In the middle of the spasm, she thought her back might break.

She thought if she tried to move anything else, her back would break.

The thing was very heavy, and he thought his back would break under the strain.

I thought how their backs must have been breaking.

The back of her open hand impelled into his cheek and more bones broke!

Yet he could not crawl through the way he had begun, or his back would break.

Under the sun their backs had broken into a sweat unrelieved by three day's march.

My back is breaking, too, because of this huge man that dances atop me.

Two days later, during salvage efforts, her back broke, and she was completely wrecked.

Practically broke the back of the rebellion on your own.