ADAPTATION / INJURY PREVENTION TIDBITS
FOOT PARTS
The human foot has 26 bones, approximately 20 muscles, 33 joints, and over 100 ligaments holding it all together.
ANKLE SPRAIN PREDICTORS
BMI and past ankle sprains were much more predictive of future injury in high school athletes than where balance, height, ligamentous laxity, ankle tape/bracing usage, and hip strength balance.
High school football players where 16 times more likely to sustain and ankle sprain if the athlete was overweight or obese and had a history of ankle sprain. Incidentally, the use of preventive taping or bracing did not reduce the incidence of injury.
STRENGTH IMBALANCE & INJURY RELATIONSHIP
Individuals with strength differences of more than 10% between the quadriceps of the right and left legs were more likely to sustain lower limb injuries compared to individuals without such strength imbalances (Bender et al, 1964).
If this strength difference was due to past injury, one could speculate that previous injury at least partly attributed to increased the risk of injury, not necessarily the strength imbalance itself, since past injury is most predictive of future injury (see above studies) and past injury typically results in weakness (and decreased range of motion) in the injured limb.
EXERCISE AND ARTHRITIS
Exercise can decrease pain and improve functional capacity, ROM, and muscular strength.
REHAB PHASES
1. Immobilization
2. Range of motion (ROM)
3. Strength
4. Return to activity
CONNECTIVE TISSUE SHEATHS
Weight training may strengthen the sheaths of connective tissue within and around the muscle by increasing their collagen content. These connective tissues sheaths provide the framework that supports muscle overload and are the main component in the tensile strength and passive visco-elastic properties of muscle.
Endomysium surrounds individual fibers
Perimysium encloses groups of muscle fibers
Epimysium surrounds the entire muscle
BONE
Tensile strength and elasticity of bones decrease about 2% per decade from age 20 to 90 years (Hayes, 1986).
Bone is only one fifth the weight of steel but can withstand two times the compression force as granite, or four times the compression force as concrete.
Weight bearing activities such as walking can prevent bone mineral loss. Weight resistive exercises can prevent bone mineral loss if the antigravity musculature is activated.
Astronauts have about the same rate of bone loss as those on bed rest: about one percent per month.
JOINT CARTILAGE
Resistance training can thicken the hyaline cartilage on the articular surfaces of the bone (Ingelmark & Elsholm 1948).
Joint cartilage depends on synovial fluid for its nutrition since it has no vascularization. Synovial fluid is forced into the cartilage surfaces when the joint is loaded, as in physical activity. Joint cartilage functions in an elastic manner during short term loading.
The cartilage becomes temporarily deformed when long term loading forces water out of the cartilage. It returns to its original shape after cessation of loading when water is again drawn into the cartilage.
The alternate compression and decompression along with the pumping of synovial fluid due to physical activity is partly responsible for nutrition to the cartilage.
TENDON & LIGAMENT
Resistance training can increase the size and strength of tendons and ligaments (Fahey et al. 1975). This may be due to an increase of collagen within the connective tissue sheaths (Laurent et al. 1978).
The elastic limit of a tendon or ligament can be enhanced by exercise and training and can be reduced by aging and inactivity. The elastic limits of ligament are estimated to be 12-50%, and the elastic limits of tendon is 9-30% (Weakest at MTJ).
Junction strength failure of a bone-ligament preparation occurs at the attachment site of the ligament. The Junction strength failure is similar in a bone-tendon-muscle-tendon-bone preparation although separation may also occur at the musculotendinous junction or in the muscle itself.
Research using animal models demonstrate that junction strength of ligaments increases with endurance-type physical activity and decreases with immobilization. Furthermore, damaged ligaments regain strength faster if physical activity is performed afterwards.