Chronic low back pain sufferers exhibit freezing-like behaviors when asked to move their trunk as fast as possible

BACKGROUND CONTEXT: The effect of chronic low back pain (CLBP) on the kinematic parameters of trunk motion has received much more interest in this last decade. However, there are no descriptions of the motor strategies that occur when patients perform trunk movements in the three anatomical planes at different pace conditions. PURPOSE: To investigate motor strategies used by CLBP patients and asymptomatic people while performing different go and back trunk movements in an upright standing position. STUDY DESIGN: A comparative study. PATIENT SAMPLE: The control group (CG, n=33) included 14 men and 19 women with no history of low back pain, and the chronic low back pain group (CLBPG, n=49) included 21 men and 28 women. OUTCOME MEASURES: Kinematic data were analyzed during six trunk movements: flexion, extension, left and right lateral bendings, and rotations under two pace conditions (preferred and fast paces). METHODS: A three-dimensional optoelectronic motion analysis system was used to assess static (trunk inclinations and base of support) and dynamic (range of motion [ROM] and mean angular velocity of the trunk) parameters during the go and back phases of trunk movements. RESULTS: In the initial position, CLBPG showed a more forward-tilted trunk inclination (2.1 degrees +/- 1.1 degrees, p=.013) compared with CG. The base of support was significantly higher in CG (+22.7 cm(2), p=.009) during the fast pace when compared with the preferred pace. Regardless of the pace condition, ROM and mean angular velocity of the trunk were significantly lower in CLBPG for all examined movements and the pace condition did not significantly alter ROM. At the preferred pace, both groups displayed the same motor strategy: they all went faster during the second phase of movement than during the first phase. However, at the fast pace, while CG was going faster during the first phase than during the second, CLBPGmaintained the same motor strategy as at the preferred pace. CONCLUSIONS: Contrary to CG who changed its motor behavior from a preferred pace to a fast pace, CLBPG exhibited freezing-like behaviors. This original result highlights the importance of studying the velocity. The use of this parameter may improve the diagnosis of CLBP patients and could be a key indicator for treatment progress and long-term monitoring. (C) 2014 Elsevier Inc. All rights reserved.