Perturbation-Based Balance Training (Intervention)
anxiety
Each of the 4 PBT sessions lasted approximately 20 minutes and consisted of 40 perturbations (20 to each leg) delivered on a uniformly moving treadmill with no lateral rails (Split 70/157/ASK; Woodway). A safety harness prevented participants from falling to the ground if they could not regain balance after a perturbation. Participants experienced only slips in the first session, only trips in the second session, and randomly ordered slips and trips (mixed perturbations) in the third and fourth sessions (The perturbation intensity was adjusted based on participants’ preferred walking speed and was divided into 5 levels with progressively longer durations (slip) or greater accelerations (trip). The intensity was increased after every fourth perturbation if (1) the combined rating of perceived anxiety and difficulty was 4 or less, (2) the participant avoided falling during the previous 4 perturbations, and (3) the participant was comfortable increasing the intensity. However, if any criterion was not met, the intensity remained unchanged (for protocol tailoring, see eAppendix 1 in 