This ethnographic study explores the unusual, lifestyle sport of unicycling with a particular focus on young riders. It arises from the author's own immersion in a unicycling culture over some 8 years, and from answers to the 3, primarily educational, questions which this involvement prompted; these concern concepts of motivation; identity; and ach/evemenf. The questions themselves provide the basis tor tne design oT tne study ana tne consequent analysis or data.

This research took an exploration into particular products which use human-power as main power source. Against the problem of over consumption of energy, it views the ‘human-powered product’ (HPP) not merely as an object that simply generates ‘free energy’; but instead considers as an interactive artefact that people can make sense of, and as a tool to practice energy saving behaviour. Efforts to improve the knowledge on design aspect of HPP and its statistical benefit have been proved, but largely by scientifically driven approaches. No such theoretical framework has been discussed or explored in relation to how people use HPP in their daily practice. Therefore, current research undertook the work into substantive area of HPP study that is understanding the actual ‘use-phase’. It explored how design can help induce a better use of HPP, and how intended behaviour of generating human-power can be reproduced, maintained, and internalised. An explorative investigation of actual HPP use was carried out through multiplecase studies, along with cross-disciplinary literature review which contributed in building an explanatory conceptual framework. The framework serves as guideline to explain, the abstract, prediction about phenomenon of HPP use; formulating questions to further study; and developing a ‘HPP Internalisation Model’ which hypothesised the suggestive design strategy for prolonging the HPP use. The hypotheoretical state of ‘HPP Internalisation Model’ was empirically iterated and final recommendations was integrated into a research artefact. Through final case study, this artefact was utilised to produce knowledge and understanding for constructing a theory. The result of study described the relationship, process, and influences between phenomena that account the explanatory concept for each dimensions of ‘HPP Internalisation Model’. As a final result, the model suggests a three dimensional (Empowerment, Feedback, and Motivation), and interdependent to each other, constituent elements in HPP design for bringing internalisation of human-power use. This research has therefore contributed to current knowledge by bringing the social-psychological theories and strategies of ‘design for sustainable behaviour’ together to develop the theoretical model of ‘HPP Internalisation Model’.

Cycling is increasing in popularity which is accompanied with a higher rate of injuries sustained due to collisions, crashes or falls. A high proportion of these events happen when the bicycle rider loses control of the bicycle. In order to improve bicycle rider control, the skill of riding a bicycle needs to be understood. Therefore, the overall aim of this PhD work was to explore bicycle rider control skills and to examine the effects of different constraints on the control of a bicycle. The first part of this thesis focuses on developing a valid and reliable methodology that can be further used for studying bicycle rider control skill. Firstly, a protocol to determine knee angle during cycling is being developed. Secondly, some technical approaches when studying muscle activity during cycling are being questioned. Lastly, a portable device based on a single angular rate sensor to record steering rate and bicycle roll rate was tested for reliability in an outdoor setup. Second part of the thesis examines the effects on bicycle rider control of three different constraints: 1) expertise, 2) body position and 3) cycle lane design. Results overall showed that all three constraints significantly affect steering and bicycle roll rate.

Cycling efficiency is a measure of the ability to convert stored energy into power, and is considered a key determinant of cycling performance. Cycling efficiency has recently been manipulated with various techniques, but most prominently with high intensity training in habitual cyclists and using calorie restriction in sedentary obese participants. It was therefore the primary aim of this thesis to explore the efficacy of utilising a short- and medium-term calorie restriction intervention, to manipulate efficiency with participants accustomed to cycling. A secondary aim was to investigate the validity of measuring efficiency in a field-based environment. Male club level cyclists were recruited for the investigations, which comprised of a moderate -500 kcal.day-1 deficit, utilising portion control and measuring efficiency at both absolute and relative steady-state intensities. Seventeen participants completed the short-term, two-week intervention which utilised a randomised cross-over design. Although a significant reduction in body mass was attained, RMR, gross and net efficiency across all intensities and TT power remained stable. Field and laboratory comparisons indicated that prior to statistical correction absolute efficiency was significantly lower in the field, but after accounting for differences in power, cadence and environmental conditions, no differences were present. Twenty-nine participants conducted the medium-term study and were assigned either to calorie restriction or to no dietary intervention. Following a reduction in mass in the calorie restriction group and an increase in the group given no dietary intervention, a significant interaction between mass and efficiency was found across gross and net efficiency workloads. A six week follow-up period indicated that the process of calorie restriction and not absolute body mass reduction was the main mechanism for altering efficiency. This thesis suggests that efficiency can be manipulated both positively and negatively with calorie manipulation, and that these changes are linked to both laboratory and field based performance.

Les études conduites au cours de ce travail de thèse ont montré que l’optimisation de la position du cycliste sur son vélo était un élément déterminant de la performance. Nos recherches ont porté sur quatre axes principaux : la conception et la validation d’outils de mesure, l’étude de la position aérodynamique, l’étude de la position assise et enfin l’étude de la position danseuse.L’ensemble des résultats obtenus montrent que la capacité de performance du cycliste peut être améliorée en position aérodynamique en augmentant le ratio entre la puissance mécanique (Pméca) et la surface frontale effective (SCx). Le confort représente également un des principaux facteurs de la performance en contre‑la‑montre (CLM) puisqu’il détermine l’aptitude du cycliste à maintenir sa position au cours du temps. Nos travaux montrent une amélioration du confort avec des semelles orthopédiques, chez les cyclistes affectés par une inégalité de longueur des membres inférieurs (ILMI), liée à une réduction des mouvements du bassin. Une correction orthopédique induit également une augmentation du rendement énergétique (+5,7 %). Ainsi, les cyclistes affectés par une ILMI sont recommandés de la compenser avec des semelles orthopédiques individualisées de façon à améliorer leur performance en CLM. Lors d’une étude préliminaire, nous avons également montré la relation entre les mouvements de la tête et le SCx, c’est pourquoi les cyclistes doivent réduire au maximum ces mouvements afin de minimiser leur SCx et ainsi maximiser leur performance. L’évaluation de la position aérodynamique doit être réalisée en conditions réelles de locomotion, que ce soit pour l’évaluation de S ou de SCx. Le développement de nos deux applications est donc un réel atout pour l’évaluation de la traînée aérodynamique (Ra) de manière individualisée dans les prochaines années puisqu’elles rendent le traitement plus accessible aux entraîneurs. Enfin, bien que nous ayons initié une nouvelle méthodologie d’évaluation de la position aérodynamique en associant numérisation 3D et modélisation numérique de la mécanique des fluides, cette méthode serait plutôt recommandée pour l’individualisation de l’équipement.La position assise peut également être optimisée en augmentant l’indice d’efficacité mécanique (IEM) du cycliste, quel que soit le niveau et le sexe. Cette augmentation de l’IEM passe principalement par une diminution de la force résistante (Fres) dans la phase de montée de la pédale. Malgré tout, le cycliste ne doit pas tirer sur la pédale pour générer un couple propulsif car cette stratégie est contre-productive d’un point de vue énergétique. Il serait intéressant d’étendre notre première étude, établie en laboratoire, sur le terrain pour analyser les adaptations biomécaniques du pédalage des cyclistes aux conditions rencontrées sur le terrain. Les différences observées en laboratoire, sur terrain plat et en montée laissent penser que les cyclistes adaptent leur pédalage selon les conditions dans lesquelles ils évoluent.Enfin, les travaux menés sur la position danseuse montrent que les cyclistes augmentent leur coût mécanique (CM) (+4,3 % en laboratoire vs. +19 % sur le terrain) par rapport à la position assise alors que la consommation d’oxygène reste stable entre les deux positions. Ces pertes mécaniques en position danseuse sont principalement dues à l’augmentation du coefficient de roulement (Cr) due aux oscillations latérales du vélo et donc à la torsion des pneus. Puisque les pertes mécaniques sont plus élevées sur le terrain que sur tapis roulant, d’autres facteurs semblent contribuer à cette différence comme la Ra (~10 W), le matériel utilisé par les cyclistes, le Cr de la route et la technique adoptée. Aussi, la position danseuse induit une augmentation du CM pour maintenir la vitesse de déplacement face aux variations de pente en montée. Les cyclistes sont donc fortement recommandés de réduire l’augmentation du CM en position danseuse comparée à la position assise. / The studies conducted during this PhD research showed that optimizing the position of the cyclist on the bicycle is a key factor influencing cycling performance. Our research focused on four main axes: the design and validation of measurement tools, the study of the aerodynamic position, the study of the seated position and the study of the standing position.All the results showed that the performance capacity of cyclists can be improved in aerodynamic position by increasing the ratio between the mechanical power (PO) and the drag area (ACd). Comfort is also a significant factor in time trial (TT) performance as it determines the ability of the cyclist to maintain position over time. Our works show that comfort can be improved via orthopaedic correction in cyclists affected by lower limb length inequality (LLLI) in the TT position, related to a reduction in pelvis movements. The orthopaedic correction also induces an increase in gross efficiency (+5.7%). Thus, this improvement in comfort could increase the PO and/or the amount of time the aerodynamic position can be maintained during a TT. Therefore, cyclists affected by LLLI should compensate LLLI with individualised foot orthotics to improve their TT performance. In a preliminary study, we also showed that there is a relationship between head movements and ACd. Therefore, cyclists should minimise these movements to minimise their ACd and maximise their performance. Aerodynamic position must be evaluated in real cycling locomotion, whether for the evaluation of A or ACd. We have developed two applications that are a real asset for the dynamic evaluation of aerodynamic drag (Ra) as they make the data analysis more accessible to coaches. Finally, although we have initiated a new method to assess ACd in the aerodynamic position by combining 3D scanning and computational fluid dynamics simulation, this method is also recommended for individualisation of cycling equipment.The seated cycling position can also be optimised by increasing the cyclists’ force effectiveness (FE), regardless of practice level or gender. This increase in FE is mainly due to a decrease in resistive force (Fres) during the upstroke phase of pedalling. Nevertheless, the cyclist should not pull on the pedal to generate propulsive torque because this strategy is counterproductive from an energy point of view. It would be interesting to extend our first study, which was set up in a laboratory, to the field to analyse the biomechanical adaptations of cyclists to the real conditions of locomotion. The differences observed in the laboratory, on level ground and over an uphill grade suggest that cyclists adjust their pedalling technique according to the conditions under which they are performing.Finally, studies of the standing cycling position show that cyclists increase their mechanical cost (MC) (+4.3% in the laboratory vs. +19% in the field) compared to the seated position; however, oxygen consumption was similar between the two positions. These mechanical losses (13 W in the laboratory vs. 49 W in the field) in the standing position are mainly due to increased rolling resistance coefficient (Crr), induced by the lateral sways of the bicycle and therefore torsion of the tyres. Because the observed mechanical losses are higher in the field than on the treadmill, other factors could contribute to this difference, such as Ra (~10 W), the equipment used by cyclists, the Crr of the road surface and the technique adopted. Also, the standing position induces an increase in MC to maintain constant speed when faced with uphill slope variations. Cyclists are therefore strongly recommended to reduce the increase of the MC in standing position compared to the seated position. This reduction in mechanical losses can be achieved by decreasing lateral sways and Ra.

Ce travail de thèse s’est déroulé dans le cadre d’une convention CIFRE entre mon laboratoire de rattachement C3S (EA4660) et le département Recherche et Développement (R&D) de l’équipe cycliste professionnelle FDJ. Les différentes études que nous avons conduites se sont articulées autour de l’amélioration de la performance sportive chez le cycliste à travers une variable centrale qui est la puissance mécanique qu’il développe lors de la locomotion (Pméca) selon deux axes principaux : 1) l’évaluation et le suivi du potentiel physique avec pour but l’amélioration du processus d’entraînement et 2) l’optimisation de l’interface homme – machine à partir de l’analyse du matériel et des équipements utilisés par les cyclistes dans l’équipe FDJ. / This thesis has been completed as part of a CIFRE agreement between the laboratory C3S(EA4660) and the Research and Development (R&D) department of the FDJ professionalcycling team. The various studies that we conducted centred on analysing sport performanceoptimisation in cyclists through a central variable: the mechanical power output (PO)developed during locomotion. There were two main areas of focus: 1) evaluation andmonitoring of physical potential, with the aim of improving the training process, and 2)optimisation of the human–machine interface via analysis of the materials and equipmentused by the FDJ team cyclists