The human ankle joint is hypothesized to be a primary controller of support, propulsion and steering during locomotion. A series of experiments were initiated to understand ankle plantarflexor muscle kinematics and kinetics in normal and pathological gait, and to define the specific locomotor demands of community ambulation. Additional experiments were then conducted to quantify the effects of walking speed on plantar pressures and centre of mass motion, to illuminate the role of the ankle in acceleration and deceleration during walking, and to examine how humans alter their kinematics and kinetics to turn. The results of these experiments provide support for the hypothesis that the ankle joint is important in a wide range of locomotor movements beyond walking straight ahead at constant speed. The ankle appears instrumental in adapting to different walking speeds, altering both the pressures on specific regions the plantar surface and the motion of the centre of mass across a range of speeds. The ankle also has subtle kinetic changes that appear to modulate acceleration and deceleration during single limb stance. For turning, the ankle plays a role during slowing into the turn and accelerating after the turn, but mediolateral shears appear to alter the trajectory of the body to negotiate a corner and the external hip rotators appear to rotate the trunk toward the new direction of travel. This work extends our understanding of the ankle in functionally relevant gait activities beyond simple straight-ahead walking at constant speed. The published papers included in this supporting statement have been cited by 180 different subsequent peerreviewed publications, suggesting that this work has had some impact on the field.

A presente investigação constitui um estudo de caso sobre a tripanossomíase americana, conhecida como doença de Chagas, em seus aspectos epistemológicos e sociais, articulados através da análise de diferentes valores envolvidos nas pesquisas sobre essa enfermidade. Na elaboração de uma biografia procuramos enfatizar dois aspectos dessa patologia. Por um lado, que a tripanossomíase americana pode ser interpretada como um agente histórico, na medida em que a identidade dessa entidade nosológica não pode ser dissociada de sua caracterização científica e social, tampouco reduzida a apenas uma dessas dimensões. Por outro lado, colocar a doença como protagonista dessa história nos permite evidenciar de que modo o predomínio da narrativa das instituições médicas e científicas legitimou a invisibilização da perspectiva das pessoas afetadas por essa patologia. A primeira parte da tese está centrada sobre a faceta científica e médica da doença, a qual permitiu que a nova patologia humana fosse estabelecida como um fato. Com relação aos aspectos sociais da doença, estes são focalizados na segunda parte da tese, onde examinamos as ideias envolvidas nas representações dos trópicos e das populações rurais como sinônimos de atraso. / The present investigation is a case study of American trypanosomiasis, known as Chagas disease, in its epistemological and social aspects, articulated through an analysis of the different values involved in research on this disease. In the elaboration of a biography, we aim to emphasize two aspects of this pathology. On the one hand, American trypanosomiasis can be interpreted as a historical agent, to the extent that the identity of this nosological entity cannot be dissociated from its scientific and social characterization, nor can it be reduced to just one of these dimensions. On the other hand, to put the disease as the protagonist of this history allows us to show the ways in which the predominance of medical and scientific institutions narrative has legitimated the invisibility of the perspectives of the ones affected by this pathology. The first part of this thesis is centered on the scientific and medical facet of the disease, which allowed the new human pathology to be established as a fact. The social aspects of the disease will be focalized in the second part of the thesis, where we examine the ideas involved in representations of the tropics and of rural populations as synonyms of backwardness.

A presente investigação constitui um estudo de caso sobre a tripanossomíase americana, conhecida como doença de Chagas, em seus aspectos epistemológicos e sociais, articulados através da análise de diferentes valores envolvidos nas pesquisas sobre essa enfermidade. Na elaboração de uma biografia procuramos enfatizar dois aspectos dessa patologia. Por um lado, que a tripanossomíase americana pode ser interpretada como um agente histórico, na medida em que a identidade dessa entidade nosológica não pode ser dissociada de sua caracterização científica e social, tampouco reduzida a apenas uma dessas dimensões. Por outro lado, colocar a doença como protagonista dessa história nos permite evidenciar de que modo o predomínio da narrativa das instituições médicas e científicas legitimou a invisibilização da perspectiva das pessoas afetadas por essa patologia. A primeira parte da tese está centrada sobre a faceta científica e médica da doença, a qual permitiu que a nova patologia humana fosse estabelecida como um fato. Com relação aos aspectos sociais da doença, estes são focalizados na segunda parte da tese, onde examinamos as ideias envolvidas nas representações dos trópicos e das populações rurais como sinônimos de atraso. / The present investigation is a case study of American trypanosomiasis, known as Chagas disease, in its epistemological and social aspects, articulated through an analysis of the different values involved in research on this disease. In the elaboration of a biography, we aim to emphasize two aspects of this pathology. On the one hand, American trypanosomiasis can be interpreted as a historical agent, to the extent that the identity of this nosological entity cannot be dissociated from its scientific and social characterization, nor can it be reduced to just one of these dimensions. On the other hand, to put the disease as the protagonist of this history allows us to show the ways in which the predominance of medical and scientific institutions narrative has legitimated the invisibility of the perspectives of the ones affected by this pathology. The first part of this thesis is centered on the scientific and medical facet of the disease, which allowed the new human pathology to be established as a fact. The social aspects of the disease will be focalized in the second part of the thesis, where we examine the ideas involved in representations of the tropics and of rural populations as synonyms of backwardness.