Background:Low back pain causes disuse and physical deconditioning, and increases disability, and may turn simple low back pain into a chronic low back pain.
Methods: Twenty subjects who suffered from low back pain entered to the study and were randomly divided in Case (low back pain group) and control group. Also 10 healthy subjects were entered to the study as a sham group. After ten minutes rest and recording of rest, cardiovascular responses of studied subjects in two exercises: Straight Partial Sit-Up (SPSU) and Oblique Partial Sit-Up (OPSU) were studied. Then the case group went through a four week regime of the exercises and cardiovascular responses of the exercises were recorded in three groups.
Findings: Systolic and diastolic blood pressure changes of LBP subjects in comparison to healthy people (p < 0.05) but heart rate changes of LBP subjects are not significantly different (p > 0.05). After the 4 weeks of training period, cardiovascular responses in low back pain test group in comparison to the beginning of the study reduced.
Conclusion: It seems that the differences between cardiovascular responses of low back pain patients and healthy subjects are due to deconditioning theory. These patients during the same exercise activity like healthy peoples use more efforts that lead to more cardiovascular responses. The reduction of exercise cardiovascular responses after the training period in the case group indicates an increase of muscle strength and decrease in central comments for motor units' recruitments, which show cardiovascular adaptation and conditioning procedure in these subjects.

Key words: Low back pain, Physical deconditioning, Cardiovascular responses, Training.