Rationale: Existing literature suggests an impaired health-related physical fitness (HRPF) (i.e., body composition, aerobic capacity, muscular strength, muscular endurance, and flexibility) in patients with inflammatory bowel disease (IBD). However, previous studies did not assess HRPF with the 5- component multidimensional concept. HRPF is not routinely screened for and measured within the IBD population in clinical practice. The lack of a simple screening tool and assessment method for HRPF validated for the IBD population hinders the ability to distinguish patients with IBD with adequate physical fitness from those who might benefit from physical exercise interventions targeting specific components. Gold standard measures are too expensive and too complex to implement in daily practice and therefore a screening tool and a simpler assessment battery for HRPF validated in patients with IBD are needed. It is necessary to obtain more objective insights into the specific components of HRPF affected in patients with IBD, and its association with patient-, disease-, and treatment-related factors in order to implement systematic screening in routine care and subsequently offer tailored physical exercise interventions.

Objective: The main objective of this study is to validate a simple screening tool and a best-practice assessment battery for the different components of HRPF against gold standard measures. Secondary objectives are to objectively assess the incidence of specific components affected in patients with IBD compared to healthy control subjects and to explore the association between these components of HRPF affected and patient-, disease-, and treatment-related factors.

The study involves one or two study visits for patients with IBD and only one study visit for healthy volunteers. During the first study visit, all participants (n=200) will perform the tests of the assessment battery for HRPF and complete several questionnaires. A representative subgroup of patients with IBD will undergo the gold standard measurements for HRPF during a second study visit. Furthermore, total physical activity measured by accelerometry will be measured in this subgroup of patients.

Inclusion criteria for all participants:

• Any gender aged 18 years or older;
• American Society of Anesthesiologists (ASA) Physical Status I or II (i.e., normal healthy patient or a patient with mild systemic disease)
• No contraindications for exercise testing based on the PAR-Q
• Being able to provide written informed consent;
• Willing and able to complete questionnaires and perform performance tests;
• Being able to understand written Dutch and speak the Dutch language.

Inclusion criteria specific for patients with IBD:

• Certified diagnosis of IBD (UC or CD) based on the combination of endoscopic, radiological, and/or histological findings;
• No active disease or experiencing mild to moderate disease activity.
• Included in eHealth clinical care-pathway using myIBDcoach.

Inclusion criteria specific for healthy volunteers:

• No certified diagnosis of IBD (CD, UC, IBD-Unclassified);

Exclusion criteria for all participants:

• ASA Physical Status > II (i.e., patient with severe systemic disease);
• Contraindications for exercise testing based on PAR-Q
• Other (temporary) injuries or severe (neuro)muscular, rheumatic, or orthopedic conditions that may interfere with study evaluations;
• Current malignancy (except for local cutaneous skin cancer) or successfully treated for a malignancy in the past 6 months;
• Pregnant or lactating women;
• Competitive and elite athletes (i.e., ≥6 hours/week of moderate to vigorous exercise)
• Not being able to understand or speak the Dutch language;
• Not being able to cooperate with test procedures or unable to provide informed consent.

Patients with IBD will be recruited at the gastroenterology outpatient clinic of the Maastricht UMC+. Healthy volunteers will be recruited by means of advertisements in publicly accessible sites such as the hospital, university, and social media, as well as via advertisements as posters in the hospital and university.