Researchers write publications in formal language using specialized terminology of their disciplines. To find relevant papers, terms that researchers are likely to use in their publications need to be chosen as keywords for searching, as opposed to popular words.
For example, someone searching for articles about sports physiology is more likely to be successful in searching for "endorphins" rather than in looking for "runner's high."
Subject encyclopedias can be good sources of background information and terminology in use within the disciple and subject area of interest. Also look for subject headings and keywords listed in search results of articles similar to what you are interested in finding.
Try a variety of terms and combinations, including synonyms or related terms to refine and focus your search. Searching for relevant and quality sources of information is an iterative process. Use what you find in early searches to inform and refine future searches.