Core exercise is a staple of many physical training regimens with goals ranging from improving athletic performance to rehabilitation of spine and knee injuries. Traditionally, dynamic movements such as flexion, lateral bending and twisting core exercise maneuvers are used in training programs; an approach consistent with training the distal limbs where muscular effort is mostly devoted to creating motion. However, knowledge of the functional anatomy of core musculature and spine injury mechanisms questions the use of these types of exercises. Alternative core exercises make use of isometric postures and static bracing to create muscular activation while minimizing spine loads and injury mechanisms linked with movement. This study aims to quantify the effect of various core training programs on the change of passive and active stiffness properties of the torso. This study was driven by several curiosities: 1) Isometric core exercises are reported to help some people who have low back pain. Is there a short lasting ???enhanced stiffness??? after performing these exercises? 2) Core training regimens use Isometric and Dynamic core exercises to enhance core bracing properties. Is one method superior to the other in terms of enhancing core stiffness? 3) If adaptations to core stiffness can be achieved with core exercise, do these adaptations differ between beginners and trained individuals? Twenty four healthy male subjects (22.9 ?? 2.7 years, 1.79 ?? 0.06 m, 77.5 ?? 10.8 kg) were recruited for short and long term core training. Of the overall population, twelve subjects (21.7 ?? 1.89 years, 1.80 ?? 0.076 m, 78.3 ?? 12.3 kg) were University students with little to no experience in performing regular core exercise. The other twelve subjects (24.2 ?? 2.89 years, 1.79 ?? 0.047 m, 76.8 ?? 9.71 kg) were athletically trained with at least one year of experience performing regular core exercise (minimum three times per week). This study was a repeated measures design examining short and long term core stiffness (active and passive) and range of motion before and after a single fifteen minute bout of isometric core exercise and a six week core training program. The long term training groups were divided evenly into isometric, dynamic and control groups. The Isometric group received a six week training program consisting of core bracing exercises ranging from basic static bodyweight exercises to weighted exercises with additional challenge of distal limb mobility while maintaining a braced core, while dynamic group exercises consisted of movement and speed based core exercises. The Control group received no further training during this period. All subjects were asked to refrain from any extra core demands not given by the researchers. After the training period was complete all subjects were retested for stiffness and range of motion. Passive stiffness tests were performed using a frictionless bending apparatus for flexion, extension, left and right lateral bend and left and right axial twist directions. Active stiffness was assessed via a ???quick release??? mechanism, preloaded with a 16 kg mass and randomly released to assess active extension. Participants were instrumented with unilateral electromyography (EMG) of selected core musculature and electromagnetic signals for motion capture for lumbar kinematics. To determine if training had an effect on dependent variables a series of repeated measures ANOVAs were performed; short term training utilized a 2x2 Repeated Measures ANOVA using the pre/post condition and training experience (na??ve vs. savvy) as factors. Long term training utilized a 3x2x2 Repeated Measures ANOVA using training group (Isometric vs. Dynamic vs. Control), training experience (na??ve vs. savvy) and pre/post condition as factors. In general, short term isometric core training increased core stiffness in all directions for na??ve and savvy subjects. Comparisons between these two subject groups did not yield any significant differences. After long term training stiffness was increased the greatest in the Isometric training group with both na??ve and savvy subjects. Dynamic training yielded significant increases in stiffness but for only one direction in each subject group (right lateral bend in na??ve subjects and left axial twist in savvy subjects). The Control group did not show any significant changes in stiffness. Comparisons between training groups and training experience did not yield any significant differences. Isometric training lead to significant stiffness increases in all test except for passive and active extension in na??ve subjects, and similar results were found for savvy subjects except for right lateral bend not showing any significant changes. Researchers believe reasons for insignificant changes are related to high variances which may be due to inadequate statistical power and a wide variety of responses within each subject group. Though some analyses showed inadequate statistical power due to small sample sizes it should be noted that this research is the first of its kind investigating the trainability of core stiffness in the short and long term, and thus difficult to establish sample sizes without any baseline values. The findings of this study can be directly applied to core training for rehabilitation and athletic function. Enhancements in core stiffness are thought to subsequently enhance traits such as load bearing ability, pain management and athletic function. The results of short term training give insight into how a short training session performed prior to a load bearing task can make the task safer and easier to perform. The results of long term training show that Isometric training performed over a long duration may induce more permanent enhancements to stiffness and core function.

Background Obesity is associated with an increased risk of back pain, attributed to elevated mechanical load. Back injury risk is also determined by movement patterns (kinematics) and physiological factors (exertion, muscle activation). Lifting, particularly repetitive, is the most frequently cited injurious activity. However, in spite of the obvious relation, a paucity of information exists quantifying the interaction of obesity and repetition during lifting. Purpose To determine the effects of obesity and repetition on mechanical, kinematic and physiological lifting outcomes. Methods: An individual-specific, biomechanical model (based upon 3D photogrammetry) was developed to estimate the effect of obesity on back load during lifting (study 1). Lifting strategy and physiological outcomes related to obesity were examined in a fixed-pace, repetitive lifting task (study 2). The effect of task constraints on lifting strategy of high and normal BMI individuals were determined (study 3), followed by an evaluation of muscle activation responses during a repetitive trunk motion similar to that encountered during lifting (study 4). Results: Obesity-specific alterations of important determinants of back load (inertia, CMloc) were revealed. Obesity was related to a substantial increase in back load (M=+197.3, SE=16.8 Nm about L5/S1), however the effect differed across lifting tasks. The lifting strategy of high-BMI individuals was characterized by an increased distance to the external mass (M=+4.7, SE=1.8 cm) and shorter lift duration (M=230, SE=130 msec), with increased cardiovascular effort (M=+7.4, SE=3.4% HRmax) but no change in perceived exertion. Lifting frequency was not a major determinant of lifting strategy, however strategy was influenced by the presence and type of external pacing. A phase-specific, rapid alteration in muscle activation response was evident in the MMG signal during the initial repetitions of a repetitive trunk motion. Conclusion: The effect of obesity during lifting is task-dependent, and cannot be attributable solely to mechanical factors. Future studies should consider tasks that are unconstrained, and examine the initial familiarization period of repetitive tasks, specifically the lowering phase of motions. These findings have relevance to back injury mechanisms related to obesity and the design of injury prevention programs for individuals with a high BMI.

As the number of total knee arthroplasty (TKA) procedures increases annually, the patient demographic is shifting to include younger patients with higher expectations for post-operative function. The aim of this study was to compare movement patterns during activities of daily living among TKA patients and a healthy, age-matched group using 3D motion analysis. Specifically, this analysis looked at walking on level and inclined surfaces, as well as sitting up and down from a chair. It was predicted that (1) TKA patients would exhibit reduced knee extension moments at the operated limb and increased adduction moments at the contralateral limb during gait, (2) walking downhill would result in greater differences between TKA and control groups, compared to level walking, and (3) TKA participants would have greater flexion angles, moments and power values at the hip, compared to controls, during the sit-stand tasks. Seventeen participants (age=62±6 years, BMI=30±3 kg/m2, time after surgery=11±5 months) were recruited from the Ottawa Hospital, having undergone unilateral TKA by the same surgeon. An age-matched control group was composed of 17 individuals (age=63±8 years, BMI=27±4 kg/m2) who were recruited from the local community. Three dimensional (3D) biomechanical assessment was conducted with all participants performing five trials of walking on level and inclined surfaces, stair ascent and descent as well as sit-stand tasks. Results from this study were focused on gait and sit-stand transitions, showing that TKA participants exhibited altered gait patterns on both walking surfaces, with significantly smaller knee flexion angles and moments, as well as reduced peak power at the knee. The TKA group also experienced reduced knee extension moments; however, this was only significant for downhill walking. Consistent with our hypothesis, downhill walking resulted in greater discrepancies between the groups compared to level walking. Contrary to our third hypothesis, TKA participants exhibited significantly smaller peak hip flexion angles and moments during the sit-stand task, along with reduced hip abduction angles and knee abduction moments. The reduced knee flexion kinematics and kinetics observed during gait tasks, combined with the differences in frontal plane mechanics observed during the sit-stand task suggest that altered loading patterns persist six to twelve months after surgery. This may be a result of continued pre-operative movement patterns as well as the surgery itself, and should be kept in mind when developing rehabilitation programs for this patient population.

Lacrosse, Canada’s national summer sport, is a sport anchored in first nations’ tradition. Its growing popularity in North America has not been reflected by a similar interest in the scientific literature more specifically on the biomechanics of the lumbar spine with its throwing motion. The aim of this study was to describe the motions, forces and muscle actions of the lumbar spine with the hybrid, overhand and sidearm throw. Twelve subjects were asked to throw at maximal speed while captured by a 3D motion analysis system. Flexion, extension and axial rotation angular velocities as well as positive and negative powers in the two planes were calculated. The first research question pertained to consistency in angular velocities and powers between trials of a given throwing technique. Subjects showed a fairly high variation on all variables but mostly with the angular velocities in extension and the peak positive power in flexion/extension which had high coefficient of variations (CVs). The contralateral rotation velocity and the positive rotation power had the lowest CVs. Overall the CVs for powers exceeded the angular velocities’. The second research question addressed if a difference in variables was present between the three throwing methods. A significant difference was observed in the peak negative power in flexion/extension and the peak positive power in rotation. The contralateral rotation angular velocity also showed a significant difference but the sphericity assumption failed. No other variable showed a significant difference but the observed power for those variables was also quite small. Due to the lack of power and the further need for controlling some unforeseen sources of error, this study can be used as a pilot study to further define and improve future studies in the field of lacrosse biomechanics.

The main purpose of this study was to measure the differences in ground reaction forces (GRFs) produced from an anteroposterior versus a mediolateral style hockey skating arm swing. Twenty four elite level female hockey players performed each technique while standing on a ground mounted force platform, all trials were filmed using two video cameras. Force data was assessed for peak scaled GRFs in the frontal and sagittal planes, and resultant GRF magnitude and direction. Upper limb kinematics were assessed from the video using Dartfish video analysis software, confirming that the subjects successfully performed two significantly distinct arm swing techniques. The mediolateral arm swing used a mean of 18.38° of glenohumeral flexion/extension and 183.68° of glenohumeral abduction/adduction while the anteroposterior technique used 214.17° and 28.97° respectively. The mediolateral arm swing produced 37% greater frontal plane and 33% lesser sagittal plane GRFs than the anteroposterior arm swing. The magnitudes of the resultant GRFs were not significantly different between the two techniques however the mediolateral technique produced a resultant GRF with a significantly larger angle from the direction of travel (44.44°) as compared to the anteroposterior technique (31.60°). The results of this study suggest that the direction of GRFs produced by the mediolateral arm swing more consistent with the direction of lower limb propulsion, perhaps resulting in a greater contribution to high velocity skating. Based on the findings from the present study ice hockey skaters should perform the mediolateral arm swing to maximize the effective GRFs produced with each stride.

This thesis aims to apply neural networks in the classification of human patterns of movement and to compare the accuracy of this technique with existing methods (conventional statistics and clinical assessment). Three different examples of human movement and one of posture were chosen for study and a variety of biomechanical parameters used to describe them. The temporal parameters of gait patterns, related to speed of walking and walking with splinted knee or weighted leg, were recorded. The angular displacement of both hips and knees was measured during stepping up or down steps of five different heights. Different standing postures were studied by measuring the disposition of body landmarks associated with imagined moods of human subjects. Finally, changes of the sit-stand-sit manoeuvre due to chronic low back pain, expressed as joint movement and forces exerted on the ground, were recorded. Patterns were classified by neural networks, linear discriminant analysis and, in the case of sit-stand patterns, by qualified clinicians. By altering the number of variables to discriminate between patterns, benefits of the above classifiers were identified. The success in classification of the measured patterns by neural networks was found to have an accuracy at least as high as that of linear discriminant analysis. A neural network is a useful tool for the discrimination of patterns of human movements; its main advantage is the ability to deal with a large number of predictor variables. A successfully trained and tested neural networks can easily be set up in a computer and, on the evidence presented, could be used to help clinicians diagnose or assess pathological patterns of movement.

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Surgery to correct cam femoroacetabular impingement (FAI) is increasingly popular. Despite this, no known study has used motion analysis and ground reaction forces to quantify the outcome of surgery for FAI. The goal of this study was to compare the preoperative and postoperative lower-extremity joint kinematic and kinetic measurements of cam FAI patients during activities of daily living with use of a high-speed motion capture system and force platforms. We hypothesized that the lower-extremity joint mechanics of FAI patients during level walking and maximal squatting would resemble more those of healthy control subjects, after surgery. Ten patients with unilateral symptomatic cam FAI, who underwent corrective surgery using an open or combined technique, performed walking and maximal depth squatting trials preoperatively and postoperatively. Thirteen healthy control subjects, matched for age, sex and body mass index, provided normative data. Results showed that postoperatively, FAI patients had reduced hip ROM in the frontal and sagittal planes, produced smaller peak hip abduction and external rotation moments, and generated less peak hip power compared to the control group during level walking. During maximal squatting, postoperative FAI patients squatted to a greater depth, and had larger knee flexion and ankle dorsiflexion angles, as well as the sum of all joint angles of the affected limb at maximal depth compared to the preoperative values. The lower-extremity joint and pelvic mechanics of FAI patients did not fully return to normal after surgery. Although surgery seemed to reduce hip pain and restore a normal femoral head-neck offset, it further impaired muscle function as a result of muscle incisions. More research is needed to determine the effects of muscle incisions, which could help improve surgical techniques and develop better rehabilitation programs for FAI patients.