The purpose of this study was to compare the effects of two methods of inversion therapy and four common exercise positions on the shape of the low back. We studied 25 healthy subjects in six exercise positions: 1) inverted with lower limbs extended (ILLE), 2) standing, 3) supine, 4) inverted with lower limbs flexed (ILLF), 5) sitting, and 6) hooklying. A manual measurement system was used to determine low back contours (LBCs) from S2 upward for 19 cm at 1-cm intervals. Contour data were reduced to mean contour values (MCVs). Results showed that the standing and sitting positions produced the largest and smallest MCVs, respectively (p less than .01). The ILLF MCV was smaller (p less than .05) than both supine MCVs but not appreciably different from the ILLE MCV. The ILLE and ILLF positions significantly reduced (p less than .01) MCVs compared with the standing position. Neither position decreased the MCV as much as the sitting position. These results support the use of inversion therapy to reduce the depth of the LBC when sitting is inappropriate.