NEW YORK ( MainStreet) — Sitting in the office is one of the worst things you can do for your health

As Brian O'Connell reported for TheStreet last year, "Silicon Valley Syndrome," which comes from sitting at a desk all day staring at a PC screen, can kill you. The U.S. Library of Medicine estimates it makes you 49% more susceptible to death, from diabetes and heart disease.

The cure, as always, is exercise. You need 150 minutes of it each week, at minimum, and you can probably use more.

But say you're ambitious, you have a long commute, or (like me) you just like to work. What can you do?

The answer is a healthier desk. Instead of sitting there thinking, you could be walking, or your legs could be riding a bike. The cost is less than you think.

If you're a bicyclist, and especially if you ride a recumbent, where you lean back low to the ground, Amazon has a host of desk cycles you can put on the floor, below your desk, with which to simulate bicycle riding.

These range from the $35 Stamina InStride Cycle XL , which has a small display showing how much time you spend peddling and a knob that lets you adjust how hard you ride, to a $150 DeskCycle, which can work with desks as low as 27 inches high, includes 8 pre-calibrated resistance levels, and features a five-function display you can link to an online calorie counter.

When you're ready for a real bicycle desk, the FitDesk FDX 2.0 costs just $300 and will let you sit upright (using more muscles than if you're leaning back). It includes both room for your laptop and a storage draw for pens and pads.

You don't have to be doing the Tour de France to get something out of one of these things. Nutri-Strategy estimates the calorie burn rate from even very-light stationery bike riding at 177 to 279 per hour, depending on your weight, but the company's calculator maxes out at 205 pounds, so I must be doing even better! As with any form of exercise, start slow and build slowly. If you can just pedal slowly for a couple of hours each day, instead of just sitting there, you're getting the equivalent of a hard half-hour gym workout.

If you'd rather just take a walk - and who wouldn't - your task starts with a higher desk.

And forget walking. Just standing can be good for you. According to a study the BBC did with the University of Chester, standing burns as many as 50 calories each hour. Do that three hours per day, five days a week and you've worked off 750 calories, as much as two regular gym visits. Over the course of one year, that's the equivalent of running ten marathons.