Background: Chronic low back pain (CLBP) is a major health concern characterized by paraspinal muscle fatigability. This can be improved following a functional restoration program. Muscle fatigability can be related to impairment in aerobic metabolism responses. In this study, we investigated paraspinal muscles aerobic metabolism in CLBP patients before and after a functional restoration program, in order to determine if the enhancement in patients' condition following the program is associated to changes in metabolism responses.
Methods: Twenty-two CLBP patients (11 women, 11 men; 41.6±1.8 years; 73.7±3.1 kg; 1.74±0.02 m) were evaluated before and after a 4-week functional restoration program, with exercise therapy as the main component. Three months later, 12 patients were seen for a follow-up visit. During each testing session, patients performed a five-minute isokinetic trunk extension exercise in measuring pulmonary gas exchanges and paraspinal muscle oxygenation. Mechanical efficiency and onset V̇O<inf>2</inf> kinetics were also calculated, in addition to usual questionnaires and exercises designed to evaluate psychosocial and physical factors.
Results: At the end of the program, paraspinal muscle oxygenation, mechanical efficiency, and the V̇O<inf>2</inf> onset kinetics were improved (P<0.05). All measures remained stable during the three-month follow-up except for paraspinal muscle oxygenation, which deteriorated (P<0.05). Return-to-work was associated with the level of workday physical activities and to a decrease in fear-avoidance beliefs.
Conclusions: At the end of the program, aerobic metabolism responses were improved in paraspinal muscles in patients. These improvements were not associated with return-to-work, which was primarily influenced by socio-psychological factors.