Are you asking for the word
Answer:
Principles
Explanation:
"Specificity and progression" are two principles related to maintaining physical health. Therefore we can say that the word "principles" is the most suitable to replace the word "thing".
Also, "Specificity and progression" are neither exercises nor muscles. Nor are they acronyms, since an acronym is the word formed by joining letters or initial syllables of a group of words, pronounced as one word.
<span>A food that offers specific health benefits beyond those supplied by the traditional nutrients it contains is called a functional food.</span>
