Superimposed effects of mental and physical factors on cognitive load in practical work backgrounds
Objective To explore the effects of simultaneous physical activities on subjective load perception,work performance and heart rate variability(HRV)in the process of accomplishing cognitive tasks.Methods Thirty-three eligible male subjects completed 2-back cognitive tasks under three isotonic physical load conditions(0,3,5 Kg)of the left upper limb(with one week interval between conditions),and their ECG signals were collected during the whole process.After the task,the National Aeronautics and Space Administration-Task load index(NASA-TLX)scale was used to evaluate the subjective task load of the subjects,and their cognitive performance(mean reaction time,correct rate,etc.)was recorded.Results Compared with none physical activity,moderate physical and high physical activities significantly increased subjects'subjective load during cognitive tasks(t=2.235～14.841,all P＜0.05),average reaction time(t=-2.263,-3.284,P=0.031,0.002)and the wrong responsing rate of cognitive tasks(Z=-2.978,P=0.003).At the same time,the physical load also significantly increased the operator's heart rate(Z=-4.899,P＜0.001)and the low-frequency power value of heart rate variability(Z=-2.253,P=0.024),while high frequency components were significantly decreased(Z=-2.010,P=0.044).However,there was no statistical difference in functional status between medium and high physical load(P＞0.05).Conclusion During cognitive tasks,the physical load of the operator will further intensify the perception of task load,reduce execution ability,and cause the increase of sympathetic nerve tension.The results of this research provide a theoretical basis for the real-time evaluation of pilots'mental load in flight.
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