Firefighting crew walking in a line near a truck.

Wildland firefighting and other forms of field work demand a high level of fitness to safely perform arduous, day-long work in difficult environmental conditions, including steep terrain, extreme temperatures, altitude, and smoke, and to meet unforeseen emergencies. When prolonged hard work is involved, fitness is the most important factor in work capacity.

Firefighter working the ground with a long handled tool.

Work capacity is a composite of fitness, acclimatization, nutrition, skill, experience, motivation, and intelligence. Fitness is the most important factor. Most wildland firefighters must meet minimum levels of fitness requirements for the type of duties they are assigned.

Firefighters marching in a line up a trail with tools and gear.

Some jobs, like firefighting, require passing a job-related Work Capacity Test to meet minimum qualifications. Such tests help ensure that prospective workers have the capacity to perform work without undue fatigue and without becoming a hazard to themselves or coworkers.