The purpose of this thesis was to investigate overtraining (OT) and burnout (BO) in young athletes. Very little data on the incidence of OT in young athletes is available, hence the purpose of the 1st study was to investigate the prevalence and symptomology of NFOR (non-functional overreaching) and OT in young English athletes practicing different sports and competing across all competitive levels. Data from 376 young athletes (age 15.00 ± 1.97 y) indicated that 29 % had experienced at least one episode of NFOR/OT, and that NFOR/OT was significantly higher at national and international competitive levels (p < 0.01). Presenting symptomology was similar to that reported in adults, with both training and non-training stressors identified as important associates: losses of appetite during periods of hard training, frequent injuries and feelings of a lack of recovery from training, combined with apathy, feeling intimidated by opponents, and being “moody” were the most frequently reported physical and psychological symptoms, respectively. Training load, the commonly believed cause of NFOR/OT, had no significant association with NFOR/OT incidence; however competitive level and gender were significant predictors of NFOR/OT, albeit of a small explained variance (~4%). This study demonstrated that NFOR/OT is evident in young athletes and that the associated factors are multifactorial. The 2nd study monitored prospectively, 4 national-level female swimmers during an 11-month competitive season. Two swimmers (16.00 ± 1.41 y) were diagnosed as OT based on performance decrements (mean decrement of 9 %). One of the OT swimmers (OT2) presented with the classical psychophysiological profile, i.e. high monthly training volumes, low IgA concentration, depressed maximal lactates and high self-reported distress. Conversely the other OT swimmer (OT1) only presented with high Training Distress Scale (TDS) scores. These findings show that both, OT is a complex problem to diagnose and that it’s approach needs to be individualized. The 3rd study investigated the acute psycho-physiological responses to a 6-day training camp in 4 young female swimmers (15.00 ± 1.21 y), of which one was OT and another burnt out (OT1 swimmer from study 2). Both mal-adapted athletes showed performance decrements of ~8 % that lasted for more than 6 months. The OT swimmer, unlike her BO friend, showed a depressed IgA concentration, an unresponsive cortisol, reduced maximal lactate production, and high psychological distress, measured by the TDS. Both swimmers reported slower reaction times on the Stroop test, with the BO swimmer evidencing the worst performance. Finally, the BO swimmer reported very high scores on the Athlete Burnout Questionnaire (ABQ; reduced sense of accomplishment = 4.3; emotional/physical exhaustion = 2.6; sport devaluation = 3.7). This study showed that the psychophysiological profile of an OT swimmer may differ considerably from a BO athlete, with the ABQ being potentially the most efficient tool to diagnose BO. Once more, the individuality of the profiles reinforces the importance of investigating this phenomenon on a case by case basis. The final study used Interpretative Phenomenological Analysis to investigate the psychosocial nature of OT and BO in a 15 year-old female swimmer (OT1 and BO from studies 2 and 3, respectively) and revealed how multiple sources of training and non-training stressors all combined to negatively affect the athlete. The swimmer revealed a past in which she experienced rapid success at an early age and a training mentality of “the more, the better” which was promoted by parents, coaches and herself. Her strong unidimensional identity – centred on swimming – provided few recreational or social opportunities outside the sport. She also reported communication difficulties with her coaches, unwelcome changes in coaching staff, periods of separation from her family, and an over-involved mother. The findings of this thesis suggest that NFOR/OT and BO are issues that many young athletes have to contend with during their sporting careers. The multifactorial nature of these conditions mean that any screening, prevention or recovery interventions must address the problem from a holistic standpoint and as such, Ken Wilber’s (1998) Integral Model is proposed as a suitable framework through which this condition may be investigated in young athletes.

Dans le contexte général du contrôle du poids, le développement de produits à haut pouvoir satiétogène apparaît comme une alternative intéressante ou une réponse complémentaire aux propositions de régimes réduits en calories. Le principal objectif de cette thèse est d'évaluer le pouvoir satiétogène simple et combinés des fibres et des protéines dans une matrice biscuitière ainsi que l'influence de facteurs psychologiques telle que l'information fournie sur un aliment sur la satiété. Concernant l'influence de paramètres psychologiques, si l'on s'en réfère aux limites du TFEQ couramment utilisées par Stunkard et Messick, une cohorte de jeunes adultes français a de faibles score de TFEQ pour la restriction cognitive, la désinhibition et la faim. Ce résultat nous a permis de proposer de nouvelles limites plus basses que celles couramment utilisées et adaptées à cette catégorie de la population, souvent étudiée dans les études cliniques de comportement alimentaire. Ces limites ont été utilisées pour définir nos groupes de volontaires pour l'étude sur l'effet d'un message sur la satiété. Nous avons conclu qu'un message sur les propriétés satiétogènes d'un produit pourrait influencer un sous-groupe de la population, que sont les femmes faiblement restreintes et fortement désinhibées. Afin d'optimiser la sélection des prototypes utilisés dans l'étude clinique sur l'effet des fibres et des protéines sur la satiété, nous avons développé avec succès un nouvel outil pour entraîner un panel d'experts sensoriels à évaluer leur satiété. Un mélange de fibres et de protéines réduit les sensations d'appétit de manière plus importante que les biscuits enrichis simplement en un des ingrédients. Cette combinaison d'ingrédients actifs stimule des mécanismes qui sont induits par les fibres (comme la réduction de l'insulinémie et le ralentissement de la vidange gastrique) et les protéines (comme la diminution de la glycémie). En conclusion, cette approche intégrative de la satiété a permis d'apporter de nouvelles connaissances sur les effets synergique des fibres et des protéines sur les sensations d'appétit. Nous avons aussi proposé de nouvelles méthodes pour évaluer le pouvoir satiétogène de différents produits en utilisant l'expertise des domaines des sciences du sensoriel et de la nutrition. Ce travail souligne aussi l'importance des aspects psychologiques dans les études de nutrition humaine.Mots clés: Satiété, Fibres, Protéines, Three-Factor Eating questionnaire, Message satiété, entraînement à l'évaluation de la satiété / In the general context of weight management, the development of food with higher satiating power appears to be an interesting alternative or a complementary answer to the proposition of calorie-reduced diets. The main aim of this thesis was to evaluate the single and combined satiating effects of proteins and fibres in biscuits and the influence of psychological factors, such as a given message about a food, on satiety. As for cognitive parameters, considering Stunkard and Messick guidelines about TFEQ limits, young French adults aged 20–39 yrs have low cognitive restraint, disinhibition and hunger scores. This finding makes it possible to suggest new limits for the TFEQ scores better adapted to this category of the population which is often used in clinical studies. We used these limits to define our groups of volunteers in the study about the influence of a message on satiety. It was found that giving a message on the satiating potential of a food may affect a sub-group of the population, such as low-restrained high-disinhibited women. To optimize the selection of the prototypes used in the clinical study about fibre and protein effects on satiety, we developed a new successful methodology to train a panel of sensorial experts in satiety assessment. A combination of fibre and protein in biscuits reduces appetite sensations more than do single enrichment in fibre or protein. The mixing of fibre and protein activates mechanisms which are induced by fibre (such as reduced insulinemia and slowed gastric emptying) and protein (such as reduced glycaemia). In conclusion, this integrative approach on satiety brings new knowledge about the synergistic effect of fibre and protein on appetite sensations. It proposes a new methodology using sensory and nutrition expertise to assess the satiety power of products and it also highlights the importance of psychometric traits in human food studies.Key words: Satiety, Fibres, Proteins, Three-Factor Eating questionnaire, Satiety message, training in satiety assessment