Human bipedal locomotion is characterized by a habitual heel-strike (HS) plantigrade gait, yet the significance of walking foot-posture is not well understood. To date, researchers have not fully investigated the costs of non-heel-strike (NHS) walking. Therefore, we examined walking speed, walk-to-run transition speed, estimated locomotor costs (lower limb muscle volume activated during walking), impact transient (rapid increase in ground force at touchdown) and effective limb length (ELL) in subjects (n=14) who walked at self-selected speeds using HS and NHS gaits. HS walking increases ELL compared with NHS walking since the center of pressure translates anteriorly from heel touchdown to toe-off. NHS gaits led to decreased absolutewalking speeds (P=0.012) and walk-to-run transition speeds (P=0.0025), and increased estimated locomotor energy costs (P<0.0001) compared with HS gaits. These differences lost significance after using the dynamic similarity hypothesis to account for the effects of foot landing posture on ELL. Thus, reduced locomotor costs and increased maximum walking speeds in HS gaits are linked to the increased ELL compared with NHS gaits. However, HS walking significantly increases impact transient values at all speeds (P<0.0001). These trade-offs may be key to understanding the functional benefits of HS walking. Given the current debate over the locomotor mechanics of early hominins and the range of foot landing postures used by nonhuman apes, we suggest the consistent use of HS gaits provides key locomotor advantages to striding bipeds and may have appeared early in hominin evolution.

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Submitted by Onia Arantes Albuquerque (onia.ufg@gmail.com) on 2018-10-15T15:02:15Z No. of bitstreams: 2 Tese - Lucas Lacerda Caldas Zanini Jardim - 2018.pdf: 5066072 bytes, checksum: 4280b5b19a9111a59fea8065049fd5b3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-10-15T15:25:17Z (GMT) No. of bitstreams: 2 Tese - Lucas Lacerda Caldas Zanini Jardim - 2018.pdf: 5066072 bytes, checksum: 4280b5b19a9111a59fea8065049fd5b3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-10-15T15:25:17Z (GMT). No. of bitstreams: 2 Tese - Lucas Lacerda Caldas Zanini Jardim - 2018.pdf: 5066072 bytes, checksum: 4280b5b19a9111a59fea8065049fd5b3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-04-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Macroecology studies ecological pattern at large geographical and temporal scales. At these scales, information about hundreds or even thousands of studied species. This lack of information may potentially bias studies’ conclusions related with macroecological processes and patterns. In this thesis, we evaluated phylogenetic imputation methods, their uses and effects in macroecological studies. The first chapter evaluated different methods used to deal with missing data, taking into account different scenarios of species trait evolution, as well as percentage and pattern of missing data. We found that dealing with missing data relies on the specific goals and data of the study. Therefore, we suggested caution while using imputed database. In the second chapter, we tested the island rule effect in body mass and brain volume of primates. To do so, we fitted evolutionary models to those traits and then imputed the body mass and brain volume for Homo floresiensis. We concluded that primates do not follow the island rule and even though our models overestimated, on average, brain and body size of Homo floresiensis, its evolution did not deviate from primates’ evolutionary expectation. Lastly, in the third chapter, we tested existence of Bergmann’s rule in mammals using multiple imputation methods, in addition to considering the consequences of ignoring missing data while testing the rule. We found that ignoring missing data can invert (eg. changing from positive to negative effect) the effect of temperature on body mass, but this bias did not turn the effect statistically significant. Therefore, we concluded that mammals do not follow Bergmann’s rule, when evaluated at the class taxonomic level. Finally, this thesis discussed pros, cons and future research avenues in order to make phylogenetic imputation a more robust tool to deal with missing data in macroecology. / A macroecologia estuda padrões ecológicos em grandes escalas geográficas e temporais, em busca de quais processos moldam esses padrões. Nessas escalas de estudo, há raramente informações completas sobre as centenas ou até milhares de espécies estudadas. Essa ausência de informações tem o potencial de enviesar as conclusões dos estudos sobre padrões e processos macroecológicos. Nessa tese, nós avaliamos métodos de imputação filogenética, a sua aplicação e consequências em estudos macroecológicos. Para avaliar potenciais vieses do uso de banco de dados imputados, no primeiro capítulo, nós aplicamos diferentes métodos utilizados para tratar dados faltantes, sob diferentes cenários de evolução dos atributos das espécies, porcentagem e padrão dos dados faltantes. Nós encontramos que a forma de tratar o dado faltante pode ser dependente dos objetivos e dos dados de cada estudo e, portanto, nós sugerimos cautela ao utilizarmos bancos de dados imputados. No segundo capítulo, nós testamos o efeito da regra de ilha na evolução da massa corpórea e do volume cerebral de primatas. A partir dos melhores modelos evolutivos ajustados a esses atributos, nós imputamos a massa corpórea e volume cerebral de Homo floresiensis. Nós concluímos que primatas não seguem regra de ilha e que apesar de nossos modelos superestimarem, em média, o tamanho do corpo e cérebro de Homo floresiensis, a sua evolução não se desvia do esperado pela evolução de primatas. Por fim, no terceiro capítulo testamos a regra de Bergmann em mamíferos, utilizando métodos de imputação múltipla e avaliamos as consequências de desconsiderar os dados faltantes na detecção da regra. Nós encontramos que testar a regra sem considerar os dados faltantes pode inverter o efeito da temperatura na massa do corpo, mas esse viés não tornou o efeito estatisticamente significante. Portanto, concluímos que mamíferos não seguem a regra de Bergmann, quando toda a classe é avaliada. Por fim, essa tese discutiu vantagens, desvantagens e futuras linhas de pesquisa para tornar a imputação filogenética uma ferramenta mais robusta para tratarmos dados faltantes em macroecologia.