I am continually amazed (not really, but...) at the necessity of specific conditioning. It's so specific that the only way to get in "game shape" really is to play the game.
Things such as tempo runs, varying distance shuttles, gassers, circuits, wind sprints are great for general fitness, but to hone in on the energy demands of specific sports, I think there needs to be greater integration of the brain. Seeing things and having to react quickly requires a lot of energy, so while it might seem like the athletes are getting in great shape with basic conditioning, when the sport suddenly demands use of all sensory systems of the brain, they aren't in quite as good of shape as one might think.
"Brain energy consumption
PET Image of the human brain showing energy consumption
Although the brain represents only 2% of the body weight, it receives 15% of the cardiac output, 20% of total body oxygen consumption, and 25% of total body glucose utilization. The demands of the brain limit its size in some species, such as bats. The brain mostly utilizes glucose for energy, and deprivation of glucose, as can happen in hypoglycemia, can result in loss of consciousness. The energy consumption of the brain does not vary greatly over time, but active regions of the cortex consume somewhat more energy than inactive regions: this fact forms the basis for the functional brain imaging methods PET and fMRI."
One thing to take away from this is that energy in the human body is not infinite and must be distributed among the body in order for survival.
Utilizing reaction drills with auditory and visual stimulus immediately heightens the intensity of a conditioning drill. Mirror drills with a partner effectively gets one athlete reacting and another strategizing. These types of drills also increase the competitive aspect of training, which for an athlete, is the essence of what they do.
Obviously care needs to be taken with competitive, reactive conditioning, because if over done, in certain situations athletes could potentially "drill" themselves in to the ground with too much competition. But, I think in team sports, this form of drilling should comprise the majority of the conditioning work.
The goal is to not only increase the capacity of the different energy systems and efficiency of the peripheral nervous system, but also the central nervous system. Specifically the sensory systems found and integrated in the brain. In athletic development it is important not to miss certain systems. Especially when it comes to training for the random chaotic environments of teams sports. Even more important than being sure to train all systems, is to train them integratively at the same time.
The only difficulty with this form of training is creativity. The key is to find drills that challenge visual, auditory, and vestibular function at extreme speeds with the movements found in sports. Loads of memory on a huge hard drive are worthless with a slow central processing unit.
I'll have more conditioning thoughts in the near future...