1. Inhibiting the movement of joints
2. Prohibiting the full contraction of opposing muscles
3. Misaligning the body
4. Decreasing body efficiency
5. Increasing the possibility of injury
6. Deterring the maximum pumping action within each muscle

Inhibiting the movement of joints
This potential difficulty is exemplified by what can happen to the hip joint. Many spend a lot of time sitting-- at the office, in the car, in front of the television-- which causes the muscles that draw the thighs up to the torso (hip flexors) to shorten and an longer accommodate full movement in the hip socket. (This joint is a ball in a socket, and is capable of a wide range of motion.) If the muscles at the front of the hip joint are shortened, the leg is not able to move backward as far as it once could. The thigh bone is no longer being moved fully in the socket. This then retards the flow of synovial fluid, which lubricates the joints, and the chances of calcium buildup increase. Tightened hip flexors also contribute to swayback, in which the front of the pelvis is pulled down.

Prohibiting the full contraction of opposing muscles
"All muscles work in pairs. For example as hip flexors draw the thigh up to the torso, the hamstring and buttock muscles lengthen. Conversely, when the leg is moved backward, the hip flexors lengthen as the hamstrings and buttocks shorten. But if the hip flexors are too tight and cannot lengthen fully, their opposing muscles cannot contract completely. Muscles or portions of muscles that are not worked lose strength and tone and are less able to move the skeleton properly."

Misaligning the body
"All muscles act as levers, and shortened muscles can pull the body out of alignment. In general, muscles are designed to move the body and bones designed to support the body. When bones are stacked up correctly-- like building blocks-- they are in balance with gravity, or aligned. The spine is in alignment when it has four long, gentle curves; the neck and lower back have concave curves, the tailbone and ribcage have convex curves. However tight muscles can pull bones out of alignment. For example, tight abdominal muscles pull the sternum down, causing a collapse of the chest and a humping in the ribcage area of the spine (kyphosis). The neck also shortens. Now instead of the body balancing on bones with minimum effort, numerous muscles and ligaments must contract to work against the pull of gravity pull. This necessitates a greater output of energy just to remain upright, and creates tension in the body, which inhibits the vital function of digestion, circulation, and breathing."

Decreasing body efficiency
"Stiffness of muscles and joints is often caused by muscles that are permanently shortened through strengthening without stretching (or through gross inactivity). This stiffness is a drain on the body's energy, for muscles use energy to remain semi contracted. Also, when a muscle is continually contracted, it cannot lengthen to accommodate the contraction of its opposing muscle. This means that the brain, which receives the major portion of its sensory information from the muscles, is receiving confusing messages. When the brain receives a message to contract a muscle, the message is muddled if the opposing muscle cannot lengthen fully."

Increasing the possibility of injury
"When a joint is surrounded by tight, shortened muscles, the body is susceptible to harm. If a muscle does not move freely, the joint may move without it, causing a dislocation or a torn ligament, tendon or muscle. Injury can also occur simply from chronic shortening. For example. if the hamstrings are continually shortened, as they are in running, they can compress the hip joint or knee joint. Such compression can lead to torn cartilage, pain in the hip, sciatica or rotation of the knee."

Deterring the maximum pumping action within each muscle
"Muscle action may be compared to a sponge. When the sponge is squeezed, which is the equivalent of a muscle contracting, fluids flow. But for the sponge to absorb fluids efficiently again, it must be released and soft. So it is with muscles. If they are to pump efficiently, they must be able to contract to move fluids onward, and then soften again to absorb the fluids they require."