Sentence:  Great emphasis should be placed on <WSD>sensitizing</WSD> the hands to the feel of the water, and the hands should remain <WSD>sensitized</WSD> throughout the workout....Swimmers should <WSD>sensitize</WSD> the hands at the beginning of every workout by swimming the first 200 meters with their fists tightly clenched. 
Meaning of the word marked with <WSD> tags:  To make (someone or something) sensitive or responsive to certain stimuli.