Exercise Adaptation / Injury Prevention Tidbits

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Dealing with Injury

Dumbbell Seated Shoulder External RotationImmediately stop an exercise that causes the joint or muscle unusual joint pain. Administer first aid. Allow time for the joint or muscle to heal as you continue to workout using exercises that do not further aggravate the injury during its recovery. After sufficient recovery time, start back very conservatively with a single set or brief bout with very light resistance. Continue to slowly progress steadily increasing the load or volume throughout the following weeks only if you can perform the load pain free. Be cautious not to aggravate the injury by attempting to progress too rapidly. Be aware that it is possible to not feel pain or discomfort after over doing it until after the workout or the next day - after it is too late. See a physician for serious injuries or if the pain persists or gets worse. A sports medicine physician specializes in exercise and athletic related injuries. A physical therapist should also be able to refer you to a physician knowledgeable in exercise related injuries for proper diagnosis. A specialist can help you determine possible underlying causes of the injury and make necessary program modifications to prevent future injuries. See Adaptation Criteria and Causes of Injury.


Rehab Phases

  1. Immobilization
  2. Range of motion (ROM)
  3. Strength
  4. Return to activity

Bomgardner, Rich (Dec 2001) Rehabilitation phases and program design for the injured athlete. Strength and Conditioning Journal , Vol 23, Num 6, pgs 24-25.


Strength Imbalance and 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 were 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 studies below) and past injury typically results in weakness (and decreased range of motion) in the injured limb.


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.

Mirabella MR, Tyler TF & McHugh MP (2004) Risk Factors for Ankle Sprains in High School Football Players. Journal of Athletic Training. Supplement 39(2), 38.

Tyler TF, McHugh MP & Tetro (2004) Risk Factors for Ankle Sprains in High School Athletes. Journal of Athletic Training. Supplement 39(2), 37.


Interdependent Strength

Strength losses from a particular movement following an injury appear to also negatively effect strength of agonist muscle group. For example, after initial recovery of left knee injury, left quadriceps still remain deconditioned. Right leg regains strength relatively quickly but left leg may lag in strength as measured by unilateral Leg Extensions or Single-leg Leg press. Consequently less force can be applied on left leg during Squats, Leg Presses, and other similar movements. Interestingly, left hamstring (quadriceps agonist and knee stabilizer) can also remain weak although it was not directly impaired by knee injury. Also see Interdependent Strength in strength training.


Exercise & Arthritis

Exercise can decrease pain and improve functional capacity, ROM, and muscular strength

Felson DT, Lawrence RC, Hochberg MC, McAlindon T, Dieppe PA, Minor MA, Osteoarthritis: New insights. Part 2. Treatment approaches. Ann Intern Med. 133:726-737, 2000.

Casper JM, Berg K. Effects of exercise on osteoarthritis: A review. J Strength Cond Res. 12:120-125, 1998.


Foot Parts

The human foot has 26 bones, approximately 20 muscles, 33 joints, and over 100 ligaments holding it all together.


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 viscoclastic 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.

In animal studies, the first 40 repetitions of an exercise stimulates greater than 95% of bone formation. Additional repetitions do not significantly increase bone formation (Riewald S. Bone of Contention: What Exercises Increase Bone Strength? Strength and Conditioning Journal. 26, 1, pg 46-47.).

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 and 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 muscletendinous 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.

Martin Paul, B.Sc. Kin., PFLC writes:

An In Vitro setting, a ligament can stretch quite a bit. The only ligament that can match the 50% elasticity is the ligamentum flavum. Even then, Nachemson & Evans (1968) reported, "Beyond this point, the stiffness increases greatly with additional loading and the ligament failed abruptly (reached Pmax) with little deformation. Furthermore, Butler et al (1978), observed that beyond 4%, "small force reductions (dips) can sometimes be observed in the loading curves for both tendons and ligaments. These dips are caused by the early sequential failure of a few greatly stretched fiber bundles. When sequential failure occurs, it compromises the strength of the ligaments and thus increases the instability of that particular joint. Fung (1981), goes on to add that the upper limit for physiological strain in tendons and ligaments is from 2 to 5%. Finally, Kear & Smith (1975) findings suggest that "normal activity a tendon in vivo is subjected to less than one fourth of its ultimate stress."

    1. Butler, D.L., Groods, E.S., and Noyes, F. R.: Biomechanics of Ligaments and Tendons. Exerc. Sport Sci. Rev., 6:125, 1978.
    2. Fung, Y.C.B.: Biomechanics: Mechanical Properties of Living Tissues. NewYork, Springer Verlag, 1981, p.222.
    3. Kear, M., and Smith, R.N.: A method for recording tendons strain in sheep during locomotion. Acta Orthop. Scand., 46:896, 1975.
    4. Nachemson, A.L., and Evans, J.H.: Some mechanical properties of the third human lumbar interlaminar ligament (ligamentum flavum). J. Biomech., 1:211, 1968.


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