We live in a Flexion society today. We are constantly bending forward or "flexing" to perform our daily tasks. From bending down to pick things up and grasping door knobs, to sitting at a computer with our arms in front of us and shoulders leaning forward. We do not do enough extension in our lives. Overtime, muscular imbalances tend to develop due to overuse of certain muscle groups like the chest muscles in the upper body, to the hamstring muscles in the lower extremity.
When muscles are used more they get stronger, as muscles get stronger, they shrink in length and increase in width. When muscles get weak they get stretched out. This happens in the body to opposing muscle groups over time. For example... Clinically we encounter forward head and shoulder postures a lot, especially in people who do desk/computer work. They have strong chest and front neck muscles that tend to overpower the opposing back and shoulder muscles. Overtime, the stronger muscles tend to pull the head and shoulders forward. Ideally, one should stretch the tight muscles and increase the strength of the opposing muscles to regain balance between the two groups which will restore normal posture and balance. I can evaluate your posture and check for muscular imbalances and give you specific exercises to start to improve your posture. Check out the STRETCHES section for some basic stretches.
One-sided Sporting Activites
Muscular imbalances are more common from front to back. Some sporting activities (uni-axial sports) such as golf, bowling and throwing can cause side to side muscular imbalances. Major postural problems tend to develop over time such as unlevel shoulders and hips. If you participate in a one-sided sport or activity, you should take steps to prevent overdevelopment of muscles on half of your body. This is easily done in golf by taking as many opposite handed swings as you do regular swings, but can be more difficult in other sporting activities.