20 subjects will be randomized to this arm. A postero-anterior (PA) mobilization, to the fourth thoracic vertebra will be applied, for 3 sets of one minute. The subject will be comfortable prone lying.

20 subjects will be randomized to this arm. A postero-anterior (PA) mobilization, to the fourth thoracic vertebra will be applied, for 3 sets of one minute, but in this case, the subject will be seated, in a position that influence the sympathetic trunk, at the thorax.

20 subjects will be randomized to this arm. Only manual contact will be applied, without any oscillation. The subject will be comfortable prone lying. The intervention time is the same of the other arms.

Experimental group

Skin conductance will be measured with Biopac MP150, the electrodes will be attached to the third and fourth fingers bilaterally. This measurement will be made during all the procedure, before, during and until 15 minutes after the intervention.

Pressure pain threshold will be measured with a digital algometer (Model FDX 10; Wagner Instruments, Greenwich, CT). This measurement will be made on the spinous process of C5 and T4, on the first dorsal interossei, and on the anterior tibial tuberosity bilaterally.

Heart rate variability will be measured with a Polar Advantage Interface (Polar Electro Oy, Kempele, Finland). The belt will be positioned centrally, directly below the xiphisternum. Heart rate data acquisition will me made for 5 minutes at baseline and for 5 minutes immediately after the intervention.