IT'S YOU RANGE OF MOTION...
Flexibility is the ability to create a range of motion (ROM) in the body. Localized flexibility is the ability to create a range of motion in a certain joint. The distinction is necessary since one joint's flexibility does not represent the entire body's flexibility. Range of motion and flexibility are used interchangeably since the range of motion is the functional representation of the idea of flexibility.
Prior to adding anything else, let's distinct between flexibility and mobility. While they are related, mobility is not the same as flexibility. Range of motion and flexibility are one and the same. Flexibility is defined by the extent of degrees of movement a joint allows, while mobility examines the quality of movement within the range of motion of a joint. For example, if the joint allows full flexibility and mobility, the person will be able to utilize the entire range of motion of the joint (maximal degrees of movement) and experience the most smooth movement throughout that range of motion (optimal mobility).
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A person can enjoy maximal mobility, yet experience limited flexibility. The same person could enjoy maximal flexibility, yet have mobility problems. In the first case, the person will not be able to complete flex or extend the joint (as an example), yet will move smoothly within that limited range of motion. In the other case, the person can flex or extend the joint (for example) fully, yet cannot move smoothly.
The number one determinant of the flexibility of a joint, is its structure. If the joint structure accommodates more movement, it will allow for greater flexibility at that specific joint. For example, a ball and socket joint allows greater movement, and thus, greater flexibility. If the joint structure accommodates less movement, it will allow for lesser flexibility at that specific joint. For example, the suture joints of the skull allow almost no movement, and thus, the least flexibility. In a previous post, the relationship between joint structure and function has been explain; You might want to revisit it is needed...
ROM is specific to a specific joint; specific to a joint on a specific side of the body (if relevant); specific to a specific movement within the specific joint; specific to a movement in a specific plane of movement; and can even be analyzed specifically to the influence of a specific skeletal muscle. Bottom line - flexibility is very specific!
At early age, joints tend to be more flexible, and lose from their flexibility as the joints mature and age. I always teach that the entire function of a human, is based on the idea of "tread-offs" since you are never ever, ever never getting a perfect package. Never ever!!!
This means that the name of the game is "give and take", always something given, in order for something to be received. Always!
For example, greater flexibility is rooted in more movement in the joint, that means lesser the stability. People that are hyper-flexible, are hypo-stable. The less stable a joint is, the more stabilizing tissue you need (ligaments and skeletal muscles most likely). The more stable a joint is, the more skeletal muscle contraction force can be applied to creating movement. On the other, greater flexibility allows smoother movement, decrease traumatic injuries, and better blood flow to the area. Tread-offs all day long. What are you giving? What are you getting?
Flexibility is further influenced not just by the structure of the joint, yet also by its content. How many muscles, ligaments, tendons, joint capsules, fluids, blood vessels, nerves, fascia, and skin, does the joint include? - The type of joint also determines the flexibility created (see a separate post about the articular system, joint types, and function).
Flexibility is additionally influenced by hormones, including sex hormones. Thus, if to are a female or male (as sex related terms), the flexibility of the person changes, where women in general tend to be more flexible than men as adults. While flexibility most definitely has a robust genetic basis to it, it can be trained, worked on, and improve. Flexibility, as are other fitness components, are hard-earned, and easily lost if you do not continue to stimulate the tissue on a regular basis.
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The following are commonly used to indicate expected ROMs according to a specific joint and movement:
Hip extension: 10-30 degrees (thigh moves backward)
Hip Flexion: 90-135 degrees (thigh moves forward)
Shoulder abduction: 0-180 degrees (arm raised sideways)
Shoulder flexion: 0-180 degrees (arm raised forward)
Knee flexion: 0-150 degrees (shin and calf move backward)
Knee extension: 0-120 degrees (shin and calf move forward)
Elbow flexion: 0-150 degrees (forearm moves towards the body)
Ankle plantar flexion: 0-40 degrees (toes pointed at the ground)
Ankle dorsi flexion: 0-20 degrees (toes pointed upward)
Lumbar flexion: 0-60 degrees (trunk moves toward the ground; bending forward)
Lumbar extension: 0-25 degrees (trunk moves away from the ground; getting erected)
Lumbar side flexion: 0-25 degrees (trunk bends sideways)
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