Investigation into the Compressive Stress on Lumbar Spine among Tractor Drivers during different Ride Conditions

Abstract

The aim of this investigation is to figure out the stress (compressive) on the lumbar spine of tractor driver posture among different ride conditions i.e., RPM (Revolutions per minute), Postures, and Road Conditions). The spinal stress under various riding conditions was assessed using the daily equivalent static compression dose (Sed). Design Expert, a statistical programme that combines Taguchi’s L9 Orthogonal Array Method, is used to determine the experimental runs with different parameters such as varying the tractor speed in RPM (700, 1000 & 1300), driver posture (Lean forward without backrest-P1, vertical erect without backrest-P2, vertical erect with backrest-P3), selected road conditions (village road, brick road and farm road). Analysis of the overall influence of riding conditions among all the experiments was done by calculating signal-to-noise (S/N) ratios. A regression model has been developed to analyze the Sed response and the desirability technique was used to minimize the Sed response. The daily dose of static compression on lumber spine was found between 0.35 and 0.67 MPa, which comes within the category of “moderate adverse health effect” as defined by ISO2631-5: 2004. Statistically, the RPM and Road type conditions were found highly significant with the percentage contribution is 77% and 21% respectively. As comfort is crucial for the tractor driver. The Sed values can be used for tractor seat design for more comfort. The approach is novel as per the Indian context for the tractor driver’s comfort. The methods of work-study and sampling in a larger context are well established.