The action of the column extensor muscles has been studied through in the electromyography in various corporal postures. We verified the electromyography responses of the iliocostalis lumborum muscle during various movements and positions. 12 individuals males, sedentary, between 36 and 52 years old (average 46.16), weighing an average of 79.66 kilos, and with an average height of 173.0 cm, all working as drivers were studied. Electromyography with six channels and surface electrodes was used. The electrodes were placed on the right side of the trunk in the direction of the third and fifth lumbar vertebrae ICL2 and (ICL1 respectively). In orthostatic position, the flexion movement presented RMS 31,18 (±5,73) in ICL1 and 58,10 (±14,81) in ICL2; in extension the RMS 32,46 (±9,17) in ICL1 and 55,31 (±16,70) in ICL2; in homolateral rotation the RMS 30,05 (±10,60) in ICL1 and 53,29 (±19,70) in ICL2; in heterolateral rotation the RMS 24,76 (±5,99) in ICL1 and 44,79 (±15,26) in ICL2. In seated in a chair without a back, the flexion presented RMS 22,42 (±2,89) in ICL1 and 43,39 (±5,68) in ICL2; in extension the RMS 22,47 (±1,95) in ICL1 and 41,28 (±6,20) in ICL2; in homolateral rotation the RMS 24,10 (±3,97) in ICL1 and 47,94 (±5,80) in ICL2; in heterolateral rotation, the RMS 22,59 (±1,95) in ICL1 and 43,15 (±5,71) in ICL2. In the position seated on the ground, the flexion presented RMS 22,83 (±3,00) in ICL1 and 50,99 (±11,19) in ICL2; in extension the RMS 22,39 (±3,22) in ICL1 and 46,44 (±8,19) in ICL2. The results are expressed in RMS, indicating the participation of the iliocostalis lumborum muscle during the movements undertaken. The place identified as ICL2 presented action potential of greater amplitude than the place identified as ICL1 in all movements and positions.434241249Andersson, G.B.J., Chaffin, D.B., Pope, M.H., Occupational biomechanics of the lumbar spine (1984) Occupational Low Back Pain, pp. 38-67Örtengren, R., Myoelectric back muscle activity during sitting (1974) Scandinavian Journal Rehabilitation, (SUPPL. 3), pp. 73-90Herberts, P., Quantitative electromyographic studies of back muscle activity related to posture and loading (1977) Othopedic Clinics of North America, 8 (1), pp. 85-95Asmussen, E., The weight-carrying function of the human spine (1960) Acta Orthop. Scand., 29, pp. 276-290Bankoff, A.D.P., Moraes, A.C., Lopes, M.B.S., Salve, M.G.C., Ferrarezi, M.P.S., Electromyographic study of iliocostalis lumborun, longissumus dorsi and spinalis thoracic muscles in various positions and movement (2000) Electromyographic and Clinical Neurophysiology, (40), pp. 345-349Basmajian, J.V., (1976) Electrofisiologia de la Acción Muscular, , Buenos Aires: PanamericanaDe Luca, C.J., (1985) Muscles Alive: Their Functions Revealed by Electromyography. 5 ed, , Baltimore: Williams & WilkinsFloyd, W.F., Silver, P.H.S., The functions of the eretores spinae muscles in certain movements and postures in man (1955) Journal Physiology, 129, pp. 184-203Gonçalves, M., Cerqueira, E.P., Levantamento manual de carga em diferentes níveis de altura, com e sem o uso de cinto: Estudo eletromiográfico (1996), Tese de Doutorado. Instituto de Ciências Biomédicas da Universidade de São PauloGray, H., (1977) Anatomia. 29 ed, p. 83. , Rio de Janeiro: Guanabara KooganJonsson, B., The functions of individual muscles in the lumbar of part of the spinae muscle (1970) Electromyography, 10, pp. 5-21Kippers, V., Parker, A.W., Postural related to myoelectric silence of erectors spinae during flexion (1984) Spine, 9 (9), pp. 740-745Kumar, S., Narayan, Y., Zedka, A., An electromyographic study of unresisted trunk rotation with normal velocity among healthy subjects (1996) Spine, 21 (13), pp. 1500-1512Lee, C., Minatami, H., Ju, K., Wakano, K., Onishi, S., Yamasaki, H., Fatigue evaluation of lumbar muscles during repeated dynamic trunk exercise (1996) Electromyographic and Clinical Neurophysiology, (36), pp. 237-245Masseli, M.R., Camargo, A.M., Berzin, F., Electromyographic study of the longissimus dorsi and iliocostalis lumborum muscles during knee flexion and extension on a plain and on a tilt Roman table (1994) Electromyographic and Clinical Neurophysiology, (34), pp. 309-314Portnoy, H., Morin, F., Electromyographic study of postural in various positions and movements (1956) Am. J. Physiol., 186, pp. 122-126