Two points - first, i believe studies have shown lifting free weights is the only exercise that improves bone density
Walking is said to be the best overall exercise but does nothing for bone strength.
And then we have to talk about satin sheets. True it's easier to move around, but your pillow will not stay in place. As you move, it slides. Anchoring a part of your body, like putting your knees up, forget it. Crawling your way into a sitting position - uh-uh. And if you think it's romantic and might benefit the 'sexual' experience, think again
They are good for a laugh.
D