Factors Affecting Strength and Power: Mechanical Factors Flashcards

1
Q

Define Strength

A

The maximum force that a muscle can generate at a specified velocity

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2
Q

How crucial is strength? What increases with strength.

A
As strength increases so does...
-RFD
-Power
-Jump Height
-Sprint performance
-COD performance 
-Potentiation
BUT
Injury occurrence reduces
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3
Q

What are the mechanical factors of Strength & Power?

A
  • Types of muscular actions
  • Length & velocity of isolated muscle
  • Moment arm
  • Joint velocity
  • Joint position
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4
Q

What are the architectural/structural factors?

A
  • Cross sectional area
  • Pennation angle
  • Fibre length
  • Fibre distribution
  • Type of fibre types stimulated
  • Innervation ratio
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5
Q

What are the neural factors of Strength & power?

A
  • Number of motor units activated

- Frequency of stimulation

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6
Q

In terms of linking factors together, what is RFD related to?

A

RFD is related to muscle structure and architecture as well as neural factors.

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7
Q

In terms of linking factors together, what is Peak force related to?

A

Peak Force is related to muscle architecture, the angle of Pennation will affect PF. Innervation ratio, muscle fibre types.

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8
Q

How does the force-length relationship differ between single-fibres and muscle-tendon units?

A

The single-fibre force-length relationship dictates that fibres are stronger at intermediate lengths because there are more binding sites available = greater number of cross-bridge attachments. When the connective tissue is added, the muscle-tendon unit is stronger at longer lengths.

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9
Q

Which changes occur during an isometric muscle action?

A

Muscle fibres shorten by up to 30% but there is no change on the muscle-tendon length.

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10
Q

Explain the force-velocity relationship.

A

The force-velocity relationship dictates that the force a fibre exerts decreases as the speed of shortening increases with peak power occurring ~30% of maximal shortening velocity

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11
Q

What is muscle stiffness?

A

Muscle stiffness is the force produced relative to the amount of displacement occurring

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12
Q

What is torque at a joint influenced by?

A

The moment arm of muscle effort and the moment arm of resistance

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13
Q

When can the length-tension relationship be applied to relevant applied practice?

A
  • Cycling position/Saddle height - higher seat more effective as muscle-tendon unit stronger at longer lengths
  • Prescription/manipulation of gym exercises
  • The sticking region during certain lifts
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14
Q

What were the findings of “joint-angle specific strength adaptations influence improvements in power in highly trained athletes”?

A

-Shorter ROM had better transfer to improvements during jumping + sprinting
-The more trained the athlete = more pronounced changes become
WHY
Neural control
Similar hip + knee angles

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15
Q

What are the mechanical adaptations of length-tension relationship?

A

Length-tension changes with training. IN CYCLING RF properties adapt to cope with demands - cyclists are stronger at short RF lengths
Force-length properties of RF for cyclists = negative
for runners = positive

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16
Q

How does the force-velocity relationship differ at Whole muscle level?

A

Maximal shortening velocity of a whole muscle depends on its fibre-type composition, fibre length, Pennation angle and the rate of change in Pennation angle.
Hill 1938 = power production is max when muscle shortens @ 1/3 of its max shortening velocity.

17
Q

How does the force-velocity relationship differ at Joint Level?

A

Peak torque exerted during concentric actions decreases as the angular velocity increases.

  • knee extensor PT @ 240 o/s smaller by 40% than PT @ 60 o/s
  • knee flexor PT @240 o/s smaller by 20-50% than PT @ 60o/s
18
Q

Which four mechanisms have been proposed towards the SSC?

A
  1. Increased time available for force generation
  2. The storage and subsequent use of elastic energy
  3. The force of cross-bridges is enhanced as a result of the pre-ceding stretch
  4. Additional sensory feedback
19
Q

Why are african runners so dominant?

A
  • Longer Achilles tendons
  • Shorter contact time during hopping
  • Greater jumping power
20
Q

What does variation in net muscke torque depend on?

A
  • The location of the attachments to the skeleton

- The contribution of multiple muscles to the net effect about a joint (1 vs 2 - joint muscles)

21
Q

What is a moment arm?

A

Perpendicular (shortest) distance from the joint centre to the line of action of the force (tendon)

22
Q

What are the advantages/disadvantages when tendon inserts further from the joint?

A

Advantage - muscular moment arm will be longer, the mechanical advantage increased.
Disadvantage - Muscle has to contract more to move joint through the ROM = less speed.

23
Q

How oes moment arm explain hamstring injuries?

A

Inter-muscle differences in hamstring moment arms about the hip and knee may be a factor contributing to the greater propensity for hamstring strain injuries to occur @ Biceps Femoris muscle.

24
Q

How does moment arm explain the effect of stature?

A

Tall athletes are immediately at a disadvantage because levers are long and form huge resistance arms.