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It is a widely assumed principle that organisms reflexively approach possibilities for pleasure and avoid possibilities for pain. However, highly evolved organisms not only reflexively react to future possibilities of pleasure vs. pain, but also evaluate the chance or risk of actually experiencing such possibilities. Given the import of optimism judgments in shaping behavior and other outcomes, the main goal of the current research was to examine the relationship between the rudimentary systems of approach-avoidance that orient us toward possible outcomes in the environment and the higher-order optimism judgments we make when evaluating whether such outcomes are likely to occur. To this end, two experiments examined the impact of approach-avoidance cues in shaping participants' optimism judgments about experiencing positive and negative future life events. For the primary operationalization of approach-avoidance, college student participants engaged in arm flexion (a motor movement associated with approach) or arm extension (a motor movement associated with avoidance) while simultaneously making optimism judgments about experiencing a range of positive and negative events in the future. A secondary operationalization involved correlations computed between participants' chronic personality tendencies related to approach-avoidance (e.g., positive vs. negative affectivity) and their optimism judgments. The results of these experiments revealed complexities in the relationship between approach-avoidance and optimism, suggesting that when, how and why approach-avoidance cues will shape optimism may critically depend upon 1) the specific operationalization of approach-avoidance, 2) how optimism is measured, and 3) characteristics of the outcomes under consideration. Explanations for the complexities in the results are offered, and attempts are made to link the current work to broader theoretical and practical aspects of the connection between approach-avoidance and optimism.

Modelling of human motion is used in a wide range of applications. An important aspect of accurate representation of human movement is the ability to customize models to account for individual differences. The following work proposes a methodology using Hill-based candidate functions in the Fast Orthogonal Search (FOS) method to predict translational force at the wrist from flexion and extension torque at the elbow. Within this force estimation framework, it is possible to implicitly estimate subject-specific physiological parameters of Hill-based models of upper arm muscles. Surface EMG data from three muscles of the upper arm (biceps brachii, brachioradialis and triceps brachii) were recorded from 10 subjects as they performed isometric contractions at varying elbow joint angles. Estimated muscle activation level and joint kinematic data (joint angle and angular velocity) were utilized as inputs to the FOS model. The resulting wrist force estimations were found to be more accurate for models utilizing Hill-based candidate functions, than models utilizing candidate functions that were not physiologically relevant. Subject-specific estimates of optimal joint angle were determined via frequency analysis of the selected FOS candidate functions. Subject-specific optimal joint angle estimates demonstrated low variability and fell within the range of angles presented in the literature. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2008-10-30 01:32:01.606

In this thesis, a passive exoskeleton spine was designed and evaluated by a series of biomechanics simulations. The design objectives were to reduce the human operator’s back muscle efforts and the intervertebral reaction torques during a full range sagittal plane spine flexion/extension. The biomechanics simulations were performed using the OpenSim modeling environment. To manipulate the simulations, a full body musculoskeletal model was created based on the OpenSim gait2354 and “lumbar spine” models. To support flexion and extension of the torso a “push-pull” strategy was proposed by applying external pushing and pulling forces on different locations on the torso. The external forces were optimized via simulations and then a physical exoskeleton prototype was built to evaluate the “push-pull” strategy in vivo. The prototype was tested on three different subjects where the sEMG and inertial data were collected to estimate the muscle force reduction and intervertebral torque reduction. The prototype assisted the users in sagittal plane flexion/extension and reduced the average muscle force and intervertebral reaction torque by an average of 371 N and 29 Nm, respectively.

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