You basically have 3 options, each of which are described below.

1. Re-take your strength tests and begin the exact same program again. This time when you start over at week 1 you will be using heavier weights and the concept of progressive overload will be taking place. Progressive overload simply means that you are continuing to stimulate your body to continue making progress. Now, keep in mind that when you start over at week 1, some of the weights will still be lighter than they were at week 12, but you will be doing more reps with a higher weight than you have ever done before!
2. Continue with the same program but add an extra day in per week. For example: If you have been performing the 3 day program, go into the 4 day program. Or, go from a 4 day to a 5 day. This will change up some of the muscle group and exercise combinations and since you will be focusing on less muscle groups in a particular training session your body will be able to handle heavier poundages during the workouts. Remember, progressive overload is the key. Finding a way to maximize your performance is always positive for progress! This example obviously requires an additional day of training so it's not for everybody.
3. Switch programs altogether. This is the option I would choose. Variation in a training program is always positive. New stimuli create the all important progressive overload, and, that again keeps the progress going. Remember this, you don't have to do the new program for the entire 12 weeks. You could try the General Fitness program for weeks 1-4, then switch to the Strength and Power program on week 5 and 6, then go back into the Get Lean program for weeks 7-12. This is a great way to continue shocking your body for optimum results.

Now, here's the kicker, if you choose to change programs like the above example, you will experience, first hand, the true beauty and power of the Fitrex.com system. I have designed the programs to have a common thread that runs through each and every workout that is 12 weeks in length. This common thread is something called the Periodization Model. The Periodization Model is demonstrated graphically in the fitness info button on our site. This modeling of the programs enables you to change within each of the separate program focuses at any time and not have any negative consequences, physically speaking! I have set optimal training intensities for each exercise and for each set and rep combination so even though one program may require sets of 8 repetitions and another may require performing sets of 12 repetitions the corresponding weight change will be perfect for you!

One other thing, I recommend re-testing your upper and lower body strength on the last workout of week 5 and the last workout of week 10. This time frame will have allowed your body to rest just enough from the big week 4 program and you should see a corresponding jump in your physical performance. You don't want to test more than this as the training cycles aren't set up for optimum results this way. Basically, it takes more than 2 weeks for significant physiological changes to take place! Testing every 5 weeks is the best way to go.

Dan Wirth M.A., C.S.C.S.
Fitness Director (Fitrex.com)
Director of Strength and Conditioning
The University of Arizona