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International audience; The purpose of this study was to analyze the influence of grade of obesity on the probability of achieving a VO2 plateau and threshold secondary criteria for verifying VO2max during a treadmill walk test in youths with obesity. Therefore, 72 youths with obesity (aged 8-16) performed an incremental treadmill walk test to exhaustion during which oxygen uptake (VO2), minute ventilation (VE), heart rate (HR) and rating of perceived exertion were continuously measured. HR corresponding to a “hard” level of perceived exertion was reported and expressed as a percentage of the predicted HRmax. The rate of achievement of criteria for validation VO2max (VO2 plateau; HR>95% theoretical HRmax; RER>1.0; rating of perceived exertion ≥ “hard”) was compared between participants with grade I and grade II obesity. 37% of the participants achieved a VO2 plateau and 23% achieved both an HR>95% and RER >1.0. Youths with grade II obesity had lower minute ventilation (p95% (OR = 0.33; P=0.06) and a “hard” rating of perceived exertion than grade I (OR = 4.5; P=0.07). However, there was no influence of grade of obesity on the achievement of VO2 plateau, and RER>1.0.

Background: In children with obesity, the imbalance between O2 delivery and extraction might be related to the inability to achieve VO2max during treadmill tests. The aim of the study is to characterize the changes in muscle deoxyhemoglobin (BPdeoxy[heme]) in the gastrocnemius medialis of children with obesity. 26 children with obesity (11.6±1.7 y) performed a treadmill walking test to exhaustion during which pulmonary gas exchanges and gastrocnemius medialis deoxy[heme] responses were measured continuously. BPdeoxy[heme] was determined for each participant using piecewise double-linear regressions. VO2peak and deoxy[heme] responses were compared between participants who achieved the criteria for verifying VO2max (VO2 plateau or both heart rate >95% and respiratory exchange ratio >1.0) and those not. Results: BPdeoxy[heme] was detected in 25 out of 26 participants at 77±9% VO2peak and occurred at a similar relative intensity both subgroups. There was no relationship between BPdeoxy[heme] and VO2peak. Conclusion: The imbalance between O2 delivery and extraction occur at high intensites during a treadmill walking test in youth with obesity, that may partly explain their difficulty to further continue the test regardless of the achievement of the criteria for verifying VO2max.

International audience; The aim of this study was to explore the relationships between maximum power and bone variables in a group of young adults. Two hundred and one young adults (53 men and 148 women) whose ages range from 18 to 35 years voluntarily participated in this study. Weight and height were measured, and body mass index was calculated. Body composition, bone mineral content (BMC) and bone mineral density (BMD) were determined for each individual by dual-energy X-ray absorptiometry. Vertical jump was evaluated using a validated field test (Sargent test). The highest vertical jump was selected. Maximum power (P max, in watts) of the lower limbs was calculated accordingly. In young men, maximum power was positively correlated to whole body (WB) BMC (r = 0.65; p < 0.001), WB BMD (r = 0.41; p < 0.01), L1-L4 BMC (r = 0.54; p < 0.001), total hip (TH) BMC (r = 0.50; p < 0.001), femoral neck (FN) BMC (r = 0.35; p < 0.01), FN cross-sectional area (CSA) (r = 0.33; p < 0.05) and FN cross-sectional moment of inertia (CSMI) (r = 0.50; p < 0.001). In young women, maximum power was positively correlated to WB BMC (r = 0.48; p < 0.001), WB BMD (r = 0.28; p < 0.001), L1-L4 BMC (r = 0.34; p < 0.001), TH BMC (r = 0.43; p < 0.001), TH BMD (r = 0.21; p < 0.01), FN BMC (r = 0.42; p < 0.001), FN BMD (r = 0.31; p < 0.001), FN CSA (r = 0.41; p < 0.001), FN CSMI (r = 0.40; p < 0.001) and FN Z (r = 0.41; p < 0.01). The current study suggests that maximum power is a positive determinant of WB BMC, WB BMD, FN CSA, and FN CSMI in young men. It also shows that maximum power is a positive determinant of WB BMC, WB BMD, TH BMD, FN BMD, FN CSA, FN CSMI, and FN Z in young women.

International audience; The purpose of this study was to investigate the relationships between skeletal muscle index (SMI) and bone variables in a group of young adults. Three hundred and thirty-five young adults (129 men and 206 women) whose ages ranged from 18 to 35 yr voluntarily participated in this study. Weight and height were measured, and body mass index (BMI) was calculated. Body composition, bone mineral content (BMC), bone mineral density (BMD), geometric indices of hip bone strength and trabecular bone score (TBS) were determined for each individual by Dual-energy X-ray absorptiometry (DXA). Appendicular skeletal mass (ASM, in kg) was calculated by summing the muscle masses of the 4 limbs, assuming that all nonfat and nonebone mass is skeletal muscle. Skeletal muscle index (SMI) was defined as ASM/height². In young men, SMI was positively correlated to WB BMC (r = 0.63; p < 0.001), WB BMD (r = 0.53; p < 0.001), L1-L4 BMC (r = 0.33; p < 0.001), L1-L4 BMD (r = 0.30; p < 0.001), L1-L4 TBS (r = 0.26; p < 0.01), TH BMC (r = 0.61; p < 0.001), TH BMD (r = 0.46; p < 0.001), FN BMC (r = 0.51; p < 0.001), FN BMD (r = 0.46; p < 0.001), FN cross-sectional area (CSA) (r = 0.56; p < 0.001), FN cross-sectional moment of inertia (CSMI) (r = 0.52; p < 0.001) and FN section modulus (Z) (r = 0.54; p < 0.001) but negatively correlated to FN strength index (SI) (r = -0.24; p < 0.01). In young women, SMI was positively correlated to WB BMC (r = 0.61; p < 0.001), WB BMD (r = 0.60; p < 0.001), L1-L4 BMC (r = 0.35; p < 0.001), L1-L4 BMD (r = 0.33; p < 0.001), L1-L4 TBS (r = 0.29; p < 0.001), TH BMC (r = 0.61; p < 0.001), TH BMD (r = 0.53; p < 0.001), FN BMC (r = 0.45; p < 0.001), FN BMD (r = 0.49; p < 0.001), FN CSA (r = 0.60; p < 0.001), FN CSMI (r = 0.52; p < 0.001), and FN Z (r = 0.40; p < 0.001) but negatively correlated to FN SI (r = -0.20; p < 0.01). The current study suggests that SMI is a positive determinant of bone mineral density and geometric indices of hip bone strength in young adults.

Background and aims. The nutritional disorders are modifiable predisposing factors of the current leading causes of morbidity and premature mortality, such as cardiovascular diseases, diabetes and cancers. An early recognition of appropriate interventions could decrease the burden of medical costs and increase the healthy life expectancy. The aims of our study were the description of nutritional status, its associated factors, and the detection of eating disorders among Romanian medical students of the “Iuliu Hatieganu” University of Medicine and Pharmacy, Cluj-Napoca.Methods. A cross-sectional study was conducted during the 2015-2016 academic year, including medical students from all study years, by an online questionnaire. The statistics, both descriptive and inferential, were calculated using EpiInfo.Results. A total of 222 students from the University Romanian section were included, with a sex-ratio (men:women) of 0.22. The average body mass index of the medical students included was 21.3±3.3 kg/m2, for females it was 20.7±3 kg/m2 and for males 23.9±3.1 kg/m2. For the nutritional disorders such as overweight, the prevalence among males (30%) had a net predominance (p

Lack of sleep is known to negatively affect adolescent's health and the links between regular physical activity and sleep are unclear.This pilot study investigated whether the regular practice of physical activities among sedentary female students would improve their sleep. Nineteen female students, identified as sedentary and having poor subjective sleep quality were assigned in two groups to a 12-week university physical activities programme in accordance with the recommendations of World Health Organisation (N = 10) or to a control condition (N = 9). Sleep was assessed with actigraphy before and after the study and with the Pittsburg Sleep Quality 15 Index (PSQI) at the beginning, middle, and end of the study. The intensity of physical activities was controlled by heart rate monitor. The analysis showed that sleep quality in the physical activities group improved, with the mean ± SD PSQI score decreasing from 9.1 ± 1.7 to 4.8 ± 2.0. Despite some limitations, these pilot data indicate that a physical activities programme is feasible to implement in students, and that participation in such a programme improves sleep in 18- 24 -year-old female adolescents. Further potential benefits remain to be investigated in follow-up research.

International audience; The aim of the current study was to explore the relationships between lower limb muscular power and bone variables (bone mineral content (BMC), bone mineral density (BMD), hip geometry indices and trabecular bone score (TBS)) in a group of young Lebanese adults. 29 young Lebanese men and 31 young Lebanese women whose ages range between 18 and 32 years participated in this study. Body weight and height were measured, and body mass index (BMI) was calculated. Body composition and bone variables were measured by DXA. DXA measurements were completed for the whole body (WB), lumbar spine (L2–L4), total hip (TH) and femoral neck (FN). Hip geometry parameters including cross-sectional area (CSA), cross-sectional moment of inertia (CSMI), section modulus (Z), strength index (SI) and buckling ratio (BR) were derived by DXA. Trabecular bone score was also derived by DXA. Horizontal jump (HJ), vertical jump, vertical jump maximum power, force-velocity maximum power and 20-m sprint performance were measured or calculated by using validated fitness tests. In men, fat mass percentage was negatively correlated to TH BMD, FN BMD, CSA, CSMI, Z and SI. In women, weight, BMI, lean mass and fat mass were positively correlated to WB BMC, CSMI and Z. Regarding physical performance variables, horizontal jump performance and force-velocity maximal power were positively correlated to TH BMD, FN BMD, CSA and Z in men. Vertical jump maximal power was positively correlated to WB BMC in women. 20-m sprint performance was negatively correlated to FN BMD, CSA, Z and SI in men. In conclusion, the current study suggests that force-velocity maximum power is a positive determinant of BMD and hip geometry indices in men but not in women.

Le test de course en navette de 20m reste l’épreuve cardiorespiratoire de terrain de référence chez les enfants et adolescents (Tomkinson et al., 2017), y compris obèses (Castro-Pineiro et al., 2011; Quinart et al., 2014). Néanmoins, derniers parviendraient difficilement à atteindre réaliser une perfor- mance maximale aérobie valide lors d’une épreuve incrémentale de course (Breithaupt et al., 2012). La présence de nombreuses phases de freinage-réaccélération (PFR) du test navette pourrait accentuer cette difficulté et expliquer la sous-estimation du pic de VO2 chez le jeune obèse (Quinart et al, 2014). Par ailleurs, l’intérêt d’un protocole intermittent de type 15-15 n’a été démontré chez l’adolescent obèse que pour des vitesses supérieures à 7 km.h 1 (Rey et al., 2016 ; Thivel et al., 2017) qui ne sont pas adaptées aux obésités sévères (Klijn et al., 2007). Ainsi, nous avons supposé qu’une évaluation de l’impact énergétique et psychologique des PFR permettrait d’identifier la principale cause d’abandon à un test de type navette chez l’adolescent obèse. Nous avons mesuré l’impact des phases de freinage- relance (PFR) et de courtes périodes de récupération (15-15) sur la consommation en oxygène (VO2) et la perception de l’effort (RPE) d’adolescents sévèrement obèses lors de trois exercices incrémentaux de marche dont la vitesse était comprise entre 3 et 6 km.h 1. 19 adolescents sévèrement obèses âgés de 15.2 ± 1.5 ans (IMC = 39.7 ± 5.9) ont complété le protocole. La présence de 2 PFR par minute n’a pas augmenté significativement la VO2 ni la RPE en comparaison avec un exercice continu contrôle. Pendant le protocole 15-15, nous avons observé une diminution moyenne de 17 à 26% de la VO2 (p

National audience; Introduction La masse osseuse est influencée par de nombreux facteurs comme la génétique, la nutrition, les concentrations de certaines hormones et les contraintes mécaniques (poids du corps et activité physique). Le pic de masse osseuse à 25 ans conditionne la courbe de décroissance de la densité minérale osseuse (DMO) menant à l’ostéoporose. Le but de ce travail était d’étudier les relations éventuelles entre des paramètres de santé facilement mesurables (facteurs anthropométriques, performances physiques et nutrition) et la BUA (Broadband Ultrasound attenuation ou atténuation du signal ultrasonore) mesurée au niveau du calcanéus. Méthodes Au total, 130 sujets (85 femmes et 45 hommes) âgés en moyenne de 21 ans (18 à 38 ans) ont participé à cette étude (Universanté-CEMHaVie). Le poids, la taille, la masse grasse, le tour de hanche et le tour de taille ont été mesurés et l’indice de masse corporelle (IMC) a été calculé. Le niveau de condition physique a été déterminé à l’aide de plusieurs tests : test de Sargent (TS), test de navette (TN) 4 × 10 m et test de force de préhension du poignet (FP). Des questionnaires validés ont été utilisés afin d’évaluer le niveau d’activité physique quotidien (Global Physical Activity Questionnaire [GPAQ]), l’indice de qualité du sommeil de Pittsburgh (IQSP) et la consommation calcique journalière (CCJ). L’atténuation du signal ultrasonique (BUA) a été mesurée au niveau du calcanéum par un appareil de type « Pegasus Smart Medlink® ». Résultats Chez les sujets féminins, le poids (r = 0,46 ; p < 0,001), l’indice de masse corporelle (r = 0,43 ; p < 0,001), la masse grasse (r = 0,27 ; p < 0,01), le tour de hanche (r = 0,25 ; p < 0,01) et le tour de taille (r = 0,31 ; p < 0,01) étaient positivement corrélés à la BUA. En revanche, nous n’avons pas retrouvé de corrélation entre la BUA et la quantité d’activité physique évaluée par le GPAQ, la condition physique (TS, TN et FP) et la consommation calcique journalière. Chez les hommes, aucune corrélation significative n’a été mise en évidence entre les paramètres mesurés et la BUA. Conclusion Les caractéristiques morphologiques mesurées dans notre étude (l’IMC, le poids, la masse grasse, le tour de hanche et le tour taille) semblent des déterminants de santé corrélés à la BUA chez les jeunes femmes mais pas chez les jeunes hommes. Ces corrélations paraissent intéressantes à étudier sur une population plus importante. Niveau de preuve III.

International audience; La sédentarité est un facteur de risque de mortalité et de morbidité indépendamment du niveau d’activité physique. La reconnaissance de l’activitéphysique et de la sédentarité comme étant des comportements différents, avec des effets propres sur la santé, est récente. La prise en compte de ces deux comportements est indispensable afin d’améliorer l’efficacité de la prise en charge de l’enfant obèse.

International audience; The aim of this paper is to describe some features of sports habits among a population of higher education students of the Opal Coast littoral (France). As part of the Universanté observatory’s activities (University of the Littoral Opal Coast, Artois University and Lille 2 University), this work has been carried out on a subset of approximately 800 students of the Opal Coast area. We will refer both to some aspects related to the macroscopic context, and to some mesoscopic ones. The first concern the Nord-Pas de Calais region, in particular the Opal Coast littoral area; the second are drawn from the Universanté research data. The data collected depicts the socio-demographic profile of the Opal Coast littoral’s students, and allows us to focus on some features and some of the main criticalities concerning this area’s high education students’ sport practice: socio-economic insecurity, the relationship between alcohol consumption and sports habits, risky behaviours. In particular, we will stress the importance of the amount of the participants concerned by regular and risky punctual alcohol consumption episodes crossing this data with sports club participation: those who declare to drink 6 glasses of alcoholic beverages one time per month or more are 42.4 % of the respondents.We will propose some interpretative keys to frame these phenomena. The first interpretative is related to the social environment, the second one to a new conception of risk emerging in youth subcultures.

BACKGROUND: Swimming is often recommended as a means of increasing physical activity and gaining health benefits. The present study examined the psychological, social, and physical health states in competitive swimmers engaged in long-term training. METHODS: The study took place during the 4 days of the French master championships in France in 2011 (from 10 to 13 March). Global health parameters were evaluated and compared with general values reported in studies aiming to describe health standard values in France or Europe. All swimmers selected for the event were invited to participate in the study. Setting questionnaires concerning mental and social health (short form 36), physical activity (International Physical Activity Questionnaire), and medication were administered. Peak expiratory flow (l.min ) was measured, and body mass index (kg.m ) was calculated from height (m) and body mass (kg). Prevalence of overweight and obesity was calculated by age and gender. Chi-squared tests were used to compare prevalence of overweight and obesity between participants and reference values. Short form 36 scores and physical activity (met.h.week ) were compared with reference values by single -tests. Two-way ANOVA was used to compare peak flow results with standard values. The level of significance was set at

The aim of this study was to explore the relationship between sleep quality and bone mineral density (BMD) of the hip in a group of young Lebanese men.Fourteen Lebanese young men from 18 to 30 years (mean age 22.6 years) participated in this study. Weight and height were measured and body mass index (BMI) was calculated. BMD of the total hip (TH) and the femoral neck (FN) was measured by DXA. Daily protein intake (DPI), daily calcium intake (DCI) and sleep quality were evaluated by validated questionnaires. The Pittsburgh sleep quality index (PSQI) was used to assess sleep habits and quality; higher scores represent worse sleep quality. Weight, height, BMI, DCI, DPI and sleep duration were not correlated to BMD values. The Pittsburgh sleep quality index was negatively correlated to femoral neck BMD (r = -0.82; p0.001) and to TH BMD (r = -0.54; p0.05).This study suggests that poor sleep quality affects negatively BMD of the hip in young adult men. Our findings may lead to the development of better preventive approaches to osteoporosis.

AIM OF THE STUDY The aim of this study was to compare geometric indices of hip bone strength in male professional soccer players and controls. METHODS Twenty-three male professional soccer players and 21 male sedentary subjects whose ages range between 18 and 30 years participated in this study. Weight and height were measured, and body mass index (BMI) was calculated. Daily calcium intake and physical activity were evaluated using validated questionnaires. Hip bone mineral density was measured by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone geometry, DXA scans were analyzed at the narrow-neck (NN), the intertrochanteric (IT) region and the femoral shaft (FS) by the Hip Structure Analysis (HSA) program. Cross sectional area (CSA), an index of axial compression strength, cross sectional moment of inertia (CSMI), an index of structural rigidity, section modulus (Z), an index of bending strength, cortical thickness (CT) and buckling ratio (BR) were measured from bone mass profiles. RESULTS CSA, CSMI, Z and CT of the three regions (NN, IT and FS) were higher in soccer players compared to controls. After adjustment for either age, body weight, height or physical activity duration (h/week), CSA, CSMI, Z and CT of the three regions remained higher in soccer players compared to controls. CONCLUSION This study suggests that, in young adult males, soccer practice is associated with greater axial strength, bending strength and structural rigidity indices at the hip.

The optimization of the benefits of an adapted physical activity program on aerobic fitness is conditioned by the ability of the test to measure and detect changes in the parameters that we wish to investigate, which are mainly maximal aerobic speed (MAS) and maximal oxygen uptake (VO₂max). However, youths with obesity have difficulties to reach a maximum cardiorespiratory state during walking/running tests of increasing intensity, which may lead to an underestimation of these parameters. The involvement of psychological and physiological factors in the non-achievement of VO₂max during a walk/run test in youths with obesity remains unclear. The objective of this thesis was to shed light on the mechanisms that may explain early dropout during walking/running tests of increaseing intensity in youths with obesity. In a first study, our work focused on shuttle walking/running tests, which are the most commonly used field tests to measure aerobic fitness (VO₂max, VMA) because of their high cost effectiveness. We assumed that the repetition of an increasing number of Braking-Reacceleration Phases (BRS) could lead to an exaggerated increase in energy cost in youths with obesity, justifying the early dropouts often described during this type of test. Thus, we measured VO₂ and ratings of perceived exertion (RPE) in 19 grade III obesity adolescents performing three 12-minute incremental tests in successive 3-minute increments at paces of 3, 4, 5, and 6 km.h⁻¹ : a continuous protocol with two BRPs per minute, and a 15-15 intermittent protocol. The results indicated that the impact of BRPs on VO₂ and RPE was non-significant at these paces and that the intermittent modality decreased aerobic energy cost by 15-25%. In the second and third study, our work focused on treadmill walking tests of increasing intensity.The literature indicates that a significant proportion of youths with obesity fail to reach the criteria defining the achievement of VO₂max during this type of test. However, no study has experimentally tested the hypothesis that muscular mechanisms could be at the origin of this. In our second study, we jointly measured gastrocnemius oxygenation and pulmonary VO₂ kinetics in 26 overweight youths aged 9 to 15 years, during a treadmill walking test of increasing intensity. A breakpoint in muscle deoxyhemoglobin was observed in 25 participants at 75-80% of VO₂peak and its time of onset correlated with test duration. In our third study, we measured the influence of gender, maturation, and grade of overweight on the likelihood of achieving 4 VO₂max verification criteria (VO₂ plateau, HR>200 bpm, RER>1.0, RPE>5/10) in 73 overweight youths aged 8 to 16 years. Overweight grade II children were more likely to achieve an RPE>5/10 ("hard" according to the Borg CR-10 scale) and had a lower peak of maximal ventilation than grade I obesity children. Together, these two studies suggest that the inability to produce maximal treadmill effort may be related to an imbalance between O₂ supply and utilization in the gastrocnemius, potentially related to lower ventilatory capacities. In conclusion, this thesis work provides new knowledge on the influence of muscular, respiratory and perceptual factors on the achievement of VO₂max during a walking test of increasing intensity in youths with obesity. For clinicians, whishing to set up this type of test, we thus encourage the implementation of strategies intended to 1) attenuate muscular solicitations and 2) promote optimal ventilatory adaptation.; L'optimisation des bénéfices d'un programme d'activité physique adaptée sur l'aptitude aérobie est conditionnée par la capacité du test à mesurer et détecter les changements dans les paramètres que l'on souhaite investiguer, qui sont principalement la vitesse maximale aérobie (VMA) et la consommation maximale en oxygène (VO₂max). Or, les jeunes en surpoids atteignent difficilement un état cardiorespiratoire maximal lors des test de marche/course d'intensité croissante, pouvant entraîner une sous-estimation de ces paramètres. L'implication des facteurs psychologiques et physiologiques dans la non-atteinte de VO₂max au cours d'un test de marche/course chez le jeune en surpoids restent peu clairs. L'objectif de ce travail de thèse fut ainsi d'apporter un éclairage sur les mécanismes susceptibles d'expliquer les abandons précoces lors des tests de marche/course d'intensité croissante chez le jeune en surpoids. Dans une première étude, notre travail s'est intéressé aux tests de marche ou de course en navette, qui sont les tests de terrain les plus pratiqués pour mesurer l'aptitude aérobie (VO₂max, VMA) en raison de leur rapport coût efficacité élevé. Nous avons supposé que la répétition d'un nombre croissant de Phases de Freinages-Réaccélérations (PFR) pouvait entraîner une augmentation exagérée du coût énergétique chez le jeune en surpoids, justifiant les abandons précoces décrits lors de ce type de test. Ainsi, nous avons mesuré VO₂ et la pénibilité de l'effort (RPE) chez 19 adolescents en surpoids de grade III lors de trois tests incrémentaux de 12 minutes par paliers successifs de 3 minutes aux allures de 3, 4, 5 et 6 km.h⁻¹ : un protocole continu comportant deux PFR par minute et un protocole intermittent 15-15. Les résultats ont indiqué que l'impact des PFR sur VO₂ et la RPE était non significatif à ces allures et que la modalité intermittente permet de diminuer le coût énergétique aérobie de 15-25%. Dans la seconde et la troisième étude, notre travail a porté sur les tests de marche d'intensité croissante sur tapis roulant. La littérature indique qu'une proportion importante de jeunes en surpoids ne parvient pas à atteindre les critères définissant l'atteinte de VO₂max lors de ce type de test. Pourtant, aucune étude n'a testé expérimentalement l'hypothèse selon laquelle des mécanismes musculaires pouvaient en être à l'origine. Dans notre seconde étude, nous avons mesuré conjointement les cinétiques d'oxygénation du gastrocnémien et de VO₂ chez 26 jeunes en surpoids âgés de 9-15 ans, lors d'un test de marche d'intensité croissante sur tapis roulant. Un point d'inflexion dans la désoxyhémoglobine musculaire a été observé chez 25 participants à 75-80 % de VO₂peak et son délai d'apparition était corrélé à la durée du test. Dans notre troisième étude, nous avons mesuré l'influence du sexe, de la maturation et du grade de surpoids sur la probabilité d'atteindre 4 critères de vérifications de VO₂max (plateau de VO₂, FC>200bpm, RER>1.0, RPE>5/10) chez 73 jeunes en surpoids âgés de 8 à 16 ans. Les enfants en surpoids de grade II avaient davantage de probabilité d'atteindre une RPE>5/10 ("dur" sur l'échelle de Borg CR-10) et avaient un pic de ventilation maximale inférieur à ceux en surpoids de grade I. Ensemble, ces deux études suggèrent que l'inaptitude à produire un effort maximal sur tapis roulant est en partie liée à la survenue d'un déséquilibre entre la demande énergétique et le niveau d'extraction de l'O₂ au niveau du gastrocnémien, ainsi qu'à de plus faibles capacités ventilatoires. En conclusion, ce travail de thèse apporte un éclairage sur l'influence des facteurs musculaires, respiratoires et perceptuels sur l'atteinte de VO₂max lors d'un test de marche d'intensité croissante chez le jeune en surpoids.

The aim of this PhD thesis were to explore the relationships between several physical performance variables and bone parameters in a group of middle-aged men, to compare composite indices of femoral neck strength in inactive middle-aged men and ages-matched former football players and to explore the effects of a 1-year recreational football protocol on bone mineral density and physical performance parameters in a group of healthy inactive 50-year-old men. Three main studies have been conducted. The first study has shown that VO₂ max (L/min), lean mass and maximum power of the lower limbs are the strongest determinants of bone variables in middle-aged men. The second study has shown that former footbal practice is associated with higher composite indices of femoral neck strength in middle-aged men. The third study has demonstrated that WB BMC, FN BMD, CSMI, CSI, BSI and ISI increased in both experimental groups (RF30 and RF60) but not in the control group. The percentages of variations in bone health parameters and in physical performance variables were not significantly different in both experimental groups. Recreational football is an effective method to improve bone health in middle-aged men.; Les buts de cette thèse de doctorat étaient d'explorer les relations entre plusieurs paramètres de performance physique et les paramètres osseux chez un groupe d'homme cinquantenaires, de comparer les indices de résistance osseuse du col fémoral chez un groupe d'homme cinquantenaires inactifs et des anciens joueurs de football de même âge et d'explorer les effets d'un an de football récréatif sur la densité minérale osseuse et les paramètres de performance physique chez un groupe d'hommes cinquantenaires. Trois principales études ont été menées. La première étude a démontré que la VO₂ max (L/min), la masse maigre et la puissance maximale des membres inférieurs sont les meilleurs déterminants des paramètres osseux chez les hommes cinquantenaires. La deuxième étude a démontré que l'ancienne pratique du football est associée à une augmentation des indices de résistance osseuse du col fémoral chez les hommes cinquantenaires. La troisième étude a démontré que le CMO CE, la DMO CF, le CSMI, le CSI, le BSI et l'ISI ont augmenté dans les deux groupes expérimentaux (RF30 et RF60) mais pas dans le groupe témoin. Les pourcentages de variation des paramètres osseux et des performances physiques n'étaient pas significativement différents entre les deux groupes expérimentaux. Le football récréatif est une méthode efficace pour l'amélioration des paramètres de santé osseuse chez les hommes cinquantenaires.

The aim of this PhD thesis were to explore the relationships between several physical performance variables and bone parameters in a group of middle-aged men, to compare composite indices of femoral neck strength in inactive middle-aged men and ages-matched former football players and to explore the effects of a 1-year recreational football protocol on bone mineral density and physical performance parameters in a group of healthy inactive 50-year-old men. Three main studies have been conducted. The first study has shown that VO₂ max (L/min), lean mass and maximum power of the lower limbs are the strongest determinants of bone variables in middle-aged men. The second study has shown that former footbal practice is associated with higher composite indices of femoral neck strength in middle-aged men. The third study has demonstrated that WB BMC, FN BMD, CSMI, CSI, BSI and ISI increased in both experimental groups (RF30 and RF60) but not in the control group. The percentages of variations in bone health parameters and in physical performance variables were not significantly different in both experimental groups. Recreational football is an effective method to improve bone health in middle-aged men.; Les buts de cette thèse de doctorat étaient d'explorer les relations entre plusieurs paramètres de performance physique et les paramètres osseux chez un groupe d'homme cinquantenaires, de comparer les indices de résistance osseuse du col fémoral chez un groupe d'homme cinquantenaires inactifs et des anciens joueurs de football de même âge et d'explorer les effets d'un an de football récréatif sur la densité minérale osseuse et les paramètres de performance physique chez un groupe d'hommes cinquantenaires. Trois principales études ont été menées. La première étude a démontré que la VO₂ max (L/min), la masse maigre et la puissance maximale des membres inférieurs sont les meilleurs déterminants des paramètres osseux chez les hommes cinquantenaires. La deuxième étude a démontré que l'ancienne pratique du football est associée à une augmentation des indices de résistance osseuse du col fémoral chez les hommes cinquantenaires. La troisième étude a démontré que le CMO CE, la DMO CF, le CSMI, le CSI, le BSI et l'ISI ont augmenté dans les deux groupes expérimentaux (RF30 et RF60) mais pas dans le groupe témoin. Les pourcentages de variation des paramètres osseux et des performances physiques n'étaient pas significativement différents entre les deux groupes expérimentaux. Le football récréatif est une méthode efficace pour l'amélioration des paramètres de santé osseuse chez les hommes cinquantenaires.

The main aim of this thesis was to explore the relationships between physical performances obtained in anaerobic physical tests and bone mineral density in young adults. To do so, three preliminary studies and two principal studies were conducted. The first preliminary study showed that maximal oxygen consumption (L/min) is an important determinant of BMD in young adults. The second preliminary study demonstrated that being active (engaging in more than 150 minutes of physical activity per week) is associated with greater composite indices of femoral neck strength (CSI, BSI and ISI) in young overweight men. The third preliminary study demonstrated in a group of overweight and obese men that physical activity level (h/week) was positively correlated to composite indices of femoral neck strength (CSI, BSI and ISI); the positive associations between physical activity and composite indices of femoral neck strength (CSI, BSI and ISI) remained significant after adjustment for body weight. The first principal study showed that maximum power of the lower limbs evaluated by the vertical jump test is positively correlated to BMD and geometric indices of hip bone strength in young adults. The second principal study demonstrated that maximum power evaluated by the force-velocity test on a cycle ergometer is a positive determinant of BMD in men but not in women. 20-meter sprint performance was positively correlated to femoral neck BMD in men. In conclusion, it seems that performances obtained in physical tests evaluating muscular power are correlated to BMD in young adults.; Le but principal de cette thèse était d’explorer les relations entre les performances obtenues aux tests physiques anaérobies et la densité minérale osseuse chez l’adulte jeune. Pour ce faire, 3 études préliminaires et deux études principales ont été menées. La première étude préliminaire a démontré que la consommation maximale d’oxygène (L/min) est un déterminant important de la DMO chez les jeunes adultes. La deuxième étude préliminaire a démontré que le fait d’être actif (pratiquer plus de 150 minutes d’activité physique par semaine) est associé à une augmentation des valeurs de CSI, de BSI et d’ISI chez les jeunes hommes en surpoids. La troisième étude préliminaire a démontré chez des jeunes hommes en surpoids et obèses que le niveau d’activité physique est un déterminant positif des indices de résistance osseuse du col fémoral (CSI, BSI et ISI) ; les corrélations positives entre le niveau d’activité physique et les indices de résistance osseuse du col fémoral (CSI, BSI et ISI) ont persisté après ajustement pour le poids. La première étude principale a démontré que la puissance maximale des membres évaluée par le test de détente verticale est corrélée positivement à la DMO et aux indices géométriques de résistance osseuse de la hanche chez les jeunes adultes. La deuxième étude principale a démontré que la puissance maximale évaluée par le test de charge-vitesse sur bicyclette ergométrique est corrélée positivement à la DMO chez les hommes mais pas chez les femmes. La performance au 20 mètres sprint était corrélée à la DMO du col fémoral chez les hommes. En conclusion de cette thèse, il apparait que les performances obtenues aux tests physiques évaluant la puissance musculaire sont corrélables à la DMO chez l’adulte jeune.