Work can be hard for a fitness nut. Sitting at a desk for hours at a time is the exact opposite of what our bodies want to be doing. Unfortunately, unless you're a personal trainer or professional athlete, "exercise" probably isn't what's paying the bills. Most of us, however, have a wonderful slice of time scheduled into our work day called the lunch break. This is one of the best times of day to shake off the stiffness of your office chair and get the blood pumping again. Not only do lunch break workouts help keep you in shape, but they also combat workplace fatigue while keeping your brain sharper. Here are five of the most effective lunch break workouts you can try next time you're clocking out to grab a bite.