The possible effects of intense physical exercise on the total body stature of low back pain patients were monitored by circadian total body height measurements. The height was measured with a statiometer, and the change in height was correlated with the changes in the range of motion, pain and subjective disability and degree of disc degeneration seen on magnetic resonance imaging (MRI) pictures. The stature of 24 low back pain patients was measured during a 3-week period. There was an increase of about 3 mm in height after only 4 days of exercise, and by the end of the programme the morning height increased on average by 7.2 mm. There were also 12 non-rehabilitated low back pain patients but no such increase was noted among them. The gain of height and reduction of pain were found to be statistically significantly correlated (P = 0.0001, r = -0.41), as did the gain of height and the decrease of back disability (Oswestry index) (P < 0.0001, r = -0.39). Circadian total height measures but not the MR images will change due to the active back rehabilitation programme.