Falls due to slipping are a serious occupational concern. Slipping is estimated to cause 40-50% of all fall-related injuries. In 2011, falls resulted in 22% of injuries requiring days away from work. Epidemiological data indicates that older and obese adults experience more falls than young, non-obese individuals. An increasingly heavier and older workforce may be exacerbating the problem of slip-induced falls in the workplace. The purpose of this study was to examine the effects of obesity and age on slip severity and fall outcome following an unexpected slip. Four groups of participants (young obese, young non-obese, older obese, older non-obese) were exposed to an unexpected slip perturbation. Slip severity (slip distance, slip duration, average slip velocity and peak slip velocity) and slip outcome (fall or recovery) were compared between groups. Obese individuals experienced 8.25% faster slips than non-obese individuals in terms of average slip velocity (p=0.022). Obesity did not affect slip distance, slip duration or peak slip velocity. Obese individuals also experienced more falls; 33.3% of obese individuals fell compared to 8.6% of non-obese (p=0.005). Obese individuals were 8.24 times more likely to experience a fall than non-obese individuals, when adjusting for age, gender and gait speed. No age effects were found for slip severity or slip outcome. This study revealed that obese participants experienced faster slips and more falls than their non-obese counterparts. These results, along with epidemiological data reporting higher fall rates among the obese, indicate that obesity may be a significant risk factor for experiencing slip-induced fall. / Master of Science

Slips are a leading cause of injury among older adults. Specific slip recovery measures, including slip distance and peak slip speed, have been shown to increase significantly among fallers as compared to non-fallers. Often, slipping kinematics are measured using optoelectronic motion capture (OMC), requiring a laboratory setting and limiting data collection to experimentally-controlled conditions. Inertial measurement units (IMUs) show promise as a portable and wearable form of motion capture. This study had two objectives. First, we investigated whether foot and ankle IMU-derived slip recovery measures could be considered equivalent to the same OMC-derived measures. Second, we investigated if both participant-placed and researcher-placed IMU-derived slip recovery measures could be considered equivalent to the same OMC-derived measures. 30 older adults (ages 65-80) were exposed to a slip while wearing both IMUs and OMC markers. Slip distance and peak slip speed were measured by both systems and compared. Equivalence testing (α = 0.05) showed that IMUs placed on the foot and the ankle were equivalent to OMC in measuring these slip recovery measures. Furthermore, it was shown that researcher and participant-placed IMUs were equivalent (α = 0.05) to OMC in measuring these slip recovery measures. These results confirm that IMUs can be a viable substitute for OMC and have the potential to expand data capture to a real-world environment. / Master of Science / Falls are a major cause of injury among older adults. Slips are a large contributor to falls, so it is important to better understand how slips occur to develop more efficient fall-prevention programs. To understand slips, previous research often utilized optoelectronic motion capture (OMC) to measure slip recovery measures. However, OMC relies on multiple cameras, limiting slip measurement to a laboratory. As we want to understand slips in the real-world, we must use a different form of motion capture. Inertial measurement units (IMUs) are sensors that can afford real-world biomechanical measurement. In this thesis research, 30 older adults (ages 65-80) were exposed to one over-ground slip. Slip recovery measures are compared between OMC and IMUs placed on the foot and ankle. Furthermore, IMU placement is compared between researchers and participants. Equivalence testing showed that IMUs placed on the foot and the ankle were equivalent to OMC in measuring these slip recovery measures. Furthermore, it was shown that researcher and participant-placed IMUs were equivalent to OMC in measuring these slip recovery measures. These results confirm that IMUs can be a viable substitute for OMC and have the potential to expand data capture to a real-world environment.

Flexor tendon lacerations in horses are traumatic injuries that can be career ending and life threatening. In the horse, a tendon repair must withstand the strains placed on the tenorrhaphy by immediate weight bearing and locomotion post-operatively. Despite the use of external coaptation, such strains can lead to significant gap formation, construct failure, longer healing time and poor quality of the healed tendon. Similar to equine surgery, gap formation and construct failure are common concerns in human medicine, with early return to post-operative physiotherapy challenging the primary repair. Early return to exercise and decreased gap formation has been shown to reduce adhesion formation. Based on these concerns, the ideal tenorrhaphy suture pattern for equines would provide: 1) high ultimate failure load, 2) resistance to gap formation, 3) minimal alteration in blood supply, and 4) minimal adhesion formation. Historically, various suture patterns and materials have been evaluated for human and equine flexor tendon repair. Results of equine studies suggest the three-loop pulley pattern (3LP) compares favorably to other patterns and is recommended for primary tenorrhaphy. However, this pattern still experiences significant gap formation and can result in failure. As a result, a technique which decreases the problems inherent in the 3LP is warranted for tenorrhaphy of equine flexor tendons. A review of the human literature highlights certain characteristics of the tenorrhaphy that may improve results including core purchase length and suture loop characteristics. Optimization of these tenorrhaphy characteristics can increase tenorrhaphy performance and patient outcome. The six-strand Savage technique (SSS) is a pattern routinely used in human hand surgery for tendon repair, and possesses high ultimate failure load and resistance to gap formation that may be beneficial for application in equine tendon repair. This study compared a novel tenorrhaphy pattern for horses, the SSS, with the currently recommended pattern, the 3LP, in an in vitro model. We hypothesize the SSS will fail at a higher ultimate load, resist pull through, and resist gap formation better than the 3LP. All testing used cadaveric equine superficial digital flexor tendons from horses euthanized for reasons other than musculoskeletal injury. All testing was approved by the IACUC. The two techniques were applied to cadaveric equine superficial digital flexor tendons. The same investigator performed all repairs (EE). Biomechanical properties were determined in a blinded, randomized pair design. Ultimate failure load, mode of failure and load required to form a 3mm gap were recorded on an Instron Electropuls materials testing system. Gap formation was determined using synchronized high-speed video analysis. Results are reported as mean + standard deviation. Statistical comparisons were made using Student's T test, with significance set at p<0.05. The tenorrhaphies were tested for their ultimate failure load and failure mode. The mean failure load for the SSS construct (421.1 ± 47.6) was significantly greater than that for the 3LP repaired tendons (193.7 ± 43.0). Failure mode was suture breakage for the SSS constructs (13/13) and suture pull through for the 3LP constructs (13/13). The maximum load to create a 3mm gap in the SSS repair (102.0N ± 22.4) was not significantly different from the 3LP repair (109.9N ± 16.0). The results of the current study demonstrate that the SSS tenorrhaphy has a higher ultimate failure load and resistance to pull through than the 3LP. The biomechanical properties of the SSS technique show promise as a more desirable repair for equine flexor tendons. However, in vivo testing of the effects of the pattern on live tissue and in a cyclic loading environment is necessary before clinical application of the pattern is recommended. / Master of Science

Over 2.4 million eye injuries occur each year in the United States as a result of trauma. Eye injuries have been investigated for years; however, the role of the extraocular muscles in relation to eye injuries has yet to be quantified. In this research, Computed Tomography quasi-static tests were conducted to investigate the effect of the presence of the extraocular muscles on the biomechanical response of the human eye in situ. Three matched pairs of human eyes were displaced in 5 mm increments using a large flat cylindrical indenter to a maximum displacement of 30 mm. The loading was similar to what is experienced during a blunt impact, which is believed to cause the most serious eye injuries. In the matched pair, one eye had the extraocular muscles intact and the other had the extraocular muscles transected. Force, pressure, and displacement measurements were collected for each test. A trend was seen where a greater amount of force was created in the eye with the extraocular muscles intact than in the eye with the muscles transected, and a correlation between them was made. The greatest force measured in an eye with the extraocular muscles intact was 92 N, while the greatest force measured in an eye with the extraocular muscles transected was 80 N. An increase in intraocular pressure was also noticed for an eye with the extraocular muscles attached, rising steadily from 2 kPa to a maximum pressure of just over 50 kPa. It was also noted that during a quasi-static impact the eye can move out of the way of the imposing force. Since the test data set was small, analytical calculations were also conducted. / Master of Science

The use of digital technology is becoming increasingly popular in equine research. Current applied technologies for livestock are being used to detect pathogens, observe locomotion patterns, determine estrus periods, and measure vital parameters. These sensors leverage global positioning systems, accelerometers, magnetometers, goniometers, optics, among other emerging sensing technologies. The success of these devices has led to the introduction of various equine wearable sensors into market. These technologies seek to promote mobile devices to be used in equine training, monitoring, and clinical contexts. Therefore, the objective of this research is to characterize advancements, opportunities, and gaps in our existing knowledge of equine wearable sensor technology. Specifically, this research explores two innovative sensors designed for equines and their potential to enhance animal safety and health. The purpose of the research on these sensors is to (1) better contextualize biomechanical data in practically applicable terms and (2) evaluate the accuracy of a photoplethysmography based pulse sensor to detect heart rates of adult horses. In addition, currently marketed equine wearable sensors are reviewed, and their limitations are evaluated. Areas of future research and developments of equine wearable technologies are also explored. / Master of Science / The use of digital technology is becoming increasingly popular in equine research. Several biosensors exist for livestock species which have been successful in helping manage health and wellbeing of these animals. Although commercial development of equine wearable sensors has begun, the success of initial industry prototypes is limited. Commercially available equine wearable sensors currently marketed often seek to provide support in equine training, monitoring, and clinical contexts. Despite several commercially available equine wearable sensors, there has been slow adoption of this type of technology in the industry. Therefore, the objective of this research is to characterize advancements, opportunities, and gaps in our existing knowledge of equine wearable sensor technology. Specifically, it explores two innovative sensors designed for equines and their potential to improve the safety and health these animals. The purpose of these sensors are to (1) better understand factors that influence the safety of equestrian sports with jumping phases and (2) evaluate the accuracy of a sensor to detect heart rates of adult horses. In addition, current marketed equine wearable sensors are reviewed, and their limitations are evaluated. Areas of future research and developments of equine wearable technologies are also explored.

Post-mortem human surrogate (PMHS) head specimens were subjected to two different angular speed pulses. Each pulse was approximately a half-sine with either a peak angular speed of either 40 or 20 rad/s and duration of either 30 or 60 milliseconds. High-speed biplane x-ray was used to record the motion of the brain and skull via radio-opaque markers implanted at specified locations in the brain, and lead markers on the skull. Specimens were perfused to physiologic conditions throughout preparation and testing to maintain the integrity of the brain tissue and ensure coupling of the brain and skull. Intracranial pressure was measured anteriorly and posteriorly. The test event was controlled by a cam-follower-flywheel mechanism, which facilitated control of pulse parameters and provided a form of "infinite energy" so that the device and therefore the test input would not be influenced by the characteristics of the object under test. This approach kept the independent and dependent variables separated. The brain targets were also deployed in a prescribed manner with two methodologies that were scalable to different specimens. The repeatable input and target deployment schemes helped reduce experimental variation (between tests and subjects) to produce consistent response data. Displacement of the brain was calculated with respect to a body-fixed basis on the skull. The relative motion of the brain with respect to the skull was shown to be dependent on the location of the target in the brain. The major deformation axis of each target followed the contour of the skull or bony landmark to which it was closest. Intracranial pressure was relatively low because the changes were due to inertial effects in the absence of impact. Tests with lower speeds and longer durations produced less deformation, lower intracranial pressures, and longer pressure durations than the tests that were high-speed, short-duration. The response of the brain to rotation of the head was quantified at two test levels and on two PMHS specimens. / Master of Science / Motor-vehicle collisions (MVCs) are the second leading cause of traumatic brain injury (TBI) in the United States and the leading cause of TBI-related death [1a]. Regulations are in place for vehicle design to reduce the occurrence and severity of head injuries during MVCs. The metric used is based on the resultant linear acceleration at the center of gravity of the occupant’s head. However, TBI are still occurring despite the current regulations. This suggests the importance of using additional injury metrics to predict TBI in MVCs. In automotive impact biomechanics, a combination of real world, experimental, and simulation data is used to determine how the human body responds during MVCs. While computer (finite element) simulations can provide extensive information about the kinematic and kinetic response of the human body, these models require experimental data to validate and evaluate their responses. This study focuses on determining the response of the human cadaver brain to angular speed loading without contact of the head. High-speed biplane x-ray and radiopaque markers were used to quantify the displacement of the brain with respect to the skull throughout rotational events. Two angular speed profiles with different peak angular speeds and durations were used. The methods were determined to reduce experimental variation to obtain data that is useful for finite element model validation. The average peak angular speed for the high-speed tests was 41.8 rad/s and the average peak angular speed for the low-speed tests was 22.0 rad/s. The peak angular speed only varied by 10% between similar tests. The motion of the brain lagged behind that of the skull, producing a relative displacement of the brain with respect to the skull. The magnitude and primary direction of the relative displacement was dependent on the location at which it was measured. The location of the radiopaque target with respect the anatomical coordinate system and bony landmarks of the skull are both important in determining the characteristics of the relative displacement profiles. The high-speed tests produced an average displacement of +/-5 mm, while the low-speed tests had an average displacement of +/-2.5 mm in the X-direction. Intracranial pressure (ICP) was also measured at two points in the cranial cavity, and showed the delayed response of the brain to the rotational loading of the head.

The research presented in this thesis focuses on head impact exposure in youth football. The on-field portion of this research investigated high magnitude head impacts that youth football players experience in games and practices. With previously validated data collection methods, linear and rotational head accelerations from head impacts were collected. Over the course of two seasons, 79 total player-seasons resulted in over 13,000 impacts. A small subset of these, 979 impacts exceeding 40 g, represented the focus of this research as these impacts pose the greatest risk of injury to individuals. Some tackling drills in practice were found to have higher acceleration severities than those observed in games. How practice activities are conducted also contributes towards the overall high magnitude head impact exposure for practice, not just the practice drill itself. Within games, players who are running backs and linebackers played most frequently and experienced higher magnitude impacts more often than their teammates. Data were also collected from all players off the field. Each player completed balance assessments at the beginning and end of the season to allow for comparison, even in absence of a clinically-diagnosed concussion. Current balance assessments were observed to fall short for detecting postural control differences in this youth population. Modifications to these assessments were recommended that might allow for further insights. Research presented in this thesis will inform youth football organizations as they continue to develop strategies to enhance player safety and mitigate head impact exposure. / Master of Science / The research presented in this thesis focuses on head impact exposure in youth football. The on-field portion of this research investigated high magnitude head impacts, which are associated with heightened risk of concussion, that youth football players experience in games and practices. With previously validated data collection methods, the specific causation for high risk head impacts in youth football practices and games was determined for the first time. In some practice drills, players were observed to hit harder and more frequently than they would in games. As youth practices occur more often than games do, limiting the time spent in these types of practice drills is recommended. How practice activities are conducted also contributes towards the overall high magnitude head impact exposure for practice, not just the practice drill itself. Events where players had the opportunity to get up to speed prior to impact were more likely to be high risk than events where players essentially impacted from a standstill. Data were also collected from all players off the field. Each player completed balance assessments at the beginning and end of the season to allow for comparison, even in absence of a clinically-diagnosed concussion. Current balance assessments were observed to fall short for detecting balance differences in this youth population. Modifications to these assessments were recommended that might allow for further insights. Research presented in this thesis will inform youth football organizations as they continue to develop strategies to enhance player safety and mitigate head impact exposure.

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