Sitting at the computer all day is not exactly good for the body. If you have to be at a desk all day long, doing some simple things can improve your posture and health.
1- Sit properly in a good chair designed for desk work. Your back should be straight, and your head should be looking directly into your monitor. If you have to look down or up, you need to adjust the height of either the screen or your chair. If you keep leaning forward, first get your eyesight checked. If your eyesight is fine use a loose belt or string to tie yourself to the chair. After a while you will improve your posture and no longer need this restraint.
Maintain an ergonomic body posture while typing. Be sure your wrists are slightly lower than your elbows. This will help prevent Carpal Tunnel Syndrome. Keep your legs bent at the knees so that the knees are only slightly higher than your hips. Feet should be flat on the floor or on a step stool of some sort.
Learn to stretch. To stretch your neck, flex your head forward/backward, side to side and look right and left. Never roll your head around your neck. This could cause damage to the joints of the neck.
3- Roll your wrists regularly (this will help prevent carpal tunnel syndrome if you spend a lot of time typing).
4- Recognize that people tend to hunch in front of the keyboard. To counter that, perform the following exercise: open your arms wide as if you are going to hug someone, rotate your wrists externally (thumbs going up and back) and pull your shoulders back. You will feel a stretch in the scapula area.
5- Contract your abdominal and gluteal muscles, hold them there for a few seconds, then release. Do this all day long while you are in your chair.
Stretch your arms, legs, neck and torso while sitting. This will help prevent you from feeling stiff.
6- Take advantage of the downtime created by rebooting or large file downloads to get up and try something more ambitious such as doing a few push-ups, sit-ups, and/or jumping jacks. Beware of your snickering co-workers though.
Acquire a hand gripper. They are cheap, small and light. When you have to read something either on the screen or on paper, you probably won't be using your hands very often so squeeze your gripper. It is an excellent forearm workout.
7- Acquire an elastic band (also cheap, small and light) and use it to do the actions mentioned in step 8 (i.e., when stretching your arms, do it by pulling apart the elastic band). You will not only stretch but it will also work the muscles slightly.
8- Take a few deep breaths. If possible, get some fresh air in your lungs.
9- Invest in a large size stability ball or stability ball style desk chair, and sit on it with back straight and abs firm. The actual stability ball is more effective, however the chair is a more viable option for use in an office environment. Sit, bounce or do basic toning exercises while watching TV or talking on the phone as well. Use the actual ball form in moderation when typing, as this is probably not the most supportive seating to prevent carpal tunnel and tendonitis.
10-While sitting, lift up your legs on the balls of your feet and set them down. Repeat these until your legs are comfortably tired. Then repeat it again about 10 minutes later. Do this whole routine for about an hour or so. This will exercise your calves.
Don't neglect the health of your eyes! It is detrimental to your eyesight to focus at one thing for long periods of time (i.e. your monitor) so take breaks to look out the window and focus at something at a further distance away to maintain good ocular health. Also consider purchasing an LCD screen which is easier on the eyes. Ophthalmologists recommend following the "20-20-20" rule--For every 20 minutes spent focusing on your computer screen, spend 20 seconds focusing on something else 20 feet away.
As long as something is moving, you will be helping to keep yourself in better shape. Constant movement will burn calories and contribute to cardiovascular health. While exercising at your computer is helpful, it is not a substitute for going to the gym or conducting a regular exercise program.
Don't sit still. Fidgeting is a good way to keep moving. Even something like tapping your foot. But don't make too much noise--however you fidget, the repetitive noises may bother other people.
Always have water nearby to drink.
If you're all alone, try shutting off the computer for a bit and exercise. If you're on a cell phone call, get up and do stretches, or leg lifts, anything to keep moving during down time away from the desk.
Try exercises that combine opposing muscle groups (flexors and extensors, e.g., biceps and triceps) to get a good workout. Clasp your hands together with palms facing each other. Pull up with one hand while pushing down with the other.
If you are a runner or jogger, you can sit on the floor and stretch as you use the computer. It will save you time too if you have to do both anyway.
Play music while working to provoke body movement and relieve stress. A smaller instrument will be more convenient.
Your body needs more exercise than just what you do at the computer, but following these steps will contribute to a healthy, balanced lifestyle.
Do not sit at your computer for a long time. Take a break every 15 minutes.
Steps 8 and 9; if not done in moderation, may cause you to start sweating, which may not be a pleasant sight or odor in an office environment. Keep in mind you are doing these to prevent stiffness, so save the enthusiasm for the gym.
From wikihow: http://www.wikihow.com