RESEARCH Open Access

Resting and active motor thresholds versus stimulus–response curves to determine transcranial magnetic stimulation intensity in quadriceps femoris John Temesi1, Mathieu Gruet2,3,5, Thomas Rupp2,3, Samuel Verges2,3 and Guillaume Y Millet1,3,4* Background: Transcranial magnetic stimulation (TMS) is a widely-used investigative technique in motor cortical evaluation. Recently, there has been a surge in TMS studies evaluating lower-limb fatigue. TMS intensity of 120-130 % resting motor threshold (RMT) and 120 % active motor threshold (AMT) and TMS intensity determined using stimulus–response curves during muscular contraction have been used in these studies. With the expansion of fatigue research in locomotion, the quadriceps femoris is increasingly of interest. It is important to select a stimulus intensity appropriate to evaluate the variables, including voluntary activation, being measured in this functionally important muscle group. This study assessed whether selected quadriceps TMS stimulus intensity determined by frequently employed methods is similar between methods and muscles. Methods: Stimulus intensity in vastus lateralis, rectus femoris and vastus medialis muscles was determined by RMT, AM