STUDY DESIGN: Two-way repeated-measures analysis of variance. OBJECTIVE: To assess pelvis and trunk three-dimensional segmental excursions and coordination differences during walking and running between runners with low back pain (LBP), runners with resolved LBP, and a control group with no history of LBP. SUMMARY OF BACKGROUND DATA: Studies have documented differences in pelvis and trunk coordination between those with moderate to severe LBP during walking. Few studies document pelvis and trunk mechanics in those with low to moderate LBP and individuals who recover from LBP even though these individuals comprise 80% of LBP cases and are at increased risk for re-injury. METHODS: Recreational runners walked and ran on a treadmill at speeds including 0.8 to 3.8 m/s at 0.5 m/s increments. Pelvis and trunk kinematic data were collected during the last 20 s of each stage. Coordination analysis quantified the portion of gait cycle each group spent in trunk only motion, pelvis-only motion, in-phase, and antiphase relationships. RESULTS: During walking, the LBP group spent more of the gait cycle in-phase in the frontal plane (P = 0.030). During running, the LBP group showed greater pelvis axial rotation than the control group (P = 0.014) and spent more of the gait cycle in-phase in the transverse plane (P = 0.019). Also during running, the LBP (P = 0.035) and the resolved LBP (P = 0.037) groups demonstrated reduced antiphase coordination compared to controls. CONCLUSION: Coordination analysis demonstrates a reduction in relative motion between the pelvis and trunk despite low disability levels in our LBP group and no pain in our group with a history of LBP.