What the Bulgarians would do, for the most part, was get into the gym multiple times a day - up to 5 times every day. Each time they'd put out their cigarettes, walk up to the bar, and hit just a few singles with heavy or very heavy weights. Then they'd walk away and take a nap or whatever they did until the next training session. No marathon training sessions, working until exhuastion, no sets of 10 or 20 or 50 (all of which are advocated by some bodybuilding authorities), and repeated many, many times over each training week.
Here's another story. When I was in high school there were a number of skateboarding afficionados at the school. They were part of the background all the time - always skating, working on various tricks, like hopping up on the board and flipping it over, then landing on it. You've seen the same thing outside malls or shopping centers I'm sure. There would be a group of skaters near every open space in New York. They'd sit or stand around, talking, then one or more would practice a couple of tricks, then sit around some more, then practice some more, with no particular structure. And they'd do this every day, all day, at least when they weren't actually in class. They never said, "I'm going to knock out 25 reps of half barrel rolls" or whatever (I have no idea what any skateboarding tricks are actually called).
One last example. Watch the way a baby learns to do something new, anything from roll over to reach for an object or eat a Cheerio or walk. They'll try, a bunch of times, then get bored and move onto something else. Then try again. Many times a day, never really doing too many in a row, but going back and revisiting the attempt over and over until they've mastered it.
Why am I bringing this up? These are all stories about skill acquisition. Every physical ability people have is a combination of muscle/ heart/ lung adaptions (think about what makes an Olympic marathon runner different from you) and neurological adaptions (a concert pianist has strong and limber fingers, but many people with strong limber fingers can't play the paino - the difference is the neurological ability the pianist has acquired). What makes a great skateboarder? Well, you have to be in decent shape, lean, and have some strength, but let's face it, Tony Hawk isn't among the strongest or fittest people on the planet (though I'm sure he's well above average). What he has is a neurological ability to skate. His brain is really good at making his muscles contract at just the right time, in the right order, with the right amount of force, to keep his feet on the board while it's doing all the crazy stuff he can do. What's the difference between a baby or toddler that can walk over and one that can't? Some of it is muscle strength, but some of it is the skill of balancing and controlling all those muscles.
What about the Bulgarian weightlifters? Isn't weightlifting about building muscles? Well, yes and no. If you're a top level weightlifter you're going to have a good amount of muscle - but so will all your competitors, and they'll have similar amounts of muscle, because you compete in a weight class. Progress at that point (not for beginners, but for advanced lifters) is about using the muscle you have more efficiently - being able to contract more of the muscle at exactly the right times to lift the heaviest weight. If you're an elite 154 lb. lifter you can't improve by just building more muscle - you'd quickly end up being a mediocre 163 lb. lifter. You improve by getting all 154 lbs. of your body to work perfectly and in concert to move the weight. That adaption is largely the brain, not the body.
Now, to build stronger muscles we have to work the muscle hard, until it is quite fatigued, which damages the fibers. Then we have to rest it for a significant period of time so the body can repair and then create supercompensations in the muscles - fix it, then make it stronger, so it can do more the next time you work it. That's why to build muscle you have to work out for longer duration, until the muscles is very tired, and then take a lot of time off - from a couple of days to a week or more depending on your genetics and level of advancement. Which is not how we get neurological adaptions.
What's the difference? Your brain changes by reinforcing patterns that are used a lot - and that means pretty much any pattern. This can happen fairly quickly and doesn't involve the kind of damage - repair cycle that controls muscle growth. Let's say you are learning to punch. You keep throwing a punch - which is a pattern of activating certain muscles in a certain order. As you repeat it, your nervous system recognizes that it needs to get good at doing that pattern of things, and it strengthens neural connections to make that pattern fire more easily and more strongly. These adaptions can happen as fast as you can make them - as far as the nervous system is concerned, you can practice more or less all day, every day, and keep improving (the stress of doing that might cause other problems, but I'm not advocating all day training in any case).
A few things are important to note at this point. If you practice sloppy punches you will reinforce the firing pattern that makes sloppy punches. You will get better and better at punching sloppy. If you practice mostly slow motion (which you need to do when first learning a technique, but maybe not so much afterwards) your nervous system will get better at moving slowly (which may not be your long term goal). Ideally, you would practice all your techniques done really, really well, and not when they're done poorly, and you'd do it very often.
How would we do that? Well, the typical way to train is to take a 1 or 2 hour class a few times a week and train all the techniques until we're super tired. That's a good way to build muscle but not to force neurological adaptions - once we're fatigued, the techniques get a little sloppy or slow, and we end up reinforcing the patterns that make sloppy, slow karate. Instead, we should do a LOT of very brief practice sessions - practice the techniques done really sharply and explosively but stop long before fatigue sets in.
For example, I like to take a minute or two out of my day, often several times a day, and throw 5-10 kicks with each leg, maybe do 3 different kicks, then a few punching combinations. Total time? Maybe 2 minutes, maybe less. When I'm done I'm breathing a little bit heavily but have barely broken out in a sweat. Then I go back to my desk and work some more or do whatever I need to be doing. These mini-sessions have the added bonus of giving me a lot more energy for the rest of my daily activities. Remember: I stop long before I'm tired, and I really focus on doing the techniques with good form, sharp, and all the power I can muster. The point is to repeatedly practice good reps, not to do 100 or 1000 kicks in a row. Think like the Bulgarian weightlifing team!
This type of training won't get you in good cardiovascular condition by itself. You also won't build a heck of a lot of muscle doing it. That's why you need to do conditioning and hypertrophy (muscle building) work as either a separate workout or tacked onto the end of a shorter skill workout. And make sure your conditioning isn't done with karate movements! Don't get in shape throwing punches and kicks (at least not all the time) - your form will deteriorate as you push deep into fatigue and you'll be practicing, and reinforcing, bad punches and kicks. Instead, do your techniques while you're fresh, and really push the fatigue levels with sprints, burpees, dumbell snatches, or something else at the end of the workout.
- Develop muscles with hard, fatigue inducing workouts spaced several days apart.
- Develop cardio (metcon, wind, endurance) with hard interval training done at the end of a workout with movements that are NOT part of your art as often as several times a week (you don't need as long for your heart/ lungs to recover as the muscles need to recover from resistance training.
- Develop neurological ability (skill) with brief, technically sound practice done as often as you can manage.
- If you combine these, do skill practice first, then muscle work, then metcon/cardio work - DO NOT rearrange these.
What about warmups? Well, if you do your dynamic flexibility and some mobility work (shoulder circles, things like that) early in the morning, then do these mini-sessions spread out through the day, you will probably be surprised at how much of your flexibility remains available to you. And isn't that the point? Don't you want to be able to throw a high kick without a long warmup and no warning?
A couple of final points. First, training your techniques in deep fatigue once in a while is probably a good thing. On special occasions throw a thousand punches in a row. Many people describe learning things about movement only when pushed to the edge of their physical ability. But make it infrequent. Second, everyone, especially beginners, are certainly going to need longer sessions periodically to really work on refining or learning new techniques. I'm not saying that the hour class is inappropriate - only that the skill refinement should be done early, the calisthenics/cardio at the end, and that the bulk of the in-between class training should be done in short, intense bursts that don't push you into exhaustion.
You can only reach your maximum potential as a martial artist if you combine muscle, endurance, and neurological efficiency to their respective maxima. That means training each trait using the appropriate methods and timing.