Because if there's any part of your body that doesn't need protection, it's your chest.
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Fantasy author Jim C. Hines decided one day to pose like the women on the cover of his novel, "The Stepsister Scheme." After realizing how awkward posing like that was, he decided to recreate other poses from fantasy book covers.
"I spent the rest of last night with pain running through most of my back. Even the pose in The Shape of Desire, which first struck me as rather low-key, is difficult to imitate and feels really forced. Trying to launch my chest and buttocks