Apr 13, 2012 - 03:31 PM
When a muscle is stretched it also stretches the muscle spindles. This in turn will cause the muscle to contract (due to the muscle spindles sensing a change in length) and if this is an ongoing stretch due to poor posture it can lead to muscle spasms or the “feeling” of tightness even though the muscle is not tight.
The text book gives the example of the hamstrings feeling tight even though they are actually in a chronically stretched position due to the pelvis being tilted forward. In other words as someone goes into more of an anterior pelvic tilt (more back arching, see figure 7.7 on page 156) the hamstrings are being placed in a stretched position. Being in this stretched position can make the hamstrings “feel” tight, but someone should not stretch the hamstrings in this example because the muscle is already too long and instead they would need to work on stretching the hip flexors and keeping the pelvis in a neutral position. When someone stands with a posterior tilt (tucking) the hamstrings are places in a shorter than normal position.