What does period mean at the end of a sentence?
The stronger your core the easier your YRG(yoga) is gonna get period
I didn't heard the sentence clearly because of the speaker's American accent.
Period in the context that you are referring to is used as an idiom of sorts. It means there is no counter argument.
For example, "Chuck Norris will kick anybody's butt, period."
"Abstinence from sex is the best STD prevention, period."
There is usually a pause after the sentence and before the word "period".
Another thing that Americans say instead of "period" is "end of story".
The stronger your core the easier your YRG(yoga) is gonna get, end of story.
'Period' is the puncutation mark known in British English as a full stop. Used as it is in the example, it means that there is no more to be said on the subject.