The Pattern of Gripping Force During Bus Driving

János Pórszász, József Tasnádi, István Bereczki and József Varga

National Institute of Occupational Health, Division of Occupational Physiology
 
Corresponding author:
János Pórszász, M.D., Ph.D.
National Institute of Occupational Health
Budapest IX. Nagyvárad tér 2.
1450. P.O.Box 22
Hungary
Tel: (+36) 1-215-7890
FAX: (+36) 1-215-6891
E-mail: 100324.2440@CompuServe.com

CEJOEM 1997, 3:67-80


Key words: Carpal tunnel syndrome, integrated surface electromyogram, gripping force, bus driving

Abbreviations:
CTS: carpal tunnel syndrome
iEMG: integrated surface electromyogram



Abstract: The calculated gripping force, based on the integrated surface electromyogram (iEMG) of the long forearm flexors has been measured on four experienced bus drivers while driving the IKARUS 415 type vehicle equipped with a power steering system. Surface electrodes were secured above the capita of long finger flexors and the iEMG was recorded. The iEMG was recorded under different experimental setups. These included: moving the steering wheel at different angles on stopped vehicle with running engine to insure that the power steering system was operating; slalom driving; driving on an ‘8’-shape; driving on a model path that was constructed on the basis of ergonomical observations and driving in real traffic situation. The gripping force changes followed an impulsive pattern with peak values less than the ergonomically allowed long-term limit for gripping force and with an average duration of less than 4 to 6 seconds, depending upon the task performed. The average calculated gripping force did not exceed the high-risk limit of 4 kp in either task. In real traffic situation the cycle time was about 19 seconds, but the time spent beyond 4 kp did not exceed 5% of the total driving time. According to these results it is concluded that driving the IKARUS 415 type vehicle even under heavy traffic conditions does not represent high enough strain of the finger flexors that could provoke the signs and symptoms of carpal tunnel syndrome.
Received: 10 January 1997
Accepted: 14 February 1997

Posted: 14 December 1998

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