Evaluation of Chronic Pathologies Impact and Their Treatments on Children and Teen Physical Fitness.

Patients will be separated in different subgroups. Subgroups will be constituted according the disease status (active vs inactive) to assess the impact of the pathology on physical fitness and according to treatments to assess the effect of treatment on physical fitness.

Patients will perform physical tests to provide information about their physical fitness (body composition, metabolic flexibility, muscle strength and fatigue, bone mineral density), which will be compared to age- and gender-matched healthy controls. Patients will also complete blood tests to provide information about their inflammatory state to best understand physiological disorders and allow a better classification of the disease status.

1. Metabolic flexibility assessment

After sitting quietly for 20 min, subjects will perform a graded exercise test to volitional fatigue on an electromagnetically braked cycle ergometer with continuous gas collection and heart rate monitoring. In all subjects, when the Respiratory Exchange Ratio will be ≥1.00, indicating zero fat oxidation, the work rate will be increased by the same increments at 1-min intervals until volitional fatigue. O2 consumption (VO2) peak will be considered maximal when the Respiratory Exchange Ratio will be ≥1.05 and the subject will achieve his age-predicted maximal heart rate [heart rate maximum: (220 - age)]. Indirect calorimetry, as will be used in this study, is the standard method to quantify substrate oxidation rates at rest and during exercise. O2 consumption (VO2) and CO2 production (VCO2) will be averaged over the final 1 min of each work rate, and the results of this test will be used to calculate fat oxidation over a wide range of exercise intensities for each subject with the equations:

Lipids (mg.min-1) = 1.6946 x VO2 - 1.7012 x VCO2 and CHO (mg.min-1) = 4.585 VCO2 - 3.2255 VO2. 2. Muscle architecture Subjects will be lied on a massage table, muscle relaxed. Ultrasound will be used on vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) to assess muscle architecture. The muscle belly will be measured according to Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles (SENIAM) recommendations. Muscle thickness (the distance between superior and inferior aponeurosis) and fascicule angle (the angle formed by muscle fascicule and the inferior aponeurosis) will be measured for each muscle. 3. Muscle quality Subjects will sit on an adjustable seat. The right tight will be placed into the antenna of the peripheral quantitative tomography, so that the femoral condyles are aligned with the laser. An antero-posterior scout-view will be performed to detect junction between tibial tray and the femur, which matched with the starting position of the measurement. Then, a measure will be performed at 40% of the length between the greater trochanter and the mid-patella of the right leg. Muscle cross sectional area (CSA) and intramuscular adipose tissue (IMAT) will be assessed. The measurements will be performed by the same investigator to avoid any inter-individual bias. 4. Muscle function