and minimal accommodation were con
firmed by study staff
verbally and via journal entries before scheduling testing.
This assured a minimum accommodation period between
fitting and testing of at least 21 days total for the duplicate
socket and 7 days per foot condition in subjects
’ home envi-
ronment (Fig. 2).
OC and Familiarization
The local law enforcement and military OC were selected
and approved as the test facility. It is routinely used to train
police of
ficers, SWAT team members, and various branches
of military service members. SWAT operators and trainers
were onsite at all times to familiarize and supervise partici-
pants during study training and assessment.
As recommended,
25
OC familiarization included three
preparatory performance trials to eliminate confounding
learning effects. The study familiarization and accommoda-
tion plan also included provision of an OC map (Fig. 3) to
participants in advance of a physical familiarization and
training trip to the OC (Fig. 2). This included a 5-day pros-
thetic
fitting and familiarization visit. Using their prestudy,
preferred prosthesis, subjects visited the OC for instruction
by SWAT operators on OC safety and completion technique.
After instructional training and supervised practice, subjects
performed three supervised OC trials independently, for a
practice time.
The OC included the following obstacle tasks:
(1) Jacob
’s Ladder
(2) Rope Climb
(3) Balance Beam
(4) A-Frame
(5) Culverts
(6) Chain-Link Fence
(7) Rope Bridge and Stumps
(8) Cargo Net
(9) High Step
(10) Angle Wall (Fig. 4)
(11) Slalom
FIGURE 1.
I. Vari
flex (Ossur, Reykjavik, Iceland) is an energy storing and return foot, II. Elite Blade (Endolite, Hampshire, United Kingdom) is an
energy-storing and vertical shock absorption foot, III. Re-Flex Rotate (Ossur, Reykjavik, Iceland) is an energy-storing and vertical shock and torsion absorp-
tion foot.
FIGURE 2.
Study timeline. The timeline included two 5-day research activity periods on either side of a 21-day accommodation period. The
first 5-day
period was for prosthetic
fitting and OC training. The second 5-day period included 3 OC test sessions and 3 laboratory evaluation sessions (reported else-
where). The 21-day accommodation period allowed for 7-day accommodation for each of the 3 study feet.
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Energy-Storing and Shock-Adapting Prosthetic Feet in Transtibial Amputees
(12) Attic and Pete
’s Dragon
(13) Monkey Bars
(14) Over/Under Walls
(15) Angle Tube
(16) Rope Traverse
(17) SWAT Ladder
(18) Sprint Finish
Study Schedule
For the individual TTA subject, the study commitment
involved 5 weeks of activity (Fig. 2) as follows:
Preparation period: Following enrollment and consent,
the preparation period commenced. This was a 5-day ses-
sion. The daily itinerary was as follows:
Monday: First meeting with a study prosthetist to initiate
duplication of preferred socket. Preliminary
fitting, adjust-
ment, and alignment of 3 prosthetic feet began on comple-
tion of socket duplication.
Tuesday: First training visit to OC. Subjects trained on OC
sequence, completion technique, and safety. Visit with
study prosthetist as needed.
Wednesday: Finalize prosthetic
fittings adjustments and
alignments.
Thursday: Second visit to OC. While supervised, subjects
physically practiced OC. Visit with study prosthetist as
needed.
Friday: Final meeting with study investigators, OC person-
nel, and study prosthetist.
Review accommodation period. Discuss and schedule the
testing period.
Accommodation period: See
“Prosthetic Fitting and
Accommodation Period
” section above.
FIGURE 3.
Obstacle Course Map. This diagram shows the general lane and obstacle
flow and sequence. It was provided to all participants in advance of
initiating training and testing. Obstacle no. 2., the Rope Climb, is shown in this
figure but was eliminated for safety reasons (see results section). Instructions
for completion of this task during the training portion of the study were to vertically ascend the rope and touch the top pipe with a hand.
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Energy-Storing and Shock-Adapting Prosthetic Feet in Transtibial Amputees
Testing period: Following accommodation, the testing
period commenced. The testing period was a 5-day session
as follows:
Monday: OC test 1 of 3 (randomized foot assignment)
Tuesday: Biomechanical and bioenergetic laboratory tests
(reported elsewhere)
Wednesday: OC test 2 of 3 (randomized foot assignment)
Thursday: Biomechanical and bioenergetic laboratory tests
(reported elsewhere)
Friday: OC test 3 of 3 (randomized foot assignment)
Biomechanical and bioenergetic laboratory testing involved
minimal walking and running at comfortable speeds suf
fi-
cient to achieve steady state yet insuf
ficient to confound
recovery between
field test days. For control subjects, OC
testing was completed in a single session. This is because of
their routine (i.e., weekly) practice, assessment, and instruc-
tion with the course.
Outcome Measures
Demographic information, anthropometric measures, fully
assembled prosthetic masses, and
final alignments (i.e., sagit-
tal and coronal distances from LASAR line to manufacturer
’s
recommended foot reference location) were recorded during
the testing period before performance data collection. Using
an ad hoc rating scale, subjects were also asked to rate their
activity level (i.e., sedentary, minimally, moderately, or
highly active) as well as to quantify the number and type of
activity bouts per week and the number of years of participa-
tion. Subjects then completed the
field OC, one time per foot
(three times total) to determine total time-to-completion and
per-task completion times. Time data were recorded using
laser timing gates (Brower TC-Gates, Brower Timing Systems,
Power Systems, LLC, Knoxville, Tennessee) situated in front
of and behind each obstacle on the OC.
25
As subjects would
pass between the laser gates, times were triggered and recorded
into a data
file for later aggregation and processing. Immedi-
ately following each individual OC completion, subjects were
asked to rate their perceived exertion (RPE) using the Borg
(6
–20) scale
26
for the entire course with the respective foot
condition. Following the third and
final OC completion, TTAs
were asked to indicate which of the three feet conditions they
preferred to utilize in order to complete the OC.
Statistical Analyses
Sample size and power calculations were based on effect
sizes calculated from performance outcomes (i.e., walking
speed, oxygen uptake, lower limb joint kinetics, and per-
ceived exertion) previously published regarding comparable
high-functioning feet (e.g., Re-Flex Shock, Vari
flex, Ossur,
Reykjavek, Iceland) in basic mobility tasks.
7,13,27
These esti-
mates provided that 10 TTA subjects would adequately
power the study with
β = 0.80. Given the available data are
from basic walking and running, the resulting sample esti-
mates were regarded as conservative. Therefore, planning
for attrition and accounting for the conservative estimates
provided from basic mobility data, recruitment was set at
14 TTA participants. Following all assessments, data were
entered into a database and veri
fied before analysis. Sub-
jects
’ performance data within a given condition (i.e.,
Vari
flex) were averaged (and variance calculated) to repre-
sent that condition for further analysis and comparison
across conditions and between groups. Descriptive statistics
were calculated (i.e., means, standard deviations) where
possible. Continuous data (i.e., OC time to completion)
were examined for normalcy and outliers using NCSS/
PASS
’s omnibus calculation of skewness and kurtosis
(2004 edition, Kaysville, Utah). A within subjects
’ repeated
measures analysis of variance model was used to reveal sta-
tistical differences in performance between prosthetic feet
conditions (dependent comparisons). Differences between
control and experimental subjects were independent com-
parisons and thus ineligible for comparison using the
repeated measures analysis of variance model. Therefore,
depending on their distribution, either independent samples
t tests (normally distributed data eligible for parametric
analyses) or the Mann
–Whitney U test was used to identify
statistically signi
ficant differences between TTA and non-
amputee controls (as independent comparisons per foot con-
dition). The protocol
’s a priori level of significance was
0.05. All comparative statistical analyses were performed
using SPSS 2012 v.20 (Armonk, New York). Finally, effect
size was calculated using Cohen
’s d
28
and interpreted as
d ≥ 0.20 represents a small effect, d ≥ 0.50 represents a
medium effect, and d
≥ 0.80 represents a large effect
FIGURE 4.
All subjects were instructed to complete the course as fast as
possible and as safely as possible. Subject is pictured traversing Angle Wall
instructed to ascend the angle wall and either climb down the ladder on the
back side or hop to the ground.
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