The habituation of human postural responses to platform perturbations

Abstract

The purpose of this study was to examine habituation and task on adaptation of postural responses to simulated wave-induced ship motions. Twenty-four participants (12 male and 12 female) performed four different tasks while being exposed to five platform motion profiles during two testing periods. The four tasks performed were: standing feet parallel stance, standing with feet in an in-step stance, holding of a 10 kg load, sagittal lifting/lowering of a 10 kg load. Motion induced correction (MIC) occurrence, corresponding platform motion parameters, and total time spent performing MICs were compared between trials and tasks. It was found that the number of MIC events and total time spent performing MICs differed significantly between trials, with the first trial for participants having more MIC events and more time spent performing postural corrections. The number of MIC events was reduced and total postural correction times were significantly quicker on the second day of testing. Results revealed significant differences in pitch and roll velocities between in-step and parallel standing and significant differences in pitch and roll accelerations between both standing tasks and MMH tasks (p < 0.05). These results suggest that MIC initiation is significantly affected by previous exposure, habituation to comparable platform motions, and task. Differences between tasks suggest that perturbation characteristics of MIC occurrence are potentially affected by shape of the base of support and additional load. These results could help explain difficulties in previous attempts to predict MIC occurrences purely upon platform motion characteristics. Relevance to industryThe results of this research suggest that when working in moving environments adaptation to motions may occur much faster than expected. Further adaptation may also occur after leaving the moving environment. These factors must be considered when evaluating offshore occupations.