Ample evidence demonstrates the beneficial role of physical activity combined with a structured dietary plan to counteract obesity. International guidelines as the World Health Organization states that to improve fitness levels at least 150 min a week of physical activity at moderate intensity, combined with resistance training composed of 8-12 repetitions with an intensity of 60-70%1RM for each muscle group, are recommended. In this regard, a minimum dosage of 60-90 min of physical activity composed by aerobic exercises in alternation with resistance training protocols, allow a sequential development of cardiorespiratory fitness and muscular strength parameters avoiding potential interference effects. Interference may occur when strength and endurance stimuli both target opposite peripheral adaptations (e.g., hypertrophy vs. muscle capillarization) and this phenomenon seems to be particularly clear during adolescence. Nevertheless, the incorporation of different training stimuli within the same training session is called Concurrent Training. This training mode, thanks to the activation of two different metabolic pathways (e.g., aerobic and anaerobic), has a variety, beneficial effects in terms of muscle mass and strength development, body composition profile regulation and neuromotor function improvement. Concurrent Training seems to be effective not only in normal-weight subjects, but also in obese individuals, reporting positive adaptations on physical fitness and health status compared with a single-mode (i.e., aerobic or strength training). Therefore, the aim of this study is to detect the effects of a 10-week-Concurrent Training protocol compared with a single training modality on physical fitness, body composition and circadian rhythms in adult outpatients with obesity.

Inclusion Criteria:

• Physical activity frequency minor of 2 days/week
• BMI major of 30 kg/m2
• informed consent signature

Exclusion Criteria:

• age over 65 years
• knee or hip pain (visual analogue scale score >7 arbitrary units
• a history of hip, knee or foot replacement or osteoarthrosis
• cardiac infarction
• neurological impairments or any other clinical condition that affects the practice of physical activity