Abstract
BackgroundFatigue is a common symptom in both sick and healthy people. We examined autonomic nervous alterations associated with fatigue to clarify the mechanisms underlying fatigue.MethodsThe study group consisted of 19 healthy participants who performed a 2-back test for 30 min as a fatigue-inducing mental task session. Before and after the session, they completed the advanced trail making test (ATMT) for 30 min for mental fatigue evaluation, subjective scales to measure fatigue sensation, and underwent electrocardiography to allow assessment of autonomic nerve activities.ResultsAfter the fatigue-inducing task, the total error counts on the ATMT tended to increase (P = 0.076); the ATMT for total trial counts (P = 0.001), the subjective level of fatigue (P < 0.001), and the % low-frequency power (%LF) (P = 0.035) increased significantly; and the % high-frequency power (%HF) decreased compared with before the fatigue-inducing task although this did not reach the statistical significance (P = 0.170). Although LF measured in absolute units did not change significantly before and after the fatigue-inducing task (P = 0.771), and HF measured in absolute units decreased after the task (P = 0.020). The %LF and LF/HF ratio were positively associated with the daily level of fatigue evaluated using Chalder's fatigue scale. In addition, %HF was negatively associated with the fatigue score.ConclusionsIncreased sympathetic activity and decreased parasympathetic activity may be characteristic features of both acute and daily levels of fatigue. Our findings provide new perspectives on the mechanisms underlying fatigue.
Highlights
Fatigue is a common symptom in both sick and healthy people
Just before and after the fatigue-inducing session, they recorded their subjective sensation of fatigue on a visual analogue scale (VAS) from 0 to 100 [26] and underwent electrocardiography (ECG) with their eyes closed for 1 min while sitting on a chair
After the fatigue-inducing task, the total trial counts of the advanced trail making test (ATMT) (P = 0.001) indicating that they became faster after the fatigue-inducing task, subjective level of fatigue (P < 0.001), and %low-frequency power (LF) (P = 0.035) increased significantly, whereas %high-frequency power (HF) decreased this did not reach statistical significance (P = 0.170)
Summary
Fatigue is a common symptom in both sick and healthy people. We examined autonomic nervous alterations associated with fatigue to clarify the mechanisms underlying fatigue. Fatigue-related alterations of autonomic nerve activities have been reported in patients with chronic fatigue syndrome (CFS) [6,7,8,9,10,11], multiple sclerosis [12,13,14], and primary biliary cirrhosis [9,15]. These reports suggest that changes in autonomic nerve activity are related to the mechanisms underlying fatigue. This relationship has been demonstrated only in patients with specific diseases and not in healthy subjects
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