OBJECTIVE: We aimed to examine the extent to which current perceived demand for energy and affect predict subsequent physical activity and fatigue in people with Long Covid using an intensive longitudinal method (ecological momentary assessment). METHODS: Analysis of data from a study of 69 adults with self-reported Long Covid combining 3-hourly self-report data perceived energy, and fatigue, on a smartphone app with continuous physical activity recording. We tested three hypotheses derived from cognitive behavioural and neuroscientific models of fatigue. These related to expectation, current affect and recalled emotional demand. Analysis used linear mixed effects models with fatigue and physical activity as outcomes. RESULTS: Expectation of energy need for the next 3 h was predictive of physical activity, fatigue and recalled demandingness of the period. (p-values 0.005 to <
0.0001). Currently feeling positive was predictive of slightly more subsequent physical activity and less fatigue 3 h later (p = 0.01). Feeling negative was not predictive of physical activity or subsequent fatigue but was predictive of subsequent recall of the period being emotionally demanding. Feeling more anxious was predictive of greater fatigue 3 h later (p = 0.001) but not of reduced physical activity. Absolute effects were small: a one-point increase in anticipated demand (on a scale of 1-7) was associated with an extra 2.2 min of moderate or vigorous physical activity and a one standard deviation increase in anxiety was associated with a one-point increase in fatigue (0-100 scale). CONCLUSION: In the day-to-day experience of Long Covid expectation and affect have little detectable effect on subsequent physical activity or fatigue.