Measuring Physiological Workload and Vehicle Movement While Driving Timber Forwarders in Both Forward and Reverse Travel

Physiological workload during timber forwarder operations presents a heavy burden due to the unpaved forestry occupational roads, and steep terrain in Japan; however, the relationship between physiological workload and vehicle movement is not clear. To assess the workload of operating forwarders, changes in heart rate and vehicle movements were measured. Five male subjects aged 35 to 53 years were assessed. The subjects were tested twice while operating a forwarder with an empty load: first driving forwards, then driving in reverse. Three inertial measurement units were used to calculate travel speed, tilt angle, and turning speed, and heart rate was assessed using a wearable heart rate sensor. Vehicle movement and heart rate were synchronized every 10 s. The subjects' average heart rates ranged from 69.09 to 87.63 bpm, which was higher than when traveling on paved forest roads. The physiological workload, based on %HRR results, was greater during reverse travel, possibly due to blind spots and road obstacles such as roots or branches. Additionally, %HRR increases with travel speed during forward travel; however, the %HRR remained high even at low speeds during reverse travel. Furthermore, forward travel tends to keep the vehicle level, whereas reverse travel involves bumps due to sudden operational changes. It is crucial to enhance machine performance and structure in the future to reduce workload, improve visibility, and minimize blind spots.