The purposes of this study were to monitor the integrated electromyographic activity of the erector spinae (ES) muscles and to measure lumbar curvature (LC) during static and dynamic postures in three chairs--a Balans Multi-Chair (BC), and office chair (OC), and a straight-back chair (SBC)--and during standing. Integrated electromyographic data were recorded in relaxed and erect postures at L2 and L5 in 20 volunteers. Lumbar curvature was measured with a flexible ruler. Analyses of variance for repeated measures (p = .05) and paired t tests were used to compare the IEMG and LC measurements. During relaxed postures, there was more IEMG activity and greater LC in standing than in the OC or the SBC. During erect postures, there was more IEMG activity in standing than in the OC and no difference in LC between chairs. The IEMG activity at L5 was greatest on the left side across chairs. In typing and writing, significant differences in IEMG activity were found between sides, but not between chairs. The LC was greater in the BC than in the SBC in relaxed sitting, typing, and writing. The pattern of IEMG activity is not similar to corresponding LC measurements. Care and prevention of low back injury is a critical focus in physical therapy. The BC could contribute to treatment. Further research is needed to support its use in back care programs.