Final answer:
Flat back posture is characterized by tight hamstrings and abdominal muscles, especially the rectus abdominis, and lengthened, weakened hip flexors and lumbar extensors. Muscular imbalances effect the natural lumbar curve and overall posture. Proper muscle contraction and relaxation are essential for maintaining spinal curvature and preventing posture problems.
Step-by-step explanation:
When discussing flat back, it refers to a posture wherein there is a decrease in the natural lumbar curvature. This leads to certain muscles becoming tight and others being lengthened. The muscles typically tight in this condition include the hamstrings and the abdominal muscles, particularly the rectus abdominis. On the other hand, the muscles that are often lengthened and weakened include the hip flexors and the lumbar extensors. It's important to note that maintaining balance and upright posture is a complex coordination of muscle contractions and relaxations, and flat back can interrupt this balance.
The intrinsic skeletal muscles of the back and neck, along with the skeletal muscles of the abdominal wall and thorax, play a key role in extending, flexing, and stabilizing the body's trunk. These muscles are managed by electrical impulses from the brain, which control posture through alternate contraction and relaxation. When muscles like the abdominal muscles or hamstrings become too tight, it can impact the natural curvature of the spine—contributing to a flat back posture.
Muscle tissue possesses elasticity, extensibility, and contractility. These qualities allow the muscles to return to their original length after being stretched and to contract with force. When there is an imbalance, such as with flat back, these properties may be compromised, leading to tightness or overstretching in certain muscles.