WebMD.com offers these short aerobic exercises that can improve your heart rate right in your office. Each exercise can be done for 60 seconds, and you can choose to do one or more of these.
Option 1: Stand up and do jumping jacks for 60 seconds. Don't worry about breaking any speed or height record with your jumping - the goal is to get yourself moving, and slow jumps will work just as well as quick jumps.
Option 2: Run in place for 60 seconds. Livestrong.com suggests that you consider pumping your arms, placing them above your head, or holding them straight out to the sides for effective muscle contraction.
Option 3: Simulate jumping rope. Jump from the balls of your feet to achieve the best muscle activity.
Option 4: Pump both arms over your head 30 seconds, then rapidly tap feet on floor, football style, for 30 seconds.