Fig. 4

Definition of the stimulation sequences for the amplitude (JND and NDI) assessment, during walking (a) and sitting (b). The parameter \(\Delta {T}_{SW}\) denotes the duration of the swing phase. During the walking condition, the stimulation activation and deactivation were triggered by the gait events, whereas during sitting, the times were predefined and corresponded to those measured beforehand during the initial walking trial (see "Preparation"). STIM 1 and STIM 2 correspond to the first and the second stimuli that are compared by the participant, while STIM off indicates that no stimulation occurs during that time. FSR 1 and 2 are the two force-sensing resistors placed on the foot sole