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Biomechanics of Strength & Injury > Lecture 9 - Factors Affecting Strength & Power: Mechanical Factors > Flashcards

Lecture 9 - Factors Affecting Strength & Power: Mechanical Factors Flashcards

1
Q

How can training be used to aid injury prevention?

A
  • The muscle can change the length tension relationship to change the optimal length.
  • E.g. Nordic curls change the optimum length resulting in the hamstrings being stronger at longer lengths where most injuries occur.
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2
Q

In what type of muscle action is force production greatest and why?
 -Eccentric
 -Isometric
 -Concentric

A
  • A greater force is generated during lengthening contractions possibly due to
  • a) the stretching of incompletely activated sarcomeres
  • b) an increase in the mean force during cross-bride cycles and
  • c) a faster reattachment phase
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3
Q

In isometric contractions does the muscle change length?

A
  • No, however the muscle shorten by up to 30%.
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4
Q

In the MTU what is the CE, SE and the PE and what is their level of control ?

A
  • CE- contractiole - active
  • SE - series eastic - active and passive
  • PE - parallel elastic - passive.
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5
Q

What aspect was found to have an increased effect on sprint velocity, CMJ, SJ and DJ performance.

A
  • Vertical stiffness (Kvert)
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6
Q

What is strength?

A
  • The maximum force that a muscle can generate at a specified velocity.
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7
Q

What are the mechanism of why the SSC works ?

A
  • Increased time available for force generation
  • The storage and subsequent use of elastic energy
  • The force of cross-bridges is enhanced as a result of the preceding stretch.
  • Additional sensory feedback
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8
Q

What are the mechanical adaptation to training for the length tension relationship?

A
  • Muscle changes the length tension relationship in demands to the sport.
  • E.g cyclists develop stronger rec fem at shorter muscle lengths
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9
Q

What can moment arm supplement for ?

A
  • Low force production
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10
Q

How does 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 in the BF muscle, as this has the smallest moment arm.
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11
Q

On the whole muscle level what governs maximal shortening velocity?

A
  • Fibre type composition
  • Fibre length
  • Pennation angle
  • Rate in change of Pennation angle.
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12
Q

What are the architectural/ stuctural factors that underlay strength and power?

A
  • Cross sectional area
  • Pennation angle
  • Fibre length
  • Fibre distribution
  • Type of fibre types stimulated
  • Innervation ratio
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13
Q

With strength increases what variables can also be improved?

A
  • Rate of force development
  • Power
  • Jump height
  • Sprint performance
  • COD performance
  • Potentiation
  • Reduction in injury occurrence.
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14
Q

In the single muscle fibre where is the force the greatest and why?

  • What happens when connective tissue in added ?
A
  • Force is greatest at intermediate lengths and decreases at shorter and longer lengths.
  • This is because there are more binding sites available and consequently greater number of crossbridge attachments at intermediate lengths.
  • The muscle-tendon unit is stronger at longer lengths.
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15
Q

How does the length - tension relationship effect cyclists?

A
  • Positioning

- Prescription/ manipulation of gym exercises.

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16
Q

What is the relationship between peak torque (PT) and angular velocity?

A
  • During concentric contraction peak torque decrease and angular velocity increases.
17
Q

What can the attachments locations influence?

A
  • The moment arm relative to the joint
  • The number of axes about which the muscle exerts a torque
  • The number of joints spanned by a muscle.
18
Q

Explain how the force-length and force-velocity relations impact upon the performance of a cyclist.

A
  • With training the cyclists are going to adapt to be able to produce higher levels of force at shorter muscle lengths
19
Q

What does a bigger moment arm mean for smaller ROM

A
  • Greater force production
20
Q

What is excitation, action potential and the order or force transmission.

A
  • Excitation - Contraction coupling
  • Action potential - release of Ca2- cross bride activity
  • Force transmission order is CE, SE, Bone.
21
Q

How can joint angle effect strength and why?

A
  • In training using smaller ROM or joint angles resulted in improvements in strength and power.
  • This is due to neural control and the similarity of the angles that are used in training to performance.
22
Q

At what speed does maximal power production occur in muscle?

A
  • At one third of the maximal shorting velocity.
23
Q

What are the neural factors that underlay strength and power?

A
  • Number of motor units activated

- Frequency of stimulation

24
Q

What can account for the variations in net muscle torque ?

A
  • The location of the attachments to the skeleton - The contribution of multiple muscles to the net effect about a joint (one vs. two-joint muscles)
25
Q

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

A
  • The muscular moment arm will be longer, and the mechanical advantage increased.
26
Q

What is the SSC and why is it important ?

A
  • A common pattern of muscle activation during many movements is the stretch of an active muscle before it subsequently performs a shortening contraction
  • Important as it improves the economy of performance (reduced metabolic cost), and muscle can perform more positive work if it is actively stretched first.
27
Q

What is muscle stiffness (Kvert)

A
  • The force produced relative to the amount of displacement occurring.
28
Q

At the joint level is the mechanical action of the muscle the force it exerts or the torque around the joint?

A
  • Torque produced around the joint
29
Q

How do you calculate torque?

A
  • Torque = FD

- FD = Force x Distance

30
Q

What is the torque at a joint influence by ?

A
  • The moment arm of muscle effort and the moment arm of resistance. By altering the length and balance between these two moment arms we can influence the
    level of mechanical disadvantage/advantage.
31
Q

What are the mechanical factors that underlay strength and power?

A
  • Types of muscular actions
  • Length and velocity of isolated muscle
  • Moment arm
  • Joint velocity (muscle groups)
  • Joint position (muscle groups)
32
Q

What is the moment arm?

A
  • The perpendicular (shortest) distance from the joint centre to the line of action of the force (tendon)
33
Q

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

A
  • The muscle has to contract more to make the joint move through a given ROM – translates to less
    speed.
34
Q

How does moment arm explain the effect of stature?

A

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

Biomechanics of Strength & Injury (16 decks)

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