over-stretching

Examples of over-stretching in the following topics:

• Benefits of Stretching

  • Stretching is a form of physical exercise, where specific skeletal muscles are stretched, improving elasticity and muscle tone.
  • Stretching can strengthen muscles, and in turn strong muscles are important to stretching safely and effectively.
  • Stretching can be dangerous when performed incorrectly.
  • It is also suggested that one stretching exercise may not be enough to prevent all types of injury, and therefore, multiple stretching exercises should be used to gain the full effects of stretching.
  • Over-stretching or stretching to a point where pain is felt may be inappropriate and detrimental.

• Proprioceptor Regulation of Breathing

  • Physiological mechanisms exist to prevent over-inflation of the lungs.
  • The Hering–Breuer reflex (also called the inflation reflex) is triggered to prevent over-inflation of the lungs.
  • Additionally, people with emphysema have an impaired Hering–Bauer reflex due to a loss of pulmonary stretch receptors from the destruction of lung tissue, so their lungs can over-inflate as well as collapse, which contributes to shortness of breath.
  • The sensitivity of the sinus-atrial node to the inflation reflex is lost over time, so sinus arryhthmias are less common in older people.
  • The vagus nerve is the neural pathway for stretch receptor regulation of breathing.

• Elasticity, Stress, and Strain

  • Elasticity is a measure of how difficult it is to stretch an object.
  • Stress is a measure of the force put on the object over the area.
  • For example, a long guitar string will stretch more than a short one, and a thick string will stretch less than a thin one .
  • Tension: The rod is stretched a length ΔL when a force is applied parallel to its length.
  • For larger deformations, the cross-sectional area changes as the rod is compressed or stretched.

• Running Injuries

  • Some claim that for runners in particular, ice baths offer two distinct improvements over traditional techniques.
  • Recent medical literature, however, finds mixed effects of stretching prior to running.
  • Another, however, has demonstrated that stretching prior to running increases injuries, while stretching afterwards actually decreases them.
  • Recent studies have also shown that stretching will reduce the amount of strength the muscle can produce during that training session.
  • Evaluate the methods (hydrotherapy, running surface, stretching, and technique) used to prevent running injuries

• Force of Muscle Contraction

  • Then, the thin filaments slide over the thick filaments as the heads pull the actin.
  • If a sarcomere is stretched too far, there will be insufficient overlap of the myofilaments and the less force will be produced.
  • If the muscle is over-contracted, the potential for further contraction is reduced, which in turn reduces the amount of force produced.
  • The reverse is true for stretching of muscle.
  • Although force increases due to stretching with no velocity, zero power is produced.

• Micturition and the Micturition Reflex

  • The brain centers that regulate urination include the pontine micturition center, the periaqueductal gray, and the cerebral cortex, which cause both involuntary and voluntary control over micturition.
  • The state of the micturition reflex system is dependent on both a conscious signal from the brain and the firing rate of sensory stretch fibers from the bladder and urethra.
  • At low bladder volumes, the afferent firing of the stretch receptors is low, and results in relaxation of the bladder.
  • At high bladder volumes, the afferent firing of the stretch receptors increases, and causes a conscious sensation of urinary urge. 
  • This reflex may lead to involuntary micturition in individuals that may not be able to feel the sensation of urinary urge, due to the firing of the stretch receptors themselves.

• Velocity and Duration of Muscle Contraction

  • However, cross-bridge formation is not immediate and if myofilaments slide over each other at a faster rate, their ability to form cross-bridges and subsequent force are both reduced.
  • The reverse is true for stretching of muscle; although the force of the muscle is increased, there is no velocity of contraction and zero power is generated (left edge of graph).
  • Although force increases due to stretching with no velocity, zero power is produced.

• Stability and Range of Motion at Synovial Joints

  • However, over the past two decades, research has also characterized the elastic properties of tendons and their ability to function as springs.
  • During a human stride, the Achilles (calcaneal) tendon stretches as the ankle joint undergoes dorsiflexion.
  • Because the tendon stretches, the muscle is able to function with less or even no change in length, allowing it to generate greater force.

• Defecation Reflex

  • A sufficient increase in fecal material in the rectum causes the stretch receptors from the nervous system, located in the rectal walls, to trigger the contraction of rectal muscles, the relaxation of the internal anal sphincter, and an initial contraction of the skeletal muscle of the external sphincter.
  • If this urge is not acted upon, the material in the rectum is often returned to the colon by reverse peristalsis where more water is absorbed, thus temporarily reducing pressure and stretching within the rectum.
  • The internal and external anal sphincters, along with the puborectalis muscle, allow the feces to be passed by pulling the anus up and over the exiting feces in shortening and contracting actions.

• Presenting the Prevailing Theories

  • In their 2004 study, Charles et. al. explicitly note the increased sockeye salmon presence along a three-hundred mile stretch of the Columbia River, which had been previously targeted as one of the most polluted stretches of the river.
  • However, what these prevailing theories do not account for is the possible drying up of other stretches of water, which cause salmon migration to shift while leaving water conditions hardly changed. "
  • This is true because most theories continue to be developed over time until they have changed significantly, become far more specific or have been proven wrong and thereby discarded.