Assessment of firefighters-rescuers' work severity in relation with interaction between physical and mental load

The present work is focused on occupational health problems caused by ergonomic risk in firefighting, which is one of the most hazardous occupations. The aim was to evaluate the work heaviness degree and to estimate the muscle fatigue for a study group consisting of 12 firefighters-rescuers. Applying qualitative ergonomic analyses (OWAS a.o.) and clinical experiments to determine consumed metabolic energy using heart rate monitoring, the following work hardness categories were observed: firefighter-rescuer — category III (hard work, 8.2 ± 1.2 kcal/min); commanding officers — category II (moderate work, 6.0 ± 1.6 kcal/min). Assessment of muscle strain and functional state (tone) using myotonometric measurements showed several muscle tone levels, allowing subdivision of firefighters into different conditional categories basing on muscle tone and fatigue: I — a state of equilibrium when muscles are able to adapt to the work load and are partly able to relax; and II — muscle fatigue and increased tone. It was also found that the increase of muscle tone and fatigue mainly depended on workers physical preparedness and length of service, and less on their age. Assessment interaction of mental and physical load using NASA-TLX method indicated that the highest degree of total workload was for several firemen, especially, commanding officers when temporary demands, task performance, effort and frustration were taken into consideration.