Procedures
The participants sat on a stable seat 40-cm high with both feet on the COP platform. Measurements were performed before and after stimulation. First, SSA was measured during the sitting position. Next, the participants stood up with their eyes open, and standing COP was measured with eyes closed for 30 s, and then with open eyes for 30 s. We tested four conditions: (1) no vibratory stimulation (control), (2) vibratory stimulation of the left neck for 30 s, (3) vibratory stimulation of the left neck for 10 min, and (4) vibratory stimulation of the left neck and left lumbar back for 10 min. Stimulation was performed with the eyes closed while in a resting, sitting position. Measurements in the four conditions were conducted with random cross-over using a random number table. There was a 5-min resting period between the conditions, and all procedures were conducted in approximately 90 minutes.