Grants and Contracts Details
Description
Statement of Work [SOW]
HJF PI Name: Betty Crosby
Site PI
Collaborator’s Name: Dr. Junfei Tong
Subaward Title: Dr. Brian Noehren at the University of Kentucky
Stratification of Musculoskeletal Injury Risk from Prolonged
Date/Revision # Use of Wearable Exoskeleton Suits
May 24, 2021
I. INTRODUCTION/BACKGROUND:
Dr. Junfei Tong, located at the Biotechnology High Performance Computing Software
Applications Institute (BHSAI), conducts research in the field of musculoskeletal injuries, and is
performing studies under prime award W81XWH-20-C-0031 to specifically study the impact of
prolonged use of exoskeleton on the lower extremities and lower back. Dr. Junfei Tong will
utilize the technical expertise of Dr. Brian Noehren and the University of Kentucky to meet the
objectives identified in the above mentioned study. Specifically, Dr. Noehren will serve as the
collaborator for this study and be responsible for ensuring recording and preparation of
computed tomography (CT), motion-capture, electromyography (EMG), and metabolic cost data
in males during walking with and without load carriage, with and without exoskeleton. BHSAI
will utilize these experimental data as inputs for musculoskeletal finite element models to
estimate tibia and lumbar spines strain metrics in males, as part of a larger effort to predict the
stress-fracture risk at the tibia.
Dr. Noehren is the director of the Human Performance and Biomotion Laboratories. Since
starting at the University of Kentucky in 2009, he has worked closely with the Department of
Orthopedic Surgery to develop a focused research program on lower extremity injuries. The
Human Performance and Biomotion Laboratories embody translational science with
investigators from the colleges of Health Sciences, Education, Medicine, and Engineering
working side by side on projects ranging from mechanistic studies in biomechanics to cutting-
edge physical therapy treatments. The laboratory occupies approximately 1,365 square feet on
the first floor and contains space dedicated to evaluating biomechanics across activities ranging
from basic tasks such as transitioning between sit-to-stand, to advanced tasks such as performing
a running cut motion at full speed. Laboratory also has outstanding laboratory equipment to
support diverse research activities, including 22 Raptor cameras, two 16-bit A-D boards, a Bertec
split-belt instrumented treadmill with dual force plates, 16 channel Delsys EMG system (Boston,
MA), and 2 Bertec force plates for overground data collections.
The overall objective of this project is to quantify the impacts of prolonged use of exoskeleton on
the biomechanics of the lower extremity and lower back. This knowledge will help inform the
safe and effective use of wearable exoskeleton devices.
Significance:
The exoskeleton is a promising device that has the potential to enhance Soldier strength and
endurance [1]. For example, lower-body exoskeleton suits allow Soldiers to carry a 200-lb load
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while marching at a speed of 4 km/h for up to 20 km [1]. However, preliminary experimental
studies on such suits suggest that the use of exoskeleton can drastically affect the walking-gait
motion and body forces (i.e., kinematics and kinetics), even during short marching periods
without additional load [2,3]. Importantly, such gait-related changes may lead to unintended
musculoskeletal injuries, for example, in the lower extremities [4] or in the lower back [5]. Yet,
to date, we do not know the impact of the prolonged use of exoskeleton suits. For example, it is
unclear what part of the human body is most vulnerable to prolonged use of a lower-body
exoskeleton. Further, it remains to be determined what impact load carriage and marching
distance would have in exoskeleton-induced injuries.
II. TECHNICAL REQUIREMENTS:
The following tasks will be performed by Dr. Brian Noehren at the University of Kentucky to
meet the objectives listed above.
Study design: For this study we will recruit 5 males from the University of Kentucky. This
project would require each individual to have four visits to the lab. To assure that the study
participants are representative of Army recruits in Basic Combat Training, we will recruit
participants whose ages range from 18 to 25 years [5]. The students in the Reserve Officer
Training Corps (ROTC) program will be prioritized for this recruitment if possible.
Inclusion criteria:
o Males
o Age 18-25 years
o Body size fit with the exoskeleton device
o Free from injuries that would have limited their ability to be physically active for
3 months prior to study participation
o Experience with treadmill walking
Major tasks that will occur during Phase 1 of the protocol:
Phase 1 will use significant lab resources and time to plan, pilot test and execute the testing
protocol to be used. To ensure the highest quality data, we will extensively pilot test the
proposed experimental procedures, develop detailed standard operating procedures, and
complete the required regulatory paperwork for the Institutional Review Board (IRB) and
Human Research Protection Office (HRPO). We have outlined major steps below:
Human subjects protections:
1) Complete informed consent document and have the protocol reviewed through a full
board review at the University of Kentucky. Make any requested changes and have full
board approval
2) Submit protocol to HRPO and complete all regulatory paperwork for approval
Pilot testing:
1) The data collections will result in occlusion of many markers and we will do
extensive pilot testing of multiple solutions to able to track the trunk and tibia which
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we suspect will be occluded. This will include testing different backpack designs,
marker placement, developing new marker attachment points on the backpack and
exoskeleton.
2) The data collections will require carrying a heavy load for an extended period of time.
It is unknown how well the backpacks will endure for such a period of time and if
they will be tolerable on the research subjects. We will test several designs selecting
the one that fits the best on subjects to help ensure adherence and completion of the
testing protocol.
3) The data collections will result in prolonged tracking of EMG and markers. We will
test EMG placement and the ability of the EMG to record during high exertion and
sweaty conditions.
4) We will also test and evaluate the data export, formatting and signal quality both
internally and through collaboration with Dr. Tong at BHSAI through sharing of early
data. Data to be checked include marker trajectories, EMG signal, force data,
anthropometric data.
5) We will need to test systems to ensure subject engagement during the prolonged walk
to facilitate completing the task. To do this we plan to offer the subjects both music
and videos that they can watch while performing the task to help them stay motivated
to finish. The optimal place to put such feedback in the lab environment, how to set it
up, volume, and ensuring that it does not occlude markers from the cameras needs to
be determined.
6) The exoskeleton will need to be extensively tested. The mode of operation, fit,
recharging, are all unknown and would need to be investigated prior to use on
subjects.
7) We will need to develop detailed checklists of standard operating procedures and data
collection forms to be used.
8) New computational models within the data collection computer to collect new models
will need to be developed. We will test optimal fit to track markers to minimize any
gaps.
9) We will need to conduct run through’ s with both the pack and the exoskeleton to
check how the participant responds to the intervention through monitoring with a
heart rate monitor and taking ratings of perceived exertion during the testing.
10) We will start to establish relationships within the community and campus to get the
word out about the study and identify where and what groups to recruit from once we
are approved to start recruitment.
11) The metabolic testing will need to be pilot tested within the lab to ensure that it does
not block other equipment and is tolerable for the subject with everything else
attached to them.
12) Proper prep and post collection disinfecting and cleaning of exoskeletons, backpacks
and other equipment used for this experiment will need to be established.
13) We will conduct a mock run through of the CT scan with the radiology to ensure they
have everything they need to perform the tests once the subjects start being recruited.
14) We will identify the optimal minimum time between collections that subjects are no
longer sore for follow up collections for the actual trial.
15) We will evaluate the learning effect of use of the exoskeleton and repeated wearing of
the backpack.
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Protocol – RQ1:
1. Visit 1: For each participant, we will acquire anthropometric measurements including
fat percent, height, weight, tibial length, and Q-angle. Participants will walk at their
preferred speed for a 5-km distance without an exoskeleton carrying no load. Motion-
capture data, electromyography (EMG) data, and ground reaction force will be collected
for 20 seconds at baseline and at each 1-km mark. Metabolic cost data will be collected
throughout the whole walking process.
2. Visit 2: This visit will be used to acclimate the participant to the use of the exoskeleton
and fit him to the backpack. Subjects will be fitted with the exoskeleton and undergo a
standardized period of instruction followed by use of the exoskeleton while walking on
the treadmill. Subjects may practice walking for up to 30 minutes. In addition, during
this visit, the subject will also be fitted for the backpack they will use during testing.
Adjustments in the overall fit of the backpack will be made to help ensure subject
comfort to improve compliance with completing the testing.
3. Visit 3: Participants will receive CT scans of the tibia and lumbar vertebrae L4 and L5.
Similar to Visit 1, participants will walk at their preferred speed for a 5-km distance
without an exoskeleton carrying a 70-lb load. Motion-capture data, EMG data, and
ground reaction force will be collected for 20 seconds at baseline and at each 1-km
mark. Metabolic cost data will be collected throughout the whole walking process.
4. Visit 4: Participants will walk at their preferred speed for a 5-km distance with an
exoskeleton carrying no load. Motion-capture data, EMG data, and ground reaction
force will be collected for 20 seconds at baseline and at each 1-km mark. Metabolic cost
data will be collected throughout the whole walking process.
5. Visit 5: Participants will walk at their preferred speed for a 5-km distance with an
exoskeleton carrying a 70-lb load. Motion-capture data, EMG data, and ground reaction
force will be collected for 20 seconds at baseline and at each 1-km mark. Metabolic cost
data will be collected throughout the whole walking process.
Global Methods
Prolonged walking
Before each experiment, we will conduct static trials to establish segmental coordinate systems.
We will also do a rigorous force platform calibration. To collect motion-capture data,
retroreflective markers will be placed on anatomical landmarks and segments of the participant’s
whole-body. Markers will be tracked using a camera motion analysis system while participants
walk on an instrumented treadmill. Motion-capture (Motion Analysis Corp, Santa Rosa, CA) and
ground reaction forces from an instrumented treadmill (Bertec, Columbus, OH) data will be
collected at sampling frequencies of 200 and 1200 Hz, respectively. If it is difficult to recruit
participants to successfully complete the 5km walking with a 70-lb load in the pilot study, we
will reduce the load carriage to 50 lb. A 52 reflective marker set will be fitted on each subject’s
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lower extremity and trunk to track each Figure 1: Standardized marker set for initial
segment during the walking task (Figure 1). calibration of anatomical markers. Note,
Twenty-seven of the markers were placed on marker set may be modified during pilot
anatomical landmarks including sternal testing to best optimize data collection with
notch, spinous process of C7, bilateral exoskeleton and backpack on.
superior acromion processes, bilateral
superior iliac crests, posterior L5/S1 vertebral
joint, bilateral greater trochanters, bilateral
medial and lateral distal femurs, bilateral
medial and lateral distal proximal tibias,
bilateral medial and lateral malleoli, bilateral
first and fifth metatarsal heads, and bilateral
distal foot. Sixteen tracking markers were
attached including four rigid plates secured
to bilateral thigh and shank with four
markers on each plate. Three tracking
markers identifying proximal, distal, and
lateral heels will be secured to the rear foot
of each shoe. Additional tracking markers
will be placed on the right anterior thigh and
shank, and second metatarsal head for
identification of right side vs left side.
EMG data for major muscles of the lower-
extremity will be collected at 1000 Hz. For
each condition, biomechanical data will be
collected for 20 seconds after subjects reach
a natural steady state, which will ensure a
minimum of 15 strides for analysis.
CT data collection
The CT scans will be acquired for each participant using a scan length that captures the entire
tibia and lumbar vertebrae L4 and L5. The CT scans will be performed using a Siemens CT
scanner. Images will be reconstructed with a slice thickness of 0.6~0.9 mm and an in-plane pixel
resolution of 0.35~0.5 mm. All scans will include a phantom in the field of view with known
calcium hydroxyapatite concentrations to convert CT Hounsfield units to bone apparent density.
All work will be overseen by Dr. Noehren. Dr. Noehren will meet once every two weeks via
teleconference and/or email correspondence with the site PI, Dr. Tong, to provide updates on
progress and discuss any unanticipated limitations and potential solutions. In collaboration with
Dr. Tong, benchmarks to measure collaborator progress will be established. Final data sets to be
used for examining the effects of exoskeleton on the biomechanical responses of the tibia and
lumbar spines during walking with a load carriage, will be delivered by Dr. Noehren
electronically to Dr. Tong via secure ftp, encrypted physical files, or encrypted email files as
appropriate.
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Status | Finished |
---|---|
Effective start/end date | 11/1/21 → 11/15/22 |
Funding
- Henry M Jackson Foundation for the Advancement of Military Medicine Incorporated: $183,717.00
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