If you’re already done your track workout and now in the gym and finished your compound lifts. What “resources” are you really wasting by doing some iso work though? You can make a 70 minute workout into a 90 min workout, whats the difference for the end result?
Something that should be included in your ‘resource toolkit’ is your ability to recover. You should work to your limit, being sure not to overtrain, but you should leave nothing on the table. If you have resources that allow you to work out for an additional 20 minutes per workout without effecting recovery, you are leaving something on the table. If your primary workout is performed at the maximum possible effort, then adding additional work will adversely affect your training.
As Josh mentioned, you can get away with much more during GPP, for several reasons. Do your mirror work then, and phase it out as you begin working more specific means during SPP. By the way, we have a name for those guys that do all the goofy front facing iso’s…Rics. Refelction Inspection Crew. We call them all Ric. They always tell us their names, but we call them all Rick anyway. Every rep done facing the mirror. Walk to the fountain, bump into other lifters all the way there looking in the mirror. Front side looks OK, back and posterior chain look completely undeveloped.
Don’t be a Ric.