Mechanisms of Fall Resistance to Diverse Slipping Conditions

Study Overview
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Brief Summary
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Using movement analysis, the investigators will determine the relationships between diverse slip conditions, reactive responses to slips from those conditions, and slip vulnerability across the gait cycle to generate new data that may guide future interventions.

Detailed Description
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Recent evidence suggests most slip-related falls in daily life happen in diverse slipping conditions where the ground is not level, or the person is turning or changing direction. While slips that occur during straight walking on level ground and the responses to those slips are relatively well understood, very little is known about slips that occur while walking on slopes or curved paths and which reactive responses are effective to prevent falls in such conditions. This limits the ability of clinicians to incorporate a diverse range of slipping experiences into fall prevention interventions. Understanding how reactive responses and slip vulnerability depend on diverse slip conditions may guide future interventions that promote a more general fall resistance to the broader range of slips we encounter in the real environment. Thus, the objective of this research project is to determine the impact of turns and slopes on reactive movements and fall vulnerability. The aims of this study are (1) to determine the effects of path curvature on reactive movements and slip vulnerability at different times in the gait cycle, and (2) to determine the effects of ground slope on reactive movements and slip vulnerability at difference times in the gait cycle. The investigators hypothesize that diverse slipping conditions will change the reactive responses involving protective stepping and arm swing. In addition, the investigators hypothesize that the distinct dynamics of turns and slopes produce maximum vulnerability to slips at different times in the gait cycle compared to slips during straight walking on level ground. To evaluate these aims, the investigators will administer slip perturbations on slopes that vary in both magnitude and direction, on curved paths that vary in curvature, and with slip onset that varies across early, middle, and late stance. Understanding the relationships between diverse slipping conditions, reactive responses, slip severity and fall vulnerability may guide future research and training interventions towards more comprehensive fall resistance ability.

Official Title
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Mechanisms of Fall Resistance to Diverse Slipping Conditions

Conditions
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Slipping and Falls

Intervention / Treatment
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* Other: Slips on Turns
* Other: Slips on Slopes


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 19-35 Exclusion Criteria: Uncontrolled hypertension Peripheral arterial disease Knee osteoarthritis Vertigo Meniere's disease Chronic dizziness History of back or lower extremity injury Surgery that affects mobility Neurological disease that limits the ability to walk

Ages Eligible for Study
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Minimum Age: 19 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Slips on Turns<br>Slips administered during walking on a curved paths of radii 1.0, or 2.0 meters in early, middle or late stance to the inside or outside foot. | Other: Slips on Turns<br>* Subjects will be administered a slip at 3 different times in the gait cycle for each of 3 different patch curvatures and 2 different legs for a total of 18 slip episodes. Slips will be delivered while walking along a straight path (infinite radius), or curved paths with radii 2, or 1 meters.<br>|
| Experimental: Slips on Slopes<br>Slips administered during walking on sloped ground of 5.0 or 10.0 degrees mediolaterally or anteroposteriorly, or flat ground, in early middle or late stance. For mediolateral slopes, slips will be administered to the uphill or downhill foot. | Other: Slips on Slopes<br>* Slips will be administered at 3 different times in the gait cycle over sloped ground surface of no slope, ±5.0 and ±10.0 degrees slopes in the direction of walking, and 5.0 and 10.0 degrees perpendicular to the direction of walking. On slopes perpendicular to the direction of walking, slips will be administered to the uphill or downhill foot. A total of 27 slip episodes will be administered. Sloped walking surfaces will be generated with the CAREN system treadmill.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Fall Rate | Percentage of trials which result in a fall. Falls are classified when a load cell embedded in the harness system measures support forces exceeding 30% body weight. | Up to 4 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Slipping foot distance | The distance travelled by the slipping foot relative to the center of mass following the administered slip perturbation | Up to 4 hours | 
| Slipping foot maximum velocity | The maximum velocity of the slipping foot relative to the center of mass following the administered slip perturbation | Up to 4 hours | 
| Trunk maximum angular momentum | The maximum angular momentum of the trunk following the administered slip perturbation | Up to 4 hours | 
| Reactive stepping response placement | Position of the placement of the reactive stepping response relative to the center of mass following the administered slip perturbation | Up to 4 hours | 
| Reactive stepping response time | Duration of time between the onset of the administered slip perturbation and the placement of the reactive stepping response | Up to 4 hours | 
| Reactive arm swing momentum change | The change in arm momentum between the onset of the administered slip perturbation and the end of the slip | Up to 4 hours |