Defining the Role of Mechanical Signals During Nerve Root Compression in the Development of Sustained Pain and Neurophysiological Correlates that Develop in the Injured Tissue and Spinal Cord

Cervical nerve root injury commonly leads to pain. The duration of an applied compression has been shown to contribute to both the onset of persistent pain and also the degree of spinal cellular and molecular responses related to nociception that are produced. This thesis uses a rat model of a transient cervical nerve root compression to study how the duration of an applied compression modulates both peripherally-evoked activity in spinal cord neurons during a root compression and the resulting neuronal and glutamatergic responses in the nerve root and spinal cord. Studies define the compression duration threshold that inhibits peripherally-evoked action potentials in the spinal cord during a root compression to be at 6.6±3.0 minutes and this is similar to the threshold for eliciting persistent mechanical allodynia after a cervical root compression that lies between 3 and 10 minutes. Furthermore, neurotransmission remains inhibited for at least 10 minutes after a painful nerve root compression and this may contribute to the subsequent development of neuropathology in the root, spinal neuronal hyperexcitability, downregulation of spinal GLT-1 and upregulation of spinal GLAST at day 7. Additional studies examine the role of the spinal glutamatergic system in mediating radicular pain by administering Riluzole to inhibit glutamate release at day 1 or ceftriaxone daily to upregulate spinal GLT-1, separately. Both treatments abolished behavioral sensitivity and the associated neuronal hyperexcitability that is normally observed in the deep laminae of the dorsal horn. Additionally, Riluzole mitigated the axonal neuropathology in the root that normally develops by day 7 while ceftriaxone restored the spinal expression of GLAST. Together these studies identify how one aspect of nerve root biomechanics, compression duration, modulates neuronal and glutamatergic responses in the nerve root and spinal cord that are associated with cervical radicular pain. Day 1 was identified as a critical time-point when inhibiting glutamate signaling in the central nervous system can prevent persistent nerve root-mediated pain that is likely maintained by downregulation of spinal GLT-1. Finally, these studies suggest that primary afferent regulation of spinal GLT-1 may have a critical role in transducing the biomechanics of a nerve root compression into radicular pain

THE RELATIONSHIP BETWEEN PITCH VELOCITY AND SHOULDER DISTRACTION FORCE AND ELBOW VALGUS TORQUE IN COLLEGIATE AND HIGH SCHOOL PITCHERS

The purpose of this study was to 1) determine the relationship between baseball pitching velocity, shoulder distraction force, and elbow valgus torque, and 2) compare these relationships between college and high school baseball pitchers. Biomechanical pitching reports from collegiate and high school baseball pitchers were analysed with linearity not assumed. A total of 273 pitches were included in this study. Pitching velocity exhibits a positive linear relationship with both shoulder distraction force and elbow valgus torque among high school and college pitchers. However, when only examining pitches thrown above 85 mph, only high school pitches have a positive linear relationship between pitching velocity and elbow valgus torque. Despite assuming non-linearity, pitching velocity exhibited a positive linear relationship with both shoulder distraction force and elbow valgus torque. Lower powered secondary analyses should be interpreted with caution

PELVIS ENERGY FLOW AND GROUND REACTION FORCE PREDICTORS OF ELBOW TORQUE IN HIGH SCHOOL AND COLLEGIATE BASEBALL PITCHERS

High joint forces and torques are associated with injury risk in baseball pitching. Energy flow (EF) analyses have provided valuable information on how segment and joint powers influence the pitching motion but have not been used to investigate EF influence on elbow torque. The purpose of this study was to determine the relationship of pelvis EF and ground reaction force (GRF) with elbow valgus torque in a sample of high school and collegiate baseball pitchers using regularized regression and statistical parametric mapping. A set of 14 GRF and EF variables were found to be predictors of maximum elbow valgus torque. Both groups differed in pitch velocity and elbow torque but exhibited similar patterns of energy generation and transfer at the stride hip and L5S1 joints. These findings could translate to lower body strategies to reduce the injury risk of high school and collegiate pitchers

LOWER BODY CONTRIBUTIONS TO PELVIS ENERGY FLOW AND PITCH VELOCITY IN COLLEGIATE BASEBALL PLAYERS

The aims of this study were to examine the generation, absorption, and transfer of energy through the pelvis at the drive hip, stride hip, and lumbosacral joints and to determine predictors of ball speed during baseball pitching. Motion capture and ground reaction force (GRF) data from 20 collegiate pitchers were analysed using energy flow and LASSO regression analyses. Energy was transferred from the drive leg to the pelvis during the stride phase while energy was transferred from the pelvis to the stride leg and trunk during arm-cocking. Drive leg GRF, impulse, and stride hip generation contribute to pitch velocity

Lacrimal equilibration time (LET): Clinical application in the assessment of dry eye

This study investigates the Lacrimal Equilibration Time (LET) test, a procedure proposed in 1994 by Lavaux and Keller to aid in the diagnosis of dry eye. The test evaluates the time required for a patient to regain his or her habitual monocular distance visual acuity after the instillation of a Celluvisc lubricating drop. In this study, the LET test is compared to rose bengal staining and to a dry eye patient questionnaire. No statistically significant relationship was found between any of these variables for the 58 subjects. In addition, the LET test was found to be highly variable within subjects

MULTI-SEGMENT CONTRIBUTIONS TO INDUCED BALL VELOCITY IN COLLEGIATE BASEBALL PITCHERS

The purpose of this study was to implement an induced acceleration analysis (IAA) to estimate the contributions of multi-segment motion to the forward velocity of the ball in collegiate baseball pitchers. Marker-based motion capture and ground reaction force data were collected from a sample of 17 pitchers throwing off an instrumented mound. Kinematic and kinetic data were extracted to drive the IAA model to calculate the muscular and non-muscular contributions to ball velocity. The shoulder joint torque and velocity-dependent torque collectively made up the largest contribution to the total induced velocity of the ball at 61% and 37%, respectively. The model underestimated ball speed by 16%, owing to limitations in distal segment definitions. Although this IAA showed that the proximal segments make a small, direct contribution to forward ball velocity, decomposition of the velocity-dependent torque could further clarify the extent to which the legs, pelvis, and trunk indirectly contributes to ball velocity

KINEMATIC AND KINETIC COMPARISON BETWEEN PRE-PROFESSIONAL DOMINICAN REPUBLIC AND AMERICAN BASEBALL PITCHERS

The purpose of this study was to compare elbow valgus torque and shoulder distraction force in pre-professional American and Dominican Republic (DR) pitchers. Kinematics that are known to influence elbow valgus torque and shoulder distraction force were also compared. Three dimensional biomechanical analyses were performed on Dominican Republic (n = 37) and American (n = 37) baseball pitchers. Potential difference between Dominican Republic and American pitchers were assessed through analysis of covariance with 95% confidence intervals. Age, hand dominance, and pitch velocity are known to influence elbow torque and shoulder force, therefore these confounding variables were controlled for within the analyses. Pre-professional Dominican Republic pitchers were found to throw fastballs with slower ball velocity but experienced increased elbow valgus torque compared to their American counterparts. Increased elbow valgus torque and inefficient pitching mechanics among Dominican Republic pitchers should be considered when developing training programs and pitching plans for professional pitchers from the Dominican Republic

RELATIONSHIP BETWEEN GROUND REACTION FORCE AND THROWING ARM KINETICS IN HIGH SCHOOL AND COLLEGIATE BASEBALL PITCHERS

The purpose of this study was to examine the relationship of ground reaction force (GRF) of the drive and stride leg and kinetics of the throwing arm in high school and collegiate baseball pitchers. Several studies have examined the relationship between GRF and ball velocity, but no one has examined the effect of GRF on maximum shoulder rotation torque (MERT) and maximum elbow valgus torque (MEVT). Understanding this relationship will be important to both enhancing performance and avoiding injury. Data that were previously collected during a pitching evaluation were analyzed. Twenty-two high school pitchers and 13 collegiate pitchers had received a pitching evaluation. Multiple regression analysis was used to examine the relationships between variables. Only the drive leg medial force (β = .372, p = .015) and stride leg braking force (β = .401, p = .009) were significant predictors of MERT

BALL SIZE AND WEIGHT EFFECTS ON THROWING KINEMATICS AND KINETICS IN YOUTH BASEBALL ATHLETES

In baseball, youth players play on smaller fields with shorter base path distance, pitching distance, and smaller mounds. Despite this, the baseball itself remains unchanged for youth athletes. This prospective cohort analyzed the kinematics and kinetics of 38 youth baseball pitchers while using modified sized and weighted baseballs. An ANOVA was used to determine statistical significance amongst ball modifications. ANOVA results show significance between the 3oz-5oz baseball with the 3oz baseball decreasing elbow varus torque. This is a preliminary study on the effects of modified baseballs on youth athletes

Observations of shallow methane bubble emissions from Cascadia Margin

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Michel, A. P. M., Preston, V. L., Fauria, K. E., & Nicholson, D. P. Observations of shallow methane bubble emissions from Cascadia Margin. Frontiers in Earth Science, 9, (2021): 613234, https://doi.org/10.3389/feart.2021.613234.Open questions exist about whether methane emitted from active seafloor seeps reaches the surface ocean to be subsequently ventilated to the atmosphere. Water depth variability, coupled with the transient nature of methane bubble plumes, adds complexity to examining these questions. Little data exist which trace methane transport from release at a seep into the water column. Here, we demonstrate a coupled technological approach for examining methane transport, combining multibeam sonar, a field-portable laser-based spectrometer, and the ChemYak, a robotic surface kayak, at two shallow (<75 m depth) seep sites on the Cascadia Margin. We demonstrate the presence of elevated methane (above the methane equilibration concentration with the atmosphere) throughout the water column. We observe areas of elevated dissolved methane at the surface, suggesting that at these shallow seep sites, methane is reaching the air-sea interface and is being emitted to the atmosphere.Funding for VP was provided by an NDSEG Fellowship. Funding for KF was provided by a WHOI Postdoctoral Scholar Fellowship. Ship time on the R/V Falkor was provided by the Schmidt Ocean Institute (FK180824)