 Risks, side effects and disadvantages Surface stimulation may cause muscle-contractions. Attachment of the surface electrodes may cause the skin to become red or irritated for some hours following the experiment. The type of electrical stimulation used in this experiment is not associated with any known risks or side effects. When the sensory threshold is determined i.e., the lowest strength of the electrical stimulation that the participant can feel, it may feel unpleasant or painful for a short period of time, but the unpleasantness or pain will disappear as soon as the electrical stimulation stops. The electrical stimulation applied during the intervention period will be adjusted such that is it not painful. 