What they do all day? Sometimes it takes a paid professional to slog you through endless squats, push-ups and burpees -- or just to get you to the gym at 6 a.m. You can thank your personal trainer for that.

How to get the job? Certification from a recognized school or organization (such as the American Council on Exercise) is the biggest asset, although strictly speaking, it's not required. Self-starters are also welcomed, since trainers more or less supervise themselves.

What makes it great? With obesity rates on the rise, trainers are in a position to change someone's health for the better -- and for the long haul. They can also work in a variety of settings beyond the gym, from hospitals to corporate wellness departments to clients' homes to outdoor boot camps.

What's the catch? Most people exercise before work, at lunchtime and after work -- so trainers might be on the job at 5 a.m. or 8 p.m. -- or both. They also may not get benefits, depending on the employer. --K.A.