This week we're kicking off a four-part question and answer series with our My Beauty Life fitness expert, personal trainer Brooke Marrone. A lifelong fitness fanatic, Marrone is excited to have the opportunity to share her passion for exercise with Total Beauty readers.

This week's question is one that all of us who work in an office can certainly relate to. Ann from Michigan wanted information on "isometric exercises I can do at my desk." Marrone says that, "If you have a job where you are sitting at your desk for most of the day, it is definitely important to take mini breaks for stretching and moving your body." Here are the moves she recommends:

Chair leg extension: Sit up straight in your chair with your shoulders back and abs pulled in. Lift your right leg one inch off the floor, trying to keep your right knee at about a 90-degree angle. Extend your leg out straight with your foot flexed, not locking your knee. Feel a good squeeze in your quad and return to your starting position. Do 20 reps with each leg a few times a day.

Seated plank or ab squeeze: Sitting in your chair with your feet flat on the floor and shoulders back, draw your belly button into your spine and hold for about 5 seconds. Do a few sets of 10 throughout the day. Make sure you continue to breathe and don't let your shoulders roll forward.

Ab holds: Sitting up straight in the middle of your chair make sure you keep your shoulders back and abs in at all times. Lift your feet a few inches off the floor and hold for about 10 seconds. You can also try to keep your knees squeezed tightly together throughout this exercise for some additional inner thigh work. It's important to make sure that you are not leaning back into your chair or you will most likely work your back more than your abs -- and not in a good way!

Inner thigh: Place a small towel or book between your knees. Squeeze and release without ever completely letting go of the object. Do a few sets of 50 throughout the day.

Marrone also says that sitting at a desk and working on a computer all day can contribute to poor posture. Here's what she suggests to reverse the damage ...

Sitting up straight, squeeze your shoulders down and back and hold for 5 seconds. While you do this, keep breathing and pull your abs in. Do a few sets of 10. You can also do the same type of move with your arms out straight in a T position: Pull your shoulders down and back, hold that same shoulder blade squeeze for 5-second intervals.

There you have 'em -- your "stay fit at your desk" moves. Be sure to check back next week when Marrone will share her suggestions for "toning up wobbly arms."