I am 52 yrs. Old, weight 133 at 5'8" tall. I am tall and skinny and I need to tone up but I have herring rods attached to my spine where I had back surgery as a teenager. I can't life weights so how do I tone up without hurting my back.

I suggest you invest some time and money in a professional to set you up with a program that you can stick with. Either a chiropractor or a personal trainer. That person should speak with your Dr. to get a complete picture of what your condition is. In my experience you need to do exercises that allow you to keep your torso on a flat surface... supporting your spine.