Determining perception thresholds of young adults to small continuous moving platform perturbations

Detecting external disturbances is vital for maintaining balance, as corrective actions are initiated to prevent falls. Quantifying people's ability to perceive such disturbances improves our understanding of how balance is maintained. This study aims to 1) quantify healthy young adults' ability to perceive external perturbations while balancing on a stabilometer, and 2) understand the relationship between balance performance and perturbation magnitude relative to participants' perception threshold. Participants (n = 22; 20-35 yr) completed a multiple staircase protocol. While standing on a stabilometer mounted on a moving platform, they attempted to keep it horizontal during 10-s trials with small continuous perturbations. After each trial, participants were asked whether they perceived the platform movement. Perturbation magnitudes were adjusted for the next trial based on their response. This process continued for each staircase until the termination criteria were met, at which point participants' individual perception threshold was determined. Participants then performed ten 40-s trials on the stabilometer, two trials in each condition: without perturbation, perturbation at the 100%, 80%, and 50% of the individual's perception threshold, and the pilot study's minimum threshold. Balance performance was defined as the time-in-balance ratio and root mean square (RMS) deviation angle from horizontal. Perception thresholds varied significantly between individual participants, with a peak acceleration ranging from 4.29 to 20.6 cm/s². The results showed that perturbation magnitude has a significant correlation with variability in deviation angle (R = 0.24; P = 0.0038). The results suggest that some participants can perceive very small perturbations during a challenging balance task. Subthreshold perturbations, although very small, can influence balance performance.NEW & NOTEWORTHY To our knowledge, this is the first study to quantitatively measure the conscious perception threshold of platform perturbations while doing a balancing task. We found that young healthy adults with little similar prior experience in tasks close to the stabilometer balancing task can detect small platform perturbations while doing such a challenging task. The results also showed that platform perturbations below the conscious threshold can influence the balance performance on the stabilometer.