JMIR Publications

ABSTRACT

Background:

Post-COVID fatigue affects millions globally, yet evidence-based management strategies remain limited. Activity pacing—regulating activity to match energy availability—may support symptom management, though optimal pacing approaches are unclear

Objective:

To explore associations between activity pacing strategies delivered through a mobile app and daily fatigue levels in individuals with post–COVID fatigue.

Methods:

In this exploratory observational study, 19 adults with post-COVID fatigue over the period of 3 months used wearable devices (Fitbit) for objective activity monitoring and a mobile application (FatigueSense) to report daily self-reported symptoms (fatigue and energy levels) and optionally select activity pacing goals (Light, Balanced, or Active). We examined associations between pacing strategies and symptom outcomes using mixed-effects linear models with random intercepts. Same-day outcomes (fatigue and energy reported on the day of goal selection) were analyzed, controlling for age and sex. Next-day outcomes (fatigue and energy reported the day following goal selection) were analyzed, controlling for age, sex, and prior-day symptoms.

Results:

Across 2,182 observation days, participants self-selected pacing goals on 816 days (37%), demonstrating symptom-responsive behavior with higher baseline fatigue on pacing days (mean fatigue 1.74 vs 1.58 on non-pacing days on a 0-3 scale where 0=none, 3=severe; p=0.004). Among pacing days (n=584 with complete data from 18 participants), Active pacing was associated with reduced same-day fatigue (β=-0.34, 95% CI [-0.49, -0.19], p<0.0001) and increased same-day energy (β=8.8, 95% CI [4.7, 12.9], p<0.0001) compared to Light pacing. Balanced pacing also showed significant reductions in fatigue (β=-0.15, p=0.008) and increases in energy (β=5.8, p=0.0002) compared to Light pacing. Next-day effects were attenuated and non-significant. Individual heterogeneity was substantial, with an intraclass correlation coefficient (ICC) of 0.32, indicating that 32% of variance was attributable to between-person differences and 68% to within-person variation. Among participants trying multiple strategies, 58% showed meaningful responses (≥0.3-point fatigue reduction, representing ≥10% improvement on the 4-point scale) to structured pacing strategies.

Conclusions:

Structured activity pacing strategies (Active, Balanced) are associated with improved same-day symptom management in post-COVID fatigue. However, substantial confounding-by-indication (self-selection of pacing based on symptom state) and individual heterogeneity limit interpretation. These exploratory findings warrant testing in randomized controlled trials to establish efficacy and identify responder characteristics.