Gait

Quantifying stair gait stability and plantar pressure in an aging community, with modifications to insoles and lighting

Submitted by Patrick Antonio

Introduction: Stair gait is an activity performed daily. Inherently falls during stair gait continue to be a concern especially for older adults 65 years +. Recently falls have become the most common cause of injury-related deaths in individuals over the age of 75 y.o. Stair descent falls account for 75% of stair falls and also present a greater injury severity. Poor shoes or insoles and lighting condition can contribute to an increased risk of falls during stair locomotion. Stability can be measured using the COM-BOS ‘stability margin’ relationship. Center of pressure (COP), another stability measure,can be calculated from a multi-axis force-plate system. As well, plantar pressure is an important indicator of gait pattern efficiency. Aim: To identify aspects of stair gait that increase the risk of falls. By measuring the COM-BOS ‘stability margin’, the COP and plantar pressure patterns of individuals during stair gait, while modifying insoles and lighting. Methods: Young and older adults will ascend and descend a 4 level staircase, with two imbedded AMTI-force platforms in varying lighting condition (low, normal). Participants will be fitted with standardized footwear with Medi-logic insoles placed under varying hardnesses of insoles. An Optotrak motion capture system will record 12 IRED markers placed on the individual to determine the COM trajectory and BOS of location. Hypothesis: Partipants should demonstrate a greater lateral displacement in the single support phase during dim lighting as opposed to normal lighting. The stability of older adults will be compromised with alteration to the insoles (soft and hard).


Listed In: Biomechanics, Gait, Other 




  

    			
Implementing Real-Time Gait Analysis Algorithm for Fall Avoidance in Parkinson’s Disease  

		    
        

      Submitted by INAM UL HAQ
    

    
        	

    		
    		

    			    			    		

    		

    			
Our thesis project is related to analyze real-time gait analysis of Parkinson's patient in order to actively respond to his non-stable movements. Based on real world data, we have developed a mechanism to implement an algorithm to trigger security alarm to avoid patient from falling. This algorithm is not hard coded i.e. user can set Sampling Rate & Threshold values to analyze motion data for fall avoidance. While other researchers can also utilize this algorithm in their study without need to implement. Maximum gait parameters are also discussed & a 4GB Test is designed first time to take measurements systematically.



    			Listed In: Gait, Neuroscience
    		

    	

        
      









  

    			
Alignment of plantar pressure data with 3D foot placement data

		    
        

      Submitted by Philip Davenport
    

    
        	

    		
    		

    			    			    		

    		

    			Measurement of the plantar pressure present on the foot during gait is of interest to clinicians prescribing orthotics. Two methods of measurement are common, an in-shoe sensor or a pressure sensitive mat. The former can measure the effect of shoes and orthotics, but cannot independently provide temporal-spatial parameters of walking. Some pressure mat systems can do this, but are unable to examine the foot-shoe interface. Foot progression angle is known to influence plantar pressure recordings and is of clinical interest as evidence of biomechanical compensation.

An analysis technique that combines in-shoe plantar pressure (FScan, Tekscan Ltd.) and 3D motion capture (VICON, Oxford Metrics Ltd.) information is presented. Markers on the heel and toe are used to provide a vector for each foot in the global co-ordinate system of the laboratory. By combining the images of peak pressure within the shoe at each stance with the position and orientation of the foot during midstance, a virtual pressure mat can be visualised and parameters such as step length, step width and foot progression angle can be reported in tandem with pressure data. Further work will be to develop this into a clinically usable tool.


    			Listed In: Biomechanics, Gait
    		

    	

        
      









  

    			
A Phenomenological Human Energy Expenditure Model in Joint Space

		    
        

      Submitted by Dustyn Roberts
    

    
        	

    		
    		

    			    			    		

    		

    			
Humans act as transducers that transform chemical energy from food, water, and air into mechanical work and the thermal energy of heat loss. Although this energy expenditure can be experimentally measured, methods of predicting energy expenditure have not been broadly studied. This work introduces a new formulation of metabolic energy consumption based on muscle physiology and the equations of motion for the human body. Kinematic and kinetic data from a gait experiment and an over-arm throwing simulation are used to illustrate and validate this new model. The results extend the capabilities of dynamic human modeling to include metabolic energy prediction in general tasks. This novel formulation is useful for the investigation of human performance with applications in physical therapy, rehabilitation, and sports.



    			Listed In: Biomechanical Engineering, Biomechanics, Gait, Mechanical Engineering, Sports Science
    		

    	

        
      









  

    			
Touching Ground: Inertial Sensors.  Accuracy and precision of spatiotemporal characteristics from fetlock mounted inertial 
measurement units compared to motion capture in horses during over ground walk 

		    
        

      Submitted by Emil Olsen
    

    
        	

    		
    		

    			    			    		

    		

    			
Accurate distal limb spatiotemporal characteristics are useful parameters for a mobile kinematic system to quantify lameness and ataxia in horses. The objective was to compare spatial (position estimates) and temporal characteristics (hoof-on/off and stance time) from fetlock mounted inertial measurement units (IMUs) to motion capture and force plates during walk. Seven horses were walked across a 25 m runway with a central 4.8 m data collection area. We used IMUs (sampling at 200 Hz) that were placed proximal to all four fetlock joints and synchronized to a 12 camera motion capture system sampling at 200 Hz and eight force plates sampling at 500 Hz. We found the temporal characteristics were obtained with an accuracy of -0.02 to -7.38 ms and spatial characteristics with an accuracy of 0.9 to -29.79 mm with good precision for spatial and temporal characteristics, showing the potential for a reliable portable kinematic system based on IMUs.



    			Listed In: Biomechanics, Gait
    		

    	

        
      









  

    			
Touching Ground: Inertial Sensors.  Accuracy and precision of spatiotemporal characteristics from fetlock mounted inertial 
measurement units compared to motion capture in horses during over ground walk 

		    
        

      Submitted by Emil Olsen
    

    
        	

    		
    		

    			    			    		

    		

    			Accurate distal limb spatiotemporal characteristics are useful parameters for a mobile kinematic system to quantify lameness and ataxia in horses. The objective was to compare spatial (position estimates) and temporal characteristics (hoof-on/off and stance time) from fetlock mounted inertial measurement units (IMUs) to motion capture and force plates during walk. Seven horses were walked across a 25 m runway with a central 4.8 m data collection area. We used IMUs (sampling at 200 Hz) that were placed proximal to all four fetlock joints and synchronized to a 12 camera motion capture system sampling at 200 Hz and eight force plates sampling at 500 Hz. We found the temporal characteristics were obtained with an accuracy of -0.02 to -7.38 ms and spatial characteristics with an accuracy of 0.9 to -29.79 mm with good precision for spatial and temporal characteristics, showing the potential for a reliable portable kinematic system based on IMUs.

    			Listed In: Biomechanics, Gait
    		

    	

        
      









  

    			
Backward walking; wider steps as stabilizing strategy

		    
        

      Submitted by Wouter Hoogkamer
    

    
        	

    		
    		

    			    			    		

    		

    			
Backward walking has been suggested to be less stable than forward walking and although some studies have reported on the variability in some gait parameters, a detailed evaluation of stability is still lacking. The aim of the current study was to evaluate the stability of backward walking using concurrent stability measures. Twelve healthy participants walked forward and backward at 1.11 m/s for 7 minutes each on a treadmill while 3D ground reaction forces were recorded. Instants of heel strike and toe-off were determined based on the center of pressure (CoP). We calculated step width, step width variability and stride time variability. We estimated the center of mass (CoM) based on the CoP and calculated the "extrapolated center of mass" (XCoM) and the safety margin between the XCoM and the base of support. Moreover, we calculated short term maximum Lyapunov exponents (λs) following Bruijn's protocol, and applied this to the medio-lateral displacement of the estimated CoM. We included 300 strides in the evaluation of all measures. Backward walking is observed to be more variable in both step width and stride time, and less locally stable than forward walking, all in all suggesting reduced control of stability during backward walking. The observed increases in step width and safety margin in backward compared to forward walking, suggests that participants increased their step width during unstable locomotion to increase the safety margin between the extrapolated center of mass and their base of support.



    			Listed In: Biomechanics, Gait
    		

    	

        
      









  

    			
Walking stabilized by body mechanics and heel-to-toe center-of-pressure shift  provides insight on control of upright posture  

		    
        

      Submitted by Wendy Boehm
    

    
        	

    		
    		

    			    			    		

    		

    			When walking humans fall, they usually fall over, not down. Analysis of whole body angular motion in human walking has received inadequate attention, leaving gaps in the understanding of how motor control and body mechanics interact to maintain upright posture. We describe a component of body mechanics that walking humans appear to exploit to rotationally stabilize upright posture. For a given state during walking, we investigate the mechanical effect of varying ankle torque on the force of the ground on the foot (F) to understand the role of heel to toe center-of-pressure (CP) and how it contributes to the overall F behavior observed in walking. Kinematic and force place data were collected for a human subject walking on a force treadmill. An inverse dynamics approach was used to calculate hip, knee, and ankle joint torques. Those calculated joint torques were applied to the model. At time points during stance phase, multiple values of ankle torque were used in the forward dynamics equations to predict the accelerations of the segments and F.  At each single-leg-stance posture within walking, variation in ankle torque altered F direction and CP such that the set of F intersected at a single point (Π). These results indicate that preference for heel-to-toe CP shift exploits mechanical properties of the human to enhance stability.  The control in the absence of heel-to-toe CP shift also has practical implications. Treatment of human balance deficits and design of walking aids and devices may benefit if designed to exploit the Π mechanics.

    			Listed In: Biomechanical Engineering, Biomechanics, Gait, Neuroscience
    		

    	

        
      









  

    			
Considerations when using a residual analysis to determine the optimum cutoff frequency for kinetic waveforms

		    
        

      Submitted by Chad Gooyers
    

    
        	

    		
    		

    			    			    		

    		

    			Despite its use in biomechanics research, there exists no standardized method for implementing a residual analysis to define the optimum cutoff frequency (OCF) of low-pass digital filters. Given the potential for this processing to have an impact on results, an objective routine is necessary for consistent data treatment between investigations and laboratories. Therefore, the goal of this study was to formalize an objective routine to implement a residual analysis, and examine whether it could be applied to kinetic signals. METHODS - Part I: The following parameters were hypothesized to effect the OCF determined through residual analysis: (i) linearity criterion magnitude, (ii) frequency axis resolution and (iii) range of cutoff frequencies included in the analysis.  Part II: Two existing datasets were used to evaluate the objective routine that was developed.   For each study, four dependent measures were calculated from ground reaction force data, including: (i) peak force, (ii) time to peak force, (iii) rate of force development and (iv) impulse. To examine the influence of using a digital Butterworth filter with OCF, each measure was compared to both the raw signal and a commonly applied cutoff frequency of 20 Hz. RESULTS - The objective routine developed was found to be most sensitive to the range of frequencies included in the analysis. In Part II, both the F-20 and OCF filtering conditions had minimal impact on all force-time dependent measures, except for rate of force development. IMPLICATIONS - Residual analysis may not be appropriate for selecting an OCF when filtering kinetic signals.


    			Listed In: Biomechanical Engineering, Biomechanics, Gait, Orthopedic Research, Sports Science
    		

    	

        
      









  

    			
The effect of a random visual perturbation on git variability

		    
        

      Submitted by jung chien
    

    
        	

    		
    		

    			    			    		

    		

    			
Vision provides information about spatial location as well as other environmental features. Manipulation of visual input alters gait patterns including gait variability. When visual input was manipulated by a periodic change in the speed of optic flow, gait parameters showed a negative correlation with the speed of optic flow. Furthermore, step length variability increased when the optic flow was disturbed by discrete oscillations appearing at random time points. However, in this latter study the environment was horizontally oscillated without affecting the optic flow. No previous research has addressed how gait variability will be altered if the optic flow is perturbed randomly. Therefore, the purpose of this study was to investigate how gait variability changes during treadmill walking under two visual conditions: 1) random optic flow perturbations, and 2) normal optic flow. Ten healthy young adults (five males; aged 25±5 years) walked on an instrumental treadmill with a surrounding virtual reality environment. The coefficient of variation (CV; %) for step length and step time was used to assess gait variability. A pairwise t-test was performed to determine condition effects on step length and step time. The level of significance was set at 0.05. Our results confirmed that gait variability in both spatial and temporal aspects was affected by random visual perturbations. Our results showed that given random visual perturbation in both the amount and time of appearance reduced the gait variability. We speculated that stress played an important role to reduce the gait variability under random visual perturbations.



    			Listed In: Biomechanics, Gait, Posturography