Maximum isometric trunk muscle strength and activity at trunk axial rotation during sitting

✍ Scribed by Anna Torén; Kurt Öberg

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 384 KB
• Volume: 30
• Category: Article
• ISSN: 0003-6870
• DOI: 10.1016/s0003-6870(99)00012-5

✦ Synopsis

This study was performed to provide information relating to the twisted posture being characteristic of the driver of an agricultural tractor working in the "eld. The relationship of trunk axial strength and muscle activity to trunk twisting angle of prerotation was determined and quanti"ed. Di!erences between tractor drivers and o$ce workers, and between the two directions of twisting action were also studied. Nine male tractor drivers and nine male o$ce workers performed isometric maximum e!orts at about !40, !20, 0, 20 and 403 of pre-set trunk twisting angles in both the clockwise and counterclockwise directions. Exerted torque, true angle of prerotation and muscle activity from left and right side of each of obliquus externus, rectus abdominis and erector spinae were measured simultaneously. The results showed that the subjects could exert the greatest torques when being prerotated in the opposite direction and the lowest torques when being prerotated in the same direction to the direction of exertion. The exerted torques were within the range of 65 } 145 Nm. There were large di!erences in obliquus externus and erector spinae activity due to the twisting direction. There were also changes in muscle activity from obliquus externus and rectus abdominis due to prerotation angle. The results raised questions concerning the involvement of the passive tissues and the use of deeper muscles during trunk axial rotation, which should be further investigated.