If you visit any of the many voice over forums online, you'll see conversations about whether to sit or stand as you are recording a voice over. We've all read articles about how unhealthy it is to sit for prolonged periods of time. But beyond that, I believe standing as you record has some solid advantages. However, as always, there are exceptions. If you are narrating an audio book or a lengthy e Learning module, you are more than likely going to sit. But for commercial work, I think standing is the way to go, especially if the copy is quite energized. Sitting while recording an uptempo car commercial would likely hamper you. You need to stand to put some motion into the read with your body. Lately, I've decided to stand in my booth. I do a lot of sitting editing the audio after recording.Bottom line-there is no right or wrong way. Whatever allows you to give your best performance.
Here's a link to a good article on CNN.com about standing desks.