Doctor of Philosophy / Department of Kinesiology / Craig A. Harms / The overall aim of this dissertation was to determine the impact of lifestyle (i.e. habitual and acute physical activity and diet), age, and sex on systemic and airway inflammation and oxidative stress. In study 1 (Chapter 2) we examined the impact of habitual physical activity level on the post-prandial airway inflammatory response following an acute bout of moderate intensity exercise. Results indicated that the mean exhaled nitric oxide (eNO; marker of airway inflammation) response increased for all groups at two hours post high-fat meal (HFM) (~6%) and returned to baseline by four hours post-HFM. However, there was a varying eNO response from baseline to four hours in the group that exercised in the post-prandial period compared to the group that remained sedentary. These findings suggest airway inflammation occurs after a HFM when exercise is performed in the post-prandial period, regardless of habitual physical activity level. In study 2 (Chapter 3) we investigated the post-prandial oxidative stress response to meals of varying calories and fat. Specifically, we assessed the post-prandial airway and systemic 8-isoprostane (a marker of oxidative stress) responses to meals with moderate-fat (8.5 kcal/kg of bodyweight) and high-fat content (17 kcal/kg of bodyweight) from baseline to six hours post-meal in a randomized crossover design. This study revealed that systemic 8-isoprostane increased from baseline to six hours post-meal (38.3%), but there was no difference between the moderate-fat meal (MFM) and HFM conditions. There were no changes in airway 8-isoprostane from baseline to six hours post-MFM or HFM, or between the MFM and HFM conditions. Lastly, in study 3 (Chapter 4), we were interested in examining 8-isoprostane responses in older adults, since 8-isoprostane has been reported to increase with age. Previous research also suggests that older women (OW) and older men (OM) have differences with regard to prevalence and severity of late-onset asthma. In this study, we sought to determine whether the airway 8-isoprostane response to a strenuous bout of exercise was different in OW compared to OM. A secondary aim was to determine whether post-exercise 8-isoprostane generation was correlated with decrements in lung function. Our results showed that the generation of 8-isoprostane from pre- to post-exercise increased ~74±77% in OW and decreased ~12±50% in OM. The decrease in 8-isoprostane generation was not correlated with improvements in lung function from pre- to post-exercise. These findings collectively contribute to the literature by enhancing our understanding of the impact of lifestyle factors, age and sex on modifying and potentially mitigating the risk of developing chronic diseases.

Considering current levels of overweight and obesity in the population and the associated adverse health consequences, engaging people with chronic exercise programmes is of heightened importance. During chronic structured exercise programmes, some adults experience adaptive compensatory behavioural responses through increased dietary intake and/or decreased free-living physical activity. These responses can negate the benefits of an exercise-induced energy deficit. However, it is unclear whether young people experience similar responses during chronic structured exercise. Therefore, the experimental research presented in this thesis examined the existence and extent of exercise-induced energy compensation in adolescent girls. To achieve this, a total of 92, 12 to 15 year old girls and 26 adults were recruited into six experimental studies. The Medical Research Council guidance for designing complex interventions was used to structure the experimental chapters into development (Chapters 4 to 7), piloting (Chapter 8) and evaluation (Chapter 9). The first experimental study (Chapter 4) demonstrated that typical daily variation of total energy expenditure (TEE) in adolescent girls is ~3% when estimated by the Actiheart. Physical activity energy expenditure (AEE) variation was found to be ~10%. In the second experimental study (Chapter 5) the agreement and variability of laboratory buffet meals test days was investigated. The results demonstrated typical daily variation of 8.7% in laboratory-based energy intake (EI) in adolescent girls aged 12 to 15 years. Furthermore, a buffet meals familiarisation day is recommended to reduce the variability in EI. Estimation of EI was further explored in Chapter 6 using a digital photography method. This study demonstrated potential for EI assessment using digital photography, but highlighted that, at present, a supplementary written record of EI is required to overcome the limitations associated with missing photographs. Chapter 7 explored themes related to recruitment and retention of adolescent girls to chronic exercise intervention studies. The seven recommendations identified were used to recruit and retain participants in a twelve week pilot exercise intervention study with adolescent girls (Chapter 8). There was no evidence of energy compensation behaviours on a group level; however, high individual variability in both EI and EE behaviours was apparent. The final experimental chapter (Chapter 9) evaluated the fidelity of the exercise intervention and compliance with the measurement of primary outcome variables. Intervention fidelity was largely upheld. On average, participants attended 94% of exercise sessions and 73% of the participants met their individual target heart rate zone. Focus groups with the participants and parents highlighted preference for school-based exercise sessions due to increased variety and convenience, and recommendations for future estimation of free-living EI and EE. Collectively, these studies suggest there is value in pursuing the investigation of energy compensation behaviours in adolescent girls using a mixed methods approach. These studies demonstrate the factors requiring attention when designing and delivering complex interventions to investigate exercise-induced energy compensation in adolescent girls. In particular, methods for estimating free-living EI and EE require further attention before attempting to conduct such research in a larger sample.

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Le sommeil, de par ses fonctions récupératrices, est essentiel à la vie. Pour autant, la modification du mode de vie et des comportements, tant sédentaires que nutritionnels, sont à l’origine d’une altération du sommeil, conduisant ensemble à des situations d’obésité. Cet excès pondéral s’accompagne fréquemment d’un syndrome d’apnées obstructives du sommeil (SAOS). Lorsque ces deux pathologies sont présentes, les troubles métaboliques s’aggravent et sont à l’origine d’une inflammation de bas grade. A notre connaissance, aucune étude ne s’est intéressée aux bénéfices d’un reconditionnement à l’exercice physique combiné à une modification des habitudes alimentaires, en dehors de ceux induits par la perte de poids, sur ces différents paramètres. L’objectif de ce travail de thèse a donc été, à partir d’une étude ancillaire, d’évaluer le sommeil d’adolescents obèses par polysomnographie (PSG) par comparaison à celui de sujets normo-pondérés. Dans l’étude principale, les effets d’un programme de 9 mois (reconditionnement à l’exercice, activités physiques adaptées, rééquilibre alimentaire) ont été évalués sur l’architecture et la durée du sommeil, le SAOS, les différents facteurs biologiques (inflammatoires, hormonaux, profils glucidique et lipidique) et sur les adaptations physiologiques à l’exercice musculaire, afin de mieux comprendre l’implication de l’endurance aérobie et des troubles du sommeil sur la santé cardio-métabolique. Trente-deux adolescents obèses (âge : 14,6 ans, z-score d’IMC= 4 ,7) ont été recrutés. Toutes les variables ont été analysées en pré et post-intervention. Les résultats montrent une durée de sommeil réduite chez les jeunes obèses avec un SAOS, diagnostiqué chez 58% d’entre eux, malgré une architecture du sommeil satisfaisante. En post-intervention, une perte de poids de 11 kg et une amélioration des paramètres d’adaptation à l’exercice maximal (PMA, VE, VO2pic…) ont été rapportées chez tous les sujets, que le SAOS soit encore, ou non, présent. En effet, ce syndrome s’est normalisé chez 46% d’entre eux. Par ailleurs, grâce à l’intervention, le sommeil s’est amélioré (qualité et quantité). Enfin, la protéine C-réactive basale du groupe SAOS, dont les valeurs atteignaient 11mg/l à l’admission, a considérablement diminué, accompagnée d’une baisse de la leptinémie et d’une hausse de l’adiponectinémie, pouvant expliquer le moindre risque cardio-métabolique. Nos résultats démontrent qu’à l’admission, l’inflammation est liée à l’obésité, alors qu’en post-intervention, sa baisse s’explique par l’augmentation de l’endurance aérobie, et ceci indépendamment du sexe, du poids, de la durée de sommeil et du SAOS. Bien que ce dernier n’ait pas été normalisé chez tous les sujets, sa prévention par l’exercice physique ainsi que celle des troubles métaboliques observés dans ces deux pathologies devrait faire partie intégrante de la prise en charge des jeunes obèses en vue d’atténuer le risque de morbi-mortalité cardiovasculaire à l’âge adulte / Sleep, through its restorative functions, is essential for life. However, lifestyle modifications, sedentary and unhealthy feeding behaviors trigger sleep curtailment and sleep disruption, leading together to weight gain. Obesity is usually associated with obstructive sleep apnea (OSA), and these two diseases both induce metabolic dysfunctions and low-grade systemic inflammation. To the best of our knowledge, no study has assessed the effects of exercise reconditioning and modified food habits on these parameters. The purpose of this work was to assess and compare, from an ancillary study, polysomnographic variables between obese adolescents and normal-weight (NW) controls. In the main study, the effects of a 9-month program (exercise reconditioning, adapted physical activities and modified food habits) on sleep architecture, sleep duration, OSA, biological factors (inflammatory, hormonal, carbohydrates and lipid profiles) and physiological adaptations at exercise were assessed, in order to a better understanding of the roles of cardiorespiratory fitness and sleep disorders on cardio-metabolic health. Thirty-two obese adolescents (age: 14.6 years, BMI z-score: 4.7) were recruited. Every parameters were assessed at admission and post-intervention. Short sleep duration and a high prevalence of OSA (58%) were observed at admission in obese adolescents despite a satisfying sleep architecture, compared with NW controls. Post-intervention, weight loss (11kg) and improved parameters of physiological adaptations at exercise (MAP, VE, VO2peak) were found in every subject and OSA was normalized in 46% of them. Sleep quantity and sleep quality were improved. Decreased C-reactive protein (6.78 vs 10.98 mg/l) and leptin concentrations, and increased adiponectin levels were found, and cardio-metabolic risk (CMR) was decreased. At admission, obesity explains by itself the systemic inflammation whereas the decrease in inflammation, post-intervention, is explained by enhanced cardiorespiratory fitness related to fat-free mass, after controlling for sex, weight loss, change in sleep duration and OSA. Prevention of OSA and metabolic dysfunctions by chronic exercise should be an integral part of the obesity management in youths in order to decrease the risk of cardiovascular morbi-mortality in adulthood

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L'objectif général de ce travail doctoral était d'étudier la plasticité de la fonction posturale à travers l’étude des effets d’un programme d'entraînement unilatéral ou d’une expérience sportive et/ou motrice. Pour cela, les effets de différents types d'exercices chroniques (volontaire et électro-induit) et aigus (tâche posturale répétée, échauffement et fatigue) ont été testés sur le contrôle postural monopodal en condition statique et dynamique. Les principaux résultats montrent que le programme d'entraînement unilatéral constitué de contractions volontaires et de contractions électro-induites n'a pas amélioré le contrôle postural du membre ipsilatéral et du membre controlatéral en dépit de l'augmentation de la force musculaire pour les deux membres chez des jeunes adultes sains non actifs. L'absence de résultat relatif au contrôle postural pourrait, principalement, être liée aux modalités et conditions des programmes d'entraînement qui n’étaient pas suffisamment proches des conditions écologiques du contrôle postural. En revanche, l'exercice aigu non-fatiguant comme l'échauffement a amélioré le contrôle postural monopodal chez des jeunes étudiants sportifs quelle que soit la jambe sur laquelle ils étaient évalués. Cependant, cette amélioration n’apparait qu’au bout de 10-15 minutes selon la jambe considérée après l'arrêt de l'exercice. Par ailleurs, chez des athlètes pratiquant des sports symétriques et asymétriques, les exercices aigus non-fatiguant comme la répétition d’une tâche posturale et l'échauffement, ont engendré des effets bénéfiques sur le contrôle postural monopodal statique et ont permis de distinguer la jambe dominante de la jambe non-dominante. En revanche, l'exercice aigu fatiguant a perturbé le contrôle postural indépendamment de la nature du sport pratiqué et de la jambe évaluée. / The overall objective of this thesis was to study the plasticity of postural function by investigating the effects of a unilateral training program or a sport and/or motor experience. Hence, the effects of various types of chronic (voluntary and electro-induced) and acute exercises (repeated postural task, warm-up and fatigue) were tested on monopodal postural control in static and dynamic conditions. The main findings show that the unilateral training program of voluntary contractions and electro-induced contractions did not improve postural control of the ipsilateral and contralateral limbs despite the increase in muscle strength for both in healthy non-active young adults. The lack of postural control outcome may be primarily related to the conditions of training programs that were not sufficiently close to the ecological conditions of postural control. In contrast, non-fatiguing high-intensity exercise such as warm-up improved monopodal postural control in young sports students regardless of which leg they were assessed. However, this improvement does not appear until 10-15 minutes according to the considered leg after stopping the exercise. Moreover, in athletes practicing symmetrical and asymmetrical sports, the non-fatiguing, acute exercises such as the repetition of a postural task and the warm-up, generated beneficial effects on the static monopodal postural control and enabled to distinguish the dominant leg of the non-dominant leg. In contrast, the fatiguing acute exercise disrupted postural control regardless of the nature of sport practiced and the leg assessed.