Trunk lean over the stance limb during gait has been linked to a reduction in the knee adduction moment, which is associated with joint loading. Differences were examined in knee adduction moments and frontal plane trunk lean during gait between subjects with knee osteoarthritis and a control group of healthy adults. Additionally, subject variability in human motion data presents a challenge to researchers when trying to detect differences between subject groups. The individual differences in neutral posture between subjects is a source of variation in joint angles. A method was developed using principal component analysis (PCA) to objectively reduce this inter subject variability. Gait analysis was performed on 80 subjects (40 osteoarthritis). Models were developed to define lateral thoracic tilt, as well as pelvic tilt. The trunk and pelvis frontal plane angles were used to describe trunk lean and pelvic tilt. Angles were calculated across the stance phase of gait. We analyzed the data, (i) by extracting discrete parameters (mean and peak) waveform values, and (ii) using principal component analysis (PCA) to extract shape and magnitude differences between the waveforms. Osteoarthritis (OA) subjects had a higher knee adduction moment than the control group (α=0.05). Although the discrete parameters for trunk lean did not show differences between groups, PCA did detect characteristic waveform differences between the control and osteoarthritis groups. The data show that subjects display similar waveform shapes, however waveforms vary in magnitude, suggesting a variation in posture between subjects. The results from the PCA reveal that the first PC, which captures the most variation in the data, represents this variation in magnitude. The second PC describes a significant difference in range of motion between the subject groups. Subjects with knee OA were found to have a different range of motion of their pelvis and trunk than control subjects. These changes are consistent with a strategy to lower the knee adduction moment. As an alternative to conventional subjective methods, PCA should be employed to reduce inter subject variability in order to ensure objective analysis in human motion waveform data. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-08-14 14:43:53.127

Backpacks are used by more than 90% of schoolchildren worldwide and over 40 million students in the United States on a regular basis. The carriage of loaded backpacks is associated with kinematic and physiological changes, as well as complaints of neck and back pain. Since a history of backpain in childhood is the strongest predictor of having musculoskeletal discomfort and back pain as an adult, development of back pain due to backpack use is of prognostic concern. The purpose of this dissertation was to examine the effects of backpack weights (up to 20% body weight (BW)) on children’s posture, subjective complaints of pain and perceived exertion, and walking endurance. A secondary goal was to examine the data to identify and recommend a weight limit for backpacks carried by elementary school children based on the results. In Chapter 2, we performed a preliminary study designed to examine the effects of loaded backpacks on forward head posture in school children. The results of this study found that forward head posture increased with both backpack weight and condition. The greatest differences were noted at the 15% and 20%BW backpack loads with initial loading, but after 6 minutes of walking the forward head posture was similar for all backpack loads. In Chapter 3, we conducted a study to evaluate multiple postural angles and the subjective complaints of pain and perceived exertion/fatigue in children to determine the effects of both the weight and time spent carrying loaded backpacks up to 20%BW. Subjects showed significant changes in all measures including the Six Minute Walk Test (6MWT), OMNI Walk/Run Scale of perceived exertion/fatigue and subjective complaints of pain, as well as the postural angles of Craniovertebral Angle, Forward Trunk Lean, and Pelvic Tilt. Subjects demonstrated immediate and significant changes in forward head posture, forward trunk lean, and pelvic tilt while wearing backpacks weighing 10%, 15% and 20%BW, but the 10%BW backpack resulted in the least amount of change. This study also found that these postural angles changed additionally after walking 6 minutes while carrying the loaded backpacks. Subjects also demonstrated decreased 6MWT distances and increased reports of perceived exertion and pain after carrying backpacks weighing 10%, 15% and 20%BW. In Chapter 4, we discussed the clinical implications of this research. It was determined that backpack loads weighing 10%, 15% and 20%BW of a child’s body weight result in immediate changes in posture, which continue to increase after walking six minutes with the loaded backpack. The backpack loads significantly impacted the children’s walking endurance as well as their reports of perceived exertion/fatigue and regional pain. This study found that of the loads tested, the 10%BW resulted in the least amount of change in all outcome measures. However, the 10%BW load was not innocuous, as it still created significant changes in posture and subjective complaints. Backpack weight limit guidelines need to be written to protect children from carrying backpacks weighing more than 10% body weight.

Sprint acceleration training has been highly researched and found that resistance sleds are one of the most effective tools for maximizing training adaptations. The resistance sled is being used by many of the world leaders in athletic training but has yet to be researched for the kinetic and kinematic effects some of its key components cause. The aim of this study was to better understand the effects of the attachment height on the sled and sled rail material on the user's trunk lean and jerking effect caused by the sled. This was done because it was hypothesized that the attachment height has a direct impact on trunk lean and sled rail material has a direct impact on jerk caused by the sled. To test these assumptions, experimental and theoretical data was collected using a single subject study analyzing trunk lean and acceleration values of the sled. The results presented a significant decrease in trunk lean (more horizontal line of action) when the attachment height was raised. Additionally, no significant values were attained to support the assumption that by modifying the sled rail material, jerking effects will decrease. The results indicate that there is a direct correlation between attachment height and trunk lean. More research is needed to better understand the relationship between sled rail material and jerk.