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This study examined the impact of several noise conditions on speech articulator movements during a sentence repetition task. Sixty participants in three age groups ranging from 20 to 70 repeated a sentence under five noise conditions. Lower lip movements during production of a target sentence were used to compute the spatiotemporal index (STI). It was hypothesized that STI would be lower (indicating greater stability) in the silent baseline condition. There were changes in speech production under several of the noise conditions. The duration for the 1-talker condition was significantly shorter when compared to the silent condition, which could be due to the impact of the 1-talker noise on the attention of the speaker. The peak velocity of a selected closing gesture increased in all of the noise conditions compared to silence. It could be speculated that the repetitive and predictable nature of the speaking task allowed participants to easily filter out the noise while automatically increasing the velocity of lip movements, and consequently, the rate of speech. The STI in the pink noise and 6-talker conditions was lower than in the silent condition, which may be interpreted to reflect a steadier manner of speech production. This could be due to the fact that in the 6-speaker noise condition, the overall effect was more similar to continuous noise, and thus potentially less distracting than hearing a single speaker talking. The count of velocity peaks was unexpectedly lower in the noise conditions compared to speech in silence, suggesting a smoother pattern of articulator movement. The repetitiveness of the task may not require a high level of self-monitoring, resulting in speech output that was more automatic in the noise conditions. With the presentation of noise during a speaking task, the intensity increased due to the Lombard effect in all of the noise conditions. People communicate in noisy environments every day, and an increased understanding of the effects of noise on speech would have value from both theoretical and clinical perspectives.

Smoothness is a hallmark of healthy movement and has the potential to be used as a marker of recovery in rehabilitation settings. While much past research has focused on shoulder and elbow movements (reaching), little is known about movements of the wrist despite its importance in everyday life and its impairment in many neurological and biomechanical disorders. Our current lack of knowledge regarding wrist movement prevents us from improving current models, diagnosis, and treatment of wrist disorders. In particular, while movement smoothness is a well-known characteristic of reaching movements and may potentially be used to diagnose and monitor recovery from neurological impairments, little is known about the smoothness of wrist rotations. Therefore, because the smoothness of wrist rotations has not been characterized, it cannot be used as a marker for diagnosis and evaluation. This study examines the smoothness of wrist rotations in comparison to the known baseline of reaching movements. Subjects were asked to perform wrist and reaching movements under a variety of conditions, including different speed and direction. To measure movement smoothness, this study used an established metric of speed profile number of maxima and presents a novel method for characterizing smoothness by fitting a minimum-jerk trajectory to real movement data.The results show that 1) wrist rotations are significantly less smooth than reaching movements (p≤0.0016), 2) smoothness decreases significantly as speed decreases (p<0.0001), and 3) wrist movements exhibit a pattern of smoothness that varies significantly between targets and outbound/inbound movement directions (p<0.0001). Potential causes for results 1 and 3 are presented and tested by simulation or reference to prior studies, because these findings were previously unknown. The decrease in smoothness with speed (result 2) has been found in prior studies of smoothness in reaching and finger movements. The reasoning behind the first result is explored by testing whether the difference in smoothness between wrist and reaching movements was due to differences in mechanical, muscular, neural, or protocol-related properties. The reasoning behind the third result is explored by testing whether the difference in wrist direction was due to anisotropy in musculoskeletal dynamics or anisotropy in movement duration. The simulations show that the wrist’s bandwidth is greater than that of the arm, and that there is nonvoluntary power in the bandwidth of the wrist that would be low-pass filtered in reaching movements, indicating that at least some of the difference in smoothness between wrist and reaching movements is due to differences in mechanical properties. Differences in muscular, neural, or protocol-related properties (signal-dependent noise, proprioceptive acuity, and the speed requirements of the task, respectively) do not appear to be the cause of the difference in smoothness between wrist and reaching movements. Differences in wrist smoothness between movement directions appears to be related to differences in movement duration between directions.

Background: Movement screens are frequently used to identify abnormal movement patterns that may increase risk of injury and/or hinder performance. However, abnormal patterns are often detected visually based on the observations of a coach or clinician leading to poor inter- and intrarater reliability. In addition, they have been criticized for having poor validity and sensitivity. Quantitative, or data-driven methods can increase objectivity, remove issues related to inter-rater reliability and offer the potential to detect new and important features that may not be observable by the human eye. The combination of motion capture data, pattern recognition and machine learning could provide a quantitative method to better assess movement competency. Purpose: The purpose of this doctoral thesis was to create the foundation for the development of an objective movement screening tool that combines motion capture data, pattern recognition and machine learning. This doctoral thesis is part of a larger project to bring an objective movement screening tool for use in the field to market. Methods: This thesis is comprised of four studies based on a single data collection and a common series of pre-processing steps. Data from 542 athletes were collected by Motus Global, a for-profit biomechanics company, with athletes ranging in competition level from youth to professional and competing in a wide-range of sports. For the first study of this thesis, an online software program was developed to examine the inter- and intra-reliability of a movement screen, with intrareliability being further examined to compare reliability when body-shape was and was not modified. The second study developed the objective movement screen framework that utilized motion capture, pattern recognition and machine learning. Study 3 and 4 assessed different types of input data, classification goals (e.g., skill level and sport played), feature reduction and selection methods, and increasingly complex machine learning algorithms. Results: For Study 1, when looking at inter- and intra-rater reliability of expert assessors during subjective scoring of movements, intra-rater reliability was better than inter-rater reliability. When assessing the effects of body-shape, on average, reliability worsened when body-shape was manipulated. Study 2 provided proof-of-principle that athletes were able to be classified based on skill level using marker-based optical motion capture data, principal component analysis (PCA) and linear discriminant analysis. For Study 3, PCA in combination with linear classifiers outperformed non-linear classifiers when classifying athletes based on skill level; feature selection increased classification rates, and classification rates when using simulated inertial measurement unit data as the input data were on average better than when using marker-based optical motion capture data. In Study 4, athletes were able to be differentiated based on sport played and recurrent neural nets (RNNs) and PCA in combination with traditional linear classifiers were the optimal machine learning algorithms when classifying athletes based on skill level and sport played. Conclusion: This thesis demonstrates that objective methods can differentiate athletes based on desired demographics using motion capture, pattern recognition and machine learning. This thesis is part of a larger project to bring an objective movement screening tool for field-use to market and provides a solid foundation to use in the continued development of an objective movement screening tool.

The objective of this study was to investigate associations between injury-related kinematic parameters and overweight measures for youth baseball pitchers. The injury-related kinematic parameters considered were measurements 1) at foot contact: stride length, front foot position, shoulder external rotation, shoulder abduction, and elbow flexion; 2) between FC and ball release: peak knee extension; and 3) at BR: shoulder abduction. Data from three separate collection sites examined pitching mechanics of 18 10- to 11-year-old pitchers, 11 14- to 16-year-old pitchers, and 104 16- to 18-year-old pitchers Linear regression analyses were performed to determine significant correlations between kinematic parameters and body mass index (BMI) for each of the three age groups (10- to 11-year-olds, 14- to 16-year-olds, 16- to 18-year-olds). The significant findings were 1) for 10- to 11-year-old pitchers, stride length was negatively correlated with BMI and front foot position was positively correlated with BMI and 2) for 16- to 18-year-old pitchers, shoulder external rotation was negatively correlated with BMI and elbow flexion was positively correlated with BMI. A key clinical implication of this study is that select kinematic parameters have been identified that could guide coaches and trainers when working with overweight pitchers. In addition, select kinematic parameters of concern have been identified for different age ranges.

Ankle foot orthoses (AFOs) are used to improve walking in some lower extremity conditions but AFOs restrict ankle motion resulting in a trade-off in ankle and hip mechanics. While the use of AFOs have been well documented, there still remain gaps in the literature. The first study compared the differences in sagittal plane ankle and hip kinematics and kinetics across three conditions at two speeds in healthy individuals while the second study compared frontal plane kinetics at the hip and knee and vertical ground reaction forces between two conditions at two speeds in healthy individuals. This was studied by collecting and analyzing three-dimensional joint kinematics and ground reaction forces from twelve healthy adults. Participants walked in three conditions (shod; i.e. athletic shoes only and two reduced push-off conditions using solid ankle foot orthoses (SAFOs); i.e. unilateral brace and bilateral brace conditions) and at two speeds (1.25m/s and 1.5m/s). In the first study, generalized linear models with general estimating equations were used to compare ankle and hip angles, moments and power for the braced and unbraced sides separately in all three conditions. In the second study, frontal plane kinetics and vertical ground reaction forces in the unbraced limb in the unilateral brace condition were compared to the same side during shod walking using paired sample t-tests. From our first study we found that the reduced push-off from the use of SAFOs results in decreased peak plantarflexion angles and power generation at the ankle and increased peak flexion angles, and first and second peak power generation at the hip in the braced limbs in both unilateral (p≤0.05) and bilateral (p≤0.05) brace conditions at both speeds. On the unbraced side in the unilateral brace condition, there were decreased peak power generation at the ankle at 1.25m/s and increased peak extension moments, first and second peak power generation at the hip compared to the shod condition (p<0.05) at both speeds. In the comparison between the unilateral and bilateral brace conditions, the changes in ankle and hip mechanics were similar to the changes between the shod condition and the bilateral brace condition on the unbraced side; in addition, participants also had higher peak extension moments in the unilateral brace condition compared to the bilateral brace condition (p<0.05). On the braced side, participants had lower peak plantarflexion moments at the ankle and lower peak flexion angles at the hip when walking with bilateral SAFOs, compared to walking with unilateral SAFOs (p<0.05). In the second study, we found that peak internal knee and hip abduction moments were 3% and 4% higher, respectively, in the unbraced limb in the unilateral brace condition at 1.25m/s (p≤0.041) compared to the same side in the shod condition. Peak vertical ground reaction force was 3% higher in the unbraced limb in the unilateral brace condition at both speeds (p=0.002). Findings indicate that walking with unilateral ankle foot orthoses presents an increased risk of developing secondary conditions.

No / In this paper we present a constrained inverse kinematics algorithm for real-time motion capture in virtual environments, that has its origins in the simulation of multi-body systems. We apply this algorithm to an articulated human skeletal model using an electromagnetic motion tracking system with a small number of sensors to create avatar postures. The method offers efficient inverse kinematics computation and it is also generalised for the configurations of an articulated skeletal model. We investigate the possibility of capturing fast gestures by analysing the convergence patterns of the algorithm with the motion tracking sampling frequency for a range of actions.

Purpose: The purpose of this dissertation was to determine the effects of chronic plantar fasciitis on intrinsic foot structures with respect to biomechanics, muscle atrophy and muscle energetics. This was accomplished in three parts. Methods: In Part I, a three-dimensional motion capture system with a synchronized force platform quantified multi-segment foot model kinematics and ground reaction forces associated with walking. Healthy individuals were compared to individuals with chronic plantar fasciitis feet. Typical kinematic variables, measures of coupling, phase and variability were examined in rearfoot, forefoot and hallux segments. In Part II, foot and leg magnetic resonance images were taken in subjects with unilateral plantar fasciitis so that within each subject, the healthy limb could be compared to the plantar fasciitis limb. Cross sectional areas (CSA) of the plantar intrinsic foot muscles (PIFM) and tibialis posterior muscle were computed from user-digitized images. In Part III, the metabolic demands of the PIFM were evaluated using phosphorous magnetic resonance spectroscopy at rest and after barefoot walking. Muscle pH and the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) were compared in healthy and plantar fasciitis feet. Results: In comparison to healthy feet, plantar fasciitis feet exhibited significantly (p < 0.05): 1) greater rearfoot motion, 2) greater sagittal plane forefoot motion, 3) fewer rearfoot-forefoot frontal anti-phase movements, 4) reduced rearfoot-forefoot transverse coordinative variability, 5) greater first metatarsophalangeal (FMPJ) joint dorsiflexion, 6) greater FMPJ-medial longitudinal arch (MLA) coupling variability, and 7) decreased vertical ground reaction forces at propulsion. Also, plantar fasciitis feet had 5.2% smaller PIFM CSA at the forefoot compared to contralateral healthy feet. No CSA differences were seen in the rearfoot PIFM or at the tibialis posterior muscle. The PIFM of healthy and PF feet were not significantly different in resting intracellular levels of pH or Pi/PCr, and there were no significant differences in the increase of Pi/PCr from rest to postwalking. Conclusions: In Part I, it was concluded that plantar fasciitis feet exhibit kinematics which are consistent with theoretical causation of the plantar fasciitis injury, that is, the plantar fasciitis foot exhibits excessive motion. Fewer number of anti-phase movements exhibited by plantar fasciitis feet may be an indication of pathology. The ground reaction force results suggested a compensatory pain response. In Part II, it was concluded that atrophy of the forefoot PIFM may destabilize the medial longitudinal arch and prolong the healing process. Lastly in Part III, it was concluded that resting energetics were consistent with muscle free of systemic disease or neuromuscular pathology. The presence of plantar fasciitis did not elicit systematic asymmetries in the metabolic response in comparison to healthy feet. Clinical Relevance: These kinematic results provided some evidence to support the clinical assertion that excessive motion is related to plantar fasciitis. These results also support treatment modalities which clinicians currently use to reduce rearfoot eversion, flattening of the medial longitudinal arch and dorsiflexion of the FMPJ (e.g. foot orthoses, insoles, taping, rocker soles). When treating plantar fasciitis patients, clinicians should assess for PIFM and tibialis posterior muscle atrophy and prescribe targeted exercises when appropriate.

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There is an increasing need for compact mechanical systems that can accomplish sophisticated tasks. Technologies like ortho-planar and lamina emergent mechanisms (LEMs) have been developed to satisfy needs like these by stowing in planar sheets from which they emerge to perform their function. They can be compact, lightweight, monolithic, scalable, and can withstand harsh environments. They are limited, however, by their base element---planar surfaces. Applications requiring these advantages often include curved surfaces, like aircraft wings, needles, and automotive bodies. In this research, developable mechanisms are presented as a solution to satisfy the need for mechanisms that can conform to or emerge from curved surfaces. Foundational principles which enable designers to leverage the advantages of developable mechanisms are described herein.Developable mechanisms result from the union of mechanisms and developable surfaces. Developable (flattenable) surfaces act as a fitting medium because of their particular advantages in manufacturability and how well they accompany four-link, revolute joint (4R) mechanisms. The definition, including specific qualifying criteria, for developable mechanisms is given. Certain types of mechanisms and classes of developable surfaces can be combined to satisy that criteria. Developable mechanism sub-classes are defined as planar, cylindrical, conical and tangent developable mechanisms. It is shown that planar and spherical mechanisms can be used to create cylindrical and conical developable mechanisms, respectively. The Bennett and other 7R mechanisms can be used for tangent developable mechanisms. Steps for developable mechanism creation are presented, and several physical prototypes are provided to demonstrate feasibility.The cylindrically curved Lamina Emergent Torsional (LET) joint is offered as an enabling technology for producing compliant developable mechanisms. A mathematical model predicting force-deflection and stress behavior is provided and verified. The relationship between stiffness and strain energy storage for curved sheet materials with incorporated LET joints is explored. Material shape factors are used to derive an effective modulus of elasticity and an effective modulus of resilience, which are compared with original values on an Ashby plot. While there is a decrease in the modulus of resilience, there is a much more significant decrease in the modulus of elasticity. A material performance index is provided as an example for determining suitable materials for a given stiffness-reduction application. It is shown that the cylindrically curved LET joint makes it possible to create highly flexible joints that maintain much of their energy storage capability in curved sheet materials.