Playing Upstrokes

This is a 1.47 minute video response from Mark Lincoln on Feb 3rd, 2009

Question:

"Lucasholland asked "Hello, is it necessary to strike all the strings belonging to a chord when doing an upstroke? I read somewhere that only the treble strings have to be played when doing upstrokes (and all of the strings for downstrokes). Is that correct or do all of the strings that belong to a chord have to be strummed when doing an upstroke? Thanks and keep up the excellent work, Lucas.""