Q: I dont think its a good idea to weight train to muscular failure. I have tendonitis on my right shoulder and had a swollen left shoulder twice because of it. I dont do it anymore.

A: I will say that training to failure is more stressful and puts higher demands on your body than other forms of training. It also requires the lifter to be very mindful when lifting (or to have a trainer) to make sure that form is never sacrificed in order to get another rep. This is what gets many people and leads to injuries -- a person gets so caught up in reaching his predetermined goal of, say, 10 reps of some exercise that he or she is willing to contort his or her body and use momentum instead of controlled strength to get the last 1-2 reps.

The other common cause of weightlifting injuries is overtraining. Lifters put too much repetitive stress on some muscle over the course of one week or one month or one year, do not give it time to sufficiently recover between training sessions, do not have adequate rest, sleep, and/or nutrition. All these things can add up to injuries.

Finally some people are so motivated to lift that they try to 'lift through injury'. This, of course, is a horrible idea which will only lead to a worse injury and more time that has to be taken off in the end. If you do feel an injury of any sort, let it rest! Your body will heal pretty much any minor injury on its own in the matter of weeks. Let it do its work and either take time off from the gym entirely or at least don't work that particular part of your body while it's recovering.

Periodization is part of any good long-term exercise regimen which means that you will have rest-weeks (at least one week every two months) as well as not-to-failure periods of training. This, this, and this are all examples of not-to-failure programs that can and should be cycled through during long-term (year or more) training cycles.

Finally shoulders are particularly prone to injury due to their anatomy and use. Shoulders don't get used just in the direct shoulder exercises such as shoulder press or side raises. Virtually all pushing and pulling movements of the upper body will involve shoulder in one way or another. That means that most of your upper back, chest, bicep, and tricep work also stresses the shoulder to some degree! So you need to be doubly careful about overtraining your shoulders.

If you cannot or are not comfortable with lifting to failure, you can still get very good results by selecting the same heavy weights but stopping a few reps short of failure. So by no means is to-failure training an absolute requirement for good results.

Should you do to-failure training after you've had an injury such as yours? The answer will vary from person to person and ideally would be answered by your doctor and/or physical therapist. I personally happened to have shoulder tendonitis (from ping-pong of all things!) and I still perform much of my training, including shoulder training, to failure. I am very careful about the volume of work I put on my shoulders and I do stop at the slightest sign of pain coming back. Because I am careful, to-failure shoulder training does no further harm to me. There are many other stories like that. It does not mean that I recommend that you return to to-failure training, of course. Certainly not if it bothers you and/or is against the advice of your doctor or physical therapist.

I firmly believe that when done right on exercise level (always maintaining good form) and program level (no overtraining, frequent rest, and cycling through different programs), to-failure training is both safe and highly effective. Yes, it does put more demand on the lifter but it gives better results as well.