Specificity is the answer. You are targeting a certain muscle in your body to improve it for an upcoming sport or activity like running a marathon or entering a Mr.Olympian body-building competition.
Found this online hope it helps!
Encontró esta esperanza en línea que ayuda!
http://www.un.org/esa/socdev/unyin/documents/ch04.pdf
I did not write this, please dont give me credit for document.
<span>No escribí esto, por favor, no me dan crédito por el documento.</span>
True, you do not want to start an exercise with tight joints and muscles.