Sentence:  So right away Claude introduced Henri to his famous `` moon '' bench and proceeded to teach him his first Push-Pull Super-Set consisting of the wide grip Straight-Arm Pullover ( the `` pull '' part of the Push-Pull Super-Set ) which dramatically widens the rib cage and strongly affects the muscles of the upper <WSD>back</WSD> and chest , and the collar-to-collar Bench Press which specifically works on the chest to build those wide , Reeves-type `` gladiator '' pecs , while stimulating the upper lats and frontal deltoids . 
Meaning of the word marked with <WSD> tags:  the posterior part of a human (or animal) body from the neck to the end of the spine