FitOrDie

As it happens, there is no science behind the lactic acid thing whatsoever. In faaact... I very recently heard of someone showing that lactic acid is actually used to produce ATP, proving an unknown-until-recently FOURTH energy pathway within the human body. Lactic acid, despite the popular belief of the past 20 or 30 years, has nothing to do with soreness. Corelation does not prove causation. I think what your students need, most likely, is more training, more fitness... and probably better eating. (After all, who doesn't?) Even still, soreness is a part of training, eventually you just have to deal with it.

Can't build a skill by NOT practicing it...

That type of training is one-dimensional and will almost certainly cause you to fail in all things except lifting big heavy weights. To answer other questions, the most important muscles a fighter uses is ALL of them! Think about it, a punch starts by being powered by the legs, that force travels through your entire body-meaning every muscle in it- and out through your hands, into your target. If you want to gain muscle in the ring, I think you have the wrong mentality. Gaining lean mass for a bigger weight class is one thing, there is a great article on the subject at rossboxing-dot-com or rosstraining-dot-com. Bottom line: train like a fighter, eat balanced like you should, just eat a little more. But what you really want to do is increase your work capacity, not muscle. (See my signature.) A lean trained fighter will demolish a steroid-pumped muscle-head. To throw and dodge and block more punches and kicks and whatever harder, faster, over a set period of time, more accurately while experiencing less fatigue... that should be your goal.

Routine is the enemy! Check out that website or you will almost certainly forever be less fit than you could be.

Meats and vegetables, nuts and seeds, some fruits, little starch, no sugar. Organic, yes, artificial, no. Keep salts to a minimum. If you want to be hard core, follow The Zone proportions. At the least, make sure you get a balance of protein, carbogydrate, and fat with every meal.