CONCENTRIC AND ECCENTRIC STRENGTH OF TRUNK MUSCLES - INFLUENCE OF TEST POSTURES ON STRENGTH AND CHARACTERISTICS OF PATIENTS WITH CHRONIC LOW-BACK-PAIN

The purpose of this study was to determine the influence of test postu res on trunk muscle strength, and to clarify the difference between co ncentric and eccentric strength of healthy subjects and patients with chronic low-back pain (CLBP). Volunteered and controlled trials took p lace at a university hospital, which is a referral center and is also open to the general community. The patients were selected from the out patient care in the university hospital. Fifty healthy subjects (25 me n and 25 women; average age 25.7 years, ranging from 23 to 34 years) a nd 48 patients with CLBP (26 men and 22 women; average age 33.5 years, ranging from 26 to 39 years) volunteered for this study. The main out come measures were flexor and extensor peak torque/body weight, and fl exor/extensor peak torque ratio during concentric and eccentric contra ctions; Eccentric/concentric peak torque ratio in flexor and extensor, Trunk-muscle strength was significantly greater in the sitting postur e when measured with the subjects' feet against the floor (p < .05). S ome patients complained of a slight low-back pain during testing, alth ough the pain was not aggravated in any patients. In both concentric a nd eccentric contraction modes, the patients with CLBP had greater fle xor/extensor ratios than the healthy subjects (p < .01). This implies that extensors are more affected in these patients. However, a great i mbalance between concentric and eccentric strength of the patients was found, not only in extensors, but also in flexors (p < .01). The curr ent study shows that one should consider the test posture carefully wh en measuring trunk-muscle strength. This study also suggests that char acteristics of trunk-muscle strength in patients with CLBP is extremel y complicated when being considered in terms of eccentric contraction mode. (C) 1995 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation