The classic sitting position, adopted by all dentists, has an iatrogenic (or accidentally harmful) effect on the spinal column. Dynamic sitting positions appear to be less iatrogenic. One of the chairs offered to us most recently is the Bambach Saddle Seat. Using global electromyography, we studied the muscular activity that it causes and compared it to that required by the classic sitting position. The subjects in this experiment were 18 dentists who simulated conservatory dental work on a lower premolar. The muscles we examined were the trapezium, the large right-hand abdominal muscle, the spinal muscles, and the quadriceps. The results obtained showed a slightly superior muscular activity on this chair, principally in the dorsal muscles, but no radical change in the posture compared with the classic sitting position. The higher sitting position of this chair, the stability of its scat, and its great mobility appears to be less iatrogenic than other sitting positions. M.Th. VERKINDERE, C LACOMB, and J.PH. LODTER Faculty of Dental Surgery University of Toulouse 3, Chemin des Maraichers 31400 Toulouse, France Electromyographic study of the dynamic sitting position suitable for dentists In our 20th century/ the sitting position has become the general working position, for school children/ students, secretaries, and even manual labourers - including dental surgeons. It was adopted by dentists in the 1960s, and was regarded as progress when compared with the standing position. Nevertheless, this sitting position is the cause of vertebral pathologies, most frequently in the lumbar region, Rhuematological studies have demonstrated that maximum pressure is exerted an the vertebral discs: 100 kilos in the case of a stated man weighing 70 kilos (Nachemson, 1975). Inclining the seat changes the pressure; a horizontal seat, the one used most often, places a pressure on the vertebral discs far greater than that exerted when the seat is EXTRACT FROM ID [L'INFORMATION DENTAIRE] VOL. 80 No. I2, 26 MARCH 1 998 PPS 911-91 6. TRANSLATED FROM FRENCH

tilted at an angle of 15° (Leiong etal., 1988). These rheumatological studies led us to study and compare two sitting positions available to the dentist: • the classic sitting position • a dynamic sitting position on a Bambach Saddle Seat (Fig. 1). We carried out an electromyographic examination on the same subjects, first in the one posture and then in the other, under the same working conditions. The experiment was carried out using global integrated electromyography with an Alvar Reega XVI computer and a 4-channel Aivar integrator. The electrical potential thus derived is measured for a period...

The two sitting positions studied were the classic and dynamic positions. The classic sitting position was that resulting from sitting on a chair with a low, horizontal seat (46 cm from the floor). The movements of the hip and the knee resulted in an angle of 90° and the feet were flat on the floor. The dynamic sitting position (defined by Reissner) is higher - 65 to 80 cm from the floor - and the movements of the hip and the knee resulted in an angle of 130° once again, the feet rested flat an the floor. The chair tested was the Bambach Saddle Seat; as its name suggests, its seat takes the form...

Abdominal Spinal Muscle Convent. Saddle Seat % var. pot. The values shown are in millivolts seems only logical that it should be more active when the back is held in a more vertical posture. The dorsal, spinal and great dorsal muscles displayed greater potential in 13 subjects at rest and 16 subjects at work. These muscles play a vital role in holding the spinal column erect. A higher and straighter posture stimulates their activity. The musculature of the back is regarded by rheumatologists as a positive element in preventing vertebral pathologies (Table V). On the abdominal muscles, at rest,...

Spinal Muscle Convent Saddle Seat In an earlier study, we compared a classic sitting position with a kneeling position (Yerkindere et al., 1992 and 1993). Sitting in a kneeling position, subjects displayed a complete loss of electrical potential in the same muscles and under identical experimental conditions to than in this study. When the subject is sitting on a chair that allows a kneeling position, the pelvis and the legs are supported and the weight of the body rests partly on the iliac crests and partly on the knees themselves; there is no flat contact with the floor, and the legs have no...

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