Connective Tissue Adaptations

How is the heel bone connected to the shin bone, and the shin bone connected to the thigh bone, as the popular song goes? The connective tissues in our body hold bone to bone (ligaments), muscle to bone (tendons), and muscle to muscle (fasciae). Tendons and ligaments are composed of parallel strands of collagen fibers tightly bundled together. Fasciae are like spiderwebs that hold layers of muscle fibers together and join at the end of the muscle to form a tendon.

Cartilage is a special type of connective tissue. Although it does help to make the connection between bones and muscles more solid and stable, its primary functions are to provide a smooth surface for joint movement and to absorb shock. The shiny hyaline cartilage at the ends of our long bones (check out the end of a drumstick) allows the bones on either side of the joint to glide smoothly during movement. The shock absorbers provide a cushion in areas where greater effects of weight bearing are seen, such as the intervertebral discs found between each of our vertebrae or the meniscus found in our knees.

The tendons, ligaments, and fasciae, like the bones, respond favorably to physical activity and need more stress and strain than just daily life provides. Long, slow endurance training allows damaged collagen to be exactly replaced with new collagen, yielding a net zero equation. But high-intensity strength training increases the amount of collagen and makes these connective tissues even thicker and stronger. Think about the example given earlier of the patella tendon pulling on the bone. The tendon responds to the muscular contractions during a strength-training session and adds more collagen to handle the stress. As the muscle hypertrophies and gets stronger, the tendon must also increase size and strength in order to hold on to the bone.

Conclusive evidence shows that cartilage needs joint mobility and physical activity-specifically of the weight-bearing variety-to stay healthy. As a joint moves through its range of motion, it lubricates and nourishes the cartilage with synovial fluid. The fluid not only feeds the cartilage, but also facilitates the joint's smooth movement. You can think of it as extra-virgin olive oil for your joints. In the knee it is easy to see the effects of weight bearing on cartilage. The cartilage is thicker where the bone bears the most weight. Since strength training incorporates both joint movement and weight bearing, it is beneficial for cartilage health. And because cartilage is viscoelastic like bone, it distributes the stress of heavy loads well and returns to the same shape when the load is removed.