Flexibility is a term used mostly to describe the stretch of soft tissue with the emphasis on the muscles of the body. Muscles come in all shapes and sizes. The length of muscles (in series) demonstrate the extensibility of muscle while the width or cross section of a muscle (in parallel) is more related to muscle strength. Amongst all of this are connective tissue sheaths that can also stretch.
If a muscle is shortened for a prolonged period of time, some of the contractile elements (sarcomeres) get absorbed and the muscle actually shortens. Only when there is a stretch applied will this muscle be stimulated again and regain its ability in length. It is important to eat protein in order for the synthesis of protein and ability lay down protein that was reabsorbed in the past to occur in the body.
If a person gets involved in a stretching program, muscles do not stretch quickly. If a significant amount of extensibility is gained in a session it is more likely that the connective tissue allowed that extensibility. If stretching is done on a regular basis, the body has the ability to stretch back to the length that it did prior.
If stretching is done too aggressively and a muscle is forced past the connective tissue limitation, muscle may become injured and will need time to heal and adjust. Patience with stretching and using the right techniques to stretch are key to increasing and maintaining flexibility.
Hypermobility and hypomobility are terms used to describe a quality of a joint. Normal joints are comprised of bones, usually with hyaline cartilage on the ends that make a healthy joint appear smooth and healthy. There are ligaments that attach bone to bone to give the joint stability. There may also be a meniscus as in the knee and all of this may be surrounded by a joint capsule with fluid inside to bathe the joint thus keeping it healthy.
A meniscus is like a washer that allows the joint congruency while at the same time providing space between two bones. The perfect joint is one that is aligned properly with the right amount of tautness in the ligament to allow for normal motion to occur without causing too many compressive or distractive forces on that joint. Together with muscles that are of proper length for the size and length someone has, movements occur with fluidity and balance.
If a joint is hypomobile, ligaments may be too taut, the fluid in the joint may be thickened, the capsule might be too tight. All of these can contribute to abnormal biomechanics. Sometimes the joints do not get properly bathed in its fluid thus the nutrition to the joint becomes a problem. Over time, this constant compression can cause more dysfunction and arthritis.
Hypermobility allows for excessive motion to occur in a joint. Many people think that this is a good thing but it is actually not. Typically, there may be ligamentous laxity or an incongruent joint that, over time, further breaks down abnormally. On the contrary, if an active person has hypermobile joints and is active, joints can stretch out further, cartilage can be disrupted, ligaments can lose their ability to control joint motion and joint damage can ensue. In addition, for example, in the spine, if someone has a hypermobile, there is usually at least one hypomobile joint in the area. Thus, the joints do not properly share the load and back dysfunction becomes present.
Overall, having normal joints with adequate flexibility of soft tissue including muscles is ideal. In this circumstance, a normal strengthening program with balance and stretching will be very helpful to propel you into a better situation for an active lifestyle. If, however, one has hyper or hypomobilites and extensibility issues, it is important for you to have the right type of program for you. In summary, it is good to know your body and know what it is capable of doing. The new year always brings new exercise programs and new ideas but choosing the right one is the key.