The relation between physical and mental load, and the course of physiological functions and cognitive performance
The data relate to a manuscript that will be published inTheoretical Issues in Ergonomics Science. Taylor & Francis. Description of variables and research design: ID=the numerical identification of examined person (EP) age=19-27 pad_chair: pad=2; chair=1 gender: man=2; female=1 BoCmin=correctly cancelled symbols of Bo test/min or BoC1min...BoC20min BoCSUMmin=sum of correctly cancelled symbols of Bo test from all 20 minutes BoCMEANmin=mean of correctly cancelled symbols of Bo test from all 20 minutes BoEmin=incorrectly cancelled symbols (errors) of Bo test/min or BoE1min...BoE20min BoESUMmin=sum of incorrectly cancelled symbols (errors) of Bo test from all 20 minutes BoEMEANmin=mean of incorrectly cancelled symbols (errors) of Bo test from all 20 minutes VTA=absolute tidal volume change. VTA was subsequently calculated and expressed in liters. 0.5 l is the initial mean value. VTR=relative tidal volume change MV=minute ventilation TEMP=body temperature SCL=skin conductance level HRVSampEn=Heart rate variability sample entropy Pulse_frequency=heart rate (HR) Resp_frequency=respiratory rate (RR) HFLF_welch=low frequency to high frequency ratio, computed by Welch phase_exp=1-4 1: The control phase of the measurement lasted 2 minutes. In this phase, all EPs sat on chairs with no pads. Its purpose was to analyze the initial values of the EPs’ physiological functions. These values were supposed to be identical or very similar in the experimental group and the control group. Minutes 0,1. 2: The following rest phase of the measurement lasted 20 minutes. Control-group EPs continued sitting on chairs without pads, while EPs in the other group were seated on pads that had been added to their chairs. They would then sit on these pads until the end of the fourth phase, the final step in the experiment. During the second phase, EPs were not to show any deliberate cognitive activity. Activities involving inadvertent attention, however, were allowed, for example, looking forward at the table or out of the window. Minutes 2...21. 3: The load phase lasted 20 minutes, during which the EPs continuously filled out of the Bo test (Bourdon test T-78: the test of sustained, selected attention). Minutes 22...41. 4: The verification phase lasted 2 minutes. Following the end of the cognitive load, this phase also served to compare the development of physiological functions in the two groups of EPs in connection with the use of the pad, particularly with respect to exploring the rate of EPs’ adaptation after performance (load). Minutes 42,43.
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Data was evaluated by using statistical-analytical computer programs SPSS (version 19), Statistica (version 12) and Matlab (version 2015b). We made descriptive statistics, normality plots with data normality tests: Shapiro-Wilk W, Wilcoxon test and Kolmogorov-Smirnov with Lillefors correction. Since the data does not always exhibit normal distribution, a comprehensive comparison was made of medians, means and retransformed means by means of Box-Cox transformation. We also considered the range of quartiles, with data distribution evaluated based on boxplots, P-P plots, Q-Q plots and histograms. Nevertheless, results following out of parametric and nonparametric statistical methods were very similar. We also used Levene's Test for Equality of Variances and T Tests (Paired-Samples T Test and Independent-Samples T Test) and for the control their nonparametric analog Mann-Whitney U for two-independent-samples and Wilcoxon test for two-related-samples. Kolmogorov-Smirnov Z (verification of Mann-Whitney U) was conducted only in sporadic cases of nonparametric data distribution. We also conducted ANOVA (Univariate Analysis of variance), Pearson´s parametric and Spearman´s nonparametric correlation and linear regression. HR, HRV: For the purposes of our research, we evaluated HR (1/1000 seconds), which was acquired from an electrocardiography (ECG) as the reverse value of the difference between consequent R-peaks detected by the QRS seeker program (Vítek and Kozumplík 2011). HRV parameters were analyzed on an RR interval series (Barbieri 2005). The series of RR intervals were detrended using wavelet packet decomposition. HRV was analyzed using time-, geometry-, frequency-, and non-linear-domain methods. The heart rate variability analysis software (HRVAS) plug-in for Matlab software was used to compute HRV parameters (Ramshur 2010; Task Force 1996). Standards for the evaluation of HRV unify the length of the assessed tachograph section to 5 minutes so that both short- and long-term HR changes can be optimally captured for a correct quantification of which a time section of at least 2 minutes is needed (Task Force 1996).