Sentence:  Mr. Claude is a specialist in torso development and he has long favored the now famous Weider Push-Pull Super-Set technique in which one exercise of the Super-Set is a pressing or `` pushing '' movement which accents one sector of a <WSD>muscle</WSD> group in a specific way , followed by a `` pulling '' exercise which works the opposing sector of the same muscle group . 
Meaning of the word marked with <WSD> tags:  one of the contractile organs of the body