RESUMEN
Backgrounds: The validity of heart rate variability (HRV) has been substantiated in mental workload assessments. However, cognitive tasks often coincide with physical exertion in practical mental work, but their synergic effects on HRV remains insufficiently established. The study aims were to investigate the combined effects of cognitive and physical load on autonomic nerve functions. Methods: Thirty-five healthy male subjects (aged 23.5 ± 3.3 years) were eligible and enrolled in the study. The subjects engaged in n-back cognitive tasks (1-back, 2-back, and 3-back) under three distinct physical conditions, involving isotonic contraction of the left upper limb with loads of 0 kg, 3 kg, and 5 kg. Electrocardiogram signals and cognitive task performance were recorded throughout the tasks, and post-task assessment of subjective experiences were conducted using the NASA-TLX scale. Results: The execution of n-back tasks resulted in enhanced perceptions of task-load feelings and increased reaction times among subjects, accompanied by a decline in the accuracy rate (p < 0.05). These effects were synchronously intensified by the imposition of physical load. Comparative analysis with a no-physical-load scenario revealed significant alterations in the HRV of the subjects during the cognitive task under moderate and high physical conditions. The main features were a decreased power of the high frequency component (p < 0.05) and an increased low frequency component (p < 0.05), signifying an elevation in sympathetic activity. This physiological response manifested similarly at both moderate and high physical levels. In addition, a discernible linear correlation was observed between HRV and task-load feelings, as well as task performance under the influence of physical load (p < 0.05). Conclusion: HRV can serve as a viable indicator for assessing mental workload in the context of physical activities, making it suitable for real-world mental work scenarios.
RESUMEN
BACKGROUND: Postural control is adversely affected by mental and physical fatigue, but its validity in fatigue assessment has not been investigated systemically among pilots. We explored the correlations of posturographic balance with physiological and psychological signals among cadet pilots.METHODS: In experiment 1, 37 cadet pilots performed a posturographic balance test, heart rate variability (HRV), and profile of mood states (POMS) during 40 h of sleep deprivation. For experiment 2, physiological signals of 60 subjects, including breathing rate (BR), systolic blood pressure (SBP), and heart rate (HR) were measured under the effects of physical fatigue. Then correlations with a mental and physical fatigue index based on effective posturographic parameters with those subjective and objective methods were analyzed by linear regression.RESULTS: The mental fatigue index correlated linearly with the depression score of the POMS (r = 0.212), standard deviation of normal to normal beats (r = 0.286), and square root of the mean differences of successive beat intervals (r = 0.207). Meanwhile, linear correlations with frequency-domain parameters of HRV such as total power, low frequency power, and high frequency power were also statistically significant. With the increase in the physical fatigue index, physiological signals such as SBP (r = 0.300), HR (r = 0.349), and BR (r = 0.266) increased linearly.CONCLUSIONS: Impairment of postural stability can reflect the aggravation of mental and physical fatigue among cadet pilots, which provides a potential method for assessing fatigue level before flight tasks and preventing errors by pilots.Cheng S, Sun J, Ma J, Dang W, Tang M, Hui D, Zhang L, Hu W. Posturographic balance's validity in mental and physical fatigue assessment among cadet pilots. Aerosp Med Hum Perform. 2018; 89(11):961-966.