M. Comm. / One function of skeletal muscle is to serve as the body's shock absorbers and thus dampen rates of loading (ROL) around joints during activities. However, it is not clear whether individuals with strong leg muscles actually demonstrate different ROL during gait than weaker individuals. The aim of this cross-sectional study was to determine the significance of muscle strength on ROL during gait. Females (ages 18 to 50) were solicited via advertisement and screened via phone interviews. Subjects (n=56) were chosen and placed into one of three groups based on training history: Strength Trained (ST), Aerobically Trained (AT), and Sedentary (S). Subjects walked barefoot (10 trials) over an 8 m walkway while ROL was sampled using a 1000 Hz force platform (AMTI OR6-6). Gait speed was controlled between 2.22 - 2.45 m.s -1 using telemetric photocells placed three meters apart. Maximum concentric and eccentric quadriceps and hamstring strength were measured at 90 degrees•s -1 using an isokinetic dynamometer (KINCOM 500H). Peak torque was divided by body weight to determine relative strength (Nrn-kg -1 ). Statistical analyses (p<0.05) included ANOVA and the Bonferroni/Dunn post-hoc test. There were no significant differences in age, height or walking speed across groups. The S group (78.3 ± 15.6 kg, n=18) weighed significantly more than the AT (60.5 ± 8.0 kg, n=19) and ST (63.1 ± 10.7 kg, n=19) groups. Body composition analyses showed that the mean body fat percentage of the S group (34.8 ± 7.3 %, n=18) was significantly higher than both AT (22.3 ± 5.7 %, n=19) and ST (23.2 ± 6.9 %, n=19) groups. Relative concentric and eccentric strength of the quadriceps of the AT (2.02 ± 0.07, n=19; 3.49 ± 0.18, n=19 respectively) and ST (2.1 ± 0.08, n=19; 3.50 ± 0.14, n=19 respectively) groups were significantly greater than the S (1.68 ± 0.07, n=18; 2.63 ± 0.10, n=18 respectively) group. Relative concentric hamstrings strength of both the AT (1.07 ± 0.05, n=19) and ST (1.08 ± 0.04, n=19) groups were significantly greater than the S (0.91 ± 0.04, n=18) group. Relative eccentric hamstring strength of only the ST (1.60 ± 0.07, n=19) group was significantly greater than the (1.34 ± 0.08, n=18) group. There were no significant differences in ROL between the S (2.21 ± 0.15 %Wt.ms -1 , n=18) and AT groups (2.14 ± 0.15 %Wt-ms 1 , n=19) (p=0.70), and the AT (2.14 ± 0.15 %Wt.ms-1 , n=19) and ST (1.82 ± 0.10 %Wt.ms -1 , n=19) (p=0.10) groups. However, the females in the ST (1.82 ± 0.10 %Wt•ms -1 , n=19) group had significantly lower ROL than the females in the S group. In addition, females in the ST group demonstrated a lower frequency of heelstrike transient (HST) occurrence. Seven of the S (n=18) females demonstrated HST while only four of the ST (n=19) females did. In conclusion, strength trained females demonstrated significantly lower rates of loading during gait than those in the sedentary group. High ROL have been associated with knee pain and osteoarthritis. These findings suggest that strength training may decrease the risk for these maladies.

A number of investigators have determined the joint forces acting at the hip and knee for normal human locomotion as related to the design of prosthetic devices. This research has been extended to allow the calculation or estimation of the muscular and ligamentous forces operating at the knee joint for normal walking. The current study expanded upon the past research to evaluate the magnitude and temporal sequence of.the muscle, ligament and articular forces acting at the knee joint for a simulated skating thrust. A skilled ice hockey player was filmed in two reference planes while making a skating thrust from a laboratory force platform. The cine film data was synchronized with the force plate output to allow calculation of the orthogonal forces and moments imposed on the knee joint. The orthogonal force system was determined from a knowledge of the inertial, gravitational and reaction forces acting on the lower limb during the skating thrust. The muscle, ligament and joint forces were determined from equations derived from the conditions of joint equilibrium. The equations of equilibrium were indeterminate and had to be reduced by making assumptions from electromyographic records to allow solution. Forces were calculated for a simplified muscle and ligament system which included the hamstrings, quadriceps and gastrocnemius muscle groups, the collateral ligaments and the cruciate ligaments of the knee joint. In addition, the articular joint force, joint torque and centre of pressure of the joint force were determined. Results of the investigation revealed that the magnitude of the muscle, ligament and joint forces developed in a skating thrust were considerably greater than respective forces exerted during level walking while the temporal sequence of the skating forces was comparable to walking upstairs. The quadriceps muscle group exerted the greatest contractile force while the gastrocnemius and hamstrings groups developed much smaller forces. The largest ligament forces were developed in the collateral ligaments and the posterior cruciate ligament to maintain stability of the joint. The knee joint is subject to the combined effects of a joint force six times body weight and a large joint torque superimposed upon each other during the skating thrust and this fact is considered important when discussing the cause of menisci knee injuries. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

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Pterosaurs represent the earliest appearance of only three clades of flying vertebrates, the pioneers of aerial vertebrate ecospace, and the lineage to produce the largest known flying organisms. The origins of the pterosaurian flight apparatus have been difficult to ascertain, in part, due to incomplete or two-dimensional preservation of the earliest (Triassic—Jurassic) pterosaur remains. An exceptional early pterosaur specimen that is preserved in three dimensions, the holotype and only known specimen of Arcticodactylus cromptonellus (Fleming Fjord Formation, Greenland) may help address these problems. However, it has remained mostly encased within matrix to protect the delicate elements, obscuring external study. Here I present new synchrotron tomographic scan data of the forelimb (wing-forming) elements of Arcticodactylus cromptonellus. I find that the forelimb of Arcticodactylus is a structural intermediate between the forelimb of early archosaurs and derived pterosaurs. In light of this intermediacy, I reexamined the phylogeny of early Pterosauromorpha, completely reviewing forelimb characters with additional consideration given to other important anatomical regions for pterosauromorph phylogeny. I find that the contents of Lagerpetidae represent a grade of non-pterosaur pterosauromorphs and that the pterosauromorph Scleromochlus taylori is actually closely-related to crocodylomorphs. I recover Arcticodactylus as the earliest-diverging pterosaur, with the pterosaurs of the early Mesozoic (Triassic—Early Jurassic) forming a highly-nested, gradational relationship around a monophyletic Late Mesozoic pterosaur clade with very few multispecific groups exclusive of this latter clade. The sum of this work is an understanding of the current pterosaur fossil record as preserving the gradual assembly of the pterosaur bauplan in exquisite detail. / Master of Science / Flight has only evolved three times within animals with backbones. The first of these three is a group of distant relatives of birds called pterosaurs, which evolved flight independently from birds and produced the largest ever flying animals. Flight requires a suite of specialized adaptations, and these can obscure our understanding of how flying animals evolved if all we have are poorly-preserved fossils or only specialized flighted forms. These problems can be found in the origins of pterosaur flight, with well-preserved (non-crushed or deformed) skeletons generally known only from very late forms. An exception to this rule is the early pterosaur Arcticodactylus cromptonellus, represented by three-dimensionally-preserved skeletal remains. Using CT imagery to study the skeletal anatomy obscured by rock, I describe the forelimb anatomy of Arcticodactylus cromptonellus and include it within an analysis of the evolutionary relationships of pterosaurs and other reptiles. Arcticodactylus is found to be the earliest-originating form of pterosaur known, and it possesses a mixture of features found in non-pterosaurs and in pterosaurs. Arcticodactylus demonstrates the gradual acquisition and timing of the assembly of pterosaur flight anatomy.

<p> Scene recognition performance is reduced when an observer undergoes a viewpoint shift. However, the cost of a viewpoint shift is less when it is caused by observer locomotion around a scene compared to scene rotation in front of a stationary observer- a phenomenon called the facilitative effect of locomotion. The present dissertation examined the characteristics of the facilitative effect of locomotion, and the mechanism underlying its existence. In each of six experiments, participants learned a spatial arrangement of five identical objects positioned on top of a rotatable table. Participants were then blindfolded and one object was relocated. Simultaneously, participants underwent a viewpoint shift of various magnitudes. The blindfold was then removed and participants identified which object had been moved. Chapter One showed that the facilitative effect of locomotion is robust across a wide range of viewpoint shifts (Experiment la), and that visual cues in the surrounding environment cannot account for this effect (Experiment lb). The results of Chapter Two suggest that active control over the viewpoint shift may partially account for the benefit of locomotion (Experiment 2a), specifically by providing participants with explicit knowledge regarding the magnitude and direction of the viewpoint shift (Experiment 2b ). Finally, Chapter Three showed that body-based cues available during locomotion (i .e. proprioceptive, vestibular, etc.) facilitate performance beyond actively controlling the viewpoint shift alone, and that those cues must be reliable and undisrupted to confer a scene recognition advantage (Experiment 3a). On the other hand, simply remaining oriented within one's environment could not fully account for the facilitative effect of locomotion (Experiment 3b ). These results provide an integrative account of the characteristics and mechanism associated with the facilitative effect of locomotion. Results are also discussed in the context of current views on egocentric and object-based mental transformations. </p> / Thesis / Master of Science (MSc)

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