[dugan51]

You want to keep your body constantly adjusting to meet the demands you place on it. Don't become predictable because the body will find the way to do what you ask it to with the least amount of effort, ie. it just gets more efficient.

There are many ways of changing up a weight resistance program - use different equipment, change the weight used and the number of reps, add more or subtract sets, decrease the amount of rest time between sets. But the goal is always to increase intensity no matter how it's done.

The same principles apply to a cardio routine. Run longer some days, then on others shorter and faster, etc. Or run stadium steps or do a spinning class occasionally.

And, I actually think the same ideas work with nutrition and dieting too. Don't eat the same way, the same foods, the same number of calories every day. Many bodybuilders allow themselves one day a week where they allow themselves to eat anything they want.