It was intendedthat as participants progressed through the training, their reliance onpredictive strategies would diminish and training of reactive balancecontrol would increase. At the end of each subsession, participantanxiety and perceived difficulty levels were assessed using a 5-pointscale (Supplementary Figure 1) (24). When these levels exceeded agiven threshold, in agreement with the participant, gait speed (40%–90% of individual’s normal gait), trip board height (7 or 14 cm), slipdistance (20–40 cm) or slip speed (with or without a friction device)were adjusted.