Sentence:  It entered her body with the ghastly intimacy of an incubus , and its particles , spreading , creeping , crawling , joined themselves into steel bands that constricted her knees so tightly that they <WSD>ached</WSD> ; stifled her lungs so that her breath came in harsh gasps ; clutched her throat and sucked up the moisture in her mouth so that her tongue was dry and hard and stuck to the roof of her mouth and her teeth were clenched together in the rigid fixture of her jaws . 
Meaning of the word marked with <WSD> tags:  feel physical pain