Using an under-desk treadmill can be more convenient than using a standing desk. Standing desks require you to stand the entire day, which isn't always possible or comfortable. Under-desk treadmills allow you to work while you walk, which is more comfortable and can help you burn more calories. Under-desk treadmills are also good choices for those who already have a standing desk and simply need a treadmill to put underneath. Again, this is a less expensive option than buying a separate desk and treadmill.