The idea is to keep your muscles "on their toes", not let them get used to your routine otherwise its effectiveness will drop. Using your chest routine as an example. It could be as simple as the order that you do things, but you could also get rid of the decline press and slip some dips in there instead. Do this every 4 weeks or so for each group.
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That's pretty much exactly what people mean by a change. Different exercises, the order you do them and even sets and reps. Keeps the body from adapting and slowing gains.
this is al valid, but there is really no need to change your routine until you start to see that you are no longer getting gains.
why wait until that happens when you could prevent it? just my theory.
lift2live summed it up. change the rep scheme, the order you do the exercises in, different exercises, rest between sets, something. i personally like changing the rep scheme. i will usually go 3-5 for about 1-2 months then 4-6 weeks of 8-12 reps.
-beef-
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I may not be smart but I can move heavy things.
I just change exercises right now doing westside... they have no problem gaining strength or size and they keep the same reps year long for strength and the same for their assistance and supplementory exercises.
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