Study	Reason for exclusion
Arroyo 1993	Not an RCT; experimental study.
Ido 2003	Not an RCT; case series.
Kesiktas 2011	TENS given as a combination of therapies which were given to each of the 3 arms and regarded as 1 single treatment; therefore, we were unable to isolate effects of TENS from other treatment.
Mutlu 2006	Error in search citation; original source does not exist.
Simons 2006	Commentaries of previously published studies. An incorrect title was tagged to this citation. The incorrect title tagged to the study was "A randomised controlled study on the effect of two different treatments (FREMS AND TENS) in myofascial pain syndrome," by Farina S, Casarotto M, Benelle M, Tinazzi M, Fiaschi S, Goldoni M, Smania N. Europa Medicophysica 2004;40(4):293‐301. Excluded because participants were excluded from the original study if they had clinical signs and symptoms of fibromyalgia.
Sunshine 1996	Microcurrent not TENS.

FREMS: frequency‐modulated electromagnetic neural stimulation; RCT: randomised controlled trial; TENS: transcutaneous electrical nerve stimulation.