Week 1

Question 1

What are the four main muscle characteristics and function?

Answer 1

Excitability - receive and respond to stimuli
Contractility - shorten forcibly when stimulated
Elasticity - ability to recoil to resting length
Extensibility - ability to be stretched

Question 2

What is plastic deformation?

Answer 2

Tendons and ligaments stretched beyond their elastic limit - injuries occur

Question 3

What are the functions of muscle?

Answer 3

Stabilise joints (posture and injury reduction)
Support skeleton (static and dynamic posture)
Protect organs
Generate heat
Produce movement/locomotion

Question 4

Where do muscular contractions start?

Answer 4

From the stimulus and receptor - nervous system.

Question 5

What is the resting membrane potential?

Answer 5

-70mV.

Question 6

What is the threshold for an action potential? How is it reached?

Answer 6

-55mV.
Stimulus causes an influx of Na and outflux of K. Overall increase to -55mV. Controlled by the sodium/potassium pump.

Question 7

How does the number of stimuli affect the outcome?

Answer 7

A single stimuli - muscle twitch with very minimal force production
Multiple stimuli - summation effect and greater force output (bigger contraction).
Too much stimuli produce too much stimulation and fatigue sets in - repeated contraction.

Question 8

What is a fascicle?

Answer 8

Bundle of muscle fibres.

Question 9

What is the sliding filament theory (overview).

Answer 9

The end of the contraction - happens in the sarcomere (deepest structure of muscle tissue).
The actin and myosin form cross bridges and are pulled towards the centre in the power stroke = muscle contraction.

Question 10

Do muscles pull or push?

Answer 10

Only ever pull (if one does not seem to be pulling, the antagonist will be).

Question 11

What happens as muscles shorten?

Answer 11

The insertion generally moves towards the origin (attachment).

When we move the shoulder the insertion is at the tip of the humerous and the origin is in the clavicle (collar bone) so it is always the insertion that moves.

Question 12

Agonist

Answer 12

Prime mover - contracts and shortens to produce movement

Question 13

Antagonist

Answer 13

Contract eccentrically to control the movement

Question 14

Synergists

Answer 14

involved but not the prime mover. Adds force to the movement, reduces undesirable or unnecessary movement.

Question 15

Fixator

Answer 15

Synergists that immobilise a bone or the muscle’s origin (it is always the insertion that moves).

Question 16

What does the area of the muscle correlate with?

Answer 16

Its force production capacity - quads have much larger cross sectional area than hamstrings so can produce more force.

Question 17

What is muscle pennation?

Answer 17

The orientation of the muscle fibres. It is important for dictating type of movement the muscle can produce.

Question 18

Give 6 types of muscle pennation.

Answer 18

Parallel - fibres extend parallel to the axis off the segment - run vertically e.g. biceps (can either be fusiform or non-fusiform)
Fusiform - start vertical then have a bow shape towards the outside.
Unipennate - fibres extend at a single oblique angle (slanted orientation)
Bipennate - split into two halves, left and right (rectus femoris - medial quad).
Multipennate - fibres extend at several angles (deltoids, glute medial).
Convergent - fan-like spread of the fibres across the muscle (pecs).

The orientation determines the movement - e.g. quads extend but also internally/externally rotate so have different muscle types.

Question 19

Structure of muscle determines function explain.

Answer 19

Muscles can either be in length (in series) or in width (in parallel).
Longer muscle fibres are organised in series, wide muscle fibres are in parallel.

Longer fibres with a medium-small physiological cross-sectional area (PCSA) are designed for velocity (in series).
Shorter fibres with a large PCSA are designed for force production (in parallel).

Question 20

What does the pennation angle change?

Answer 20

Greater pennation angle = compresses more fibres in the same place increasing force production.

Longer muscle fibres, smaller angle = greater velocity
Shorter fibres, greater angle = more force production.

Question 21

What is the muscle tendon unit?

Answer 21

The interaction between the muscle and the tendon which generates movement.
When muscle is shortening (concentric contraction), tendons are lengthening.

Question 22

What is the reactive strength index (RSI)?

Answer 22

The transition from eccentric to concentric contraction (tendons going from short to long).
An effective stretch shortening cycle means energy return from tendon to muscle is optimal.

Question 23

What is the eccentric utilisation ratio?

Answer 23

SJ height divided by CMJ height.
A measure of how well you use the SSC.

Question 24

What three things are involved in a level system?

Answer 24

Fulcrum/pivot (fixed point), effort (muscle force) and resistance (load).
If effort > resistance movement occurs. The hardest part of any movement is when the load is furthest away from the pivot.

Question 25

Tendon compliance

Answer 25

Tendon's ability to elongate and shorten but maximise energy return. A stiff muscle won't change length that much affecting force generated by the muscle. If a tendon is restricted it won't return much energy into the contraction. Too much elongation is also bad, reduced muscle force and tendency for rupture.

Question 26

Plyometric vs isometric

Answer 26

Plyometric - rapid movements that require higher force outcomes (lower resistance). Isometric - static strength exercises.

Question 27

Onambele et al., 2006 plyometric vs isometric study

Answer 27

Right leg plyometric training, left leg isometric training. Muscle thickness, CSA and force production increased in both over 12 weeks. More force generated per mm deformation (change in length) of the muscle in plyo group. Only the plyo group increased tendon properties.