Before I begin to rant, I just wanted to let you know that I am not going to ask any stupid questions, and also that you came highly recommended by one of my SF combat medic course instructors. I was recently invited to try out for the Air Force Para-Rescue program. This is my problem: I am in good shape, I PT regularly with my unit, also I am currently doing the 300 work out on my lunch break and lift weights in the evening. I am not getting the results I want, and do not feel that I will perform very well for the PJ indoc test if I continue down this path. Should I only concentrate on circuit training and cardio? Should I stop body-building all together? I want to be the fastest, strongest baddest guy out there. I am motivated, and extremely dedicated... I just need a point in the right direction. If you could write back that would be great! Thank you for your time.
The so-called 300 workout is not meant to be done with any regularity. Use it 2-3 times per year IF you have decided it is a valid test of the fitness you require for your job. It might not be valid, and other tests will provide more relevant information.
Circuit training was developed as a way to prepare unfit people to begin formal, structured training. It is, like any method done exclusively, a dead end. Once you adapt to the stress it must be changed in some way. Circuit training is a tool in the box and useful during certain periods but not as a guiding principle.
Cardio? Does running or working on a stair machine or riding a spin bike have anything to do with the demands of your future job? It can be useful, of course, but all endurance capacity is movement-specific so if you're a runner then riding a bike won't produce meaningful results, i.e. high level results. Make the cardio demands movement-specific, load-specific, speed-specific to achieve the greatest results.
Body-building? Do you need to be bigger? That's the result of genuine body building style training (and diet). You can be the strongest, fastest, baddest guy in the selection without being big. In fact, if you have to carry your engine - and we all do - then power-to-weight ratio should be the ideal that guides all of your training. Size matters, but not how most people think it matters. That being said, the greater percentage of bodyweight you carry on the job the greater its negative effect upon you. Up to about 35% the energy cost is not too bad, but carrying 50% of bodyweight is more than 15% more difficult and damaging. You'll go out the door carrying a minimum of 80 pounds of kit so perhaps being a bit bigger and heavier will be advantageous. It will be tricky to balance strength, muscular endurance, and systemic endurance in the most efficient manner, and the balance will change according to the environment.
Hopefully, this points you in the right direction. There is not one recipe. There is only your own recipe. And you have to develop it on your own.