The present study is conceived as a pilot study aimed to determine the efficiency of the newly available Positron Emission Tomography (PET) - Magnetic Resonance Imaging (MRI) hybrid scan technique for muscular activity evaluation, creation of anatomic images of muscle activity and resolution of metabolic activity distribution within exercising skeletal muscle.

Inclusion Criteria:

MRI exam inclusion criteria

• Male volunteer aged in the range 18 to 35 years.
• Acceptance of the research protocol: signature of the informed consent form after oral and written information about the protocol through the patient information document.
• Volunteers that could undergo 1h15 to 1h30 immobilization (MRI exam duration in time).

PET/MRI exam inclusion criteria

• Male volunteer aged in the range 18 to 35 years.
• Acceptance of the research protocol: signature of the informed consent form after oral and written information about the protocol through the patient information document.
• Volunteers that could undergo 1.5 to 2.0 hours immobilization (PET/MRI exam duration in time).
• Volunteers should practice regular physical activity, defined as 50 min per day (in a single session), 2 days per week of physical activity as a minimum (no maximum is fixed).

Exclusion criteria MRI exam exclusion criteria

• Pre-existing neurological or muscular lesions on the legs.
• Co morbidities impeding on the protocol comprehension or fulfilment.
• Illnesses that do not allow to lay down on an examination table.
• Pacemaker holder.
• Metal implants that would preclude MRI imaging
• Claustrophobia: Subjects will be questioned about possible discomfort with being in an enclosed space (e.g., MRI scanner). Those who report such problems will be excluded.

PET/MRI exam exclusion criteria

• Medical radiation exposure within the last five years (normal population should not be exposed to medical radiation higher or equal to 1 mSv per year).
• Pre-existing neurological or muscular lesions on the legs.
• Co morbidities impeding on the protocol comprehension or fulfilment.
• Illnesses that do not allow to lay down on an examination table.
• Pacemaker holder.
• Metal implants that would preclude MRI imaging
• Claustrophobia: Subjects will be questioned about possible discomfort with being in an enclosed space (e.g., MRI scanner). Those who report such problems will be excluded.