EFFECTS OF TREADMILL SLOPE AND SPEED ON VERTICAL GROUND REACTION
FORCES DURING TREADMILL WALKING.
V.M. Pittenger1,2, S.T. McCaw1 , M.R. Torry2, M.J. Decker2, & J.R. Steadman2
1Biomechanics Laboratory, Illinois State University 2SteadmanHawkins Sports Medicine
Foundation
Weight bearing activity inducing high impact loads on the lower extremity has been implicated
with knee joint injury. Although higher vertical ground reaction forces (vGRF) have been
measured at faster than usual speeds and vGRF are affected by walking surface slope, the
interaction of slope and speed has not previously been reported. The purpose of this study was
to measure vGRF with grade a speed manipulation. Eleven healthy subjects (5 female, 6 male)
volunteered in this study. vGRF data were collected (500 Hz) under the left foot while subjects
walked on a motorized treadmill with two speed conditions (self-selected and constant) and six
treadmill slopes (-5%, 0%, 5%, 10%, & 20%). At least 10-trial mean of each subject/variable was
entered into a 2X6 repeated measures ANOVA (alpha =0.05) with Bonferroni modifications to the
post hoc tests. Results indicated a significant speed X slope interaction on the variable loading
rate and a significant main effect on the first maximum force. The results suggest that both slope
and speed must be taken into consideration when attempting to reduce the magnitudes of critical
vGRF parameters in treadmill walking programs.
Factors Influencing Peak Horizontal Velocity during the Sit-to-Stand Transition of Older
Adults
P.K. Schot1, S.M. Poole1, L.A. Mrotek1, K.M. Knutzen2
1Department of Human Kinetics, University of Wisconsin-Milwaukee
2Department of Physical Education, Western Washington University
The purpose of this study was to examine the influences of gender, fall history, and strength gain
on peak horizontal velocity of the center of mass during a sit-to-stand task for older adults.
Subjects (N=38) participated in an 8-week strength training program (1-1.5 hrs./day, 3
days/week). Participants performed three sit-to-stand trials for analysis before and after the
exercise program. Video and strength data were processed, and data reduction was conducted
to identify performance differences associated with the independent variables. The results
provided evidence that men classified as non-fallers had a significantly greater increase in centerof-mass peak horizontal velocity than men classified as fallers and women classified as either
fallers or non-fallers. Additionally, women classified as fallers had a significantly greater increase
in center-of-mass peak horizontal velocity than women non-fallers. Strength gains were
assessed in relation to these findings.
Physical predictors of success in rock climbing
Spring 2000 Biomechanics Class, University of Northern Iowa.
The purpose of this study was to determine whether measures of grip strength, BMI, leg span,
thigh separation angle, leg strength and upper body strength predict eventual success in
beginning rock climbers. Subjects were 70 students enrolled in 8-week rock climbing classes.
Tests of the variables of interest were done on the first day of class. During the last class meeting
climbing skill was assessed based on the greatest route difficulty acheived by each student.
Results are currently being evaluated.
WHEELCHAIR MECHANICS WHILE TRAVERSING SURFACE IRREGULARITIES
Matthew T. Gregg and Timothy R. Derrick
Department of Health & Human Performance, Iowa State University, Ames, IA
INTRODUCTION
According to Cooper (1995), more than 20 million people worldwide rely on wheelchairs as their
primary source of mobility. Despite the growing acceptance and push to accommodate individuals in
wheelchairs, these individuals still deal with obstacles and inconveniences on a daily basis, ranging from
small cracks on a sidewalk to extremely rough terrain to un-cut curbs. According to Gaal et al. (1997),
many improvements could be made to wheelchair design to decrease the number of accidents that occur.
Gaal reported that 42 percent of incidents were tips and falls, many of which required medical attention.
The purpose of the study was to investigate the mechanism of slipping and/or tipping out of the wheelchair.
METHODS
Five non-wheelchair users volunteered to participate in the study. Three factors were investigated—
caster type, wheelchair velocity, and obstacle height. An Action Pro-T lightweight manual wheelchair
(Invacare®) was used for data collection with two caster types—the first of the caster types was a standard
rigid caster (STC) while the second set was a new shock absorbing caster (FLC) manufactured by Frog
Legs® (Vinton, IA). Two bumps (1.27 cm, 1.91 cm) were used to act as obstructions. A wooden ramp
(3.05 m long, 1.2 m wide, 5 degree angle) was used to produce constant repeatable velocities. Two starting
locations on the ramp corresponded with velocities of 1.6 and 1.96 m/s at impact, velocities similar to those
used in other studies and were determined to be appropriate for testing purposes. Force platform data were
collected via two AMTI force platforms, the second of which was adapted with the steel bump. Data were
sampled at 3000 Hz using a 12-bit analog to digital converter.
RESULTS
Four variables were analyzed to determine which of the factors effect slipping/tipping of the
wheelchair. Means were calculated for the following ground reaction force (GRF) variables: maximum
braking force (MAXBR) caused by the obstruction, the maximum resultant GRF (MAXRES), and the
maximum angle of the resultant GRF vector with respect to the horizontal (MAXANG). See table below.
Standard Casters
High Bump
Low Bump
Fast
Slow
Fast
Slow
-540.5
-469.7
-351.8
-302.5
37.9
44.0
27.9
15.5
1100.0
889.9
887.5
775.7
125.5
115.0
99.7
83.8
46.2
48.0
37.6
36.9
0.8
1.3
0.6
0.7
Frog Legs® Casters
High Bump
Low Bump
Fast
Slow
Fast
Slow
-260.2
-237.0
-192.5
-175.7
26.5
30.3
44.9
27.6
592.8
577.2
459.8
454.1
72.7
81.3
72.9
62.1
57.8
56.6
45.9
44.7
2.2
2.4
3.5
2.1
Mean
MAX
BR (N)
s.d.
Mean
MAX
RES (N) s.d.
Mean
MAX
s.d.
ANG()
DISCUSSION
The results suggest an advantage while using the Frog Legs casters with respect to traversing
obstructions. The MAXBR is approximately half that of the standard casters for all conditions, thus
displaying the ability of the Frog Legs to cause less slowing and a decrease potential for the user to slip on
the seat while crossing the bump. The magnitude of MAXRES is significantly less in the Frog Legs casters
for all conditions, suggesting that the bump is less significant while crossing the bump with the shockabsorbing Frog Legs. MAXANG had a decreased value during the conditions that used the standard
casters. A greater angle represents a more vertical direction. If the angle is low enough to cause the line of
action of the force vector to go below the axis of rotation and the MAXRES is large enough the wheelchair
will begin to tip. The results also suggest that the low bumps are safer to traverse. There seems to be a
decreased chance of slipping during the slow speeds but the effect on tipping is unclear.
REFERENCES
Cooper, R.A. (1995). Rehabilitation Engineering Applied to Mobility and Manipulation.
Gaal, R.P., Rebholtz, N., Hotchkiss, R.D., & Pfaelzer P.F. (1997). J Rehabil Res Dev, 34(1), 58-71.
A COMPARISON OF THE KINETICS AND KINEMATICS OF DROP LANDINGS WITH ANKLE
BRACES AT THREE DIFFERENT HEIGHTS
Andrew T. Billing and Steven T. McCaw
Illinois State University
Ankle sprains in athletic competitions are common across all sports and recreational
activities. Therefore, many athletes wear prophylactic ankle braces during practices and
competitions to provide support and stability to prevent the occurrence of ankle sprains.
Prophylactic ankle braces provide support by restricting the ranges of motion at the ankle joint. A
recent study (McCaw & Cerullo, 1999) showed various prophylactic ankle braces during drop
landings significantly reduced dorsiflexion range of motion. Dorsiflexion aids in absorbing energy
due to an impact force from the ground. If dorsiflexion is reduced, then the ankle joint absorbs
less energy. It is possible that any forces not absorbed by the ankle joint will be transferred up to
the knee and hip joint. There have been few research studies that have investigated the kinetics
and kinematics of the knee and hip joint during various sport movements while wearing
prophylactic ankle braces. The purpose of this study was to measure and compare the kinetics
and kinematics of the ankle, knee, and hip during drop landings from three different heights using
various prophylactic braces. In this current pilot study two females and one male landed using 3
forms of ankle support: 1) unsupported; 2) swedo brace; 3) active ankle brace. Within each
support, subjects performed 5-drop landings from three different heights: 1) 0.3m; 2) 0.6m; 3)
0.9m. Subjects landed on a force platform while being video-recorded.
Reference
McCaw, S.T., & Cerullo, J.F. Prophylactic ankle stabilizers affect joint kinematics during drop
landings. Med. Sci. Sports & Exer. 31, 5, 702-707.
LONGITUDINAL GAIT ANALYSIS OF SUBJECTS WITH AMYOTROPHIC LATERAL
SCLEROSIS
Jonathan Frank 1, Jeanne McCrory 1, Edward Kasarskis 2, David Gater 1,2,
and Robert Shapiro 1
1University
2VA
of Kentucky, Lexington, Kentucky
Hospital, Lexington, Kentucky
Email: jefran0@pop.uky.edu Web: home.image.uky.edu/biodynamics
Amyotrophic Lateral Sclerosis (ALS), or Lou Gehrig’s disease, is a progressive, neurodegenerative disease that causes the death of motor neurons, and eventually death. This loss of
motorneurons leads to muscle weakness, wasting, fasciculations, and the erosion of everyday
functions. There is no known cause of this disease, nor is there a cure. Since there is no known
cure, disease management comes in the form of symptom management. This is done to keep
patients functioning and as comfortable as possible. One of the most important functions that
have been identified is being able to ambulate. One of the common recommendations for ALS
patients is to exercise in hopes that it will prolong their ability to walk and function independently.
It is very difficult, however, to gauge the effects of exercise without first knowing how gait
variables change over the course of their disease progression. The purpose of this study was to
identify 3-D kinematic and kinetic gait parameter changes over a six-month period, and to
correlate these changes with tests that are performed clinically on ALS patients. These clinical
tests included isometric strength, isokinetic strength, and pulmonary function, and functional
rating scale testing.
Blank PAGE FOR Otto abstract
The effect of backpack carrying on the gait of young children
Kenny Ng, University of Northern Iowa
The purpose of this study was to examine the effects of backpacks (bookbags) of varying
weights on the gait of children. Variables to be examined include posture, gait kinematics and
kinetics, and the timing of muscle activity by EMG. At the current time the study consists of a
review of literature and the development of methods.
Load carriage in young males.
Jennifer L. Rogers and Scott McLean, Iowa State University
Repetitive lifting and carriage, such as that used in farm tasks, can cause overexertion and lead
to soft tissue strains and sprains. These chores are often given to children because they are
thought to be safer than other farm chores. Due to environmental constraints, these chores,
lifting and carriage, are better suited for adults. Therefore, young males performing these tasks
constitute a high-risk group for farm injuries because of their stage in physical development. The
purpose of this study is to quantitatively analyze the difference between pre-pubescent and postpubescent males when carrying similar loads.
Reed and Nadzadi and Wentorf and Carson abstracts
The Effects of Anterior Cruciate Ligament Reconstruction on Lower Extremity Movement
Variability During Locomotion
Ugo H. Buzzi & Nick Stergiou
HPER Biomechanics Lab, University of Nebraska at Omaha, Omaha, NE, 68182
The purpose of this study is to determine if anterior cruciate ligament reconstruction affects lower
extremity movement variability during walking and running. Based on the premise established in
other fields, such as cardiology and neuroscience, that healthier systems experience greater
variability than do pathological systems, this study will analyze the variability present in various
kinematic parameters in order to determine if such a premise exists for the musculoskeletal
system. Traditional statistics as well as chaotic analysis will be performed to determine the
degree and nature of the variability present. This study is currently in the data collection phase.