Fig. 1. Vehicles used in the experiment to evaluate the load environment of truck drivers. From top left A. Tatra 815, C. Tatra Phoenix I and down B. and D. Tatra Phoenix II.

Fig. 2. Example record obtained physiological biosignals from electromyogram (EMG), galvanic skin response (SCL) measured on the hands, body temperature measured peripherally (ST) and heart rate (PF) - Example from measuring cycle No. 12. View larger in new window/tab.

Fig. 3. Comparison of the course of the change in muscle load expressed in μV of electric potential in order of working routes when driving a timber truck with trailer and a logging truck without trailer.

Fig. 4. Analysis of variance of dependence of values of muscle load (a) and heart rate (b) on type of vehicle used. Driving a logging truck with trailer increases muscle strain by approximately 22% and heart rate by approximately 6% compared to driving a logging truck. The average and limit values for the monitored vehicle types are displayed. The variance of the limits of measured values is ±2.8% for both muscle load and heart rate.

Fig. 5. Analysis of variance of dependence of values of muscle load (a) and heart rate (b) on number of years’ experience. The number of years’ experience significantly reduces muscle load and heart rate, but only until the moment when the effect of long-term hard work on the organism begins to manifest itself and subsequently the physical and mental load on the organism increases, up to the level of load with little years’ experience. The average and limit values for the monitored number of years’ experience displayed. Differences in muscle load range in the variance of the average values are up to 18% (the variance of the limits of measured values is ±6.8%); for heart rate, the variance is up to 3.6% (the variance of the limits of measured values is ±2.1%).

Fig. 6. Analysis of variance of dependence of values of muscle load (a) and heart rate (b) on height of operator. The dependence of muscle load and heart rate on body height is related to the relationship between body height and workplace ergonomics. A shorter driver will expend more energy reaching for controls and steering. The average and limit values for the monitored body heights displayed. Differences in muscle load range in the variance of the average values are up to 15% (the variance of the limits of measured values is ±6.6%); for heart rate, the variance is up to 3.6% (the variance of the limits of measured values is ±1.7%).

Fig. 7. Analysis of variance of dependence of values of muscle load (a) and heart rate (b) on weight of operator. The dependence of muscle load and heart rate on body weight is related to the relationship between body weight and workplace ergonomics. The lower weight of the driver increases their physical workload when controlling the vehicle i.e. the need to use more force to control the vehicle. The average and limit values for the monitored body weights displayed. Differences in muscle load range in the variance of the average values are up to 15.2% (the variance of the limits of measured values is ±7.3%); for heart rate, the variance is up to 3.6% (the variance of the limits of measured values is ±1.9%).

Fig. 8. Analysis of variance of dependence of values of muscle load (a) and heart rate (b) on phase of work shift. The dependence of muscle load and heart rate on the phase of the work shift did not show significant differences in load. The average and limit values for the monitored phases of work shift displayed. Differences in muscle load range in the variance of the average values are up to 6.4% (the variance of the limits of measured values is ±5.4%); for heart rate, the variance is up to 1.2% (the variance of the limits of measured values is ±1.5%). The middle part of the work shift, when work performance is at full capacity, shows the expected highest load. The loads at the beginning and at the end of the shift were lower because, at these times, empty vehicles were moved to the pick-up points or the empty vehicle was returned from the dispatch warehouse to the parking area.