You can also replace out equipment for the exact same bodyparts. For example, you can switch out free weights for machines (i.e. do flat bench dumbbell presses for a few weeks and then use a seated chest press machine for the next few weeks). Or, you can switch out compound joint movements (both joints working at once) for single joint movements (one joint working at a time). For example, do camber bar bicep curls for a few weeks and then seated alternating arm dumbbell curls the next few weeks.
Another fun way to change up your circuit training routine is change the tempo by which you perform an exercise. For example, one week you can perform each repitition super slow and the next week you can perform each repitition relatively quickly. I like using the tempo counting method to determine exact tempo speeds. For example, a 3:1:3:1 tempo for a flat bench dumbbell press would look like this: take 3 seconds to lower the weight, hold for 1 second at the bottom, take 3 seconds to push it up, and then hold for 1 second at the top before lowering it again. So, you could do a 3:1:3:1 tempo for a few weeks followed by a 2:2:2:2 tempo the next few weeks. Or, use different tempos for different exercises within the same workout and then reverse the tempos the next workout.
Circuiting the Circuit
You can even create mini-circuits within a circuit training routine. One good way to do this is to group exercises for complimentary bodyparts together into their own circuit. For example, group all your chest, shoulders, and triceps exercises together in one circuit by resting 15 seconds between those exercises. Then, once you're done with them, take a 60-90 second break and go into another circuit for another group of complimentary bodyparts (back and biceps for example).
There are literally hundreds of ways you can tweak a circuit training program to keep it constantly fresh and challenging. And, as the above suggests, you don't even have to make huge changes to get great benefits and results.
Word of Caution
Circuit training can be very demanding on the body. Before you start a circuit training routine, be honest with yourself about your current level of conditioning and keep that in mind when designing your program. Start slow and gradually increase the intensity over time as your conditioning improves.
So, if you need a program that is easy to update and keep fresh yourself and/or if you are finding it hard to fit in your workouts into your busy schedule, I highly recommend trying circuit training. It can certainly be a fun, challenging, beneficial, and time efficient way to meet your fitness goals.
About the Author
Matt is a certified fitness trainer through the International Sports Sciences Association, author of numerous health and fitness related articles, an entrepreneur, investor, and co-founder of the Internet's biggest search engine and directory of fitness related websites, articles, and news stories: DeepFitness.com.