Shown were testing protocols for (a) training and control groups, and (b) the hypotheses and analyses for evaluation of interference and mixed (interference) training effects. The protocol for the training group consisted of eight regular walking trials followed by a block of eight slips [including the first novel slip (S1) and another seven consecutive slips (S2–S8)], a block of three unperturbed trials (N), a block of eight trips [including the first novel trip (T1) and another seven consecutive trips (T2–T8)], another block of three unperturbed trials, a second block of five slips (S9–S13) followed by a block of three unperturbed trials, a second block of five trips (T9–T13) followed by a block of three unperturbed trials, and then a mixed block of seven slips (S14–S20), seven trips (T14–T20), and four unperturbed trials interspersed. NS and NT represented the last regular walking trial prior to the first novel perturbation (S1), and respectively served as the baseline walking performance for comparison with data from slip and trip trials. The protocol for the control group consisted of eight regular walking trials followed by an unannounced, novel trip (TC).