Sentence:  It speeds muscle <WSD>growth</WSD> and power development even for the advanced bodybuilder because each hip and leg is exercised separately , thus enabling a massive , concentrated effort to be focused on each . 
Meaning of the word marked with <WSD> tags:  (biology) the process of an individual organism growing organically; a purely biological unfolding of events involved in an organism changing gradually from a simple to a more complex level