If you have bad posture it will impair your health. It is important to keep good posture, God created man to live in this way. Some people's backs become curved when they become old. This comes from bad posture or sleeping in a bad position. So we must keep good posture in order to maintain good health as God intended.
Exercise is another important point.
Even if you don't do any special exercises if you walk enough, you can maintain your health. God created man to walk, but nowadays we ride rather than walk. If we walk, as God originally intended us to, we can stay healthy. Actually walking is the best exercise. We can do other exercises to improve our circulation and train our muscles, but simply walking and maintaining a good posture can keep us healthy.