“…These ten studies were published from 2008 to 2020. Generally, for participant selection, these studies were performed on healthy subjects [ 45 – 47 , 49 , 54 ], patients with migraine [ 48 , 50 , 51 ], patients with chronic low back pain [ 53 ], and patients with functional dyspepsia [ 52 ], respectively. The sample size of these studies ranged from 12 to 94, and the average sample size of healthy subjects was 28.…”