A tourniquet is used to stop abundant bleeding when simple compression is not effective. The investigators will study the vascular suffering of the tourniquets according to their location on the limb: limb (arm / thigh) or distal (forearm / leg). Vascular suffering will be evaluated by the loss of the radial doppler flux for the tourniquets placed on the upper limb and in the tibial anterior to the lower limb by the loss of the pulse oximetry pulse and the collection of the signs described by the volunteers (pain, Paresthesia, cold sensation).