Chronically tight, overused muscles cause their opposing muscles to become weak and atrophied. This imbalance spread through the entire body as muscles compensate for each other, and long term pain and joint degeneration can result.
There are three very common patterns identified by rehabilitation specialist Dr. Vladimir Janda:
Lower-crossed syndrome occurs when tight hip flexors and lower back result in weak abdominal muscles and gluteals. People like this tend to have an exaggerated arch in their lower back and lower back pain.
Upper-crossed syndrome occurs when tight chest, shoulder, and neck muscles result in weak upper to mid back muscles. People with this imbalance tend to have neck and upper back pain, forward leaning head, and hunched shoulders.
Layer syndrome occurs when you are a real over-achiever and have both upper-crossed and lower-crossed syndromes.
If you think you have an imbalance like this, you may be in really, really good shape but you would improve your performance and longevity by strengthening the weaker muscles and stretching and relaxing the tighter muscles. These two things need to be done simultaneously to achieve long-lasting results. More at: The Janda Approach to Chronic Pain.