Teenagers: Impact of Eccentric eXercise Training on Overweight and Obesity

Nowadays, eccentric exercise can be realized in a dynamic way with an ergocycle which permits eccentric (ECC) lower limbs contractions at a defined power output. With this type of ergometer, O2 consumption (VO2) in ECC is three fold lower than in concentric (CON) for the same power output. Consequently, ECC program could be used in chronic disorders with limited capacities, such as obesity. The investigators hypothesis that an eccentric training program, as it will induce higher mechanical constraints, would improve body composition, especially by reducing fat mass. This effect could be explained by an increased rest energy expenditure and a better improvement in biological parameters (particularly lipid profile and insulin-resistance) after ECC training (versus CON training). This study aims to compare the modification of fat mass after an ECC program versus a CON program at the same VO2.. The secondary goal is to assess the physiological mechanisms involved in the modification of body composition.

Inclusion Criteria: * Adolescent (12 to 17 years old) * BMI\>90th percentile * Post puberty (Tanner 3 to 5) * Inactive (\