Mechanisms of Fall Resistance to Diverse Slipping Conditions

Falls are the leading source of injury for all ages, and for older adults are the primary cause of injury related death. Loss of foot to ground traction accounts for 25-40% of falls, typically referred to as a slip. Slips alter the relationship between center of mass and lower limb base of support resulting in altered whole-body angular momentum and inability to support body weight due to loss of stability. But not all slips lead to falls. Stability may be recovered through a combination of response movements, such as swinging the arms or rapid recovery steps. Stability must be recovered quickly otherwise insufficient bodyweight support rapidly leads to a damaging ground collision. A high percentage of falls result in fractures, contusions and sprains to both the trunk and limbs, while slips disproportionately cause lower back injuries. A primary goal of fall prevention training is to improve the ability to resist slips using perturbations that mimic the specific sensory and biomechanical context of natural slip events. However, generating lifelike slip perturbations that mimic the diversity of slipping conditions poses a significant hurdle to improving a more general slip resistance ability. 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.

Study Overview

• Status: Completed
• Conditions: Slipping and Falls
• Intervention / Treatment: Other: Slips on Turns; Other: Slips on Slopes

Detailed Description

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 encountered in the real environment.

This project will determine the impact of turns and slopes on reactive movements and fall vulnerability by determining the effects of path curvature on reactive movements and slip vulnerability at different times in the gait cycle and determining the effects of ground slope on reactive movements and slip vulnerability at difference times in the gait cycle. It is hypothesized that diverse slipping conditions will change the reactive responses involving protective stepping and arm swing and 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.

• Study Type: Interventional
• Enrollment (Actual): 43
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Nebraska
    • Omaha, Nebraska, United States, 68182
      • Biomechanics Research Building

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 19 years to 35 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Slips on Turns; Slips will be 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; A slip will be administered to participants 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.
Experimental: Slips on Slopes; Slips will be 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; Slips will be administered to participants 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 Computer Assisted Rehabilitation Environment (CAREN) system treadmill.

What is the study measuring?

Primary Outcome Measures

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

Collaborators and Investigators

• Sponsor: University of Nebraska
• Collaborators: National Institute on Aging (NIA)
• Investigators: Principal Investigator: Nathaniel H Hunt, PhD, University of Nebraska

Study record dates

Study Major Dates

• Study Start (Actual): December 15, 2019
• Primary Completion (Actual): November 16, 2021
• Study Completion (Actual): November 16, 2021

Study Registration Dates

• First Submitted: November 27, 2018
• First Submitted That Met QC Criteria: November 27, 2018
• First Posted (Actual): November 29, 2018

Study Record Updates

• Last Update Posted (Actual): July 4, 2025
• Last Update Submitted That Met QC Criteria: June 17, 2025
• Last Verified: April 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: 0861-18-EP; 1R15AG063106 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data for all primary and secondary outcome measures will be made available.
• IPD Sharing Time Frame: Data will be available within 6 months of study completion.
• IPD Sharing Access Criteria: Data access requests should be emailed to the PI.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No