Abstract
BACKGROUND AND OBJECTIVE: Inflammatory bowel disease (IBD) fatigue aetiology is poorly understood. This study quantified body composition and physical function alongside proton magnetic resonance imaging (1H MRI) and spectroscopy (31P MRS) measures of organ structure and function in quiescent Crohn's disease patients (CD) and healthy volunteers (HVs), to identify a physiological basis for IBD fatigue. METHODS: Body composition was determined using dual-energy X-ray absorptiometry and 1H MRI. Knee extensor isometric strength and isokinetic fatigue were measured using dynamometry. 1H MRI was used to quantify cardiac output, cerebral blood flow (gmCBF), and brain oxygen extraction fraction (OEF) at rest, and during supine, steady-state exercise, and recovery. 31P MRS was used to quantify post-exercise muscle phosphocreatine (PCr) resynthesis. RESULTS: Sixteen CD and 12 HV (age, sex, and BMI matched) were recruited. Fatigue perception was greater (13.9 ± 1 vs 8.3 ± 0.9, P = .001), and daily step count was less (5482 ± 684 vs 8168 ± 1123, P = .04) in CD. During steady-state exercise, gmCBF was less in CD (653 ± 30 vs 823 ± 40 mL/min, P = .003). Cardiac output and brain OEF were no different. Post-exercise PCr resynthesis was less in CD (17.2 ± 2.0 vs 25.3 ± 2.4 mM·min-1, P = .02). Body composition, isometric strength, and isokinetic fatigability were no different. CONCLUSIONS: CD self-reported increased fatigue perception and exhibited a slower rate of post-exercise PCr resynthesis compared to HV. This occurred independently of changes in body composition, muscle strength, and fatigability. IBD fatigue may be linked to peripheral muscle deconditioning and lower gmCBF during submaximal exercise.