I always use my serger standing up. Usually I have a longer area of straight sewing to do when using the serger so standing is less back breaking. The only other machine I use standing is my Brothers 1500se on a Grace Frame. It sometimes is hard on the back and so I take periodic rest periods. I don't think I would like to do piece working for making blocks or piecing a quilt together or for FMQ standing up. Good question for a physical therapist.