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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.

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.

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.

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

The aim of this study was to explore the relationship between maximal oxygen consumption (VO2 max) and bone mineral density (BMD) in a group of young Lebanese adults. Twenty women and 37 men whose ages range from 18 to 32 yr participated in this study. Informed written consent was obtained from the participants. Body weight and height were measured, and body mass index was calculated. VO2 max was determined by direct measurement while exercising on a bicycle ergometer (Siemens-Elema RE 820; Rodby Elektronik AB, Enhorna, Sweden). Whole body bone mineral content (WB BMC), whole body bone mineral density (WB BMD), lumbar spine BMD (L1eL4 BMD), total hip BMD (TH BMD), and femoral neck BMD (FN BMD) were measured by dual-energy X-ray absorptiometry. In women, VO2 max (expressed as L/mn) was positively correlated to WB BMC (r 5 0.82; p ! 0.001), WB BMD (r 5 0.80; p ! 0.001), L1eL4 BMD (r 5 0.73; p ! 0.001), TH BMD (r 5 0.80; p ! 0.001), and FN BMD (r 5 0.85; p ! 0.001). In men, VO2 max (expressed as L/mn) was positively correlated to WB BMC (r 5 0.57; p ! 0.001), WB BMD (r 5 0.53; p ! 0.001), L1eL4 BMD (r 5 0.50; p ! 0.001), TH BMD (r 5 0.38; p ! 0.01), and FN BMD (r 5 0.30; p ! 0.05). In both sexes, the positive associations between VO2 max and bone variables (BMC and BMD) remained significant after adjustment for age (p ! 0.001). This study suggests that VO2 max (L/mn) is a positive determinant of BMC and BMD in young adults. Aerobic power seems to be a determinant of BMC and BMD in young adults.

AIM OF THE STUDY The aim of this study was to compare bone mineral content (BMC), bone mineral density (BMD) and bone mineral apparent density (BMAD) in obese, overweight and normal weight adolescent boys. METHODS & RESULTS This study included 23 obese, 19 overweight and 25 normal weight adolescents (aged 14-20 years) boys. The three groups (obese, overweight and normal weight) were matched for age and maturation index. Body composition, BMC and BMD were assessed by dual-energy X-ray absorptiometry (DXA). The expressions whole body (WB) BMC/height and WB BMD/height were used to adjust for WB bone size. BMAD was calculated for the WB. WB BMC, WB BMC/height, total hip (TH) BMD, femoral neck (FN) BMD and ultra distal (UD) radius BMD) were higher in obese and overweight boys in comparison to normal weight boys (p < 0.05). WB BMAD was lower in obese boys in comparison to overweight and normal weight boys (p < 0.05). After adjustment for either weight or lean mass, obese boys displayed lower WB BMC, WB BMC/height and WB BMD values in comparison to overweight and normal weight boys (p < 0.05). CONCLUSION This study suggests that WB BMC, WB BMC/height and WB BMD do not adapt to the increased body weight in obese adolescent boys.

The aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent girls using hip structure analysis (HSA). This study included 64 postmenarcheal adolescent girls (14 obese, 21 overweight, and 29 normal weight). The 3 groups (obese, overweight, and normal weight) were matched for maturity (years since menarche). Body composition and bone mineral density (BMD) of whole body, lumbar spine, and proximal femur were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at the femoral neck (FN) at its narrow neck (NN) region, the intertrochanteric (IT), and the femoral shaft (FS) by the HSA program. Cross-sectional area and section modulus were measured from hip BMD profiles. Total hip BMD and FN BMD were significantly higher in obese and overweight girls in comparison with normal-weight girls (p < 0.05). However, after adjusting for weight, using a one-way analysis of covariance, there were no significant differences among the 3 groups regarding HSA variables. This study suggests that in obese and overweight adolescent girls, axial strength and bending strength indices of the NN, IT, and FS are adapted to the increased body weight.

In this study, we examined fat oxidation rates during exercise in obese pubescent boys. Three groups of pubescent boys (16 pre-pubescent, Tanner's stage I; 16 pubescent, Tanner's stage III; and 14 post-pubescent, Tanner's stage V) performed a graded test on a leg cycle ergometer. The first step of the test was fixed at 30 W and power was gradually increased by 20 W every 3.5 min. Oxygen consumption (VO(2)) and carbon dioxide production (VCO(2)) were determined as the means of measurements during the last 30 s of each step, which allowed us to calculate fat oxidation rates versus exercise intensity. Between 20 and 50% of peak oxygen consumption (VO(2peak)), fat oxidation rate in relative values (mg . min(-1) . kg FFM(-1)) decreased continuously with pubertal development. In the same way, the maximum rate of fat oxidation occurred at a lower percentage of VO(2peak) (pre-pubescent: 49.47 +/- 1.62%; pubescent: 47.43 +/- 1.26%; post-pubescent: 45.00 +/- 0.97%). Our results confirm that puberty is responsible for a decrease in fat free mass capacities to use fat during exercise. The results suggest that post-pubescent obese boys need to practise physical activity at a lower intensity than pre-pubescent boys to enhance lipolysis and diminish adipose tissue and the consequences of obesity.

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.

Although osteoporosis is known to mainly affect postmenopausal women, there is enough evidence to support substantial bone losswith aging inmen aswell (1,2). Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) is the best single predictor of fracture risk in elderly subjects (1,2). Among all fragility fractures, hip fractures are the most important in terms of morbidity andmortality (1,2). Highermortality rates after hip fracture have been reported in men compared with women (3). Peak BMD attained at the third decade of life is a strong predictor of fracture risk later in life (4). An increase in peak BMD of 10% would delay the onset of osteoporosis by 13 yr (4). Long-term practice of weight-bearing physical activities stimulates bone formation and enhances BMD of stressed sites (5,6). According to the mechanostat hypothesis, bones adapt their strength tomechanical loads generated fromvoluntarymechanical usage (7). This has been supported bymany animal-based studies (8,9). In humans, it has been shown that body weight and lean mass are the strongest predictors of BMD in both sexes (10,11). Other human-based studies have shown that BMD is correlated to the performances done in some physical tests (12,13). Identifying simple determinants of BMD may be useful for the prevention and early detection of osteoporosis and/or osteopenia. The aim of this study was to explore the relationships between performances in different physical tests (vertical jump [counter-movement jump], standing long jump test, 3-jump test, and 5-jump test) and BMD of the total hip in a group of young adult men. We hypothesized that the objective measures of muscular strength would be correlated to BMD of the hip because hip BMD is strongly correlated to mechanical factors on one hand and the physical tests, which were used in our study to measure the strength and the power of the lower limbs, on the other hand. Ten healthy Lebanese males whose ages ranged from 18 to 30 yr participated in this study. Weight and height were measured, and body mass index (BMI) was calculated. Daily calcium intake, daily protein intake (DPI), and sleep quality were evaluated using

The aim of the present study was to investigate effect of puberty on substrate oxidation rates using a graded exercise test to exhaustion. Two groups of obese adolescent males (34 prepubertal: body mass index (BMI) = 25,94 +/- 2,63; Z-score = 4,43 +/- 1,83; and 26 postpubertal: BMI = 31,14 +/- 4,88; Z-score = 5,264 +/- 1,76) performed an exercise test on a cycle ergometer. The test consisted in a series of graded exercises on a cycle ergometer. Stage duration was 3 min 30 s. Fat and carbohydrate rates were calculated during the last 30 s of each stage using stoichiometric equations, and this permitted us to calculate substrate oxidation according to exercise intensity. Lipid oxidation rates are significantly higher in the postpubertal group. When the fat oxidation rates are reported relative to fat free mass, fat oxidation rates are higher in the prepubertal group. Puberty decreases significantly the capacity of fat free mass to oxidize fat for a same level of exercise.