We move now to the first of several 'reference' electrode sites.

If there is hair over the area discussed here, shave it before proceeding.

Swab a 3x3cm area on the back of the participant's left shoulder, near where the shoulder meets the curve of the neck. Many people will know this as the 'pressure point' area.

Any hair over this area should be removed before the skin is prepared.

Following the swab, abrade for 30 seconds.