Effect of carrier frequency of interferential current on pressure pain threshold and sensory discomfort

INTERVENTION: Participants will be randomised to one of 5 treatment groups: a) Carrier frequency set at 1 KHz b) Carrier frequency set at 2 KHz c) Carrier frequency set at 4 KHz d) Carrier frequency set at 8 KHz e) Carrier frequency set at 10 KHz In all groups the amplitude‐modulated frequency (AMF) will be set at 100 Hz. The duration of application will be 20 minutes and the treatment will be applied in a single session for each participant. The electrodes (50 x 90 mm) will be placed on anterior and lateral aspect of the forearm to stimulate the median nerve and the superficial radial nerve. Pressure Pain Thresholds will be recorded from one point at the hand and another point at the forearm, before the treatment (baseline), 10 min and 20min after the beginning of the treatment, and 20 min after the end of the treatment. Visual Analog Scale will be used to assess the discomfort during the electrical stimulation at 10 min and 20min after the beginning of the treatment. CONDITION: Pressure pain threshold PRIMARY OUTCOME: Pressure pain thresholds will be assessed using a pressure algometer in 2 points: ; a) 3 cm distal to the distal end of the anatomical snuff box in the midline of the belly of the first dorsal interosseous muscle; ; b) on the anterior aspect of the forearm, 7.5 cm proximal to ; the distal wrist crease. SECONDARY OUTCOME: Sensory discomfort, assessed by the VAS. INCLUSION CRITERIA: Healthy subjects, Interferential naïve.