Check out this article, "Muscle imbalances can wreck your workout," with some great tips on keeping your body and muscles in balance and happy harmony with one another. Our bodies are amazing at accommodating for an injury or any slight imbalance - this goes for the serious athlete and the casual exerciser. For anyone this could lead to a more serious problem down the road if not properly addressed.
I love how the article points out we do the exercises we LIKE not the ones we NEED. For me, I like almost anything involving cardiovascular exercise but I am not so much a fan of stretching and flexibility! What does THAT tell me?