SUMMARY

• Incorrect walker is associated with increased fall risk in older adults, but little is being done to correct the issue.
• Our product, the Stride Tech Go, measures the two most common methods of incorrect walker use: 

1. Excessive weight through the handles (measured as left- and right-hand force on the left- and right-hand handles)
2. Excessive distance between the user and the device (measured as the distance between the user’s hip and the frame of the walker) 

• With data from Stride Tech Go, we can characterize walker behavior into Incorrect Walker Use and Correct Walker Use
• Incorrect use can be distinguished between High Hip Distance, High Weight Bearing, and both High Hip Distance and High Weight Bearing

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INTRODUCTION

Stride Tech Medical Inc.’s mission is to prevent falls. Seniors widely use walkers to maintain mobility while reducing the risk of falls. Despite the benefits, habitually poor walker use, marked by excessive weight on the walker handles and/or excessive distance between the user and the walker, can lead to muscle atrophy, poor posture, and falls. A widely publicized investigation in 2009 showed that over 87% of severe falls with an assistive device occurred with a walker. They recommended increased time devoted to fitting and education on proper use. Eleven years later, most seniors still do not receive individualized fitting or training on how to use their walkers.

Our product, the StrideTech Go (STG), is an attachable walker accessory that integrates sensors and biofeedback onto existing walkers to correct common misuses in real-time. Grip covers embedded with sensors Velcro over the handles of a walker. An additional sensor is mounted to the frame which measures the distance from the user’s hip to the walker frame. The grip covers vibrate if the sensors detect either of the two primary indicators of walker misuse:

• Excessive weight through the handles
• Excessive distance between the frame of the walker and the use

StrideTech Go is the first commercial product to help fill the urgent need for long-term walker use training. This white paper will outline the technical background and testing that has been done to establish efficacy and briefly outline the next steps and improvements. 

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PROTOCOL

Stride Tech defines characterization as the ability to distinguish between types of walker misuse using data alone. The data presented was collected in Denver University’s Human Dynamics Laboratory. A Stride Tech team member and walker were outfitted with motion capture markers. They performed four different walking tasks with a Stride Tech Go outfitted walker while the laboratory’s motion capture system monitored their movement. 

The four different walking tasks were:

1. Upright, correct walker use
2. Incorrect walker use: high hip distance, correct weight-bearing
3. Incorrect walker use: correct hip distance, high weight-bearing
4. Incorrect walker use: high hip distance, high weight-bearing

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For each of the incorrect use scenarios, the team member would start from standing, exaggerate the incorrect use to their maximal range of motion, then begin walking while attempting to maintain their position. The Stride Tech hip-distance and weight-bearing data were graphed and categorized to establish if patterns in the data could be established and to ensure reliable accuracy of our system’s sensors as compared to a research standard instrument. 

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RESULTS

Above are graphs of the Hip Distance (mm) as measured by the STG sensors (blue line) and Human Dynamics Motion Capture System (orange line) against the frame rate of the motion capture system. (Because the motion capture is captured in frames, we adjusted the sampling frequency of our sensor system to match that of the motion capture frame rate.) Proper posture and correct use (top left) can be compared against the three different incorrect use scenarios: high hip distance and correct weight-bearing (top right), correct hip distance and high weight-bearing (bottom left), and high hip distance and high weight-bearing (bottom right). Three key takeaways were established during this testing phase.

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First, in each of the test scenarios, the accuracy of the STG hip-distance sensor was comparable with that of the motion capture system. Allowing comparison against industry standards and accepted measurement systems is vital to the product’s viability and efficacy. Now, with a justifiable degree of confidence, we can reasonably measure hip distances for a wide range of motion. Compared with the motion capture system average, the STG sensors had a 4% error in measuring average hip distance. 

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Second, during high hip-distance scenarios, a clear pattern of increased hip distance can be visualized and a clear increase in average hip-distance can be calculated. Incorrect use and correct hip-distance/high weight-bearing scenarios, the average hip-distance measured was about 300mm and 340mm, respectively. For high hip-distance scenarios, the average hip distance was 680-690mm.  This nearly 300mm increase is vital for further understanding. While this testing scenario utilized the maximal range of motion of a healthy young adult trying to simulate incorrect walker use, it allows us to have a benchmark in understanding future testing with older adults and how they might compare to these testing scenarios. 

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Third, comparing the correct use trial against the correct hip distance and high weight-bearing trial, we see little difference in visual or calculated hip distance. This is useful as in the second scenario, the walker was still misused. This effectively tells us that 1: we cannot see any secondary effects of high weight-bearing any hip-distance data, as we have previously hypothesized, and 2: we are justified in having a dual sensor (i.e. sensing hip distance and weight-bearing. This allows us to effectively capture walker misuse by measuring multiple modes of misuse. 

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CONCLUSION

To be able to effectively correlate data with real behaviors, more data collection is needed, particularly with older adult walker users as there may be an additional mode of misuse we can not replicate. Additionally, more testing with people of different heights, weights, and mobility will allow us to have a greater repository of hip distance ranges that may be normal vs. unhealthy. 

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