Mechanisms of Fall Resistance to Diverse Slipping Conditions
Phase: NA
Conditions: Slipping and Falls
Sponsor: University of Nebraska

Title: Mechanisms of Fall Resistance to Diverse Slipping Conditions 
NCT03758040 
11 Mar 2021 

Study Protocol 
For all gait collections, participants will arrive at the Biomechanics Research Building on the University of 
Nebraska at Omaha campus. All participants will be consented and screened prior to gait testing. During 
the consent process, participants will be asked if they can be contacted again for future research studies. 
During the screening, participants will undergo a short medical history. 
Participants will be asked to put on a form fitting suit for data collection. Body weight, height and 
extremity anthropometry will be collected (length of arm and leg segments). Retroreflective markers will 
be placed on the legs, arms, torso and head to obtain whole-body kinematic data. A ceiling-mounted 
safety harness will also be fitted to each participant. Prior to performing any walking trials, the 
participants will be allowed to "sit" in the harness to experience how it feels when it catches them. 
 
 
Aim 1 Specific Methods 
Young healthy participants will undergo overground gait and stabilization movement analysis sessions 
that will last approximately 210 minutes. All participants will be fitted with a form-fitting singlet, ceiling 
mounted safety harness, lab-provided shoes, and a full-body retroreflective marker set. A load cell 
placed in line with the safety harness will allow for the quantification of forces exerted on the harness at 
80 Hz. A 17 camera 3D motion capture system will be used to collect kinematic data at 120 Hz 
throughout each trial. Data will be collected at a comfortable walking speed of 1.3 m/s53. Walking 
speed will be monitored using timing gait plates placed along the path. Participants will be coached to 
maintain prescribed walking speed. A repeated measures design will have participants slip both feet at 3 
different times in the gait cycle for each of 3 path curvatures for a total of 18 slip episodes. Slips will be 
delivered while walking along a straight path (infinite radius), or curved paths with radii of 2 or 1 meters. 
A path consisting of multiple turns will be marked on the floor of the lab, including turning radii of 2 and 
1 meters. 
Only right turns will be examined, as previous research has found no difference between the kinematics 
of left and right turns. Participants will follow the path for a randomly selected amount of time between 
1 and 3 minutes. After this time has elapsed, the investigator will initiate a slip during a randomized turn 
on the path in early, middle, or late stance. Participants will be given a seated rest period of 5 minutes 
between each trial. 
 
 
Aim 2 Specific Methods 
Young healthy participants will undergo treadmill gait and stabilization movement analysis sessions that 
will last approximately 270 minutes. All participants will be fitted with a form-fitting singlet, a safety 
harness mounted to the rigging of the CAREN system, lab-provided shoes, and a full- body retroreflective 
marker set. A load cell placed in line with the safety harness will allow for the quantification of forces 
exerted on the harness at 80 Hz. Data will be collected with the treadmill set at a comfortable walking 
speed of 1.3 m/s53. A repeated measures design will have participants slip at 3 different times in the 
gait cycle for each of 5 different uphill/downhill slopes and at 3 times to both feet for 2 cross-slopes for 
a total of 27 slip episodes (3 phases x 5 slopes that foot doesn't matter + 3 phases x 2 feet x 2 slopes that 
foot matters). 

Specifically, slips will be delivered 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. 
Sloped surfaces will be generated with the CAREN system treadmill, which is capable of pitch and roll 
±16 degrees.55Slip onset will be triggered by the experimenter in a randomized order at early, mid, or 
late stance. Participants will walk on the prescribed slope and a slip will be triggered on after a randomly 
predetermined amount of time between 1 and 3 minutes at either early, middle, or late stance. 
Participants will be given a seated rest period of 5 minutes between each trial. To quantify the effects of 
the slip perturbation, whole body angular momentum, COM characteristics, arm movements, and slip 
characteristics will be derived from the kinematic data. 
 
 
Statistical Analysis Plan 
For each variable, investigators will test for normality and employ the appropriate parametric or non-
parametric descriptive statistics. Histograms and plots for each variable will be made and examined. 
Statistical hypothesis testing will be done using custom software written in R statistical computing 
language (R Core Team). General linear mixed-effects model will be used to determine the effects of 
diverse slip conditions on reactive movements and slip severity measures for all aims. This mixed-effects 
model will be used to include participants and order as random factors while testing for differences 
between conditions. For example, even though these data will have repeated measures from the same 
subject, a linear mixed effect model can resolve those non-independencies by including participants as a 
random factor and accounting for changes from baseline participant variation. Aim 1: independent 
variables will be a) turn radius (4 levels: no turn, 2m, 1m, 1/2m), b) slip timing (3 levels: early, mid, and 
late stance). Aim 2: independent variables will be a) slope (7 levels: no slope, ±5.3 degrees AP, ±10.6 
degrees AP, ±5.3 degrees ML, ±10.6 degrees ML).