Feasibility of an Augmented Two-Day Step Test and Causal Modeling for Post-Exertional Symptom Exacerbation in Post Covid-19 Syndrome

Difference in oxygen uptake at peak (VO2 peak) between day 1 and day 2 measured with the CPET compared to measured with the Calibre device

The goal is to show that the Calibre device is a feasible alternative to the CPET.

Time frame: From day 1 and day 2 of experimental session 1 to day 1 and day 2 of experimental session 2, one month apart (±10 days)

Difference in Rate of Perceived Exertion (RPE) measured with the CPET compared to measured with the Calibre device

Rate of Perceived Exertion is measured with the Borg RPE Scale which is a subjective measurement instrument. The scores range from 6 to 20, in which 6 is equal to no exertion at all and 20 is maximal exertion.

Time frame: RPE will be measured during two experimental sessions, each with two days, one month apart. On day 1, RPE is recorded 15 minutes (±15 min) before and after the test. On day 2, RPE is measured 24 hours (±120 min) after test 1 and before test 2.]

Resting Energy Expenditure (kcal/kg/day), measured through Indirect Calorimetry (IC)

Measuring Resting Energy Expenditure as part of the Directed Acyclic Graph (DAG).

Time frame: Baseline (measured once, during the first study visit)

Total Energy Expenditure (TEE) in kcal/kg/day, measured through Indirect Calorimetry (IC)

Measuring Total Energy Expenditure as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Phase angle (degrees), measured through Bioelectrical Impedance Analysis (BIA)

Measuring Phase Angle as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Muscle mass (kg/m2), measured through Bioelectrical Impedance Analysis (BIA)

Measuring muscle mass as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Fat mass index (kg/m2), measured through Bioelectrical Impedance Analysis (BIA)

Measuring fat mass index as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Fat-free mass index (kg/m²), measured through Bioelectrical Impedance Analysis (BIA)

Measuring fat free mass index as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Fat to fat-free mass ratio, measured through bioelectrical impedance analysis (BIA)

Measuring fat-free mass ratio as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Hydration (%), measured through Bioelectrical Impedance Analysis (BIA)

Measuring hydration as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Ratio of calorie and protein intake to individual need, measured through food diaries

Adequacy of feeding: the ratio between intake of calories and proteins and the individual need. Record of all food and drinks consumed over a 3-day period as part of the DAG.

Time frame: Between day 1 of study visit and day 1 of experimental session

Mean daily intake of calories, fats, proteins, and carbohydrates, measured through food diaries

Mean daily intake: calories, fats, proteins, carbohydrates Record of all food and drinks consumed over a 3-day period.

Time frame: Between day 1 of study visit and day 1 of experimental session

Oxygen availability as the partial pressure of oxygen (mitoPO2) (mmHg), measured through Near-infrared spectroscopy (NIRS)

Measuring oxygen availability as the partial pressure of oxygen as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Kinesiophobia with the Tampa Scale for Kinesiophobia (TSK)

The Tampa Scale for Kinesiophobia (TSK) consists of 17 statements, each scored from 1 to 4, with 1 being 'strongly disagree' and 4 being 'strongly agree.' Higher scores indicate greater kinesiophobia. Measuring kinesiophobia as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Ability to bounce back after stressful events with the Brief Resilience Scale (BRS) Questionnaire

The Brief Resilience Scale (BRS) consists of 6 statements, each scored from 1 to 4, with 1 being 'strongly disagree' and 4 being 'strongly agree.' Higher scores indicate greater resilience. Measuring resilience as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Coping style with the Ways of Coping (WAYS) Questionnaire

Sixty-six statements about a stressful situation that participants experienced in the past week, for which they need to give a score ranging from 0 to 3, with 0 being "does not apply" or "not used," and 3 being "used a great deal". Measuring coping style as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Autonomic symptoms, measured with the COMPASS-31 questionnaire

Measuring autonomic symptoms as part of the DAG.

Time frame: Baseline (measured once during the first study visit)

Level of Physical Activity (PA) and sedentary behavior assessed by accelerometry (activity tracker)

Using an actigraph, with a frequenncy of 60 Hertz, that participants wear at their hip on their dominant side. Measuring physical activity as part of the DAG.

Time frame: During 7 days before the first experimental session