TABLE 2.

Stimulation parameters for non-invasive peripheral stimulation.

Study	Constant Current or Constant Voltage Stimulation	Pulse Rate	Pulse Duration	Pulse Amplitude	Channel Delay	Out-of-phase or In-Phase	Duty Cycle
Popović Maneski et al., 2011 [47]	Constant current, (voltage maximum limit: 95V)	40 Hz	250us	Minimal value (between 0 and 50mA) able to induce full flexion or extension at the wrist.	0-1000ms	Out-of-phase	N/A
Dosen et al., 2015 [68]	Constant current. (voltage maximum not reported)	100 Hz	300 us	Current amplitude to obtain flexion or extension of the joint (motor stimulation). Mean (wrist flexor) 15 +− 3 mA, mean (wrist extensor) 18 +− 5 mA. Highest current amplitude which did not cause muscle contraction (sensor stimulation). Mean (wrist flexor) 9 +− 3 mA, mean (wrist extensor) 10 +− 3mA.	N/A	Out-of-phase	N/A
Widjaja et al., 2011 [69]	Constant current. (voltage maximum not reported)	25 Hz	200 us	23 mA	N/A	Out-of-phase – possibly only applied to wrist extensors.	N/A
Pahwa et al., 2019 [17] and Isaacson et al., 2020 [53]	Constant current. (voltage maximum not reported)	150 Hz	300 us biphasic pulses, 50 us interpulse duration	Highest tolerable stimulation level (below threshold for muscle contraction). Mean 5.4mA +− 2.9	N/A	Alternating between stimulating the median and radial nerve at a frequency equal to the patient’s dominant tremor frequency as measured during a calibration period.	N/A
Kim et al., 2020 [18]	Constant voltage. (current limits not reported)	50, 100 or 200 Hz	200 us (biphasic, 100us per phase)	Between 3.57 V to 17.33V depending on the minimal strength of stimulation that could be discerned by the subject.	N/A	In-phase for the closed-loop trials, based on the dominant tremor frequency.	12.5%, 25% and 37.5% of the tremor cycle were trialled.
Prochazka et al., 1992 [65]	Constant current. (voltage maximum not reported)	30 Hz	200 us	Between 20mA to 100mA, amplitude-modulated based on filtered tremor measurement signal.	N/A	Out-of-phase	N/A

Note: N/A = not available