BACKGROUND Chronic low back pain (LBP) has been reported with a high incidence in elite rowers. It results in less effective training, long interruptions in training, and a drop in performance. OBJECTIVE The authors hypothesized that exercise-induced LBP in rowers is caused by a chronic functional compartment syndrome (CFCS) of the multifidus muscle. METHODS Controlled clinical trial. METHODS The rowers were tested in their training camp. The control group was tested at a university hospital. METHODS 14 volunteer elite rowers complaining of LBP and 16 healthy volunteer amateur athletes. METHODS Intramuscular pressure (IMP), tissue oxygenation pressure (pO2), and median frequency (MF) shift in the electromyographic power density spectrum during isometric fatiguing extension at 60% of maximum voluntary contraction. RESULTS At the beginning (controls 186.6 mm Hg vs rowers 60.2 mm Hg, P = .002) and the end (controls 224.1 mm HG vs rowers 77.1 mm Hg, P < .001) of the endurance exercise the median IMP was significantly higher in the healthy controls. Nearly identical resting pO2 was measured in both groups (controls 37.6 mm Hg vs rowers 37.3 mm Hg, P = .740). Rowers showed higher median MF shift (rowers -11.5 Hz vs controls -8.5 Hz, P = .079) during contraction. CONCLUSIONS These observations cannot sufficiently be explained by the CFCS model and suggest that factors other than IMP have an additional effect on pain generation during exercise in elite rowers.