Methods Four hundred participants with cLBP were randomized to 4 doses (n = 100/group). Participants were seen three times per week for six weeks, receiving 0, 6, 12, or 18 sessions of SMT, and a light massage control on visits without manipulation. Data were collected until 52 weeks after randomization. Outside care outcomes included prescription and non-prescription use, and treatments outside of the study including the following healthcare providers: chiropractor, primary care physician, surgeon, neurologist, psychiatrist, naturopath/ homeopath, nurse practitioner, acupuncturist, physical therapist / occupational therapist, or massage therapist. Preliminary analysis used the chi-square test or Fisher’s exact test of categorized data as appropriate.