Low back pain is a common but severe health problem. Chronic low back pain accounts for the bulk of the burden of low back pain. Exercise interventions are effective in the management of chronic low back pain. Current clinical thinking in physical therapy treats low back pain as a heterogeneous entity seeking to match specific interventions to subpopulations. None of these subgroups assess the role of gluteus medius dysfunction in chronic low back pain. These projects seek to describe the prevalence of gluteus medius weakness in people with chronic low back pain and test the effectiveness of a gluteus medius strengthening exercise intervention in people with chronic low back pain. Gluteus medius strength was assessed in 150 people seeking care for chronic low back pain and 75 healthy people without low back pain. Gluteus medius was found to be weaker on affected sides compared to unaffected sides within people with chronic low back pain and weaker than people without low back pain. Gluteus medius weakness was a strong predictor of the presence of low back pain. A gluteus medius strengthening program was compared with lumbar stabilization exercises in 56 people with chronic low back pain. Although there was a clinically significant improvement in pain in people who performed the gluteus medius strengthening exercise program, this was not significantly different from the stabilization exercise intervention. Adherence to exercise was significantly correlated with reduction in pain and perceived improvement of low back pain. Although gluteus medius weakness is common in people with low back pain and treating this weakness with a targeted exercise intervention is effective, it is not better than a standard stabilization exercise intervention. Doing exercise is likely more important than what exercise is done.