Many jobs require constant physical activity, or place people in danger if they aren't able to act quickly on their feet. For that reason, CareerCast, in its compilation of the most stressful and least stressful occupations for this year, puts military occupations on the top of its list. (Update: Here is a list of the 15 most rewarding jobs this year as well.)

There are a few surprises, such as public relations executives, who apparently have as much on-the-job stress as people who face life-or-death situations, at least according to CareerCast's rating system. Here are the 10 most stressful occupations, followed by a list of the 10 least stressful occupations.

Enlisted military personnel: Among the most dangerous jobs, at relatively low pay levels. Median salary: $41,998 (E-7, 8+ years experience). Military general: The pay is much better than it is for enlisted personnel, but so is the weight of responsibility. No mention of lower-grade officers such as colonels, captains or lieutenants, however. And it's not clear if their Navy counterparts, admirals, also experience as much stress. Median salary: $196,300. Firefighter: Potentially as dangerous as being in the military. Median salary: $45,250. Commercial airline pilot: You would think that all the computers on board, planes would fly themselves. But there are lives on the line if you make a mistake, and many hours away from home. Median salary: $92,060. Public relations executive: Huh? This probably depends on who you are working for -- perhaps if it's a politician under indictment, or a company that just caused a big oil spill, there is no shortage of stress. But still a head-scratcher how this is ranks the fifth most stressful occupation in the world. Median salary: $57,550. Senior corporate executive: Not as much fun as it used to be. No more practicing putting on the office carpet, as you see in old movies. Nowadays, you need to show revenue growth. Median salary: $101,250. Photojournalist: Soldiers have the most stressful jobs, but often, photojournalists have to follow them into combat. Wages are notoriously low, too. Median salary: $29,130. Newspaper reporter: It's about deadlines, deadlines, deadlines. And an ability to confront public and corporate officials making ten times your salary. Median salary: $36,000. Taxi driver: Long hours, unruly passengers and endless traffic jams. What's not to love? Median salary: $22,440. Police officer: Surprisingly not on top of the list with firefighters, and ranked lower than public relations executives on the stress scale. Median salary: $55,010.

Here are the top 10 least stressful jobs for this year:

University professor: Never mind the politics, and classrooms of non-responsive students -- it's a nice place to be. Median salary: $62,050. Seamstress/tailor: Most work in peaceful atmospheres. Median salary: $25,850. Medical records technician: Most work behind the scenes, away from the commotion and illness within healthcare settings. Median salary: $32,350. Jeweler: You work with gold and diamonds all day. Median salary: $35,170. Medical laboratory technician: No distractions, you can concentrate on analyzing lab specimens all day. Median salary: $46,680. Audiologist: You set your own hours, and patients are generally cooperative. Median salary: $66,660. Dietitian: You deal with food all day long, and help people eat right. Median salary: $53,250. Hair stylist: You work in a fast-paced environment, but usually catch people in their best moods. Median salary: $22,500, but tips can be very generous. Librarian: Work in a quiet place surrounded by books and digital resources -- not too shabby. Median salary: $54,500. Note: Check out the comments on the CareerCast page for this category. One librarian begs to differ, saying this "serene" ranking perpetuates a stereotype. Librarian jobs are actually quite hectic, dealing with tight budgets while wearing many hats in efforts to provide a range of services. Drill press operator: Probably not in the most relaxing atmosphere, but it's safe and you can work at your own pace. Median salary: $31,910.

(Thumbnail photo credit: James Martin, CNET.)

This post was originally published on Smartplanet.com