This case report is about two patients with two different types of ICDs who underwent electrical muscle stimulation (EMS) therapy. In one patient with an ICD that has epicardial screw-in bipolar sensing leads, electromagnetic interference (EMI) from the EMS device caused the delivery of an inappropriate ICD discharge. In a second patient with an ICD with endocardial true bipolar sensing, there was no evidence of EMI during the EMS therapy despite all of our attempts to reproduce it. The sensing circuits in the two different ICDs are compared.