Performance level of chronic low back pain patients in different treadmill test conditions.

An experimental group of 39 chronic low back pain (CLBP) patients and an equal number of control subjects matched for age and sex were tested with a standardized back stress physical test. The subjects were given no indication of the performance expected and no feedback was given during the test. The test was repeated with a high frame of reference and feedback offered to the subjects. In the latter condition the control group improved their performance in contrast to the CLBP group. The poorer performance of the CLBP patients in both conditions was unrelated to pain increase, post-test pain level or poor physical condition. However, there is a clear relationship between performance and pre-test pain level, especially in the feedback condition. In this condition, it also seems that increasing pain level during the test is used as a 'rationalization' for the built-in failure experience. Compared to the control group the CLBP patients were less able to estimate their physiological level of exertion and were inclined to overrate their actual effort.