The purpose of this study was to determine the influence of 2 different periodized exercise rehabilitation programs (resistance training [RT] and aerobic training [AT]) on musculoskeletal health, body composition, pain, disability, and quality of life (QOL) in chronic (>or=3 months; >or=3 d.wk) nonspecific low-back pain (CLBP) persons. Twenty-seven CLBP subjects were randomly assigned to 1 of 3 groups, 1) RT (n = 9), 2) AT (n = 9), or 3) control (C; n = 9). Subjects were tested at baseline and at weeks 8 and 16 of training. Intensity and volume were periodized in the training groups. Significance was set at p <or= 0.05. No significant differences were noted among the groups at baseline. The RT group significantly decreased body fat percent from baseline to week 8 and from baseline to week 16, whereas the AT group significantly decreased body fat percent and body mass from baseline to week 16. The RT group significantly improved most musculoskeletal fitness, pain, disability, and QOL outcomes from baseline to week 8, baseline to week 16, and weeks 8 to 16. However, the AT group showed significant improvements in flexibility from baseline to week 8 and in cardiorespiratory and peak leg power from baseline to week 8 and baseline to week 16. The AT groups showed no significant improvements in pain, disability, or QOL. The primary finding was that periodized RT was successful at improving many fitness, pain, disability, and QOL outcome measures, whereas AT was not. This study indicates that whole-body periodized RT can be used by training and conditioning personnel in the rehabilitation of those clients suffering with CLBP.