Three participants became light-headed or fainted once standing up 5–10 min after insertion of the psoas electrode, leaving 17 participants. The age, weight, height and BMI of the participants were 28.7 ± 2.8 years (mean,SD), 60.7 ± 9.7 kg, 167.6 ± 7.5 cm, and 21.5 ± 2.4, respectively. Participants gave written informed consent.The protocol was approved by the Local Medical Ethical Committee.