Fatigue But Not Fatigability Is Prominent In People With Post-covid-19

Abstract

PURPOSE: To compare fatigue and fatigability in people with and without post-COVID-19 symptoms. METHODS: COVID-19 survivors were divided into a fatigue group (F; n = 18, 13 females, age = 32 ± 15 years) and a non-fatigue group (NF; n = 11, 8 females, age = 32 ± 15 years) based on the Chalder Fatigue Scale (scores ≥6 = fatigue). Perceived fatigue and fatigability were assessed with the Fatigue Severity Scale (FSS), Fatigue Assessment Scale (FAS), Visual Analog Scale for Pain (VAS) and a quality-of-life questionnaire (EQ-5D-5L) and an isokinetic fatigue task (FT) was performed to objectively assess leg muscle fatigability of the right and left knee extensors and flexors. A torque-derived fatigue index (FI-T) was calculated as: ([mean of first five reps - mean of last five reps]/mean of first five reps)*100 and a work-derived fatigue index (FI-W) was calculated as: (total work performed in the last half of the FT/total work performed in the first half of the FT)*100. RESULTS: Compared to the non-fatigue group, the fatigue group reported significantly higher scores on the FSS (F = 30 ± 7.03, NF = 15.45 ± 4.50, p < 0.01), FAS (F = 5 ± 1.15, NF = 1.98 ± 0.56, p < 0.01), VAS (F = 29 ± 22.66, NF = 6.45 ± 15.10, p < 0.01), EQ-5D-5L Utility (F = 1 ± 0.3, NF = 0.96 ± 0.09, p < 0.01) and EQ-5D-5L Overall Health (F = 67 ± 18.92, NF = 87.18 ± 7.44, p < 0.01) scores. Interestingly, there were no significant differences between the FI-T and FI-W for the right and left knee extensors and flexors (all p ≥ 0.10). Moreover, the FSS, FAS, VAS, and EQ-5D-5L scores were not associated with the fatigability indices (all p ≥ 0.27 and r ≤ 0.27) in the fatigue group. CONCLUSION: Although subjects with post-COVID-19 symptoms self-reported greater fatigue than people without post-COVID-19 symptoms, they demonstrated similar objective fatigability. This suggests that the level of fatigue experienced by people with post-COVID-19 at a specific time might be derived from the interoceptive networks that influence body homeostasis. People with post-COVID-19 might have a reduced capacity to accommodate a challenge to homeostasis, which appears to be responsible for elevated levels of fatigue.