There is an unfortunate misconception that an injury to any area of the body immediately halts all progress in an exercise regimen. Actually, that is the farthest from the truth.
Let’s say that you have a knee injury and literally don’t need to do any resistance training or full weight bearing for about 4-6 weeks. If we look at a big picture of what happens when the knee and its supporting cast (hip and ankle of the same leg) are immobilized, we can plainly see that we have about 75% of our body that is still able to be worked. Now, for balance sake, it wouldn’t be prudent to work the other leg to its extreme and try to make amazing gains there during this time. But it still can go through conditioning movements to maintain its capacity. More importantly, this is a great time to work on mobility, otherwise known as joint capacity, for both legs (minus the injured knee joint). Following this protocol, I’ve witnessed numerous people come out of an injury period with amazing mobility in their hips simply because that was all they were focused on in that region, not resistance training which tightened them up.
So that’s the lower body stuff. The upper body is a completely different story. This is a perfect time to plan a program and make great strides in performance, be it strength, flexibility, mobility, whatever you choose. There simply is no reason to say that you’re done for with an injury because that’s just not true. The same applies to injuries of other areas as well, which of course have their own specific protocols. All this being said, it is best to check with a professional to make sure that you aren’t going to hinder your progress to the injured area while continuing in your program. But if they’re any good at their job, they should have no problem pointing out the parameters in which you can work.