable inertial sensors in the field of clinical human movement analysis.

AREAS COVERED

Six main areas of application are analysed: gait analysis, stabilometry, instrumented clinical tests, upper body mobility assessment, daily-life activity monitoring and tremor assessment. Each area is analyzed both from a methodological and applicative point of view. The focus on the methodological approaches is meant to provide an idea of the computational complexity behind a variable/parameter/index of interest so that the reader is aware of the reliability of the approach. The focus on the application is meant to provide a practical guide for advising clinicians on how inertial sensors can help them in their clinical practice. Expert commentary: Less expensive and more easy to use than other systems used in human movement analysis, wearable sensors have evolved to the point that they can be considered ready for being part of routine clinical routine.

Trunk muscles activation during pole walking vs. walking performed at different speeds and grades

Given their functional role and importance, the activity of several trunk muscles was assessed (via surface electromyography-EMG) during Walking (W) and Pole Walking (PW) in 21 healthy adults. EMG data was collected from the external oblique (EO), the erector spinae longissimus (ES), the multifidus (MU), and the rectus abdominis (RA) while performing W and PW on a motorized treadmill at different speeds (60, 80, and 100% of the highest speed at which the participants still walked naturally; PTS60, PTS80 and PTS100, respectively) and grades (0 and 7%; GRADE0 and GRADE7, respectively). Stride length, EMG area under the curve (AUC), muscles activity duration (ACT), and percentage of coactivation (CO-ACT) of ES, MU and RA, were calculated from the averaged stride for each of the tested combinations. Compared to W, PW significantly increased the stride length, EOAUC, RAAUC and the activation time of all the investigated muscles, to different extents depending on treadmill speeds and grades. In addition, MUAUC was higher in PW than in W at GRADE0 only (all speeds, p<0.01), while ESAUC during W and PW was similar at all the speeds and grades. These changes resulted in longer CO-ACT in PW than W, at GRADE0-PTS100 (p<0.01) and GRADE7 (all speeds, p<0.01). In conclusion, when compared to W, PW requires a greater engagement of the abdominal muscles and, in turn, a higher control of the trunk muscles. These two factors taken together may suggest an elevated spinal stability while walking with poles.

Gyroscopic corrections improve wearable sensor data prior to measuring dynamic sway in the gait of people with Multiple Sclerosis

Accelerometers are incorporated into many consumer devices providing new ways to monitor gait, mobility, and fall risk. However, many health benefits have not been realised because of issues with data quality that results from gravitational 'cross-talk' when the wearable device is tilted. Here we present an adaptive filter designed to improve the quality of accelerometer data prior to measuring dynamic pelvic sway patterns during a six minute walk test in people with and without Multiple Sclerosis (MS). Optical motion capture was used as the gold standard. Improved wearable device accuracy (≤4.4% NRMSE) was achieved using gyroscopic corrections and scaling filter thresholds by step frequency. The people with MS presented significantly greater pelvis sway range to compensate for their lower limb weaknesses and joint contractures. The visualisation of asymmetric pelvic sway in people with MS illustrates the potential to better understand their mobility impairments for reducing fall risk.

Biomechanical metrics of aesthetic perception in dance

The brain may be tuned to evaluate aesthetic perception through perceptual chunking when we observe the grace of the dancer. We modelled biomechanical metrics to explain biological determinants of aesthetic perception in dance. Eighteen expert (EXP) and intermediate (INT) dancers performed développé arabesque in three conditions: (1) slow tempo, (2) slow tempo with relevé, and (3) fast tempo. To compare biomechanical metrics of kinematic data, we calculated intra-excursion variability, principal component analysis (PCA), and dimensionless jerk for the gesture limb. Observers, all trained dancers, viewed motion capture stick figures of the trials and ranked each for aesthetic (1) proficiency and (2) movement smoothness. Statistical analyses included group by condition repeated-measures ANOVA for metric data; Mann-Whitney U rank and Friedman's rank tests for nonparametric rank data; Spearman's rho correlations to compare aesthetic rankings and metrics; and linear regression to examine which metric best quantified observers' aesthetic rankings, p < 0.05. The goodness of fit of the proposed models was determined using Akaike information criteria. Aesthetic proficiency and smoothness rankings of the dance movements revealed differences between groups and condition, p < 0.0001. EXP dancers were rated more aesthetically proficient than INT dancers. The slow and fast conditions were judged more aesthetically proficient than slow with relevé (p < 0.0001). Of the metrics, PCA best captured the differences due to group and condition. PCA also provided the most parsimonious model to explain aesthetic proficiency and smoothness rankings. By permitting organization of large data sets into simpler groupings, PCA may mirror the phenomenon of chunking in which the brain combines sensory motor elements into integrated units of behaviour. In this representation, the chunk of information which is remembered, and to which the observer reacts, is the elemental mode shape of the motion rather than physical displacements. This suggests that reduction in redundant information to a simplistic dimensionality is related to the experienced observer's aesthetic perception.

Bracing of the trunk and neck has a differential effect on head control during gait

During gait, the trunk and neck are believed to play an important role in dissipating the transmission of forces from the ground to the head. This attenuation process is important to ensure head control is maintained. The aim of the present study was to assess the impact of externally restricting the motion of the trunk and/or neck segments on acceleration patterns of the upper body and head and related trunk muscle activity. Twelve healthy adults performed three walking trials on a flat, straight 65-m walkway, under four different bracing conditions: 1) control-no brace; 2) neck-braced; 3) trunk-braced; and 4) neck-trunk braced. Three-dimensional acceleration from the head, neck (C7) and lower trunk (L3) were collected, as was muscle activity from trunk. Results revealed that, when the neck and/or trunk were singularly braced, an overall decrease in the ability of the trunk to attenuate gait-related oscillations was observed, which led to increases in the amplitude of vertical acceleration for all segments. However, when the trunk and neck were braced together, acceleration amplitude across all segments decreased in line with increased attenuation from the neck to the head. Bracing was also reflected by increased activity in erector spinae, decreased abdominal muscle activity and lower trunk muscle coactivation. Overall, it would appear that the neuromuscular system of young, healthy individuals was able to maintain a consistent pattern of head acceleration, irrespective of the level of bracing, and that priority was placed over the control of vertical head accelerations during these gait tasks.

Age-related differences when walking downhill on different sloped terrains

Despite the common situation of walking on different sloped terrains, previous work on gait has focused on level terrain. This study aims to assess whether any age-related differences exist in spatiotemporal and stability parameters when walking downhill on three different sloped walkways. Two tri-axial accelerometers were used at the levels of head and pelvis to investigate spatiotemporal parameters, magnitude (root mean square, RMS), harmonic content of accelerations (harmonic ratios, HR) and attenuation between body levels (ATT) in 35 older adults (OA, 69 ± 4.5 y.o.) and 22 young adults (YA, 22.1 ± 1.9 y.o.). Older adults walked at the same speed and cadence as young adults in flat terrain (FL, 0%) and moderate hill (MH, 8%). In the highest slope (PH, 20%), older adults reduced speed and step length and both groups increased cadence. Age had no effect on attenuation and RMS profiles. RMS increased with slope in all directions at both head and pelvis, except, for medio-lateral direction (ML), with similar head RMS in all slopes. There is an important shift in ATT from anteroposterior direction (AP) to ML at the highest slope, resulting in smaller antero-posterior attenuation and greater medio-lateral attenuation. Age differences appeared in the smoothness (HR) at the flat terrain, with increased vertical and antero-posterior values for young adults. As slope increased, group differences disappeared and HR decreased for all directions of motion. In general, spatiotemporal adaptations to increased slope seem to be part of a mechanism to improve ML attenuation, in both young and old adults.

Use of smartphones and portable media devices for quantifying human movement characteristics of gait, tendon reflex response, and Parkinson's disease hand tremor

Smartphones and portable media devices are both equipped with sensor components, such as accelerometers. A software application enables these devices to function as a robust wireless accelerometer platform. The recorded accelerometer waveform can be transmitted wireless as an e-mail attachment through connectivity to the Internet. The implication of such devices as a wireless accelerometer platform is the experimental and post-processing locations can be placed anywhere in the world. Gait was quantified by mounting a smartphone or portable media device proximal to the lateral malleolus of the ankle joint. Attributes of the gait cycle were quantified with a considerable accuracy and reliability. The patellar tendon reflex response was quantified by using the device in tandem with a potential energy impact pendulum to evoke the patellar tendon reflex. The acceleration waveform maximum acceleration feature of the reflex response displayed considerable accuracy and reliability. By mounting the smartphone or portable media device to the dorsum of the hand through a glove, Parkinson's disease hand tremor was quantified and contrasted with significance to a non-Parkinson's disease steady hand control. With the methods advocated in this chapter, any aspect of human movement may be quantified through smartphones or portable media devices and post-processed anywhere in the world. These wearable devices are anticipated to substantially impact the biomedical and healthcare industry.

Development and decline of upright gait stability

Upright gait is a peculiar characteristic of humans that requires the ability to manage upper body dynamic balance while walking, despite the perturbations that are generated by movements of the lower limbs. Most of the studies on upright gait stability have compared young adults and the elderly to determine the effects of aging. In other studies, the comparison was between healthy subjects and patients to examine specific pathologies. Fewer researches have also investigated the development of upright gait stability in children. This review discusses these studies in order to provide an overview of this relevant aspect of human locomotion. A clear trend from development to decline of upright gait stability has been depicted across the entire lifespan, from toddlers at first steps to elderly. In old individuals, even if healthy, the deterioration of skeletal muscle, combined with sensorial and cognitive performance, reduces the ability to maintain an upright trunk during walking, increasing the instability and the risk of falls. Further, the pathological causes of altered development or of a sudden loss of gait stability, as well as the environmental influence are investigated. The last part of this review is focused on the control of upper body accelerations during walking, a particularly interesting topic for the recent development of low-cost wearable accelerometers.

A gait abnormality measure based on root mean square of trunk acceleration

Background

Root mean square (RMS) of trunk acceleration is seen frequently in gait analysis research. However, many studies have reported that the RMS value was related to walking speed. Therefore, the relationship between the RMS value and walking speed should be considered when the RMS value is used to assess gait abnormality. We hypothesized that the RMS values in three sensing axes exhibit common proportions for healthy people if they walk at their own preferred speed and that the RMS proportions in abnormal gait deviate from the common proportions. In this study, we proposed the RMS ratio (RMSR) as a gait abnormality measure and verified its ability to discriminate abnormal gait.

Methods

Forty-seven healthy male subjects (24–49 years) were recruited to examine the relationship between walking speed and the RMSR. To verify its ability to discriminate abnormal gait, twenty age-matched male hemiplegic patients (30–48 years) participated as typical subjects with gait abnormality. A tri-axial accelerometer was attached to their lower back, and they walked along a corridor at their own preferred speed. We defined the RMSR as the ratio between RMS in each direction and the RMS vector magnitude.

Results

In the healthy subjects, the RMS in all directions related to preferred walking speed. In contrast, RMSR in the mediolateral (ML) direction did not correlate with preferred walking speed (rs = -0.10, p = 0.54) and represented the similar value among the healthy subjects. Moreover, the RMSR in the ML direction for the hemiplegic patients was significantly higher than that for the healthy subjects (p < 0.01).

Conclusions

These results suggest that the RMSR in the ML direction exhibits a common value when healthy subjects walk at their own preferred speed, even if their preferred walking speed were different. For subjects with gait abnormality, the RMSR in the ML direction deviates from the common value of healthy subjects. The RMSR in the ML direction may potentially be a quantitative measure of gait abnormality.

The interacting effect of cognitive and motor task demands on performance of gait, balance and cognition in young adults

Mobility limitations and cognitive impairments, each common with aging, reduce levels of physical and mental activity, are prognostic of future adverse health events, and are associated with an increased fall risk. The purpose of this study was to examine whether divided attention during walking at a constant speed would decrease locomotor rhythm, stability, and cognitive performance. Young healthy participants (n=20) performed a visuo-spatial cognitive task in sitting and while treadmill walking at 2 speeds (0.7 and 1.0 m/s).Treadmill speed had a significant effect on temporal gait variables and ML-COP excursion. Cognitive load did not have a significant effect on average temporal gait variables or COP excursion, but variation of gait variables increased during dual-task walking. ML and AP trunk motion was found to decrease during dual-task walking. There was a significant decrease in cognitive performance (success rate, response time and movement time) while walking, but no effect due to treadmill speed. In conclusion walking speed is an important variable to be controlled in studies that are designed to examine effects of concurrent cognitive tasks on locomotor rhythm, pacing and stability. Divided attention during walking at a constant speed did result in decreased performance of a visuo-spatial cognitive task and an increased variability in locomotor rhythm.

Analyzing individual and group differences in multijoint multiwaveform gait data using the Parafac2 model

Locomotion research often involves analyzing multiwaveform data (e.g., velocities, accelerations, etc.) from various body locations (e.g., knees, ankles, etc.) of several subjects. Therefore, some multivariate technique such as principal component analysis is often used to examine interrelationships between the many correlated waveforms. Despite its extensive use in locomotion research, principal component analysis is for two-mode data, whereas locomotion data are typically collected in higher mode form. In this paper, we present the benefits of analyzing four-mode locomotion data (subjects × time × joints × waveforms) using the Parafac2 model, which is a component model designed for analyzing variation in multimode data. Using bilateral hip, knee, and ankle angular displacement, velocity, and acceleration waveforms, we demonstrate Parafac2's ability to produce interpretable components describing (i) the fundamental patterns of variation in lower limb angular kinematics during healthy walking and (ii) the fundamental differences between normal and atypical subjects' multijoint multiwaveform locomotive patterns. Also, we illustrate how Parafac2 makes it possible to determine which waveforms best characterize the individual and/or group differences captured by each component. Our results indicate that different waveforms should be used for different purposes, confirming the need for the holistic analysis of multijoint multiwaveform locomotion data, particularly when investigating atypical motion patterns.

Contributions of muscles to mediolateral ground reaction force over a range of walking speeds

Impaired control of mediolateral body motion during walking is an important health concern. Developing treatments to improve mediolateral control is challenging, partly because the mechanisms by which muscles modulate mediolateral ground reaction force (and thereby modulate mediolateral acceleration of the body mass center) during unimpaired walking are poorly understood. To investigate this, we examined mediolateral ground reaction forces in eight unimpaired subjects walking at four speeds and determined the contributions of muscles, gravity, and velocity-related forces to the mediolateral ground reaction force by analyzing muscle-driven simulations of these subjects. During early stance (0-6% gait cycle), peak ground reaction force on the leading foot was directed laterally and increased significantly (p<0.05) with walking speed. During early single support (14-30% gait cycle), peak ground reaction force on the stance foot was directed medially and increased significantly (p<0.01) with speed. Muscles accounted for more than 92% of the mediolateral ground reaction force over all walking speeds, whereas gravity and velocity-related forces made relatively small contributions. Muscles coordinate mediolateral acceleration via an interplay between the medial ground reaction force contributed by the abductors and the lateral ground reaction forces contributed by the knee extensors, plantarflexors, and adductors. Our findings show how muscles that contribute to forward progression and body-weight support also modulate mediolateral acceleration of the body mass center while weight is transferred from one leg to another during double support.

Age- and speed-related differences in harmonic ratios during walking

Harmonic ratios (HRs), derived from trunk accelerations, measure smoothness of trunk motion during gait; higher ratios indicate greater smoothness. Previous research indicates that young adults optimize HRs at preferred pace, exhibiting reduced HRs at speeds faster and slower than preferred. Recent studies examining HRs and other trunk acceleration measures challenge this finding. The purpose of this study was to examine age-related differences in HRs across a range of self-selected overground walking speeds. Anteroposterior (AP), vertical (VT), and mediolateral (ML) HRs were examined in 13 young adults (ages 20-23), 13 healthy older adults (ages 60-69), and 13 healthy old-old adults (ages 80-86) while walking overground at very slow, slow, preferred, fast, and very fast speeds. Young and older adults exhibited similar HRs in all directions of motion across speeds, while old-old adults exhibited lower AP- and VT-HRs. All groups exhibited reduced HRs at speeds slower than preferred. However, there were no differences in HRs between preferred and faster speeds, with the exception of reduced VT-HRs in the very fast condition for the older groups. The ML-HR was not different between groups, and varied less across speeds. Stride time variability exhibited inverse relations with, and independently contributed to, HRs across speeds; lower stride time variability was associated with greater smoothness of trunk motion. Older groups were not disproportionately affected by walking more slowly and smoothness of trunk motion did not show a clear pattern of optimization at preferred pace for any group.