The purpose of this study was to examine the effects of landing on a combined inverted and plantarflexed surface on the ankle kinematics and electromyographic (EMG) activities of the medial gastrocnemius (MG), peroneal longus (PL) and anterior tibialis muscles (TA). Twelve recreational athletes performed five drop landings from an overhead bar of 30 cm height on to each of these surfaces: a flat surface, a 25° inversion surface (inverted), and a combined surface (combined) of 25° inversion and 25° plantarflexion. The three dimensional kinematic variables and integrated EMG (IEMG) of the three muscles were assessed using one-way repeated measures analysis of variance (ANOVA, p < 0.05) and a 3 × 3 (surface × muscle) ANOVA, respectively. The IEMG results showed a significant muscle by surface interaction. The flat surface induced higher TA activity than the two tilted surfaces. The inverted surface produced significantly higher inversion peak angle and velocity than the flat surface, but similar PL activity across the surfaces. The MG IEMG and ankle plantarflexion angle were significantly higher for the combined surface compared to the inverted surface. These findings suggest that compared to inversion, a combination of plantarflexion and inversion provides a more realistic surface for simulating lateral ankle sprains.

The purpose of this study was to examine the effects of landing on a combined inverted and plantarflexed surface on the ankle kinematics and electromyographic (EMG) activities of the medial gastrocnemius (MG), peroneal longus (PL) and anterior tibialis muscles (TA). Twelve recreational athletes performed five drop landings from an overhead bar of 30 cm height on to each of these surfaces: a flat surface, a 25° inversion surface (inverted), and a combined surface (combined) of 25° inversion and 25° plantarflexion. The three dimensional kinematic variables and integrated EMG (IEMG) of the three muscles were assessed using one-way repeated measures analysis of variance (ANOVA, p < 0.05) and a 3 × 3 (surface × muscle) ANOVA, respectively. The IEMG results showed a significant muscle by surface interaction. The flat surface induced higher TA activity than the two tilted surfaces. The inverted surface produced significantly higher inversion peak angle and velocity than the flat surface, but similar PL activity across the surfaces. The MG IEMG and ankle plantarflexion angle were significantly higher for the combined surface compared to the inverted surface. These findings suggest that compared to inversion, a combination of plantarflexion and inversion provides a more realistic surface for simulating lateral ankle sprains.

People experiencing mobility deficiencies in their lower limbs caused by genetics, injuries, diseases, etc. struggle with their physical and mental health. The goal of this research is to design an exoskeleton that will connect the upper limb (e.g., arm extension) to the ankle joint during walking movements. We advanced the first prototype of the Workshare Upper Lower Limb (WULL) by only targeting the ankle joint as the lower limb component. We found that this change would have the biggest impact on an individual's walking movements. The benefit of this research will be found in answering the question: will harnessing the kinetic energy from a person's upper limb (e.g., arm extension or arm flexion) to transfer into the ankle joint for gait assistance reduce the lower limb muscle activation during walking movements? A series of experiments were run to test the efficacy of the wearable device. Six participants were fitted to the device and six electromyography (EMG) sensors to track the muscle activation during a comfortable walking pace. This gait analysis study used pressure insoles to calculate ground reaction forces and multiple IMUs to track the individuals' limbs and joints kinetic motion. The overall effectiveness of the device was explored based on the data collected in this study. This device decreased muscle activation of the gastrocnemii medialis and increased the anterior deltoid activation. These results support the goal of the experiment to utilize the upper limbs (anterior deltoid) to assist the lower limbs (ankle joint) during walking.

L’objectif de ce travail de thèse est de caractériser, chez les amputés unilatéraux du membre inférieur, les modalités posturales qui interviennent dans la régulation de l’équilibre orthostatique et d’étudier l’impact de l’amputation sur la production de force à la cheville physiologique. Une première étude a révélé la présence de trois modalités posturales afin de réguler le contrôle postural : les amputés transfémoraux adoptent une modalité posturale basée sur les paramètres de stabilité, les amputés transtibiaux optent pour une modalité posturale mixte et les non amputés se réfèrent aux paramètres de l’attitude posturale. Etant donné que l’articulation de la cheville joue un rôle essentiel dans la régulation de l’équilibre postural, il était alors pertinent d’investiguer la production de force à la cheville physiologique. Toutefois, les ergomètres permettant d’étudier l’articulation de la cheville présentent des biais de mesure majeurs. Dans ce cadre, une deuxième étude a été menée afin de développer et valider un nouvel ergomètre pour cheville : le B.O.T.T.E. Parallèlement, la mise en place d’une méthode de mesure basée sur le retour visuel permettant une quantification fiable du couple de force a fait l’objet d’une troisième étude. Ensuite, une quatrième étude visait à utiliser le B.O.T.T.E. pour investiguer l’impact de l’amputation sur la production de force à la cheville physiologique. Les résultats de cette étude confirment la présence d’un déficit au niveau du couple de force généré en flexion plantaire (conditions maximale et sous maximale) chez les amputés transfémoraux. Enfin, ce travail de thèse vise à aider les rééducateurs et les cliniciens à optimiser la prise en charge des patients amputés. / This Ph.D. thesis aims to evaluate the standing posture modalities and the ankle joint torque in the intact limb in unilateral lower limb amputees. A first study shows the presence of three posture modalities: the non-amputee group relied on standing erect, the transfemoral amputees’ stance depended on balance control and the transtibial amputees exhibited a mixed modality of simultaneously maintaining an upright stance and standing balance. Since the ankle muscles have a functional importance in standing posture modalities, it is imperative to investigate the ankle joint torque in the intact limb. However, the current devices used to assess the ankle joint present substantial limitations for the measurement. Thus, a second study was designed to develop and to validate a new ankle ergometer B.O.T.T.E. Moreover, a third study was achieved in order to estimate the effect of visual feedback on enhancing isometric maximal voluntary contractions. A fourth study was realized to investigate the ankle joint torque in the intact leg of unilateral lower limb amputees. The results show that transfemoral amputees produce less torque and are less steady compared to transtibial amputees and able-bodied individuals. Overall, the present findings of this Ph.D. thesis could have implications for clinical practice and for rehabilitation of patients with a lower limb amputation.