Concentric ContractionConcentric Contraction

Shortening of muscleShortening of muscle

Force is generatedForce is generated

Train: increase strengthTrain: increase strength

Isometric ContractionIsometric Contraction

No change in lengthNo change in length

Force is generatedForce is generated

Train: specific to joint angleTrain: specific to joint angle

Eccentric ContractionEccentric Contraction

Lengthening of muscle Lengthening of muscle

Force is generatedForce is generated

Ability to generate most forceAbility to generate most force

Utilizes less OUtilizes less O22 than concentric than concentric

More hypertrophy and strength gainsMore hypertrophy and strength gains

More muscle damageMore muscle damage

Acute Muscle SorenessAcute Muscle Soreness

Blood flow plays an important partBlood flow plays an important part

Build up of LA stimulates pain Build up of LA stimulates pain receptorsreceptors

Soreness disappears when you stop Soreness disappears when you stop activityactivity

Delayed Onset of Muscle Soreness Delayed Onset of Muscle Soreness (DOMS)(DOMS)

Eccentric work (pain peaks after 48 Eccentric work (pain peaks after 48 hours)hours)

Isometric work (pain peaks after 12 Isometric work (pain peaks after 12 hours)hours)

LA disappears in one hourLA disappears in one hour

Eccentric contractions cause most Eccentric contractions cause most damagedamage

Could be due to:Could be due to:Strains in the MUStrains in the MUPopping of sarcomeresPopping of sarcomeresStretching produces over-extended Stretching produces over-extended sarcomeressarcomeresMay be that myosin heads are May be that myosin heads are “loosely” bound during eccentric “loosely” bound during eccentric contractions and heads are “popped contractions and heads are “popped off” the chain, causing damageoff” the chain, causing damage

Lactic Acid TheoryLactic Acid Theory

Not likelyNot likely

Why not?Why not?

Spasm TheorySpasm Theory

Spasm due to ischemiaSpasm due to ischemia

Release of p substance that causes Release of p substance that causes pain stimuluspain stimulus

Pain reflex: muscle continues to Pain reflex: muscle continues to contractcontract

Break spasm by: massage, ice, and Break spasm by: massage, ice, and stretchingstretching

p substance is unknownp substance is unknown

Connective Tissue TheoryConnective Tissue Theory

4 substances: LDH, 3mH (increases in 4 substances: LDH, 3mH (increases in urine), hydroxyproline (HP), and CPKurine), hydroxyproline (HP), and CPK

CPK and LDH leak into blood when CPK and LDH leak into blood when muscle breaks downmuscle breaks down

HP increases in blood and urine when HP increases in blood and urine when break down connective tissuebreak down connective tissue

All four are markers of muscle damageAll four are markers of muscle damage

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

Can analyze damage viaCan analyze damage via

MRIMRI

SwellingSwelling

Muscle protein in bloodMuscle protein in blood

Impaired substrate utilizationImpaired substrate utilization

Decrease in strength and ROMDecrease in strength and ROM

Decrease in motor controlDecrease in motor control

If entire muscle is not damaged, If entire muscle is not damaged, small areas can recoversmall areas can recover

In resting state, z lines are zig-zaggedIn resting state, z lines are zig-zagged

Connection between titin and Connection between titin and myomesin is broken, distorting the myomesin is broken, distorting the myofibril arrangementmyofibril arrangement

Desmin (connects z lines of different Desmin (connects z lines of different myofibrils) is gone 3 days post myofibrils) is gone 3 days post exerciseexercise

Fibronectin (connects membrane to Fibronectin (connects membrane to matrix inside fiber) is also disruptedmatrix inside fiber) is also disrupted

Most damage is repaired after Most damage is repaired after 10 days10 days

Soreness decreases with repeated Soreness decreases with repeated boutsbouts

AdaptationAdaptation

Use of NSAIDS and DOMSUse of NSAIDS and DOMS

Short term pain/repairShort term pain/repair– Actual Actual – PlaceboPlacebo

Long term pain/repairLong term pain/repair