CHAPTER 4: BONE, MUSCLE, AND CONNECTIVE TISSUE ADAPTATIONS

BONE ADAPTATIONS New bone formation occurs when a minimal essential strain is surpassed. This MES may equate to around 1/10 the amount of force required to fracture the bone. The strain is of a weight bearing nature. Axial Skeleton & Appendicular Skeleton

Trabecular & Cortical Trabecular responds more quickly than cortical Cortical bone has a series of canals which run from the spongy part of the bone. MES causes Osteoblasts to migrate to the cortical bone for reinforcement.

BONE BUILDING To stimulate bone growth, programs need to look at: Specificity of loading Exercise selection Progressive overload Variation

SPECIFICITY OF LOADING The strain must be placed on the areas where bone formation is required (hip, spine, etc.). Multijointed Osteogenesis is specific to the area worked.

EXERCISE SELECTION Those exercises that are multijointed and use more muscle groups tend to be more effective. Isolation exercises tend not to be as effective. Squat vs leg extension

PROGRESSIVE OVERLOAD Just like any program, the strain placed on the bones (and muscles) must increase gradually over time to reduce the chance of injury (stress fractures). Ten percent rule

VARIATION One of the keys in overall osteogenesis is to place the strain on the bones at different angles. Vary the exercises performed Starting young also seems to be a key. Enhance as much bone development early in life through weightbearing activities.

MECHANICAL LOADS FOR STIMULUS Magnitude of the load (more is better) Speed of loading (faster/powerful is better) Direction of forces (variations are better) Number of repetitions is not a significant stimulus (more is not better). Look at page

CHAPTER 4 Four components of Mechanical Loading which stimulate bone growth: Intensity of load Speed of loading Direction of Force Number of Reps (volume) ***Also known as Osteogenic Stimuli, Table 4.1)

Mechanical Loading from Aerobic Exercise -Interval, stair climbers and weight packs seem to generate more osteoblasts.  Mechanical Loading for Athletes  Basically the same as other programs (see pg. 64 & 65)

CHAPTER 4 Mechanical Loading for Untrained or Elderly Physicians clearance Analysis of joint stability Recommend using “projected 1RM” Important point regarding musculoskeletal strength gains!  Strength, Size or Endurance

As the bone grows the insertion becomes buried in the bone, thus strengthening the junction.

CONNECTIVE TISSUE The degree of tissue adaptation is proportional to the intensity of the exercise stimulus. Positive adaptations occur at the tendon-bone junction, within the body of the tendon/ligament, and in the network of fascia around the muscle.

TENDONS, LIGAMENTS, FASCIA Ligament connects bone to bone and has its own blood supply Tendon connects muscle to bone and also has a blood supply High intensity loading results in a net growth of the involved connective tissue.

CARTILAGE The internal environment of the cartilage tissue is call the cartilage matrix. Comprised of “ground substance”. Hyaline – More articular in nature. Composed of water, protein and carbohydrates. Collagen fibers Fibrous – Intervertebral disks & junctions where tendons attach to bones

Weight bearing forces and complete movement through the ROM is essential. Moderate aerobic exercise increases cartilage thickness. Strenuous exercise does not seem to cause degenerative joint disease pg. 70.