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Biomechanics of Sports Injury > Architectural and Structural Factors > Flashcards

Flashcards in Architectural and Structural Factors Deck (19):

What are structural parts of the muscle?

Epimysium, Perimysium, Endomysium, Myofibrils
Thick & Thin Filaments, Cross-bridges
Troponin and Tropomyosin


What is the architecture of the muscle?

CSA, Pennation Angle, Fibre Length


What is CSA?

What is PCSA and ACSA and the differences?

How big the muscle is - max force is proportional to the number of fibres placed parallel to another

PCSA = physiological = fibre direction
ACSA = anatomical = perpendicular to long axis


What are some methods for measuring CSA?

Ultrasound, MRI, CT Scan, DEXA


What are some of the flaws in studies measuring for CSA?

Poor muscle size measurements
Small sample size
Day-to-day variability


How does body size affect strength?

Larger people generally stronger than smaller people
However normalisation according to body weight would prove otherwise
Larger people have larger moment arms


What are the key properties of Motor Unit types?

How can you measure these?

Contractile Speed (time to peak force)
MU force (amplitude of twitch)
Fatigueability (reduced peak force)

Via direct/indirect methods - examine MU twitches


What is the difference between Type I and Type II Motor Units?

Type I = slow contractile, fatigue resistant

Type II = fast contractile, large neuron size and diameter


What are the 2 different fibre organisation and pennation types and what do they mean?

In-series = increases ROM and faster contractions

Parallel = increases ROM and more force production


What is the difference between pennate and non-pennate muscles?

Pennate = fibres arranged around one/many central tendons

Non-pennate = parallel to the muscles line of pull (fusiform)


How does pennated muscles affect influence, thickness and training abilities?

Increases strength = Increases force production
Increases thickness of the muscle
Increases amount of fibres in set volume and reduces force transmission to the central tendon


What is the relationship between fibre length and CSA?

What happens if you have a longer fibre?

Increase CSA = Reduced fibre length

Longer fibre = Increased ROM and contraction velocity


What happens if you have an increased fascicle length?

Limits the degree of change in pennation angle


How does fibre length relate to injury?

Eccentric contractions increase fascicle length
Nordic hamstrings reduce this length and increases pennation on previous injured legs


What is the relationship between the soleus and gastrocnemius in terms of fibre lengths?

What is the relationship between the hamstrings and quadriceps in terms of fibres?

Soleus => Increased CSA, Reduced FTF, Large pennation
Gastroc => balanced fibres, faster but fatigue more

Hamstrings => Fusiform (increase contraction reduce force)
Quads => Pennate (dominant muscle and increase force)


How critical are these architectural and structural factors?

Muscle size & fascicle length exerted an increased influence on force production
Fibre type not significant to CSA:Torque ratio
Fascicle length important for force production in high velocity activities


What is rate of force development?

Derived from force/torque time curves during explosive activities


Does muscle design affect RFD?

Max strength correlated with RFD
Pennation = increase PCSA = increased RFD
Fibre type is a major factor


What is muscle slack?

Occurs before the movement & force is produced - but must be removed
Used for PAP activities - take up slack in MTU