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Concentric Contraction

Concentric Contraction. Shortening of muscle Force is generated Train: increase strength. Isometric Contraction. No change in length Force is generated Train: specific to joint angle. Eccentric Contraction. Lengthening of muscle Force is generated Ability to generate most force

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Concentric Contraction

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  1. Concentric Contraction • Shortening of muscle • Force is generated • Train: increase strength

  2. Isometric Contraction • No change in length • Force is generated • Train: specific to joint angle

  3. Eccentric Contraction • Lengthening of muscle • Force is generated • Ability to generate most force • Utilizes less O2 than concentric • More hypertrophy and strength gains • More muscle damage

  4. Acute Muscle Soreness • Blood flow plays an important part • Build up of LA stimulates pain receptors • Soreness disappears when you stop activity

  5. Delayed Onset of Muscle Soreness (DOMS) • Eccentric work (pain peaks after 48 hours) • Isometric work (pain peaks after 12 hours) • LA disappears in one hour

  6. Eccentric contractions cause most damage • Could be due to: • Strains in the MU • Popping of sarcomeres • Stretching produces over-extended sarcomeres • May be that myosin heads are “loosely” bound during eccentric contractions and heads are “popped off” the chain, causing damage

  7. Lactic Acid Theory • Not likely • Why not?

  8. Spasm Theory • Spasm due to ischemia • Release of p substance that causes pain stimulus • Pain reflex: muscle continues to contract • Break spasm by: massage, ice, and stretching • p substance is unknown

  9. Connective Tissue Theory • 4 substances: LDH, 3mH (increases in urine), hydroxyproline (HP), and CPK • CPK and LDH leak into blood when muscle breaks down • HP increases in blood and urine when break down connective tissue • All four are markers of muscle damage

  10. DOMS: 5 components • Structural components of skeletal muscle and CT are disrupted • Structural damage causes a change in permeability in muscle cell, allowing high levels of calcium into cells (kills cells) • High calcium causes a release of proteolytic enzymes • Fragments of broken protein leak into serum/blood and lead to an immune response; WBC flood the area • Histamine response: fluid flows to area, swelling and heat production, stimulates pain receptors

  11. Can analyze damage via • MRI • Swelling • Muscle protein in blood • Impaired substrate utilization • Decrease in strength and ROM • Decrease in motor control

  12. If entire muscle is not damaged, small areas can recover • In resting state, z lines are zig-zagged • Connection between titin and myomesin is broken, distorting the myofibril arrangement • Desmin (connects z lines of different myofibrils) is gone 3 days post exercise • Fibronectin (connects membrane to matrix inside fiber) is also disrupted

  13. Most damage is repaired after 10 days • Soreness decreases with repeated bouts • Adaptation

  14. Use of NSAIDS and DOMS • Short term pain/repair • Actual • Placebo • Long term pain/repair

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