A novel wearable biofeedback system to prevent trip-related falls

Real-time gait monitoring of older adults and gait-impaired individuals while providing real-time biofeedback has the potential to help reduce trip-related falls. A low or unsuccessful Minimum Toe Clearance (MTC) is considered a predictor of tripping risk. Thus, increasing the MTC can be a key component in minimizing the likelihood of tripping. This paper discusses a proof-of-concept wearable system that estimates the MTC in real-time using two Time-of-Flight (ToF) sensors and provides auditory biofeedback to alert users if they have a low MTC during everyday walking activities. Ten healthy female adults were asked to perform two experiments: 1) walk at a predetermined speed to evaluate the proposed real-time MTC detection algorithm, and 2) walk in four conditions: baseline, biofeedback with no distraction, biofeedback with distraction 1 (talking on the phone), and biofeedback with distraction 2 (playing a simple mobile game). The average MTC values were significantly greater during all feedback conditions than the baseline, indicating that the proposed system could successfully warn users to increase their MTC in real-time.

The effect of tibialis anterior weakness on foot drop and toe clearance in patients with facioscapulohumeral dystrophy

BACKGROUND

Facioscapulohumeral dystrophy is a genetic disease characterized by progressive muscle weakness leading to a complex combination of postural instability, foot drop during swing and compensatory strategies during gait that have been related to an increased risk of falling. The aim is to assess the effect of tibialis anterior muscle weakness on foot drop and minimum toe clearance of patients with facioscapulohumeral dystrophy during gait.

METHODS

Eight patients allocated to a subgroup depending on the severity of tibialis anterior muscle weakness, assessed by manual muscle testing (i.e., severe and mild weakness), and eight matched control participants underwent gait analysis at self-selected walking speeds.

FINDINGS

Walking speed, for all facioscapulohumeral dystrophy patients, and step length, for patients with severe weakness only, were significantly decreased compared to control participants. Minimum toe clearance was similar across all groups, but its variability was increased only for patients with severe weakness. A greater foot drop was systematically observed for patients with severe weakness during swing and only in late swing for patients with mild weakness. Individual strategies to compensate for foot drop remain unclear and may depend on other muscle impairment variability.

INTERPRETATION

Although all patients were able to control the average height of their foot trajectory during swing, patients with severe tibialis anterior muscle weakness exhibited increased foot drop and minimum toe clearance variability. Manual muscle testing is a simple, cheap and effective method to assess tibialis anterior muscle weakness and seems promising to identify facioscapulohumeral dystrophy patients with an increased risk of tripping.

Vibrations on mastoid process alter the gait characteristics during walking on different inclines

Background

Eighty-eight percent of the persons with bilateral vestibular dysfunction have reported at least one fall within the past 5 years. The apparent alternations due to the bilateral vestibular dysfunctions (BVD) are the gait characteristics, such as slower walking speed, prolonged stance phase, and shorter step length. Unexpectedly, due to the prevalence of this BVD being relatively low, attention is not obtained as same as in other vestibular disorders. Moreover, how does walking on different inclines, part of daily activities, alter the gait characteristics under the unreliable bilateral vestibular systems? Previous studies used vibration-based stimulations (VS) as a perturbation to understand the postural control during walking while the bilateral vestibular systems were perturbed. Therefore, this study attempted to extend the knowledge to understand the alternations in spatial-temporal gait characteristics under perturbed bilateral vestibular systems while walking on different inclines.

Methods

Nineteen healthy young adults participated in this study. Eight walking conditions were randomly assigned to each participant: 0%, 3%, 6%, and 9% grade of inclines with/without VS. The preferred walking speed was used for gait analysis. The dependent variables were stance time, double support time, step length, step time, step width, foot clearance, and respective variabilities. All dependent variables were defined by two critical gait events: heel-strike and toe-off. Pre-Hoc paired comparisons with Bonferroni corrections were used to prioritize the dependent variables. A two-way repeated measure was used to investigate the effect of VS and the effect of inclines on the selected dependent variables from Pre-Hoc analysis. Post-Hoc comparisons were also corrected by the Bonferroni method.

Results

The step length, step time, foot clearance, and foot clearance variability were selected by the Pre-Hoc analysis because the corrected paired t-test demonstrated a significant VS effect (p < 0.05) on these gait parameters at least one of four inclines. The significant interaction between the effect of VS and the effect of inclines was found in step length (p = 0.005), step time (p = 0.028), and foot clearance variability (p = 0.003). The results revealed that implementing a VS increased step length and step time when walking on 0%, 3%, and 9% of grade inclines. In particular, the foot clearance variability was found when walking on 9% of grade inclines.

Conclusion

The observations in the current study suggested that VS increased the step length, step time, foot clearance, and foot clearance variability while walking on inclines. These results suggested that these gait parameters might be promising targets for future clinical investigations in patients with BVD while walking on different inclines. Importantly, the increases in spatial-temporal gait performance under bilateral VS might be an indicator of gait improvement while walking on different inclines.

A multi-segment modelling approach for foot trajectory estimation using inertial sensors

BACKGROUND

Kinematic gait analysis employing multi-segment foot models has been mainly conducted in laboratories by means of optical motion capture systems. This type of process requires considerable setup time and is constrained by a limited capture space. A procedure involving the use of multiple inertial measurement units (IMUs) is proposed to overcome these limitations.

RESEARCH QUESTION

This study presents a new approach for the estimation of the trajectories of a multi-segment foot model by means of multiple IMUs.

METHODS

To test the proposed method, a system consisting of four IMUs attached to the shank, heel, dorsum and toes segments of the foot, was considered. The performance of the proposed method was compared to that of a conventional method using IMUs adopted from the literature. In addition, an optical motion capture system was used as a reference to assess the performance of the implemented methods.

RESULTS

Employing the suggested method, all trajectory directions of the shank, heel and dorsum segments, as well as the Z (yaw) direction of the toes segment, have exhibited an error reduction varying between 8% and 55%. However, X (roll) and Y (pitch) direction of the toes segment presented an error increase of 17% and 26%, respectively. The estimation of the vertical displacement, corresponding to the foot clearance, was improved for all segments, resulting in a final mean accuracy and precision of 3.5 ± 2.8 cm, 2.7 ± 2.1 cm, 0.8 ± 0.7 cm and 1.1 ± 0.9 cm for the shank, heel, dorsum and toes segments, respectively.

SIGNIFICANCE

It has been demonstrated that as an alternative to tracking each foot segment separately, the fusion of multiple IMU measurements using kinematic equations, considerably improves the estimated trajectories, especially when considering vertical foot displacements. The proposed method could complement the use of smaller and cheaper sensors, while still matching the same performance of other published methods, making the suggested approach very attractive for real life applications.

Joint movements associated with minimum toe clearance variability in older adults during level overground walking

BACKGROUND

Approximately one-third of falls are caused by the swing foot contacting an object or the ground, resulting in a trip. The increased incidence of trip-related falls among older adults may be explained by greater within-person minimum toe clearance (MTC) variability.

RESEARCH QUESTION

Will kinematic variability at any of the 6 major joints in the lower limbs, individually or in combination, be associated with MTC variability?

METHODS

This cross-sectional study investigated whether single or multiple joint movements best explained MTC variability in older adults. Twenty healthy older adults (7 males, 13 females; mean age = 71.3 ± 7.2 years) were recruited. Participants were fitted with a modified Cleveland Clinic marker set and walked for 50 trials at self-selected speeds over a 7-meter walkway (with a rest at 25 trials) while 6 infrared cameras recorded kinematics.

RESULTS

Seven joint movements were evaluated, and swing hip flexion-extension variability was the only joint movement significantly associated with MTC variability (r = 0.577, p = 0.008) and explained 29.6% (adjusted R²) of the variance of MTC variability in older adults (F (1, 18) = 8.897, p = 0.008).

SIGNIFICANCE

Identifying the joint movement/s associated with inconsistencies in toe clearance will improve our understanding of endpoint control in older adults and may lead to the development of effective trip prevention strategies.

Impact of diabetic neuropathy severity on foot clearance complexity and variability during walking

BACKGROUND

The control of foot trajectory during swing phase is important to achieve safe clearance with the ground. Complexity of a physiological control system arises from the interaction of structural units and regulatory feedback loops that operate to enable the organism to adapt to a non-static environment. Diabetic polyneuropathy (DPN) impairs peripheral feedback inputs and alters ankle control during gait, which might affect toe clearance (ToC) parameters and its complexity, predisposing DPN-subjects to tripping and falling.

RESEARCH QUESTION

How do different DPN-severity degrees change ToC trajectory and minimum ToC, and its complexity during gait of diabetic subjects?

METHODS

15 healthy controls and 69 diabetic subjects were assessed and classified into DPN-severity degrees by an expert fuzzy model: absent (n = 26), mild (n = 21) and severe (n = 22). Three-dimensional kinematics was measured during comfortable walking. ToC was the minimum vertical distance between the marker placed at the first metatarsal head and the ground during swing. Mean ToC, ToC standard deviation (SD) between trials, and sample entropy (SaEn) and standard deviation (SD) of ToC trajectory were calculated from the ToC temporal series. ANOVA and ANCOVA (with the walking speed as the covariate) and Bonferroni pairwise post-hoc tests (P < 0.05) were used to compare groups.

RESULTS

Mean ToC and ToC SD did not show differences between groups (ANCOVA F = 0.436; df = 3; P = 0.705; F=1.719; df=3; P=0.170, respectively). ToC trajectory SD also did not show differences between groups (ANCOVA F = 3.98; df = 3; P = 0.755). Severe-DPN subjects showed higher ToC_Traj_SaEn than controls (ANCOVA F=2.60; df=3; P = 0.05).

SIGNIFICANCE

Severe-DPN subjects showed a more complex pattern of overall foot-ankle trajectory in swing phase in comparison to controls, although did not present lower minimum ToC values. The higher complexity of ToC might lead to an increase in the motor system output (more strategies, increase in variability), resulting in a more unstable system and selected motor strategies.

Tempo-spatial gait adaptations in stroke patients when approaching and crossing an elevated surface

BACKGROUND

In ambulatory stroke survivors, outdoor walking is important for participation, so adapting to heightened levels (e.g. curbs) is essential. This needs precise step regulation and foot positioning and has to be achieved despite impaired balance and motor regulation.

RESEARCH QUESTION

How do stroke patients approach and cross elevated surfaces?

METHODS

Gait of 12 hemiparetic stroke patients (62.8 ± 10.3 years; Functional Ambulatory Category 3-5) and 13 controls (60.0 ± 12.4 years) was compared using a sensor carpet and 3D motion capturing to collect tempo-spatial parameters and foot trajectories in two conditions: flat walking vs. approaching to and stepping onto an elevated surface (height 15 cm) in a self-selected manner (6 trials each). Tempo-spatial adaptations were normalized to flat walking while trajectory analysis focused on foot clearance and placement. Complementary assessments included the Dynamic-Gait-Index, the Berg-Balance-Test and the Falls Efficacy Scale.

RESULTS

Patients showed significantly worse Dynamic-Gait-Indices, less balance and more fear of falling. During the approach phase, patients slowed down, partly accompanied by shorter steps which controls did not. During crossing, no preference for a specific leading leg was detected. Clearance of the leading leg on average was not reduced but patients landed closer to the edge. Still clearance of the paretic leg was less than that of the non-paretic leg and the minimal clearance across all trials suggested an increased tripping risk, most evident for the trailing leg. In particular slower approaching caused difficulties to ensure sufficient leg clearance and to place the foot safely. Independent from that, better balance correlated with safer clearance.

SIGNIFICANCE

When managing elevated levels, leading with the paretic leg causes more difficulties to safely clear the legs which is considerably dependent upon speed. Therapists should consider that slow walking may not increase safety while faster gait and aspects of postural control potentially facilitate crossing a curb.

Effects of simulated firefighting and asymmetric load carriage on firefighter obstacle crossing performance

Slips, trips, and falls (STF) of firefighters may occur while traversing stationary obstacles. STF risk may be amplified by fatigue from firefighting and carrying an asymmetric load. Vertical and horizontal clearances of the lead (VCL, HCL) and trailing (VCT, HCT) foot and contact with a 30 cm obstacle were examined in 24 firefighters. We examined the impact on obstacle crossing performance due to three exercise protocols (treadmill walking or simulated firefighting in an environmental chamber, and simulated firefighting in a live-fire burn building) and carrying a hose load on the right shoulder. Post-activity fatigue resulted in significant decreases in HCL and VCT. Adding a hose load did not affect choice of lead/trailing foot, but did significantly decreased HCL and increased VCL. The hose load amplified acute fatigue effects by causing a sharper decrease in both VCL and VCT. Clearances were significantly impacted by interaction effects of exercise protocol type and acute fatigue. HCL decreased and VCL remained consistent following both simulated firefighting tasks, but HCL remained unchanged and VCL increased following the treadmill protocol. Contact errors increased with fatigue and load, and more errors occurred following simulated firefighting task protocols compared to treadmill walking. Our findings suggest that both acute fatigue and carrying an additional load can cause decrements in firefighter movement, which may place a firefighter at greater STF risk. Simulated firefighting testing protocols may have greater impact on movement performance than treadmill walking. Knowledge of these results may assist in the development of a reliable, laboratory based, and standardizable simulated firefighting exercise protocol.

Control of vertical posture while elevating one foot to avoid a real or virtual obstacle

The purpose of this study is to investigate the control of vertical posture during obstacle avoidance in a real versus a virtual reality (VR) environment. Ten healthy participants stood upright and lifted one leg to avoid colliding with a real obstacle sliding on the floor toward a participant and with its virtual image. Virtual obstacles were delivered by a head mounted display (HMD) or a 3D projector. The acceleration of the foot, center of pressure, and electrical activity of the leg and trunk muscles were measured and analyzed during the time intervals typical for early postural adjustments (EPAs), anticipatory postural adjustments (APAs), and compensatory postural adjustments (CPAs). The results showed that the peak acceleration of foot elevation in the HMD condition decreased significantly when compared with that of the real and 3D projector conditions. Reduced activity of the leg and trunk muscles was seen when dealing with virtual obstacles (HMD and 3D projector) as compared with that seen when dealing with real obstacles. These effects were more pronounced during APAs and CPAs. The onsets of muscle activities in the supporting limb were seen during EPAs and APAs. The observed modulation of muscle activity and altered patterns of movement seen while avoiding a virtual obstacle should be considered when designing virtual rehabilitation protocols.

Characterisation of foot clearance during gait in people with early Parkinson׳s disease: Deficits associated with a dual task

Tripping is a common cause of falls in older adults and people with Parkinson׳s disease (PD). Foot clearance during gait may be impaired when distracted by a dual task and thus inform trip risk. This study aimed to evaluate whether foot clearance is impaired in PD and is adversely affected by a dual task. 81 older adults and 76 PD walked at a comfortable pace for two minutes under single and dual task conditions (digit recall). Temporal spatial gait was measured using an instrumented walkway. Heel and toe trajectories were obtained bilaterally using 3-dimensional motion capture. Foot clearance was reduced in PD (p<.001) and under dual task (p<.027). The take-off (toe) gradient was reduced under dual task irrespective of group and the landing (heel) gradient was reduced in PD irrespective of task (p<.001). An increased proportion of unimodal toe distributions were observed for PD, particularly under dual task. Group differences were retained when controlling for step length (landing gradient and peak toe clearance in late swing) and gait velocity (landing gradient). Distinct differences in foot clearance were observed even in the early clinical stages of PD. Dual tasking may increase trip risk due to insufficient toe clearance (early swing) for both older adults and PD. Inadequate heel clearance (late swing) may increase falls risk in PD. Clearance deficits in PD are partially related to a reduced gait velocity and step length which may be targeted in tailored therapies. Further work is necessary to understand the mechanisms underlying this pathology-associated deficit.

Strategies for obstacle crossing in older adults with high and low risk of falling

[Purpose] Tripping is a frequent cause of falls among aging adults. Appropriate limb movements while negotiating obstacles are critical to trip avoidance. The aim of our study was to investigate the mechanics of obstacle crossing in older adults at low or high risk of falling. [Subjects and Methods] Twenty community-dwelling adults aged ≥55 years, were evaluated with the Tinetti Balance and Gait scale and classified as being at high or low risk of falling. Between-group comparisons of kinematics were evaluated for obstacle heights of 10%, 20%, and 30% of leg length. [Results] The high-risk group demonstrated greater toe-obstacle clearance of the leading leg. Increasing obstacle height led to increased maximal toe-obstacle clearance, toe-obstacle distance, and shortened swing phase of the leading limb. Adaptation of clearance height was greater for the trailing leg. Individuals at high risk of falling demonstrated less symmetry between the leading and trailing legs and a narrower step width, features that increase the likelihood of tripping. [Conclusion] Kinematic parameters of obstacle clearance, including the symmetry index described in our study, could provide clinicians with a quick screening tool to identify patients at risk of falling and to evaluate outcomes of training programs.

Estimation of foot trajectory during human walking by a wearable inertial measurement unit mounted to the foot

To establish a supportive technology for reducing the risk of falling in older people, it is essential to clarify gait characteristics in elderly individuals that are possibly linked to the risk of falling during actual daily activities. In this study, we developed a system to monitor human gait in an outdoor environment using an inertial measurement unit consisting of a tri-axial accelerometer and tri-axial gyroscope. Step-by-step foot trajectories were estimated from the sensor unit attached to the dorsum of the foot. Specifically, stride length and foot clearance were calculated by integrating the gravity-compensated translational acceleration over time during the swing phase. Zero vertical velocity and displacement corrections were applied to obtain the final trajectory, assuming the slope of the walking surface is negligible. Short, normal, and long stride-length walking of 10 healthy participants was simultaneously measured using the proposed system and a conventional motion capture system to evaluate the accuracy of the estimated foot trajectory. Mean accuracy and precision were approximately 20 ± 50 mm, for stride length, and 2 ± 7 mm for foot clearance, indicating that the swing phase trajectory of the sensor unit attached to the foot was reconstructed more accurately and precisely using the proposed system than with previously published methods owing to the flat floor assumption. Although some methodological limitations certainly apply, this system will serve as a useful tool to monitor human walking during daily activities.

Analysis of foot clearance in firefighters during ascent and descent of stairs

Slips, trips, and falls are a leading cause of injury to firefighters with many injuries occurring while traversing stairs, possibly exaggerated by acute fatigue from firefighting activities and/or asymmetric load carriage. This study examined the effects that fatigue, induced by simulated firefighting activities, and hose load carriage have on foot clearance while traversing stairs. Landing and passing foot clearances for each stair during ascent and descent of a short staircase were investigated. Clearances decreased significantly (p < 0.05) post-exercise for nine of 12 ascent parameters and increased for two of eight descent parameters. Load carriage resulted in significantly decreased (p < 0.05) clearance over three ascent parameters, and one increase during descent. Decreased clearances during ascent caused by fatigue or load carriage may result in an increased trip risk. Increased clearances during descent may suggest use of a compensation strategy to ensure stair clearance or an increased risk of over-stepping during descent.

Restricting ankle motion via orthotic bracing reduces toe clearance when walking over obstacles

BACKGROUND

When trans-tibial amputees cross obstacles leading with their prosthesis, foot clearance is achieved using compensatory swing-phase kinematics. Such compensation would suggest able-bodied individuals normally use swing-phase ankle dorsiflexion to attain adequate obstacle clearance; however, direct evidence of such contribution is equivocal. This study determined the contribution of sagittal plane ankle motion in achieving lead-limb clearance during obstacle negotiation.

METHODS

Twelve male able-bodied individuals (ages 18-30) completed obstacle crossing trials while walking on a flat surface. Lead-limb (right) ankle motion was manipulated using a knee-ankle-foot orthosis. Trials were completed with the ankle restricted at a neutral angle or unrestricted (allowing ∼±15° plantar/dorsiflexion).

FINDINGS

Restricted ankle motion caused significant increase in trail-limb foot placement distance before the obstacle (p=0.005); significant decrease in vertical toe clearance (p<0.003), vertical heel clearance (p=0.045), and lead-limb foot placement distance after the obstacle (p=0.045); but no significant changes in knee angle at instant of crossing or in average walking speed.

INTERPRETATION

The shifts in foot placements altered the part of swing that the lead-limb was in when the foot crossed the obstacle, which led to a decrease in clearance. These adaptations may have been due to being unable to dorsiflex the ankle to 'lift' the toes in mid-swing or to plantarflex the ankle during initial contact following crossing, which changed how the lead-limb was to be loaded. These findings suggest individuals using ankle bracing or those with ankle arthrodesis, will have reduced gait safety when negotiating obstacles.