Focus on strength and power. Do interval training for anaerobic endurance.
That's what you need.
"Caveman" training and all of that other crap is either a) for variety or b) for the cameras.
Look at Rich Franklin's old routine when he did the circuit stuff on the UFC All-Access show. Guess what? Rich Franklin has a new strength coach. He's not using that guy that was in the All-Access anymore. That type of circuit training was not focused on strength & power.
Here's the problem with just doing circuit stuff - is it difficult? Absolutely. But, is it intense enough? Not even close. It can't be - because of fatigue due to the duration. You can't work with weights heavy enough to bring about the necessary level of intensity.
The very definition of intensity from a purely strength sense is measured by one's % of 1-RM. Well, if you're fatigued, you obviously can function at a high percentage of your 1-RM. The focus should be on developing power and "power endurance" (not a real term in classic exercise physiology texts). But, definitely something that can be trained and/or developed in a round-about way.
Power = force x velocity. You develop the force component via pure strength development. Focusing on the speed of the movement completes the velocity component.
My friend and his colleague are doing a presentation at the National Strength & Conditioning Association conference in July in Orlando, Florida. (I have had the opportunity to view the "trial run" of the presentation twice already.)
They only found 4 research papers that dealt specifically with the physiology of MMA fighting. So, they had to pull research that dealt with wrestling, judo, tae kwon do, karate, kickboxing, muay thai, etc. and ended up reviewing over 1700. What they found was that those individuals who showed greater strength and power were most successful in all of these other areas.
So, you're all saying - well, duh?
So, why is everybody doing all of this circuit training crap?
Guys, look at GSP in the Countdown show that was on before his fight with Dan Hardy. Did you watch him doing Olympic lifts? Advanced plyo work? sprint work? I think that these things develop power if I'm not mistaken?
Highest power outputs - Olympic lifting. I can show you that via biomechanical research. Of course, these are highly technical lifts and most people do them wrong, so they probably aren't maximizing their power output.
What Dan Hardy was doing was definitely a good approach as well. (Weighted trap/hex bar deadlift jumps) He was being helped by Joe DeFranco, who's a prominent strength coach in his own right. He doesn't do Olympic lifts due to the complexity and prefers a modified Westside System adapted to athletes that emphasizes dynamic effort (power development) coupled with max strength. That's fine. And, for some folks, Olympic lifting may not be the best option due to a host of factors - injury history, body size/stature/dimensions, etc.
But, at the end of the day - train for strength & power and do interval work that will maximize anaerobic endurance. This will more mimic the intermittent type of activity in MMA, grappling, boxing, kickboxing, etc. It will train the appropriate energy system while teaching the muscles to generate and develop force rapidly and explosively.