Factors affecting strength and power

Question 1

What is strength?

Answer 1

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

Question 2

The importance of strength (Study) findings?

Answer 2

Strength increased
Rate of force development
Power
Jump height
sprint performance
COD performance
potentiation
decreased injury occurrence

Question 3

Mechanical factors affecting strength

Answer 3

Types of muscular actions
Length and velocity of isolated muscle
moment arm
joint velocity
joint position

Question 4

Force-length relationship

Answer 4

The curve of the length-tension relationship is a combination of two components: the contractile (sarcomere) and the elastic component

Question 5

When is force greatest?

Answer 5

At intermediate lengths

Question 6

How does the stretch shorten cycle help perfromance

Answer 6

Improves the economy (reduced metabolic cost)

Question 7

Why are African distance runners so dominant?

Answer 7

Longer Achilles tendons

Shorter contact times during hopping

Greater jumping power

Question 8

Four mechanics propesed from SSC

Answer 8

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

Question 9

Testing stiffness

Answer 9

Hopping, running and jumping

Question 10

Joint angle selection

Answer 10

Shorter ROM has better transfer to improvements in jump and sprint performance

has been linked to neural control

Question 11

Length tension changes with training

Answer 11

Cyclists stronger at short RF lengths

RF adapt to cope with demands

Question 12

Types of muscle action

Answer 12

Static - isometric

Dynamic - isotonic

Question 13

What is isometric

Answer 13

No change in length

Question 14

What is isotonic

Answer 14

Change in length

Question 15

What is a concentric movement

Answer 15

Muscle shortens

Question 16

What is a eccentric movement

Answer 16

muscle lengthens

Question 17

In what type of muscle action is force production greatest?

Answer 17

A greater force is generated during lengthening contractions possibly due to

the stretching of incompletely activated sarcomeres

an increase in the mean force during cross-bride cycles and

a faster reattachment phase.

Question 18

Eccentric contractions vs concentric contractions

Answer 18

Eccentric contractions can produce greater force than concentric contractions

Eccentric contractions are more efficient

Eccentric contractions present different neural
control strategies - EMG amplitude greater during concentric than eccentric actions

Question 19

Single muscle fibre - force velocity relationship

Answer 19

The force that the
fibre exerts decreases as the speed of
shortening increases due to limited
availability of binding sites.

Question 20

Whole muscle fibre - force velocity relationship

Answer 20

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.

Question 21

Power

Answer 21

Force x velocity

Question 22

Influence of moment arm

Answer 22

The joint position affects the magnitude of the torque produced by the muscles

Question 23

What is a moment arm

Answer 23

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

Question 24

Resistance arm

Answer 24

The distance from the axis to the point

of resistance application

Question 25

Effort arm

Answer 25

The distance from the axis to the point of force application is called the

Question 26

What are the advantages when the tendon inserts further

from the joint?

Answer 26

The muscular moment arm will be longer, and the mechanical advantage increased

Question 27

What are the disadvantages when the

tendon inserts further from the joint?

Answer 27

The muscle has to contract more to make the joint move through a given ROM – translates to less speed

Question 28

How does moment arm explain hamstring injuries?

Answer 28

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.

Question 29

How does moment arm explain the effect of stature?

Answer 29

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

Shorter levers = better suited to strength
activities