Sensor Ankle Brace for Special Operations Rehabilitation

All human subjects activities are taking place at the Indiana University Bloomington (IUB) campus. Potential participants for the Phase 2 study protocol will be recruited from the community and the IUB campus. Potential participants will either contact the research team to complete the initial screening or respond to the flyer via a QR code that takes them directly to the online version of the screening form. The screening form asks yes/no questions from the Physical Activity Readiness Questionnaire (PARQ+) and additional questions about the individuals health history, musculoskeletal injury history, and current physical activity levels. After initial screening to determine eligibility, provisionally eligible participants will come to the laboratory on the IUB campus to complete enrollment and study procedures.

At the first in-person visit, participants will read the informed consent document and, after all questions have been answered, sign the informed consent document if they agree to participate in the study. Next, participants will complete a health history questionnaire which repeats the PARQ+ questions and additional health history questions presented in the initial screening to confirm eligibility. Foot length measurements and additional surveys (i.e., the Identification of Functional Ankle Instability (IDFAI) and International Physical Activity Questionnaire - Short Form (IPAQ)) will be administered. If eligibility is confirmed, participants will be enrolled and complete the study procedures. After eligibility is confirmed, participants will also complete the past-year physical activity questionnaire (PYPAQ) and a running history questionnaire.

Following the surveys, height and weight will be measured then the dominant limb test and the preferred speed test will be performed. The dominant limb test determines whether the right or left lower limb is the dominant limb by observing which limb participants use to kick a ball. The preferred speed test involves the participant walking or running at or near their reported preferred speed (or 2.9 mph for walking and 4.5 mph for running if preferred speed is unknown). The speed will be blinded to the participant. The researcher will increase or decrease the speed in 0.5-1.0 mph increments until the participant identifies the same speed as their preferred speed three times.

Next, the participant will be prepared for data collection. Participants will be asked to change into form fitting clothing (provided by the laboratory, if needed) and combat boots provided by the laboratory (Phase 2). Reflective markers and the lab's research-grade inertial measurement units (IMUs) will be placed on anatomical landmarks of both feet, lower-legs, thighs, and pelvis, and the sensor-enabled ankle brace ("sXAB") will be secured on the dominant limb, if the first randomized condition is the brace condition. Participants will warm-up by walking on a treadmill before completing each of the brace conditions (brace and no-brace) to acclimate wearing the brace and/or the reflective markers and lab IMUs. Participants will then be asked to complete the movement tests specific to each protocol (Phase 2: standing balance, stairs, drop landing, walking at preferred speed, and running at preferred speed) while wearing the sXAB and without wearing the brace ("no brace" condition) as three-dimensional motion capture data, force plate data, IMU data, and data from the sXAB (if worn) are recorded. The order of the bracing conditions will be presented in a random order. The brace will be worn on the dominant limb. Within each brace condition, the standing balance test will be performed first then the remaining movements will be presented in a random order. After the first brace condition is complete, the participant will be prepared to complete the second brace condition then repeat the warm-up, standing balance test, and the movement tests.

Participants may complete Phase 2 activities in either one or two study visits, depending on participant preference.

• Sensor-enabled Athletic X Ankle Brace (sXAB) (Device): The intervention is a sensor-enabled version of the TayCo Brace, Inc. Athletic X Ankle Brace (sXAB), which integrates commercially available inertial measurement units (IMUs) into the structure of the brace. The brace is worn on the ankle of the dominant limb during functional movement tasks to evaluate its ability to produce valid gait and balance metrics compared to laboratory-grade measurement systems.

Primary outcomes

• Validation of kinematic data collected by the sensor-enabled ankle brace (sXAB) [At study visit(s), completed up to 1 week after enrollment.]: This outcome evaluates whether kinematic data collected using the sensor-enabled ankle brace (sXAB) are sufficiently accurate and reliable compared to gold-standard laboratory systems (motion capture and force plates). Agreement between sXAB and laboratory reference systems will be assessed using measures of validity and reliability for ankle kinematic variables, including sagittal plane joint angles and range of motion. Data are collected during brace conditions across multiple movement tasks.
• Validation of spatiotemporal parameters collected by the sensor-enabled ankle brace (sXAB) [At study visit(s), completed up to 1 week after enrollment.]: This outcome evaluates whether spatiotemporal parameters collected using the sensor-enabled ankle brace (sXAB) are sufficiently accurate and reliable compared to gold-standard laboratory systems (motion capture and force plates). Agreement between sXAB and laboratory reference systems will be assessed using measures of validity and reliability for stance time, stride length, gait speed. Data are collected during brace conditions across multiple movement tasks.

Secondary outcomes

• Validation of kinetic data collected by the sensor-enabled ankle brace (sXAB) [At study visit(s), completed up to 1 week after enrollment]: This outcome evaluates whether kinetic data collected using the sensor-enabled ankle brace (sXAB) are sufficiently accurate and reliable compared to gold-standard laboratory systems (motion capture and force plates). Agreement between sXAB and laboratory reference systems will be assessed using measures of validity and reliability for peak vertical ground reaction force and total vertical impulse. Data are collected during brace conditions across multiple movement tasks.
• Validation of balance data collected by the sensor-enabled ankle brace (sXAB) [At study visit(s), completed up to 1 week after enrollment]: This outcome evaluates whether balance data collected using the sensor-enabled ankle brace (sXAB) are sufficiently accurate and reliable compared to gold-standard laboratory systems (motion capture and force plates). Agreement between sXAB and laboratory reference systems will be assessed using measures of validity and reliability for postural sway amplitude and velocity. Data are collected during brace conditions across multiple movement tasks.
• Equivalence of kinematic data collected by the sensor-enabled ankle brace (sXAB) [At study visit(s), completed up to 1 week after enrollment]: This outcome evaluates whether kinematic data collected using the sensor-enabled ankle brace (sXAB) are equivalent to data collected using laboratory systems (research-grade IMUs). Agreement between sXAB and laboratory reference systems will be assessed using measures of validity and reliability for sagittal plane joint angles, range of motion. Data are collected during brace conditions across multiple movement tasks.
• Equivalence of spatiotemporal parameters collected by the sensor-enabled ankle brace (sXAB) [At study visit(s), completed up to 1 week after enrollment]: This outcome evaluates whether spatiotemporal parameters collected using the sensor-enabled ankle brace (sXAB) are equivalent to data collected using gold-standard laboratory systems (research-grade IMUs). Agreement between sXAB and laboratory reference systems will be assessed using measures of validity and reliability for stance time, stride length, gait speed. Data are collected during brace conditions across multiple movement tasks.
• Activity Recognition [At study visit(s), completed up to 1 week after enrollment]: The inertial measurement unit (IMU) data collected from the sensor-enabled ankle brace (sXAB) will be analyzed to determine what activity was occurring at which times during the data set.

Sex: All, ages: 18 Years to 40 Years, accepts healthy volunteers

Inclusion Criteria:

* Healthy adults: ages 18 - 40 years
* considered "healthy to exercise" as determined by the physical activity readiness questionnaire (PAR-Q)
* Classified as "moderate" or "high" activity level as defined by the scoring criteria of the International Physical Activity Questionnaire - Short Form (IPAQ)
* Comfortably fit into combat boots provided by the laboratory (Men's sizes 8, 9, 10, 11, 12 and Women's sizes 6, 7, 8, 9, 10 will be purchased, and so participants with foot lengths of 22.54-29.27.8 cm are expected to fit in the boots provided).

Exclusion Criteria:

* Smoking tobacco on a regular basis
* Previous lower back or lower limb surgery (including the joints of the pelvis and lower limbs)
* Musculoskeletal injury sustained within the 12-weeks prior to enrollment . A musculoskeletal injury is defined as musculoskeletal pain causing a reduction or stoppage of normal physical activity for at least 3 days within a 7-day period, and have not returned to their normal physical activity and exercise without pain for at least the last 6-weeks.
* Pregnant (women only)
* Current or history of an unresolved musculoskeletal, neurological, cardiovascular, pulmonary/respiratory, metabolic, renal condition, disease, or problem.
* Torn anterior or posterior cruciate ligament (ACL or PCL).
* Any other disease or problems that may affect movement or the ability to exercise even at a low intensity.
* Identification of Functional Ankle Instability (IDFAI) score of <11.
* unable to comfortably perform the drop landing condition.
* Feet are too large or too small to fit comfortably in the combat boots provided.

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• Allison H Gruber, PhD, Principal investigator, Indiana University