In the last decade, fatigue in clinical populations has been re-conceptualized, including dimensions such as perceived fatigue (trait and state fatigue) and fatigability. The aim of this study was to evaluate different expressions of fatigue in Spinal Cord Injury (SCI) and Multiple Sclerosis (MS) participants compared to able-bodied controls, during activities of daily living, especially during gait.
A total of 67 participants were included in this study (23 with SCI, 23 with MS, and 21 able-bodied controls). All participants performed two functional tests (6-Minute Walk Test and 10-Meter Walk Test) and they completed the Fatigue Severity Scale (FSS). The rate of trait fatigue was different between groups, with MS participants showing the highest rate. Moreover, scores on functional tests and state fatigue were different between groups after the tests. Our results indicate that trait fatigue and state fatigue in individuals with SCI and MS are different with respect to able-bodied population. Both SCI and MS groups experienced more trait fatigue than control group in daily life. In addition, walking tasks produced similar levels of state fatigue between healthy people and patients with MS/SCI. However, these tests induced longer-lasting levels of state fatigue in the patients.
Fatigue is a universal experience and refers to the difficulty in initiating or sustaining voluntary activities, although a universally accepted definition of fatigue has not been reached. However, the knowledge about pathophysiology of fatigue is limited1,2. In healthy subjects, fatigue is a physiological reaction to a prolonged and/or intense physical activity. Fatigue is task-dependent, it reduces with rest and usually does not interfere with daily activities3.
However, individuals with certain pathologies describe fatigue as an overwhelming sense of tiredness at rest, exhaustion with activity, lack of energy that precludes daily tasks, inertia, or loss of vigor4. The prevalence of fatigue is high in many neurological illnesses. It occurs in over 50% of community-dwelling people with Spinal Cord Injury (SCI)5. Fatigue is also the most common symptom in Multiple Sclerosis (MS), affecting up to 90% of patients during their life. Two-thirds of patients describe it as their most disturbing symptom6.
In these patients, the effects of fatigue on function may create an additional barrier to community reintegration; therefore, fatigue needs to be better understood to improve treatment in these patients7. Scientific research on fatigue includes several terminologies used inconsistently in the literature8. Fatigue is a widely used term that refers to several meanings, causalities, and dimensions: amongst the latter “the perception of fatigue” and “performance fatigability”9. The perception of fatigue is divided into “state fatigue” and “trait fatigue”10. “State fatigue” has been defined as a person’s self-reported transient sensation of weariness or “subjective feeling” of diminished capacity during or right after exercise9,11,12.
It has been measured by an analog of the Borg scale to assess state fatigue right after exercise9,13. “Trait fatigue” refers to a frequent, prolonged sensation of fatigue experienced during the preceding several days and can be assessed by the Fatigue Severity Scale (FSS)14,15. This questionnaire measures the impact of fatigue on functional disability and has been shown to be internally consistent, and sensitive to clinical changes7,16. On the other hand, fatigability is an objective decline in performance (force development, power, speed, reactivity, or accuracy) observed during cognitive or motor tasks2,9,17. What remains unclear is whether fatigue (trait fatigue and state fatigue) and performance fatigability are similarly affected in MS and SCI18,19. The aim of this study was to evaluate perceived fatigue and performance fatigability during a functional daily task (walking) in two pathological (SCI & MS) and able-body groups of participants. We hypothesize that patients would have greater trait fatigue, greater fatigability while walking as well as larger levels of state fatigue than able controls.