RD is correct about this...while the distinction is often misunderstood - there is a trend here - although some arts often not classified as internal such as Bajimen or SanPowChuan (sp) use 'internal' mechanics...
But Coach Ross is correct also that this is a recent concoction or distinction - check Adam Hsu's 'Sword Polishers Record' for a great essay on this point...
"Never interrupt your enemy when they are making a mistake."
--- Napoleon
"MonkeySlap is a brutal b@stard." -- SevenStar
"Forgive them Lord, they know not what MS2 can do." -- MasterKiller
"You're not gonna win a debate (or a fight) with MST. Resistance is futile." - Seven Star