Non-invasive Approaches to Identify the Cause of Fatigue in Inflammatory Bowel Disease Patients.

Measurement of maximum voluntary isometric contraction of the quadricep muscle on a cybex isokinetic dynomometer. This will be followed by a fatigue assessment where the torque decrement over 20 isokinetic knee extensions at a fixed angular velocity will be quantified to assess muscle fatigue

Body composition will be assessed via DEXA scan (Lunar Prodigy, GE Medical Systems, Bucks, UK)

VO2 peak will be quantified during completion of a continuous, incremental exercise test performed in the supine position on an MR adapted stepper machine (Ergospect, Innsbruck Austria)

Measurement of cardiac output and, cerebral and regional perfusion using Blood-Oxygen-level-dependent (BOLD) measures and arterial spin-labelling (ASL)-MRI as well as fractional oxygen extraction using TRUST-MRI during supine exercise of the quadriceps with the MR compatible cardiostepper (Ergospect, Innsbruck, Austria) at 50% of relative VO2 peak as measured during the supine cardiorespiratory fitness assessment.

Limb blood flow will be occluded with a cuff, whilst participants perform repeated plantar flexion exercise in a MRI scanner. This will drive PCr, (the available reserve of ATP) to zero. Once the cuff is removed, they will undergo non-invasive and well-established in vivo 31P magnetic resonance (31P MRS) measurements on the gastrocnemius to determine PCr re-synthesis rate during resting recovery.