your body is already in a catabolic state after you are done lifting, you would just be keeping it there a little longer.
I wouldn’t agree with that at all- your body does not need to be in a catabolic state during workouts given pre & intra workout nutrition. In the studies presented in Nutrient Timing, people drinking the carb/protein drink ended their workouts in a positive protein balance.
To the OP:
Here’s the thing about cardio - the very basic principle behind doing cardio after your weight workout is that lifting weights causes increased free fatty acid circulation, and doing low-intensity cardio runs primarily off fat. Here’s the problem- you want to do cardio to be in better shape for a fitness test, not to burn fat. Low-intensity cardio (40-50% of VO2 Max) will result in modest gains at best in the untrained individual, and do less for someone who’s already in decent shape. If you are going to want to get good results, you are going to need to work your way to 60-85% of your VO2 max during your cardio sessions. At these speeds, your body will be running almost entirely off glycogen… and if you just had a hard leg workout you might already be running low on that.
My suggestion is to if you insist on doing cardio on lifting days, same time, just keep the nutrients flowing with a pre/during workout shakes and then Surge afterwards. Otherwise, you might want to do cardio on your offdays, and supplement with a little pre workout shake and again Surge after you finish.