Study Design. A prospective single-arm trial.
Objective. To investigate whether dynamic isolated resistance training of global lumbar extensor muscles leads to changes in lumbar multifidus (LM) morphology in terms of cross-sectional muscle, and, if so, whether these changes are associated with observed changes in self-experienced functional status of chronic nonspecific low back pain (CNSLBP).
Summary of Background Data. LM morphology is associated with the recurrence of CNSLBP.
Methods. Sixteen male patients underwent a dynamic isolated resistance-training program for the lower back muscles of approximately 10 sessions in 12 weeks. In the next 12 weeks, frequency of training was tailored to the patients' need. Participants underwent lumbar magnetic resonance imaging at baseline (T0), after 12 weeks (T12), and after 24 weeks (T24). Functional cross-sectional area was obtained by analyzing the magnetic resonance images. Functional status was assessed using the patient-specific functional scale, Roland-Morris disability questionnaire, and global perceived effect scale.
Results. Roland-Morris disability questionnaire and patient-specific functional scale scores showed significant and clinically relevant improvements between baseline and T12, with 44% and 39%, respectively. Between T12 and T24, these scores did not change significantly. Seven participants (44%) reported clinically relevant improvements in global perceived effect at T12. At T24, 1 more participant reported a relevant global perceived effect improvement, whereas 2 participants (13%) reported worsening of their condition. The magnetic resonance imaging analysis showed minor nonsignificant changes in functional cross-sectional area.
Conclusion. Our study shows that 10 weeks of dynamic isolated training of the lumbar extensors, once a week, leads to clinically relevant improvements in functional status of men with CNSLBP, without accompanying improvements in functional cross-sectional area of LM. These findings suggest that improvement in LM morphology is not a critical success factor in restoring functional status of patients with CNSLBP, at least in the short term (6 mo).