Grant C. Goulet

Poroelastic evaluation of fluid movement through the lacunocanalicular system

A poroelastic lacunocanalicular model was developed for the quantification of physiologically relevant parameters related to bone fluid flow. The canalicular and lacunar microstructures were explicitly represented by a dual-continuum poroelastic model. Effective material properties were calculated using the theory of composite materials. Porosity and permeability values were determined using capillaric and spherical-shell models for the canalicular and lacunar microstructures, respectively. Pore fluid pressure and fluid shear stress were calculated in response to simulated mechanical loading applied over a range of frequencies. Species transport was simulated with convective and diffusive flow, and osteocyte consumption of nutrients was incorporated. With the calculated parameter values, realistic pore fluid pressure and fluid shear stress responses were predicted and shown to be consistent with previous experimental and theoretical studies. Stress-induced fluid flow was highlighted as a potent means of species transport, and the importance of high-magnitude low-frequency loading on osteocyte nutrition was demonstrated. This new model can serve as the foundation for future hierarchical modeling efforts that may provide insight into the underlying mechanisms of mechanotransduction and functional adaptation of bone.

Influence of cortical canal architecture on lacunocanalicular pore pressure and fluid flow

Bone is a dynamic tissue that undergoes structural modification in response to its mechanical environment, but how bone cells sense and respond to loading conditions remains incompletely understood. Current theories focus on strain-induced fluid flow for the primary means of mechanotransduction. To examine the influence of age-related cortical rarefaction on lacunocanalicular fluid characteristics, coupled fluid flow and mechanical computational models of bone specimens representing young, mid-age and aged samples were derived artificially from the same original micro-computed tomography image data. Simulated mechanical loading was applied to the bone models to induce pressure-driven interstitial fluid flow. Results demonstrated a decrease in pore pressure and fluid velocity magnitudes with age as a result of increased cortical porosity. Mean canal separation, as opposed to canal size, was implicated as a primary factor affecting age-related fluid dynamics. Future investigations through refinement of the model may implicate fluid stasis or inadequate nutrient transport experienced by osteocytes as a key factor in the initiation of cortical remodelling events.

Influence of vascular porosity on fluid flow and nutrient transport in loaded cortical bone.

Load-induced fluid flow is a key factor in triggering bone modeling and remodeling processes that maintain bone mass and architecture. To provide an enhanced understanding of fluid flow in bone, unique computational models of a tibial section were developed. The purpose of the study was to examine the effects of incorporating vascular porosity on pore fluid pressure and resulting lacunocanalicular flow and to determine the role of load-induced fluid flow in tracer transport. Simulations revealed large local pressure gradients surrounding the vascular canals that were dependent on the magnitude and state (i.e., compressive or tensile) of the stress. Fluid velocity magnitudes were increased by over an order of magnitude in the dual-porosity model, relative to the single-porosity model. Fluid flow had a marked effect on tracer perfusion within the cortex. After 10 loading cycles, a 9-fold increase in tracer concentration, relative to diffusion alone, was observed in the compressive region where fluid exchange was greatest between the lacunocanalicular porosity and the vascular canals. Agreement was achieved between computational results and experimental investigations of electrokinetic phenomenon, tracer transport, cellular stimulation, and functional adaptation. The models produced substantial improvements in bone fluid flow simulation and underscored the significance of incorporating vascular porosity in models designed to quantify fluid pressure and flow characteristics within mechanically loaded cortical bone.

Quantification of competitive game demands of NCAA division I college football players using global positioning systems

Abstract Wellman, AD, Coad, SC, Goulet, GC, and McLellan, CP. Quantification of competitive game demands of NCAA Division I college football players using global positioning systems. J Strength Cond Res 30(1): 11–19, 2016—The aim of the present study was to examine the competitive physiological movement demands of National Collegiate Athletic Association (NCAA) Division I college football players using portable global positioning system (GPS) technology during games and to examine positional groups within offensive and defensive teams, to determine if a players physiological requirements during games are influenced by playing position. Thirty-three NCAA Division I Football Bowl Subdivision football players were monitored using GPS receivers with integrated accelerometers (GPSports) during 12 regular season games throughout the 2014 season. Individual data sets (n = 295) from players were divided into offensive and defensive teams and subsequent position groups. Movement profile characteristics, including total, low-intensity, moderate-intensity, high-intensity, and sprint running distances (m), sprint counts, and acceleration and deceleration efforts, were assessed during games. A one-way ANOVA and post-hoc Bonferroni statistical analysis were used to determine differences in movement profiles between each position group within offensive and defensive teams. For both offensive and defensive teams, significant (p ⩽ 0.05) differences exist between positional groups for game physical performance requirements. The results of the present study identified that wide receivers and defensive backs completed significantly (p ⩽ 0.05) greater total distance, high-intensity running, sprint distance, and high-intensity acceleration and deceleration efforts than their respective offensive and defensive positional groups. Data from the present study provide novel quantification of position-specific physical demands of college football games and support the use of position-specific training in the preparation of NCAA Division I college football players for competition.

Predictors of Ulnar Collateral Ligament Reconstruction in Major League Baseball Pitchers

Background: Ulnar collateral ligament (UCL) reconstruction surgeries in Major League Baseball (MLB) have increased significantly in recent decades. Although several risk factors have been proposed, a scientific consensus is yet to be reached, providing challenges to those tasked with preventing UCL injuries. Purpose: To identify significant predictors of UCL reconstruction in MLB pitchers. Study Design: Case control study; Level of evidence, 3. Methods: Demographic and pitching performance data were sourced from public databases for 104 MLB pitchers who underwent UCL reconstruction surgery and 104 age- and position-matched controls. These variables were compared between groups and inserted into a binary logistic regression to identify significant predictors of UCL reconstruction. Two machine learning models (naïve Bayes and support vector machine) were also employed to predict UCL reconstruction in this cohort. Results: The binary linear regression model was statistically significant (χ2(12) = 33.592; P = .001), explained 19.9% of the variance in UCL reconstruction surgery, and correctly classified 66.8% of cases. According to this model, (1) fewer days between consecutive games, (2) a smaller repertoire of pitches, (3) a less pronounced horizontal release location, (4) a smaller stature, (5) greater mean pitch speed, and (6) greater mean pitch counts per game were all significant predictors of UCL reconstruction. More specifically, an increase in mean days between consecutive games (odds ratio [OR], 0.685; 95% CI, 0.542-0.865) or number of unique pitch types thrown (OR, 0.672; 95% CI, 0.492-0.917) was associated with a significantly smaller likelihood of UCL reconstruction. In contrast, an increase in mean pitch speed (OR, 1.381; 95% CI, 1.103-1.729) or mean pitches per game (OR, 1.020; 95% CI, 1.007-1.033) was associated with significantly higher odds of UCL reconstruction surgery. The naïve Bayes classifier predicted UCL reconstruction with an accuracy of 72% and the support vector machine classifier with an accuracy of 75%. Conclusion: This study identified 6 key performance factors that may present significant risk factors for UCL reconstruction in MLB pitchers. These findings could help to enhance the prevention of UCL reconstruction surgery in MLB pitchers and shape the direction of future research in this domain.

Grading the Functional Movement Screen : a Comparison of Manual (Real-Time) and Objective Methods

Abstract Whiteside, D, Deneweth, JM, Pohorence, MA, Sandoval, B, Russell, JR, McLean, SG, Zernicke, RF, and Goulet, GC. Grading the Functional Movement Screen: a comparison of manual (real-time) and objective methods. J Strength Cond Res 30(4): 924–933, 2016—Although intertester and intratester reliability have been common themes in Functional Movement Screen (FMS) research, the criterion validity of manual grading is yet to be comprehensively examined. This study compared the FMS scores assigned by a certified FMS tester to those measured by an objective inertial-based (IMU) motion capture system. Eleven female division I collegiate athletes performed 6 FMS exercises and were manually graded by a certified tester. Explicit kinematic thresholds were formulated to correspond to each of the grading criteria for each FMS exercise and then used to grade athletes objectively using the IMU data. The levels of agreement between the 2 grading methods were poor in all 6 FMS exercises and implies that manual grading of the FMS may be confounded by vague grading criteria. Evidently, more explicit grading guidelines are needed to improve the uniformity and accuracy of manual FMS grading and also facilitate the use of objective measurement systems in the grading process. Contrary to the approach that has been adopted in several previous studies, the potential for subjective and/or inaccurate FMS grading intimates that it may be inappropriate to assume that manual FMS grading provides a valid measurement tool. Consequently, the development and criterion validation of uniform grading procedures must precede research attempting to link FMS performance and injury rates. With manual grading methods seemingly susceptible to error, the FMS should be used cautiously to direct strength and/or conditioning programs.

Femoroacetabular Impingement in Elite Ice Hockey Goaltenders Etiological Implications of On-Ice Hip Mechanics

Background: Femoroacetabular impingement (FAI) is particularly prevalent in ice hockey. The butterfly goalie technique is thought to involve extreme ranges of hip motion that may predispose goaltenders to FAI. Purpose: To quantify hip mechanics during 3 common goaltender movements and interpret their relevance to the development of FAI. Study Design: Descriptive laboratory study. Methods: Fourteen collegiate and professional goaltenders performed skating, butterfly save, and recovery movements on the ice. Hip mechanics were compared across the 3 movements. Results: The butterfly did not exhibit the greatest range of hip motion in any of the 3 planes. Internal rotation was the only hip motion that appeared close to terminal in this study. When subjects decelerated during skating—shaving the blade of their skate across the surface of the ice—the magnitude of peak hip internal rotation was 54% greater than in the butterfly and 265% greater than in the recovery. No movement involved levels of concomitant flexion, adduction, and internal rotation that resembled the traditional impingement (FADIR) test. Conclusion: The magnitude of internal rotation was the most extreme planar hip motion (relative to end-range) recorded in this study (namely during decelerating) and appeared to differentiate this cohort from other athletic populations. Consequently, repetitive end-range hip internal rotation may be the primary precursor to symptomatic FAI in hockey goaltenders and provides the most plausible account for the high incidence of FAI in these athletes. Resection techniques should, therefore, focus on enhancing internal rotation in goaltenders, compared with flexion and adduction. While the butterfly posture can require significant levels of hip motion, recovering from a save and, in particular, decelerating during skating are also demanding on goaltenders’ hip joints. Therefore, it appears critical to consider and accommodate a variety of sport-specific hip postures to comprehensively diagnose, treat, and rehabilitate FAI.

Accuracy of Femur Angles Estimated by IMUs During Clinical Procedures Used to Diagnose Femoroacetabular Impingement

We present a novel method for quantifying femoral orientation angles using a thigh-mounted inertial measurement unit (IMU). The IMU-derived femoral orientation angles reproduce gold-standard motion capture angles to within mean (standard deviation) differences of 0.1 (1.1) degrees on cadaveric specimens during clinical procedures used for the diagnosis of Femoroacetabular Impingement (FAI). The method, which assumes a stationary pelvis, is easy to use, inexpensive, and provides femur motion trajectory data in addition to range of motion measures. These advantages may accelerate the adoption of this technology to inform FAI diagnoses and assess treatment efficacy. To this end, we further investigate the accuracy of hip joint angles calculated using this methodology and assess the sensitivity of our estimates to skin motion artifact during these tasks.

Quantification of Accelerometer Derived Impacts Associated With Competitive Games in NCAA Division I College Football Players.

Abstract Wellman, AD, Coad, SC, Goulet, GC, and McLellan, CP. Quantification of accelerometer derived impacts associated with competitive games in National Collegiate Athletic Association division I college football players. J Strength Cond Res 31(2): 330–338, 2017—The aims of the present study were to (a) examine positional impact profiles of National Collegiate Athletic Association (NCAA) division I college football players using global positioning system (GPS) and integrated accelerometry (IA) technology and (b) determine if positional differences in impact profiles during competition exist within offensive and defensive teams. Thirty-three NCAA division I Football Bowl Subdivision players were monitored using GPS and IA (GPSports) during 12 regular season games throughout the 2014 season. Individual player data sets (n = 294) were divided into offensive and defensive teams, and positional subgroups. The intensity, number, and distribution of impact forces experienced by players during competition were recorded. Positional differences were found for the distribution of impacts within offensive and defensive teams. Wide receivers sustained more very light and light to moderate (5–6.5 G force) impacts than other position groups, whereas the running backs were involved in more severe (>10 G force) impacts than all offensive position groups, with the exception of the quarterbacks (p ⩽ 0.05). The defensive back and linebacker groups were subject to more very light (5.0–6.0 G force) impacts, and the defensive tackle group sustained more heavy and very heavy (7.1–10 G force) impacts than other defensive positions (p ⩽ 0.05). Data from the present study provide novel quantification of positional impact profiles related to the physical demands of college football games and highlight the need for position-specific monitoring and training in the preparation for the impact loads experienced during NCAA division I football competition.

Long-term effects of adolescent concussion history on gait, across age

The aim of this study was to examine the possible long-term effects of high school concussion history on gait performance across the lifespan. Individuals with and without a concussion history were grouped into 20-year-old (yo) (n=40), 40yo (n=19), and 60yo (n=18) age groups. Participants completed five trials of four walking conditions: a normal walk, a dual task walk, an obstructed walk, and an obstructed, dual task walk. Spatiotemporal gait parameters for gait analyses during single and dual task conditions. Gait velocity, step width, stride length, percent of time in double support, and obstacle toe clearance were the gait variables assessed along with number correct from dual task. Gait was analyzed via optical motion capture. Data were analyzed by two-factor, multivariate ANOVAs and significant interactions were explored using post hoc contrasts. A significant (F=2.62, p=0.03) interaction was observed for the obstructed walk condition. Further analyses yielded no significant concussion history and control group differences, within age. The data indicate that an adolescent concussion history has a non-observable effect on gait across the lifespan.