Since the COVID-19 pandemic began, rehabilitation facilities have seen an influx of
patients suffering from Post-COVID Syndrome (PCS), also referred to as postacute sequelae
of SARS-CoV-2 infection (PASC).

PCS is characterized by symptoms persisting for more than 12 weeks post-infection,
including chronic cognitive and motor fatigue, muscle pain, headaches, balance issues,
autonomic dysfunction, sleep disturbances, and memory difficulties. Chronic fatigue
syndrome (CFS), while lacking a universally accepted definition, can be understood as an
intense fatigue that interferes with daily activities and worsens under stress. Patients
often describe a significant lack of mental energy and muscle strength, with prolonged
recovery times following physical exertion. The presence of Post-Exertional Malaise
(PEM), which exacerbates symptoms after inadequate physical or mental activity, further
complicates the clinical picture, causing overlap with symptoms of myalgic
encephalomyelitis/chronic fatigue syndrome (ME/CFS).

The impact of PCS and chronic fatigue on patients' occupational, educational, and social
activities can be as severe as that seen in other chronic illnesses, such as multiple
sclerosis or cancer, leading to substantial economic burdens. Therefore, the demand for
effective rehabilitation approaches is critical. However, managing fatigue presents
challenges, as it may limit both the number and effectiveness of therapy sessions. It is
essential to balance activity levels to prevent exacerbation of symptoms, making energy
management a key component of therapeutic guidance.

The cognitive behavioral approach of "Pacing," which encourages patients to maintain a
manageable level of activity without worsening symptoms, has been suggested for ME/CFS
management. The PACE trial indicated that cognitive behavioral therapy and graded
exercise therapy could support effective pacing, though these findings have sparked
debate. A recent meta-analysis found that pacing interventions significantly reduced
fatigue and psychosocial distress, particularly when participants were encouraged to
gradually increase physical and cognitive activities. Nevertheless, there is a call for
further randomized controlled trials (RCTs) using standardized pacing methods over longer
durations, as current practices vary widely.

A retrospective analysis involving 86 PCS patients indicated that adherence to pacing, as
measured by the Engagement in Pacing subscale (EPS), correlated with quicker recovery and
symptom improvement. This aligns with recommendations to avoid both overexertion and
underexertion in PCS cases. Consequently, graded exercise therapy may not be suitable in
this context.

Diaries can serve as valuable tools for individuals to document their health experiences
over time, revealing symptom and behavior trends with less recall bias compared to
traditional questionnaires. In various medical fields, diaries have proven useful for
evaluating behavior and therapy efficacy. With the rise of digital applications, tracking
health behaviors has become more accessible, offering substantial data for analysis.
However, a validated PCS-specific diary, created in collaboration with PCS patients, is
currently lacking.

The present study aims to develop such a diary to monitor energy levels of patients with
PCS throughout their rehabilitation process, hypothesizing that it will effectively
document the impact of different therapies on daily energy levels.