Statistical analysis
All statistical analyses were performed using SAS version 9.4 (SAS Institute, Inc., Cary, NC, USA). A sample size calculation was performed using previous results of the simulator with a two-sided paired t-test [Each variable was analysed with a mixed model analysis of variance with fixed factor condition (separate for each set of assessments) and random factor subject. Simulator mean speed, simulator standard deviation speed, GRIDT mean speed, and body sway were log-transformed to correct for a log-normal distribution before statistical analysis.The repeatability was quantified by the coefficient of variation (CoV) within and between subjects, as estimated from the subject (between-subject) variability and residual (within-subject) variability of the mixed model analysis and the mean over the three conditions of the estimated least square means. The common variance is the sum of the inter and intrasubject variability. For log-transformed variables the CoV is calculated from the same estimated variabilities of the mixed model analyses which are back transformed by Pearson correlations were calculated for the SDLP and each variable in each condition (well rested and sleep deprived). In case of log normal distribution of a variable the log values of the variable are used.