Architectural & Structural Factors Affecting Strength & Power Flashcards
Architectural/ structures in muscles
Cross sectional area Pennation angle fibre length fibre distribution type of fibre innervation ratio
limitation to diagram about physiological and mechanical factors in muscle group function
no mention of neural factors
What is cross sectional area
Muscle size
Pennation angle
how fibres are arranged
muscle strength depends on
muscle size
Number of fibres placed parallel to one another
What do ACSA and PCSA mean
Physical cross sectional area
anatomical cross sectional area
Techniques for measuring changes in CSA
girth ultrasound MRI DEXA scan CT scan
Limitations for measuring changes in CSA
Placement of measurement taken
Why doesn’t CSA explain everything
Inability to activate entire muscle
co-activation of antagonist muscles
Limitations with measurement of strength and muscle size
different specific tension
CSA definition
how much force can be produced per unit are of muscle fibres
Body size
has an effect on force production
larger people are stronger than smaller in general pop
Structural factors: Motor unit types key properties
Contractile speed
MU force
Fatiguability
Type II motor unit
fast contraction velocity (up to 6 fls) fatiguable increased motoneuron size fibre diameter iinnervation ratio
Type I motor unit
Slow contraction velocity (up to 2 fls)
fatigue resistant
Are parallel or in series muscle (architecture) stronger
In parallel due to sum of all three in sequence
influence of pennation on thickeness
high pennation = decreased thickness
low pennation = increased thickness
why are pennated (fan) muscles better for strength
pack more muscle fibres into set volume of muscle
Fibre length
muscle fibres are generally shorter than muscle length
Muscles that tend to have large CSA have short fibres
Longer fibre length on ROM and velocity
Greater ROM and velocity contraction
fibre length and injury in cruciate ligament reconstruction
Shows shorted fascicles
greater pennation angles
lower eccentric strength
measurement of pennation angle and fascicle length
ultrasound
MRI
CT
measurement of pennation angle and fascicle length
ultrasound
The hamstrings are fusiform muscle group, what are they characterised by
Fast contractions
absolute force of contraction is small compared to pennate muscle groups
strength
peak force under a given set of condidtions
what happens during isokinetic muscle actions
the peak torque exerted during concentric actions decreases as the angular velocity increases
rate of force development is made up of
maximum force
time taken to reach given % force
Does muscle tendon stiffness influence RFD
tissue stiffness is inversely proportional to length, longer muscles and tendons are more compliant and force transmission may be slower
