They changed the history after the event. In the first film he delivers electric shocks to Adam, which he couldn't do if he was unable to move.
(I take it we aren't bothering with spoiler tags in this thread.)
In fact the opening makes no sense whatever way you look at it. Lawrence says something like, "It's no use shouting, I've tried", which makes it clear he was awake before Adam and has been for a little time before the movie starts. Yet he didn't hear Jigsaw moving around? Or Amanda, if you think she was there (in which case, how did she leave when Lawrence was right by the door?). Remember also that Adam's head was completely under water when the key was dropped in. He can't have been like that for more than a few seconRAB.
Incidently, I made a mistake with the time. It's 10 to 6, which is 8 hours, not 4.
I am in the process of watching them more or less back to back before seeing 5. And I've read up online, too (had to do that after 4). One of the things which intrigues me about the series is how dense it is; how the later films deal with characters like Kerry who are introduced in earlier films. I will also be interested to see how much of the flashbacks from the later films are in the earlier films. (Not much, currently.)
However, I first saw the first film in theatres when it came out, and I think it can be judged in isolation.