Interest of isometric F/E ratio to determine deconditioning syndrome in chronic low back pain patients (CLBP).

OBJECTIVE: Is it possible to substitute the isokinetic tests by isometric tests to determine back muscle deconditioning syndrome in CLBP patients?

PATIENTS AND METHODS: Thirty-five CLBP patients, of a 39.7 years median age, 14 females and 21 males, included in a program of the type trunk reconditionning carried out the isokinetic and isometric tests on dynamometer CONTREX 2000*. The isometric tests were carried out with 15°, 30° and 45° of inflection of the trunk with and without correction of gravity. The data were collected to be analyzed by the test of correlation of Pearson. The sensitivity and the specificity of the isometric test were calculated.

RESULTS: Without correction of gravity, the correlation to 15°, 30° and 45° of flexion between the isokinetic and isometric tests was for the flexor muscles respectively of 0.94, 0.84 and 0.79 and for the extensor muscles of 0.58, 0.62 and 0.48. With correction of gravity, it was for the flexor muscles of 0.82 to 15 and 30° and 0.72 with 45° of flexion, whereas it was for the extensors of 0.67, of 0.72 and 0.67, respectively for the same angles. The best correlation for ratio F/E between the isokinetic and isometric tests was obtained with 30° inflection without correction of gravity and proved very poor of 0.51.

DISCUSSION/CONCLUSION: The correlations of the peak of force of flexor were very good whereas those of the extensor muscles are weaker. The correlations for the flexor/extensor ratio were poor. With the results of this study the use of the isometric ratios does not seem relevant to identify back muscle deconditioning syndrome, such as usually definite with inversion isokinetic ratio (flexor/extensor).