<p>For primates, and other arboreal mammals, adopting suspensory locomotion represents one of the strategies an animal can use to prevent toppling off a thin support during arboreal movement and foraging. While numerous studies have reported the incidence of suspensory locomotion in a broad phylogenetic sample of mammals, little research has explored what mechanical transitions must occur in order for an animal to successfully adopt suspensory locomotion. Additionally, many primate species are capable of adopting a highly specialized form of suspensory locomotion referred to as arm-swinging, but few scenarios have been posited to explain how arm-swinging initially evolved. This study takes a comparative experimental approach to explore the mechanics of below branch quadrupedal locomotion in primates and other mammals to determine whether above and below branch quadrupedal locomotion represent neuromuscular mirrors of each other, and whether the patterns below branch quadrupedal locomotion are similar across taxa. Also, this study explores whether the nature of the flexible coupling between the forelimb and hindlimb observed in primates is a uniquely primate feature, and investigates the possibility that this mechanism could be responsible for the evolution of arm-swinging. </p><p> To address these research goals, kinetic, kinematic, and spatiotemporal gait variables were collected from five species of primate (Cebus capucinus, Daubentonia madagascariensis, Lemur catta, Propithecus coquereli, and Varecia variegata) walking quadrupedally above and below branches. Data from these primate species were compared to data collected from three species of non-primate mammals (Choloepus didactylus, Pteropus vampyrus, and Desmodus rotundus) and to three species of arm-swinging primate (Hylobates moloch, Ateles fusciceps, and Pygathrix nemaeus) to determine how varying forms of suspensory locomotion relate to each other and across taxa. </p><p> From the data collected in this study it is evident the specialized gait characteristics present during above branch quadrupedal locomotion in primates are not observed when walking below branches. Instead, gait mechanics closely replicate the characteristic walking patterns of non-primate mammals, with the exception that primates demonstrate an altered limb loading pattern during below branch quadrupedal locomotion, in which the forelimb becomes the primary propulsive and weight-bearing limb; a pattern similar to what is observed during arm-swinging. It is likely that below branch quadrupedal locomotion represents a “mechanical release” from the challenges of moving on top of thin arboreal supports. Additionally, it is possible, that arm-swinging could have evolved from an anatomically-generalized arboreal primate that began to forage and locomote below branches. During these suspensory bouts, weight would have been shifted away from the hindlimbs towards forelimbs, and as the frequency of these boats increased the reliance of the forelimb as the sole form of weight support would have also increased. This form of functional decoupling may have released the hindlimbs from their weight-bearing role during suspensory locomotion, and eventually arm-swinging would have replaced below branch quadrupedal locomotion as the primary mode of suspensory locomotion observed in some primate species. This study provides the first experimental evidence supporting the hypothetical link between below branch quadrupedal locomotion and arm-swinging in primates.</p> / Dissertation

This study describes the development and testing of a virtual reality locomotion system that uses the user’s arm swings as input. This system has also been integrated with audio and haptic feedback that reacts to the user’s velocity and the surface they’re currently walking on, in an attempt to provide an intuitive and immersive VR locomotion experience. To achieve this, an open source ArmSwinger implementation has been adapted, and custom haptic belts were crafted to display haptic feedback around the user’s feet. Tests with three participants have shown that the system is able to be operated even by users unfamiliar with VR, and the addition of locomotion feedback mostly succeeds in improving the user experience, albeit some issues with synchronization were brought up. / Denna studie beskriver utvecklingen och testningen av ett virtuell verklighet lokomotivsystem som använder användarens armsvängningar som ingång. Detta system har också integrerats med ljud och haptisk feedback som reagerar på användarens hastighet och ytan de för närvarande går på, i ett försök att ge en intuitiv och uppslukande VV rörelseupplevelse. För att uppnå detta har en öppen källkod ArmSwinger implementering anpassats och anpassade haptiska bälten har utformats för att visa haptisk feedback runt användarens fötter. Test med tre deltagare har visat att systemet kan drivas även av användare som inte känner till VV, och tillägget av rörelseåterkoppling lyckas främst förbättra användarupplevelsen, även om vissa problem med synkronisering togs upp.