Great thread topic Elizabeth. There are two seperate training issues you bring up here. One is posible injuries form fight training/practice/sparring and the other weight training injuries. I will address them seperately.
First regarding fight training. If it is non-contact, the risks are very minimal I think. Once contact is involved anything can happen. There are two risks. One is from the weapon of your opponent and the other is you twisting your body in some way it does not like to be twisted in. If the weapon is foam, then the risk of the weapon is minimal and consequetly the training unrealistic. As the weapon gets harder and heavier to padded wood, the risks go up. When you go to wood or alluminum things get serious. To paraphrase what I read somewhere " in the race between armor and weapons, armor lost". No matter how much protection you have, a wooden waster is still as dangerous as a bat or club. So as the realism goes up, the risks go up. There is always some way for the weapon to harm you.
On the other side you have the risk of hurting yourself from a miss-step or slip. Sprained ankles are not fun. Danger is inharrent in what we do. We are training for war after all. Traditionaly when men trained for combat they are faced with the reality of death on the battlefield. The idea of getting hurt in practice is nothing compared to getting killed in battle. So they trained much harder and were more willing to take risks in training so they may survive in battle. I don't know if any of us have trained for combat on horseback. That would have been a key element to a mideval knights training. The risks go much higher. Consider the tournaments... getting thrown from a horse was common. Death from accidents in tornaments was common.
Now I will turn my attention to weight training injuries since you mentioned the other thread. Weight training in contrast to fighting is very controlled. The various lifts are perfromed in a manner that follows the natural motion of the body. There is not outside intervention. Contrast this to sparring where you may twist or be twisted in any direction. The point of weight training is to stess the muscle. Not the joint or the tendon. To do this I think it is best to think in terms of straight lines and right angles (90 degrees). When I bench for example, I will place my arms so that when the bar hits my chest my elbows are at 90 degree angle. The same when I squat. I position my feet so that when I sqaut down my knees form a 90 degree angle and my back is errect. This will stress the muscle. The significance of this is that the muscle has large blood vessels that supply it with oxygen and nutrients. If hurt muscle recovers more quickly then tendons. The tendons and ligiments do not have the same direct supply nutriants and oxygen as muscles do. Tendons are hard to damage and likewise when they do get damaged are slow to heal. In many cases they do not and require surgery.
When you use proper techinque, placing the stress on the muscles rather then the tendons and ligaments, the muscle will give out long before the tendons do and your spotter can help you. The tendon by nature are much tougher then muscle.
Also consider that strong muscles can go a long way to prevent injury. Take for example the shoulder joint. The armbone (humerus) is held connected to only two bones in you shoulder. The scapula on the back side and small clavical on the front. The muscles of your chest, back, shoulder help keep it in place and protect the joint. The stronger those muscles the more protected that joint will be. Same goes for the all important hip joint. It is almost completly coverd by muscles. Now consider the spine. On an untrained people you can see the spine bones sticking out of their back through the skin. If you strike this person on the back with a wooden waster you will impact the bone directly. It is sticking right out after all. Now walk into a gym and look at the spines of those guys. Not the bodybuilding monsters, but the average guy that trains. You will notice that the spine bones are not visible. You will instead see two muscles running down on either side of the spine like two pipes. If you strike this person over the spine with the wooden waster you will not impact the bone directly. You will hit the two muscles. Yeah, it will hurt, but there is less chance of a crippling injury. The bones of the body will also get denser with weight training. To quote one orthopedic doctor I met in the gym, "bones love stress".
This is all well and good provided you don't have a pre-existing injury. Then all bets are off. You can do more damage by training hard if you are already injured. The natural mechanics of the body do not apply to you and you should consult a physical therapist. If the joint is not working properly in the first place, training will not improve it.
I put some pictures up on my webpage so you can see what I mean by right angles in weight training. Observe the angles of my elbows and knees as I take the stress off the joints and place it on the muscle where it belongs.
http://mysite.verizon.net/tsafa1/workout.htm
Let me know if I can be more clear on anything.
