Fig. 1

Stimulation preference selection protocol flow chart. First participants of 10 years and older were presented two motion direction (side-to-side or head-to-toe) while the bed was moving with a frequency of 0.5 Hz, and were asked to choose a preferred direction. For safety reasons participants under 10 years tried only the head-to-toe direction. All participants were then presented three frequencies and were instructed to indicate whether for the bed to promote sleep it should move faster (F) or slower (S). These responses were taken into account to narrow down the stimulation frequency for a second round of three frequencies. All conditions were presented for 1 min. Amplitude and frequency were set to result in a maximum velocity of 0.1 m/s. Outcome of the stimulus preference protocol was a direction and frequency to be used during the intervention night