We orthopedic surgeons spend our entire careers studying the health status of the body’s musculoskeletal tissues. Fitness participants should understand the 5 “connective” tissues involved in body movement.
- BONE sets the structural foundation of the limb, and each bone is linked to others by joints. The risk of sustaining a bone injury is low during pure fitness training (as opposed to sports participation); so from this point forward we will focus on the “connective tissues” that comprise joints.
- The end of each bone where it meets others inside the joint is capped with a layer of highly specialized hyaline CARTILAGE. In many joints, wedged between the hyaline cartilage caps can be found a separate structure made of fibroCARTILAGE. When discussing an athlete sustaining a “torn cartilage” in a joint, it is important to distinguish between these two types. Singular traumatic sports injuries usually involve fibrocartilage. Repeated trauma wears out both types, but with serious arthritis consequences for wearing down the hyaline cartilage.
- Joints are kept stable from dislocating by their LIGAMENTS, bands of fibrous tissue that connect one bone directly to other bones.
- Joints are spanned by TENDONS, fibrous bands that connect a muscle on one side of the joint to a bone on the other side of the joint.
- MUSCLE contractions then pull back and forth on the tendons to cause joint movement.
Just about everyone already knows the above information. But, I went through the list anyways to set up the following points:
In the last article (here), a dictionary definition of fitness read, “the capability of the body of distributing inhaled oxygen to muscle tissue during increased physical effort”. The order of events in the biologic sequence goes:
- inhale oxygen through the lungs
- deliver the oxygen via blood flow to the muscles
- oxygen combines with stored nutrients to produce energy for muscle contraction
- muscle contraction moves joints, usually against some amount of added resistance
When we design fitness programs, we work backwards through this sequence. We start by planning out a series of joint movements against a certain amount of resistance. Performing those movements then creates a demand for energy that forces the biologic sequence to occur.
Of all the 5 connective tissues, only one can be developed through fitness training, MUSCLE. Although participating in a well-designed fitness plan keeps bone, cartilage, ligament, and tendon tissues fundamentally healthy, none of them can actually be developed through training. However, cartilage, ligament, and tendon tissues can easily be injured by a poorly designed fitness program, and that will be the subject of our next article.