How do you measure levels of fatigue?

Levels of fatigue can be measured using self-report questionnaires, such as the Fatigue Severity Scale (FSS) or the Multidimensional Fatigue Inventory (MFI), which assess subjective feelings of tiredness and energy levels. Objective measures may include actigraphy, which tracks physical activity and sleep patterns, or performance tests that evaluate cognitive and physical functioning. Additionally, physiological indicators like heart rate variability and cortisol levels can provide insights into fatigue. Combining these methods can offer a comprehensive view of an individual's fatigue levels.