Muscle Fatigue as a Measure of Work Stress in Tractor Operation

Abstract

Tractor driving is more strenuous than any other vehicle operation, where, nearly half the energy of the driver is spent in bracing himself against the seat and damping out jerks. This, along with the extreme conditions of temperature, humidity and solar radiation, impose tremendous stress on the operator’s health and working efficiency. An insight into the muscle fatigue of the operator can be gained through study of electrical activity of the concerned muscles. This muscle fatigue study could be used as an indicator to assess the stress level of the operator. Considering the movement in the hand-arm and whole body system in tractor operation, four muscles of handarm viz., flexi carpi radialis (FCR), extensor digitorum (ED), brachio-radialis (BR) and middle deltoid (MD) and four body muscles on the right side of trunk, viz., trapezius- superior region (UT), trapezius- intermediate region (MT), latissimus dorsi (LD) and erector spinae (ES) were selected for the current study. The average value of muscle load in terms of reference voluntary electrical (RVE) activity was observed to be the highest in FCR (15.14%) and the lowest in BR (4.44%) in transportation operation. The frequent turning of the trunk during field operation have resulted in higher load on UT muscle. A decrease of the median power frequency (MPF) of all the muscles with time was observed, which indicates muscle fatigue during tractor operation. The study indicated that work stress assessment in tractor operation could be done through muscle fatigue analysis, which needs to be reduced by suitable interventions.