High-frequency Alternating Current Stimulation for Tremor in Parkinson's Disease.

"For electrical stimulation in the active groups, unmodulated alternating currents with a symmetrical rectangular waveform of 10 kHz will be applied for 20 minutes. The current intensity shall be adjusted individually for each participant by increasing the current intensity until the participant reports a strong but comfortable tingling sensation just below the motor threshold. One electrode will be placed over the median and radial nerves, while the other over the radial nerve.~The intensity of the current shall be adjusted every two minutes if the tingling sensation decreases. This protocol had been used in previous studies conducted by our research group."

"Sham electrical stimulation will be performed with the same equipment, time, and electrodes as in the active groups without the participants and the evaluator having a view of the device screen. The intensity of the current will be increased for 30 seconds until the sensory threshold (strong but comfortable tingling sensation) will be reached and after that, the intensity will be reduced to 0 milliamperes (mA) with 30 seconds ramp down. Participants will not receive electrical current during the rest of the placebo intervention. This protocol was used in other studies with similar interventions to blind participants."