Assessment of human locomotion by using an insole measurement system and artificial neural networks

A new method for measuring and characterizing free-living human locomotion is presented. A portable device was developed to objectively record and measure foot-ground contact information in every step for up to 24h. An artificial neural network (ANN) was developed to identify the type and intensity of locomotion. Forty subjects participated in the study. The subjects performed level walking, running, ascending and descending stairs at slow, normal and fast speeds determined by each subject, respectively. The device correctly identified walking, running, ascending and descending stairs (accuracy 98.78%, 98.33%, 97.33%, and 97.29% respectively) among different types of activities. It was also able to determine the speed of walking and running. The correlation between actual speed and estimated speed is 0.98, p< 0.0001. The average error of walking and running speed estimation is -0.050+/-0.747 km/h (mean +/- standard deviation). The study has shown the measurement of duration, frequency, type, and intensity of locomotion highly accurate using the new device and an ANN. It provides an alternative tool to the use of a gait lab to quantitatively study locomotion with high accuracy via a small, light and portable device, and to do so under free-living conditions for the clinical applications.     

Classification accuracy of a single tri-axial accelerometer for training background and experience level in runners

Accelerometers are increasingly used tools for gait analysis, but there remains a lack of research on their application to running and their ability to classify running patterns. The purpose of this study was to conduct an exploratory examination into the capability of a tri-axial accelerometer to classify runners of different training backgrounds and experience levels, according to their 3-dimensional (3D) accelerometer data patterns. Training background was examined with 14 competitive soccer players and 12 experienced marathon runners, and experience level was examined with 16 first-time and the same 12 experienced marathon runners. Discrete variables were extracted from 3D accelerations during a short run using root mean square, wavelet transformation, and autocorrelation procedures. A principal component analysis (PCA) was conducted on all variables, including gait speed to account for covariance. Eight PCs were retained, explaining 88% of the variance in the data. A stepwise discriminant analysis of PCs was used to determine the binary classification accuracy for training background and experience level, with and without the PC of Speed. With Speed, the accelerometer correctly classified 96% of runners for both training background and experience level. Without Speed, the accelerometer correctly classified 85% of runners based on training background, but only 68% based on experience level. These findings suggest that the accelerometer is effective in classifying athletes of different training backgrounds, but is less effective for classifying runners of different experience levels where gait speed is the primary discriminator.     

A new training algorithm using artificial neural networks to classify gender-specific dynamic gait patterns

The aim of this study was to present a new training algorithm using artificial neural networks called multi-objective least absolute shrinkage and selection operator (MOBJ-LASSO) applied to the classification of dynamic gait patterns. The movement pattern is identified by 20 characteristics from the three components of the ground reaction force which are used as input information for the neural networks in gender-specific gait classification. The classification performance between MOBJ-LASSO (97.4%) and multi-objective algorithm (MOBJ) (97.1%) is similar, but the MOBJ-LASSO algorithm achieved more improved results than the MOBJ because it is able to eliminate the inputs and automatically select the parameters of the neural network. Thus, it is an effective tool for data mining using neural networks. From 20 inputs used for training, MOBJ-LASSO selected the first and second peaks of the vertical force and the force peak in the antero-posterior direction as the variables that classify the gait patterns of the different genders.     

Evaluation of a Smartphone-based Human Activity Recognition System in a Daily Living Environment

An evaluation method that includes continuous activities in a daily-living environment was developed for Wearable Mobility Monitoring Systems (WMMS) that attempt to recognize user activities. Participants performed a pre-determined set of daily living actions within a continuous test circuit that included mobility activities (walking, standing, sitting, lying, ascending/descending stairs), daily living tasks (combing hair, brushing teeth, preparing food, eating, washing dishes), and subtle environment changes (opening doors, using an elevator, walking on inclines, traversing staircase landings, walking outdoors). To evaluate WMMS performance on this circuit, fifteen able-bodied participants completed the tasks while wearing a smartphone at their right front pelvis. The WMMS application used smartphone accelerometer and gyroscope signals to classify activity states. A gold standard comparison data set was created by video-recording each trial and manually logging activity onset times. Gold standard and WMMS data were analyzed offline. Three classification sets were calculated for each circuit: (i) mobility or immobility, ii) sit, stand, lie, or walking, and (iii) sit, stand, lie, walking, climbing stairs, or small standing movement. Sensitivities, specificities, and F-Scores for activity categorization and changes-of-state were calculated.The mobile versus immobile classification set had a sensitivity of 86.30% ± 7.2% and specificity of 98.96% ± 0.6%, while the second prediction set had a sensitivity of 88.35% ± 7.80% and specificity of 98.51% ± 0.62%. For the third classification set, sensitivity was 84.92% ± 6.38% and specificity was 98.17 ± 0.62. F1 scores for the first, second and third classification sets were 86.17 ± 6.3, 80.19 ± 6.36, and 78.42 ± 5.96, respectively. This demonstrates that WMMS performance depends on the evaluation protocol in addition to the algorithms. The demonstrated protocol can be used and tailored for evaluating human activity recognition systems in rehabilitation medicine where mobility monitoring may be beneficial in clinical decision-making.     

The effect of cane length and step height on muscle strength and body balance of elderly people in a stairway environment

Background

It has been reported that 75% of stairway accidents occur while descending stairs. Using a cane can help to prevent older people and those with limited mobility from falling. However, studies have shown that two-thirds of older cane users use a cane that is longer than the recommended length, which may cause unnecessary muscular loads. This study aims to assess balance and muscular load in older people descending different height steps with different cane lengths.

Methods

Nine participants (5 males and 4 females) aged over 65 years participated in this study. Cane length and stair height were independent variables. Electromyography signals were recorded from the biceps brachii of the arm that usually held the cane and from both gastrocnemius muscles. In addition, the center of pressure (CoP) was assessed as an indicator of balance in older people descending a step.

Results

Descending from higher steps resulted in the use of greater arm and leg strength at the time of first foot contact. However, cane length did not affect any of the root mean square values. In addition, the CoP Stabilometric Parameters showed that mean distance, antero-posterior mean distance, total excursions, antero-posterior total excursions, mean velocity, and antero-posterior mean velocity were significantly affected by step height, but not by cane length.

Conclusions

If cane length is within the currently suggested range, then it has little effect on the force load on the arm and legs when descending a step. Step height has a greater effect than cane length on the strategies used by older people to maintain stability.     

Patterns in the knee flexion-extension moment profile during stair ascent and descent in patients with total knee arthroplasty

The aim of this study was to investigate the prevalence of abnormal knee biomechanical patterns in 40 patients with a modern TKA prosthesis, compared to 40 matched control participants when ascending and descending stairs. Fewer patients were able to ascend (65%) or descend stairs (53%) unassisted than controls (83%). Of the participants who could ascend and descend, cluster analysis classified most patients (up to 77%) as demonstrating a similar knee moment pattern as all controls. A small subgroup of patients who completed the tasks did so with distinctly abnormal biomechanics compared to other patients and controls. These findings suggest that recovery of normal stair climbing is possible. However, rehabilitation might be more effective if it were tailored to account for these differences between patients.     

Forces and moments telemetered from two distal femoral replacements during various activities.

Two distal femoral replacements were instrumented to measure axial force, torque and bending moments in the prosthesis shaft. Data are reported up to 2.5 years for the following activities: uni- and bi-lateral standing, walking, stair climbing and descending, treadmill walking, jogging and jumping. In the first subject the greatest averaged peak shaft forces found were: jogging 3.6Bodyweight (BW), stair descending 3.1BW, walking 2.8BW, treadmill walking 2.75BW, and stair ascending 2.8BW. Bending moments about the antero-posterior axis (varus-valgus) and medio-lateral axis (flexion-extension) peaked in the range 8.5-9.8 and 4.7-7.6BWcm respectively, over the follow-up period. Axial torques peaked in the range 0.2-1.3BWcm, outwardly directed. At most follow-up sessions, forces and moments during jogging were generally greater than those for other gait activities. In the second subject forces and moments were generally only 45-70% of those in the first subject, due to inadequate musculature around the knee. The data can be applied to the design and testing of distal femoral replacements and even to total knee replacements, and contributes to the knowledge of forces acting in the distal femur during activity.     

心肌带收缩率与急性心肌梗死患者左心室收缩功能关系

目的:急性前壁心肌梗死明显影响室间隔收缩率和左心室射血分数(left ventricular ejection fraction LVEF)。本文旨在探讨心肌带降段及升段收缩率与急性前壁心肌梗死患者LVEF的相关性。方法:收集2015年4月-2017年2月在心内科住院的急性前壁心肌梗死患者36例,正常对照组患者39例。所有患者取左心室长轴M型超声心动图,测量室间隔收缩率、升段收缩率及降段收缩率。心肌梗死左心室射血分数采用双平面Simpson's法计算。结果:与正常对照组相比,心肌梗死组患者舒张末期心肌带升段厚度没有统计学差异(P=0.69),收缩末期升段厚度(P=0.014)更薄、升段收缩率(P0.01)明显降低;心肌梗死组舒张末期降段厚度(P0.01)更薄、收缩末期降段厚度(P0.01)更薄、降段收缩率(P0.01)明显降低;心肌梗死组左心室射血分数与降段收缩率(r~2=0.13,P=0.026)、室间隔增厚率(r~2=0.19,P0.01)呈正相关,与升段收缩率没有相关性(P0.05)。正常对照组左心室射血分数与室间隔增厚率、降段增厚率及升段增厚率无相关性。经过相关分析,筛选出与心肌梗死LVEF的相关因素,进一步经逐步回归分析,得多元线性回归方程为LVEF=48.206+18.914*LVDD(cm)-25.414*LVSD(cm)。结论:急性前壁心肌梗死室间隔降段收缩率明显受损,与左心室射血分数降低有关。多元线性回归方程可估算前壁心肌梗死LVEF。     

Gait and posture discrimination in sheep using a tri-axial accelerometer

Temporo-spatial observation of the leg could provide important information about the general condition of an animal, especially for those such as sheep and other free-ranging farm animals that can be difficult to access. Tri-axial accelerometers are capable of collecting vast amounts of data for locomotion and posture observations; however, interpretation and optimization of these data records remain a challenge. The aim of the present study was to introduce an optimized method for gait (walking, trotting and galloping) and posture (standing and lying) discrimination, using the acceleration values recorded by a tri-axial accelerometer mounted on the hind leg of sheep. The acceleration values recorded on the vertical and horizontal axes, as well as the total acceleration values were categorized. The relative frequencies of the acceleration categories (RFACs) were calculated in 3-s epochs. Reliable RFACs for gait and posture discrimination were identified with discriminant function and canonical analyses. Post hoc predictions for the two axes and total acceleration were conducted, using classification functions and classification scores for each epoch. Mahalanobis distances were used to determine the level of accuracy of the method. The highest discriminatory power for gait discrimination yielded four RFACs on the vertical axis, and five RFACs each on the horizontal axis and total acceleration vector. Classification functions showed the highest accuracy for walking and galloping. The highest total accuracy on the vertical and horizontal axes were 90% and 91%, respectively. Regarding posture discrimination, the vertical axis exhibited the highest discriminatory power, with values of RFAC (0, 1]=99.95% for standing; and RFAC (−1, 0]=99.50% for lying. The horizontal axis showed strong discrimination for the lying side of the animal, as values were in the acceleration category of (0, 1] for lying on the left side and (−1, 0] on the right side. The algorithm developed by the method employed in the present study facilitates differentiation of the various types of gait and posture in animals from fewer data records, and produces the most reliable acceleration values from only one axis within a short time frame. The present study introduces an optimized method by which the tri-axial accelerometer can be used in gait and posture discrimination in sheep as an animal model.     

High-precision satellite positioning system as a new tool to study the biomechanics of human locomotion

New Global Positioning System (GPS) receivers allow now to measure a location on earth at high frequency (5 Hz) with a centimetric precision using phase differential positioning method. We studied whether such technique was accurate enough to retrieve basic parameters of human locomotion. Eight subjects walked on an athletics track at four different imposed step frequencies (70–130 steps/min) plus a run at free pace. Differential carrier phase localization between a fixed base station and the mobile antenna mounted on the walking person was calculated. In parallel, a triaxial accelerometer, attached to the low back, recorded body accelerations. The different parameters were averaged for 150 consecutive steps of each run for each subject (total of 6000 steps analyzed). We observed a perfect correlation between average step duration measured by accelerometer and by GPS (r=0.9998, N=40). Two important parameters for the calculation of the external work of walking were also analyzed, namely the vertical lift of the trunk and the velocity variation per step. For an average walking speed of 4.0 km/h, average vertical lift and velocity variation were, respectively, 4.8 cm and 0.60 km/h. The average intra-individual step-to-step variability at a constant speed, which includes GPS errors and the biological gait style variation, were found to be 24.5% (coefficient of variation) for vertical lift and 44.5% for velocity variation. It is concluded that GPS technique can provide useful biomechanical parameters for the analysis of an unlimited number of strides in an unconstrained free-living environment.     

PCA-based SVM for automatic recognition of gait patterns

In this technical note, we investigate a combination PCA with SVM to classify gait pattern based on kinetic data. The gait data of 30 young and 30 elderly participants were recorded using a strain gauge force platform during normal walking. The gait features were first extracted from the recorded vertical directional foot- ground reaction forces curve using PCA, and then these extracted features were adopted to develop the SVM gait classifier. The test results indicated that the performance of PCA-based SVM was on average 90% to recognize young- elderly gait patterns, resulting in a markedly improved performance over an artificial neural network-based classifier. The classification ability of the SVM with polynomial and radial basis function kernels was superior to that of the SVM with linear kernel. These results suggest that the proposed technique could provide an effective tool for gait classification in future clinical applications.     

Upper body accelerations during planned gait termination in young and older women

Transitory tasks, such as gait termination, involve interactions between neural and biomechanical factors that challenge postural stability and head stabilization patterns in older adults. The aim of the study was to compare upper body patterns of acceleration during planned gait termination at different speeds between young and older women. Ten young and 10 older women were asked to carry out three gait termination trials at slow, comfortable and fast speed. A stereophotogrammetric system and a 15-body segments model were used to calculate antero-posterior whole-body Center of Mass (AP CoM) speed and to reconstruct the centroids of head, trunk and pelvis segments. RMS of three-dimensional linear accelerations were calculated for each segment and the transmission of acceleration between two segments was expressed as a percentage difference. Older women reported lower AP CoM speed and acceleration RMS of the three upper body segments than young women across the three speed conditions. A lower pelvis-to-trunk attenuation of accelerations in the transverse plane was observed in older compared to young women, and mainly in the medio-lateral direction. As possible explanations, older women may not need to reduce acceleration as young women because of their lower progression speed and the subsequent acceleration at upper body levels. On the other hand, older women may prioritize a decrease in the whole body progression speed at expense of the involvement of upper body segments. This limits the attenuation of the accelerations, particularly in the transverse plane, implying an increased dynamic unbalance in performing this transitory task.     

Characterization of motor patterns in isolated human colon: are there differences in patients with slow-transit constipation?

The patterns of motor activity that exist in isolated full-length human colon have not been described. Our aim was to characterize the spontaneous motor patterns in isolated human colon and determine whether these patterns are different in whole colons obtained from patients with slow-transit constipation (STC). The entire colon (excluding the anus), was removed from patients with confirmed STC and mounted longitudinally in an organ bath ～120 cm in length, containing oxygenated Krebs' solution at 36°C. Changes in circular muscle tension were recorded from multiple sites simultaneously along the length of colon, by use of isometric force transducers. Recordings from isolated colons from non-STC patients revealed cyclical colonic motor complexes (CMCs) in 11 of 17 colons, with a mean interval and half-duration of contractions of 4.0 ± 0.6 min and 51.5 ± 15 s, respectively. In the remaining six colons, spontaneous irregular phasic contractions occurred without CMCs. Interestingly, in STC patients robust CMCs were still recorded, although their CMC pacemaker frequencies were slower. Intraluminal balloon distension of the ascending or descending colon evoked an ascending excitatory reflex contraction, or evoked CMC, in 8 of 30 trials from non-STC (control) colons, but not from colons obtained from STC patients. In many control segments of descending colon, spontaneous CMCs consisted of simultaneous ascending excitatory and descending inhibitory phases. In summary, CMCs can be recorded from isolated human colon, in vitro, but their intrinsic pacemaker frequency is considerably faster in vitro compared with previous human recordings of CMCs in vivo. The observation that CMCs occur in whole colons removed from STC patients suggests that the intrinsic pacemaker mechanisms underlying their generation and propagation are preserved in vitro, despite impaired transit along these same regions in vivo.     

膝骨性关节炎患者登梯时下肢肌肉活动和膝关节负荷的分析

目的:分析膝骨性关节炎患者(KOA)登梯时下肢肌群肌电活动与关节角冲量与正常人的差异,为康复方案设计提供生物力学参考。方法:采用Qualisys三维运动分析系统以及Delsys无线表面肌电系统对招募10名符合纳排标准的膝骨性关节炎患者和10名正常人进行登梯活动的步态检测,采用下肢肌群均方根值、股内外侧肌协同收缩比值、股二头肌和股外侧肌共同活动比值和髋、膝关节在冠状面和矢状面上角冲量对比分析与两组登梯时下肢肌群收缩模式对关节负荷的影响。结果:与正常对照相比,上梯时膝骨性关节炎患者股直肌均方根值RMS(Root Mean Square)增大(P0.05),膝骨性关节炎患者股内外侧肌收缩均方根值比值(RMS(Vastus Medialis)VM/(Vastus Lateralis)VL)减小(P0.05),膝骨性关节炎患者腘绳肌与股外侧肌收缩比值(RMS(Biceps Femoris)BF/VL增大(P0.05)。下梯时,膝骨性关节炎患者股直肌均方根值(RMS)增大(P0.05),臀大肌均方根值(RMS)减小(P0.05),股内外侧肌收缩均方根比值(RMS VM/VL)减小(P0.05)。上梯时,膝骨性关节炎患者髋、膝关节冠状面上的关节角冲量大于正常人(P0.05),膝关节在矢状面上关节角冲量大于正常组(P0.05),下梯髋、膝关节冠状面、矢状面上的角冲量无统计学差异(P0.05)。KOA组VM/VL、BF/VL与膝关节在冠状面和矢状面上的角冲量的改变没有直接的相关性(P0.05)。结论:膝骨性关节炎患者在登梯活动时股直肌的收缩活动增加,股内外侧肌的协同收缩下降,主动肌与拮抗肌的共同收缩增加,膝骨性关节炎患者在面对登梯活动时下肢肌群选择性激活和高激活状态协调一致,促进关节稳定。虽然下肢神经肌肉的收缩模式和膝关节负荷之间没有直接的相关性,可能是对膝关节负荷产生影响的生物力学因素较多,神经肌肉的收缩模式只是部分影响因素,后续将增加其他生物力学因素进一步研究。     

Functional coordination of motor activity in colonic smooth muscles in rat experimental model

Spontaneous and electrically-elicited motor activity was recorded by triple organ bath in rat segment-model preparation as display of excitation of local nerve networks and ascending or descending reflex pathways underlying contractile potency and functional coordination of colonic longitudinal and circular muscles. Spontaneous high-amplitude contractions, but not relaxations, appeared synchronously in both muscles. Electrical field stimulation applied to proximal or distal part of segments elicited both tetrodotoxin (0.1 microM)-sensitive local motor responses of the stimulated part and ascending or descending motor responses of the contralateral, nonstimulated part of the preparations. Contractions characterized the local response of longitudinal muscle. The circular muscle responded with relaxation followed by contraction. Synchronous ascending contractions and descending contraction of the longitudinal muscle and relaxation followed by contraction of the circular muscle were observed when the middle part of segments was stimulated, thus indicating that locally-induced nerve excitation propagated via intrinsic ascending or descending nerve pathways that could be synchronously coactivated by one and the same stimulus. The ascending motor responses were more pronounced and the motor responses of longitudinal muscle were expressed more than those of circular muscle suggesting an essential role of ascending reflex pathways and longitudinal muscle in the coordinated motor activity of colon.     

A treadmill ergometer for three-dimensional ground reaction forces measurement during walking.

This report describes new treadmill ergometer designed to measure the vertical and horizontal ground reaction forces produced by the left and right legs during walking. It was validated by static and dynamic tests. Non-linearity was from 0.2% (left vertical force) to 1.4% (right antero-posterior force). The resonance frequency was from 219 (right vertical direction) to 58 Hz (left medio-lateral direction). A calibration "leg", an air jack in series with a strain gauge, was developed and used to produce force signals comparable to those obtained during human locomotion. The mean differences between the force measured by the calibration leg and treadmill ergometer at 5 km h(-1) were 3.7 N (0.7%) for the left side and 6.5 N (1.2%) for the right. Measurements obtained during human walking showed that the treadmill ergometer has considerable potential for analysing human gait.     

Trunk's Natural Inclination Influences Stance Limb Kinetics,but Not Body Kinematics,during Gait Initiation in Able Men

The imposing mass of the trunk in relation to the whole body has an important impact on human motion. The objective of this study is to determine the influence of trunk''s natural inclination - forward (FW) or backward (BW) with respect to the vertical - on body kinematics and stance limb kinetics during gait initiation.Twenty-five healthy males were divided based on their natural trunk inclination (FW or BW) during gait initiation. Instantaneous speed was calculated at the center of mass at the first heel strike. The antero-posterior impulse was calculated by integrating the antero-posterior ground reaction force in time. Ankle, knee, hip and thoraco-lumbar (L5) moments were calculated using inverse dynamics and only peaks of the joint moments were analyzed. Among all the investigated parameters, only joint moments present significant differences between the two groups. The knee extensor moment is 1.4 times higher (P<0.001) for the BW group, before the heel contact. At the hip, although the BW group displays a flexor moment 2.4 times higher (P<0.001) before the swing limb''s heel-off, the FW group displays an extensor moment 3.1 times higher (P<0.01) during the swing phase. The three L5 extensor peaks after the toe-off are respectively 1.7 (P<0.001), 1.4 (P<0.001) and 1.7 (P<0.01) times higher for the FW group. The main results support the idea that the patterns described during steady-state gait are already observable during gait initiation. This study also provides reference data to further investigate stance limb kinetics in specific or pathologic populations during gait initiation. It will be of particular interest for elderly people, knowing that this population displays atypical trunk postures and present a high risk of falling during this forward stepping.     

Ambulatory estimation of mean step length during unconstrained walking by means of COG accelerometry

It has been reported that spatio-temporal gait parameters can be estimated using an accelerometer to calculate the vertical displacement of the body's centre of gravity. This method has the potential to produce realistic ambulatory estimations of those parameters during unconstrained walking. In this work, we want to evaluate the crude estimations of mean step length so obtained, for their possible application in the construction of an ambulatory walking distance measurement device. Two methods have been tested with a set of volunteers in 20 m excursions. Experimental results show that estimations of walking distance can be obtained with sufficient accuracy and precision for most practical applications (errors of 3.66 ± 6.24 and 0.96 ± 5.55%), the main difficulty being inter-individual variability (biggest deviations of 19.70 and 15.09% for each estimator). Also, the results indicate that an inverted pendulum model for the displacement during the single stance phase, and a constant displacement per step during double stance, constitute a valid model for the travelled distance with no need of further adjustments. It allows us to explain the main part of the erroneous distance estimations in different subjects as caused by fundamental limitations of the simple inverted pendulum approach.     

Alternate stair descent strategies for reducing joint moment demands in older individuals

Descending stairs requires elevated joint moment-generating capability in the lower limbs, making it a challenging daily activity, particularly for older individuals. The aim of the study was to investigate the influence of three different strategies for descending standard and increased height stairs: step-over-step (SoS), step-by-step (SbS) and side-step (SS) on lower limb kinetics in older people. Eleven participants (mean ± SD age: 74.8 ± 3.1 years, height: 1.63 ± 0.07 m, mass: 67.7 ± 9.5 kg) descended a four-step custom built instrumented staircase at a self-selected speed, adopting each of the three strategies, at two configurations: a step-rise height of 170 mm (standard; STD) and a step-rise height of 255 mm (increased; INC). 3D motion capture, synchronised with embedded force plates enabled the calculation of joint kinetics of lead and trail limbs. Data were analysed using a Linear Mixed Model with gait speed selected as a covariate during weight acceptance (WA) and controlled lowering (CL) phases. A large increase in hip extensor moment in both WA and CL in the lead limb was evident during both SoS and SbS at INC step height compared to STD (P < .015 for all), with no such increase in hip flexor moment evident in SS strategy (P = .519). Lead limb knee extensor moment decreased and plantarflexor moment increased in INC SoS compared to STD SoS during CL (P < .001 for both). In the trail limb, increased hip extensor and plantarflexor moments were seen in INC SS compared to STD SS (P < .001 for both). The alternate strategies result in the overall task demand being split between the lead limb (weight acceptance) and trail limb (controlled lowering). Differential demand distribution patterns exist between strategies that imply targeted interventions and/or advice could be provided to older individuals in order to promote safe descent of stairs, particularly for those with specific muscle weaknesses or at high risk of falls.