Using Heavies

I’ve been playing k.i for about a month now & 1 thing i can’t understand is when i do heavy attacks in my combos it causes either a juggle state or a combo to end prematurely however i was wondering if i had to actually hold either light or mediums to get a heavy attack instead of just pressing it & how long do i have to hold the button down?

In order to do a heavy linker just hold any button that isn’t a hard attack down (hold LP or LK or MP or MK). Doing a special move with a hard attack as a linker will turn it into an ender. Hard attack specials are always enders.

^^ much appreciated i always get combo breakered because of that