Thesis (M Sport Sc (Sport Science)--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Knee injuries are common among the physically active population and are often severe enough that it requires surgery. Rehabilitation specialists are on the constant look-out for the most efficient and cost-effective treatment alternatives to provide athletes with an early return to sport. The inclusion of backward locomotion in knee rehabilitation programs has been proposed since it is considered a safe closed kinetic chain exercise which has been found to increase quadriceps strength and power as well as cardiorespiratory fitness. The primary aim of the study was to establish the efficacy of backward locomotion training during a knee rehabilitation program. Thirty nine men and women (aged 18 to 59 years) with knee pathologies volunteered for the study and were randomly assigned to the experimental group (EXP, n = 20) and control group (CON, n = 19). All participants underwent a 24 session knee rehabilitation program which included 20 – 30 minutes of cardiorespiratory training, either in backward mode (EXP), or forward mode (CON). Aerobic fitness, quadriceps and hamstrings strength and power, single leg balance, lower limb circumferences, and lower limb flexibility were measured before and after the rehabilitation program. Backward locomotion training resulted in a borderline statistical significant improvement in ventilatory threshold (VT) (p = 0.07) and a statistical significant improvement in peak power output (PPO) (p < 0.05). The VT and PPO of the backward locomotion group increased by 9 and 14%, respectively, compared to 0 and 4% in the forward locomotion group. Both groups showed statistically significant improvements in quadriceps and hamstrings strength, except the quadriceps of the uninvolved leg of the forward locomotion group. Similarly, both groups showed a statistically significant improvement in quadriceps and hamstrings average power, except the quadriceps of the uninvolved leg of the forward locomotion group. Single leg balance of the involved and uninvolved legs improved statistically significantly in both groups (p < 0.05). The differences in change between the two interventions were not statistically significantly different (p > 0.05) and the practical differences were small (ES ± 0.2). No statistically significant differences in the change in leg circumferences were observed between the two groups. Only the change in flexibility of the involved soleus was significantly different between the EXP and CON groups. The results show that backward locomotion training result in greater improvements in aerobic fitness and equal or greater improvements in quadriceps and hamstrings muscle strength and power, compared to forward locomotion training. Backward locomotion as well as forward locomotion contributes to the recovery of knee injuries, however, the practical significance of backward locomotion is greater than for forward locomotion. The conclusion of this is that backward locomotion is a better alternative rehabilitation program for athletes as this will affect a quicker return to their sport. / AFRIKAANSE OPSOMMING: Kniebeserings kom algemeen voor in die fisiek aktiewe bevolking en is dikwels so ernstig dat dit chirurgie vereis. Rehabilitasie-spesialiste is voortdurend op soek na die mees doeltreffende en koste-effektiewe alternatief vir behandeling om die atlete vinnig te laat terugkeer na hul sport. Die insluiting van agteruitbeweging in knie-rehabilitasieprogramme is al in die verlede voorgestel, aangesien dit beskou word as 'n veilige geslote-kinetieseketting oefening wat al geskik bevind is om quadriceps sterkte en krag, asook kardiorespiratoriese fiksheid te verbeter. Die hoofdoel van die studie was om die effektiwiteit van agteruitbewegingoefening in 'n knierehabilitasieprogram te bepaal. Nege-en-dertig mans en vroue (tussen die ouderdom van 18 en 59 jaar) met kniepatologieë het vrywillig ingestem om aan die studie deel te neem en is lukraak verdeel in die eksperimentele groep (EXP, n = 20) en kontrole groep (CON, n = 19). Alle deelnemers het 24 sessies voltooi waarvan 20 – 30 minute kardiorespiratoriese oefeninge was. Dit het óf in die agteruitrigting (EXP), óf vorentoe-rigting (CON) plaasgevind. Aërobiese fiksheid, quadriceps en hamstrings sterkte en krag, eenbeenbalans, omtrekke van die onderste ledemaat, en soepelheid van die onderste ledemaat is gemeet, voor en na die rehabilitasieprogram. Agteruitbeweging-oefening het 'n geringe verbetering in ventilatoriese draaipunt (VT) (p = 0.07) opgelewer wat grens aan 'n statisties betekenisvolle verbetering, asook 'n statisties betekenisvolle verbetering in piek kraguitset (PPO) (p <0.05). Die VT en PPO van die agteruitbeweging groep het onderskeidelik verbeter met 9 en 14%, in vergelyking met 0 en 4% in die vorentoe-beweging groep. Beide groepe het statisties betekenisvolle verbeteringe in quadriceps en hamstrings sterkte getoon, behalwe die quadriceps van die onbeseerde been van die vorentoe-beweging groep. Soortgelyk daaraan het beide groepe statisties betekenisvolle verbeteringe in quadriceps en hamstrings gemiddelde krag getoon, behalwe die quadriceps van die onbeseerde been van die vorentoe-beweging groep. Eenbeenbalans van die beseerde en onbeseerde bene het statisties betekenisvol verbeter in beide groepe (p < 0.05). Die verskil in verandering tussen die twee intervensies was nie statisties betekenisvol verskillend nie en die praktiese verskil was klein (ES ± 0.2). Geen statisties betekenisvolle verskille is waargeneem tussen die twee groepe in die verandering in beenomtrekke nie. Slegs die soepelheid van die beseerde soleus van die EXP groep het statisties betekenisvol verbeter tussen die twee groepe. Die resultate toon dat agteruitbeweging-oefening tot groter verbetering gelei het in aërobiese fiksheid en gelyke of groter verbetering in quadriceps en hamstrings sterkte en krag, in vergelyking met vorentoe-beweging oefening. Agteruitbeweging-oefening sowel as vorentoe-beweging oefening dra by tot die herstel van kniebeserings, maar die praktiese beduidendheid van agteruitbeweging-oefening is groter as vorentoe-beweging oefening. Die gevolgtrekking van die studie is dat agteruitbeweging 'n beter alternatiewe rehabilitasieprogram vir atlete is, met 'n gevolglike vinniger terugkeer na hul sport.

BACKGROUND: Descending kerbs during locomotion involves the regulation of appropriate foot placement before the kerb-edge and foot clearance over it. It also involves the modulation of gait output to ensure the body-mass is safely and smoothly lowered to the new level. Previous research has shown that vision is used in such adaptive gait tasks for feedforward planning, with vision from the lower visual field (lvf) used for online updating. The present study determined when lvf information is used to control/update locomotion when stepping from a kerb. METHODOLOGY/PRINCIPAL FINDINGS: 12 young adults stepped down a kerb during ongoing gait. Force sensitive resistors (attached to participants' feet) interfaced with an high-speed PDLC 'smart glass' sheet, allowed the lvf to be unpredictably occluded at either heel-contact of the penultimate or final step before the kerb-edge up to contact with the lower level. Analysis focussed on determining changes in foot placement distance before the kerb-edge, clearance over it, and in kinematic measures of the step down. Lvf occlusion from the instant of final step contact had no significant effect on any dependant variable (p>0.09). Occlusion of the lvf from the instant of penultimate step contact had a significant effect on foot clearance and on several kinematic measures, with findings consistent with participants becoming uncertain regarding relative horizontal location of the kerb-edge. CONCLUSION/SIGNIFICANCE: These findings suggest concurrent feedback of the lower limb, kerb-edge, and/or floor area immediately in front/below the kerb is not used when stepping from a kerb during ongoing gait. Instead heel-clearance and pre-landing-kinematic parameters are determined/planned using lvf information acquired in the penultimate step during the approach to the kerb-edge, with information related to foot placement before the kerb-edge being the most salient.

Undesirable landing area (e. g. , a hole, a fragment of glass, a water puddle, etc) creates the necessity for an alternate foot placement planning and execution. Previous study has proposed that three determinants are used by the central nervous system (CNS) for planning an alternate foot placement: minimum foot displacement, stability and maintenance of forward progression. However, validation of these determinants is lacking. Therefore, the general purpose of the series of studies presented here is to validate and test the generality of the decision algorithm of alternate foot placement selection developed previously. The first study was designed to validate the use of a virtual planar obstacle paradigm and the economy assumption behind minimum foot displacement determinant. Participants performed two blocks of trials. In one block, they were instructed to avoid stepping in a virtual planar obstacle projected in the screen of a LCD monitor embedded in the ground. In another block, they were instructed to avoid stepping in a real hole present in walkway. Behavioral response was unaffected by the presence of a real hole. In addition, it was suggested that minimum foot displacement results in minimum changes in EMG activity which validates the economy determinant. The second study was proposed to validate the stability determinant. Participants performed an avoidance task under two conditions: free and forced. In the free condition participants freely chose where to land in order to avoid stepping in a virtual obstacle. In the forced condition, a green arrow was projected over the obstacle indicating the direction of the alternate foot placement. The data from the free condition was used to determine the preferred alternate foot placement whereas the data from the forced condition was used to assess whole body stability. It was found that long and lateral foot placements are preferred because they result in a more stable behavior. The third study was designed to validate the alternate foot placement model in a more complex terrain. Participants were required to avoid stepping in two virtual planar obstacles placed in sequence. It was found that participants used the strategy of planning the avoidance movement globally and additional determinants were used. One of the additional determinants was implementation feasibility. In the third study, gaze behavior was also monitored and two behaviors emerged from this data. One sub-group of participants fixated on the area stepped during adaptive step, whereas another sub-group anchor their gaze in a spot ahead of the area-to-be avoided and used peripheral vision for controlling foot landing. In summary, this thesis validates the three determinants for the alternate foot placement planning model and extends the previous model to more complex terrains.

Walking around in dynamically changing environments require the integration of three of our sensory systems: visual, vestibular, and kinesethic. Vision is the only modality of these three sensory systems that provides information at a distance for proactively controlling locomotion (Gibson, 1958). The visual system provides information about self-motion, about body position and body segments relative to one another and the environment, and environmental information at a distance (Patla, 1998). Gibson (1979) developed the idea that everyday behaviour is controlled by perception-action coupling between an action and some specific information picked up from the optic flow that is generated by that action. Such that visual perception guides the action required to navigate safely through an environment and the action in turn alters perception. The objective of my thesis was to determine how well perception and action are coupled when approaching and walking through moving doors with dynamically changing apertures. My first two studies were grouped together and here I found that as the level of threat increased, the parameters of control changed and not the controlling mechanism. The two dominant action control parameters observed were a change in approach velocity and a change in posture (i. e. shoulder rotation). These findings add to previous work done in this area using a similar set-up in virtual reality, where after much practice participants increased success rate by decreasing velocity prior to crossing the doors. In my third study I found that visual fixation patterns and action parameters were similar when the location of the aperture was predictable and when it was not. Previous work from other researchers has shown that vision and a subsequent action are tightly coupled with a latency of about 1second. I have found that vision only tightly couples action when a specific action is required and the threat of a collision increases. My findings also point in the same direction as previous work that has shown that individuals look where they are going. My last study was designed to determine if we go where we are looking. Here I found that action does follow vision but is only loosely correlated. The most important and common finding from all the studies is that at 2 seconds prior to crossing the moving doors (any type of movement) vision seems to have the most profound effect on action. At this time variability in action is significantly lower than at prior times. I believe that my findings will help to understand how individuals use vision to modify actions in order to avoid colliding with other people or other moving objects within the environment. And this knowledge will help elderly individuals to be better able to cope with walking in cluttered environments and avoid contacting other objects.

The purpose of this study was to examine the relationship between leg dominance and knee mechanics to provide further information about the etiology of ACL injury. Sixteen healthy females between the ages of 18 and 22 who were NCAA Division I varsity soccer players participated in this study. Subjects were instructed to perform a cutting maneuver; where they sprinted full speed and then performed an evasive maneuver (planting on one leg and pushing off to the other leg in a new direction) at a 45° angle with their dominate leg (DL) and non-dominate leg (NDL). Subjects were required to perform five successful cuts on each side given in a random order. Bilateral kinematic and kinetic data were collected during the cutting trials. After the cutting trials, subjects performed bilateral isometric and isokinetic testing using a Cybex Norm dynamometer at a speed of 60°/sec to evaluate knee muscle strength. During the braking phase the NDL showed greater (P=0.003) power absorption, greater (P=0.01) peak internal rotation angle and greater (P=0.005) peak flexion velocity. During the propulsive phase the DL showed greater (P=0.01) power production, greater (P=0.038) peak internal adductor moment and greater (P=0.02) peak extension velocity. In addition, no differences (P>0.05) in knee extensor and flexor isometric and isokinetic torques between the two limbs were shown. The results of this study show that a difference in knee mechanics during cutting does exist between the DL and NDL. The findings of this study will increase the knowledge base of ACL injury in females and aid in the design of more appropriate neuromuscular, plyometric and strength training protocols for injury prevention. / School of Physical Education, Sport, and Exercise Science

Male crickets produce a species specific song to attract females which in response move towards the sound source. This behaviour, termed phonotaxis, has been the subject of many morphological, neurophysiological and behavioural studies making it one of the most well studied examples of acoustic communication in the animal kingdom. Despite this fact, the precise leg movements during this behaviour is unknown. This is of specific interest as the cricket’s ears are located on their front legs, meaning that the perception of the sound input might change as the insect moves. This dissertation describes a methodology and an analysis that fills this knowledge gap. I developed a semi-automated tracking system for insect motion based on commercially available high-speed video cameras and freely available software. I used it to collect detailed three dimensional kinematic information from female crickets performing free walking phonotaxis towards a calling song stimulus. I marked the insect’s joints with small dots of paint and recorded the movements from underneath with a pair of cameras following the insect as it walks on the transparent floor of an arena. Tracking is done offline, utilizing a kinematic model to constrain the processing. I obtained, for the first time, the positions and angles of all joints of all legs and six additional body joints, synchronised with stance-swing transitions and the sound pattern, at a 300 Hz frame rate. I then analysed this data based on four categories: The single leg motion analysis revealed the importance of the thoraco-coxal (ThC) and body joints in the movement of the insect. Furthermore the inside middle leg’s tibio-tarsal (TiTa) joint was the centre of the rotation during turning. Certain joints appear to be the most crucial ones for the transition from straight walking to turning. The leg coordination analysis revealed the patterns followed during straight walking and turning. Furthermore, some leg combinations cannot be explained by current coordination rules. The angles relative to the active speaker revealed the deviation of the crickets as they followed a meandering course towards it. The estimation of ears’ input revealed the differences between the two sides as the insect performed phonotaxis by using a simple algorithm. In general, the results reveal both similarities and differences with other cricket studies and other insects such as cockroaches and stick insects. The work presented herein advances the current knowledge on cricket phonotactic behaviour and will be used in the further development of models of neural control of phonotaxis.

Superior swimming stamina in adult fish is presumably passed on to their offspring, but the ontogeny of the appearance of superior stamina and the requisite enhanced cardio-respiratory support for locomotion in larval fishes has not been determined. Is the expression of the suite of parental traits enabling superior swimming stamina in their offspring dependent upon their achieving juvenile/adult morphology, or does it appear earlier in their larvae? To answer this, adults were classified into three groups based on swimming stamina, followed by measurement of length, mass, and width. Larval offspring from the two parental groups -high stamina larvae (HSL) and low stamina larvae (LSL)- were reared at 27°C in aerated water (21% O2). Routine and active heart rate, routine and active mass specific oxygen consumption were recorded through 21dpf, and cost of transport (COT) and factorial aerobic scope were derived from oxygen consumption measurements. Routine heart rate at 2dpf of LSL was 164 ± 1 b·min-1, compared to only 125 ± 2 b·min-1 for HSL. Routine heart rate subsequently peaked at 203 ± 1 b·min-1 at 5dpf in the HSL group, compared to 207 ± 1 b·min-1, at 4dpf in the LSP larvae. Active heart rate at 5 dpf of LSL was 218 ± 2 b·min-1 compared to 216 ± 2 b·min-1 for HSL. Active heart rate increased slightly to 227 ± 2 b·min-1 for LSL before decreasing again, while active heart rate remained relatively constant for HSL. Routine O2 consumption at 2dpf of HSL was 0.09 μmol·mg-1·hr-1, compared to 0.03 μmol·mg-1·hr-1 in LSL. Routine O2 consumption subsequently peaked at 0.70 μmol·mg-1·hr-1 at 9dpf in the HSL, compared to 0.71 μmol·mg-1·hr-1, at 9dpf in the LSL. These values dramatically decreased before leveling off at around 0.20 μmol·mg-1·hr-1 and 0.15 μmol·mg-1·h-1, respectively. Active O2 consumption at 5dpf for HSL was 0.38 μmol·mg-1·hr-1, compared to 0.57 μmol·mg-1·hr-1 for LSL. Active O2 consumption subsequently peaked at 0.97 μmol·mg-1·hr-1 at 10dpf in HSL, compared to 1.19 μmol·mg-1·hr-1 at 7dpf in LSL. These values also dramatically decreased and leveled off. Significant differences (p < 0.05) in heart rate and oxygen consumption persisted through 21dpf. The onset of differences observed in routine and active heart rate in early larvae, correlated with parent stamina, show that juvenile or adult features are not required as a precondition for the emergence of phenotypic physiological differences.

<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

La robotique humanoïde arrive a maturité avec des robots plus rapides et plus précis. Pour faire face à la complexité mécanique, la recherche a commencé à regarder au-delà du cadre habituel de la robotique, vers les sciences de la vie, afin de mieux organiser le contrôle du mouvement. Cette thèse explore le lien entre mouvement humain et le contrôle des systèmes anthropomorphes tels que les robots humanoïdes. Tout d’abord, en utilisant des méthodes classiques de la robotique, telles que l’optimisation, nous étudions les principes qui sont à la base de mouvements répétitifs humains, tels que ceux effectués lorsqu’on joue au yoyo. Nous nous concentrons ensuite sur la locomotion en nous inspirant de résultats en neurosciences qui mettent en évidence le rôle de la tête dans la marche humaine. En développant une interface permettant à un utilisateur de commander la tête du robot, nous proposons une méthode de contrôle du mouvement corps-complet d’un robot humanoïde, incluant la production de pas et permettant au corps de suivre le mouvement de la tête. Cette idée est poursuivie dans l’étude finale dans laquelle nous analysons la locomotion de sujets humains, dirigée vers une cible, afin d’extraire des caractéristiques du mouvement sous forme invariants. En faisant le lien entre la notion “d’invariant” en neurosciences et celle de “tâche cinématique” en robotique humanoïde, nous développons une méthode pour produire une locomotion réaliste pour d’autres systèmes anthropomorphes. Dans ce cas, les résultats sont illustrés sur le robot humanoïde HRP2 du LAAS-CNRS. La contribution générale de cette thèse est de montrer que, bien que la planification de mouvement pour les robots humanoïdes peut être traitée par des méthodes classiques de robotique, la production de mouvements réalistes nécessite de combiner ces méthodes à l’observation systématique et formelle du comportement humain. / Humanoid robotics is coming of age with faster and more agile robots. To compliment the physical complexity of humanoid robots, the robotics algorithms being developed to derive their motion have also become progressively complex. The work in this thesis spans across two research fields, human neuroscience and humanoid robotics, and brings some ideas from the former to aid the latter. By exploring the anthropological link between the structure of a human and that of a humanoid robot we aim to guide conventional robotics methods like local optimization and task-based inverse kinematics towards more realistic human-like solutions. First, we look at dynamic manipulation of human hand trajectories while playing with a yoyo. By recording human yoyo playing, we identify the control scheme used as well as a detailed dynamic model of the hand-yoyo system. Using optimization this model is then used to implement stable yoyo-playing within the kinematic and dynamic limits of the humanoid HRP-2. The thesis then extends its focus to human and humanoid locomotion. We take inspiration from human neuroscience research on the role of the head in human walking and implement a humanoid robotics analogy to this. By allowing a user to steer the head of a humanoid, we develop a control method to generate deliberative whole-body humanoid motion including stepping, purely as a consequence of the head movement. This idea of understanding locomotion as a consequence of reaching a goal is extended in the final study where we look at human motion in more detail. Here, we aim to draw to a link between “invariants” in neuroscience and “kinematic tasks” in humanoid robotics. We record and extract stereotypical characteristics of human movements during a walking and grasping task. These results are then normalized and generalized such that they can be regenerated for other anthropomorphic figures with different kinematic limits than that of humans. The final experiments show a generalized stack of tasks that can generate realistic walking and grasping motion for the humanoid HRP-2. The general contribution of this thesis is in showing that while motion planning for humanoid robots can be tackled by classical methods of robotics, the production of realistic movements necessitate the combination of these methods with the systematic and formal observation of human behavior.

Cette recherche propose d’étudier l’incidence de l’environnement urbain sur certains aspects du déplacement de la personne aveugle. Dans une approche écologique, nous prenons en considération plusieurs paramètres en étudiant, en situation réelle, la perception et le ressenti liés à l’environnement, la vitesse de marche, la représentation mentale et enfin le stress, vécu et objectivé. Nous faisons l’hypothèse que la structure urbaine a un effet notable sur l’ensemble de ces paramètres, affectant ou facilitant le déplacement. Notre protocole a mobilisé 27 personnes aveugles, utilisant une canne blanche ou un chien-guide sur un trajet urbain de 1 km, qui offre cinq scènes urbaines successives (« Ruelle A », « Place », « Berges », « Rue » et « Ruelle B »). La première session s’est faite au bras du chercheur afin d’étudier la perception et le ressenti liés à l’environnement, grâce à la technique des trajets commentés. La seconde session a été consacrée à la mémorisation du trajet. Enfin, la troisième session, intégralement enregistrée sur vidéo, a consisté en un déplacement autonome. Nous avons également enregistré l’activité électrodermale in situ, afin d’en saisir les variations au fur et à mesure du trajet. Nous avons, enfin, demandé aux participants de dessiner le trajet effectué (carte mentale).Les résultats indiquent que les différentes scènes présentent des ambiances vécues comme très différentes par les marcheurs aveugles. L’environnement influence le ressenti en termes de plaisir, de sentiment de sécurité et de stress. Il influence également la vitesse de marche, ainsi que la capacité à mener le trajet à son terme. Les « Ruelles » et la « Rue » sont les scènes les plus favorables au déplacement, alors que les espaces ouverts comme la « Place » et les « Berges » se sont avérés défavorables. L’analyse de l’activité électrodermale révèle également un effet de la scène. Elle nous a permis d’identifier des zones problématiques sur le trajet. Ces nœuds correspondent aux lieux où les marcheurs aveugles doivent prendre des décisions importantes (traverser la chaussée, choisir une orientation). Enfin, la représentation mentale semble être en rapport avec les aspects précédents et varie en fonction des scènes. Les lieux les plus sécurisants sont sous-représentés, alors que les lieux vécus comme les plus stressants sont surreprésentés dans les dessins. Ces résultats invitent à prendre en considération la perception incarnée et l’expérience que les personnes aveugles ont de leur environnement dans l’élaboration des aménagements de nos cités, pour permettre à tous une meilleure autonomie et liberté de déplacement. / This study investigates the influence of urban environment on some aspects of the mobility of blind people in the city. Using an ecological approach, we explore some mobility parameters in real conditions: environmental perception and feeling, walking speed, cognitive mapping and subjective and objective stress.Our hypothesis suggests that environmental setup and features have a significant effect on these parameters, affecting or facilitating mobility. Twenty-seven blind subjects were requested to perform a 1-kilometer journey consisting of five successive urban scenes in Lyon (“Street 1”, “Square”, “River-bank”, “Avenue”, “Street 2”). Subjects walked using a white cane or a guide dog. There were three sessions. During the first walking session, blind pedestrians were accompanied all along. We asked them to comment on their perception of and feeling about the surroundings as they walked. The second walking session was devoted to memorizing the route. Finally, we asked subjects to walk independently for the third and last session, which was integrally recorded on video. We also monitored electrodermal physiological signals with an ambulatory device. Once the journey was over, we asked subjects to make a line-drawing depicting the route (i.e. a map).Results suggest that blind pedestrian’s experience of the environment differs according to the urban scene. Environmental conditions affect enjoyment, safety and stress levels. They also affect walking speed and spatial skills. “Streets” and “Avenue” are the most favorable scenes for those mobility parameters, where wide open-spaces like “Square” and “River-bank” are unfriendly. The cognitive map seems to be related to these previous observations: its accuracy varies with environmental conditions. Analysis of the drawings indicates that the most secure scenes (i.e. “Avenue”) were under-represented while the most stressful scenes and least secure scenes were over-represented (i.e. “Square”). Electrodermal monitoring yielded the same scene-effect on the physiological signals, as well as the existence of high-activation areas in the journey, apparently corresponding to node-places requiring blind subjects to make important decisions (e.g. having to cross a road, or to choose a direction).These results invite us to consider the environment spectific-perception of the visually impaired persons in the development of accessibility aids, in order to offer a greater autonomy and freedom in mobility in our modern cities.