Stress? Very little stress of any sort while riding a recumbent bike. Kind of stressful having to pedal to keep moving forward, but that's the nature of cycling, kind of the whole object.
The seats that I use support my back and butt very nicely. Any road vibrations that reach me are spread out over a large area, as opposed to just the areas around the sit bones, as on an upright bike.
No stress on my hands, wrists or arms as I am not leaning on them --> they support no weight.
No kind of cycling builds upper body or core strength; that requires work away from the bike.

I don't ride 'bents because of back problems; I just enjoy them and very much appreciate the comfort that is inherent to most 'bent designs.