Module 4: Lecture 6

Question 1

what is a key muscle characteristic that dictates how much force is going to be produced?

Answer 1

• muscle - length relationship
• contraction type

Question 2

when we talk about length of muscle, what are we talking about?

Answer 2

the overall length of a single one of the sarcomeres

Question 3

will the amount of overlap between your thick and thin filaments dictate how much force you can generate?

Answer 3

yes
- the idea of length - tension relationship

Question 4

at optimal muscle length, maximum ______ can be developed.

Answer 4

tension

Question 5

why is tension production decreased when your muscle length is greater than optimal?

Answer 5

because there will be a decrease in available sites for crossbridge formation

Question 6

why is tension production decreased when your muscle length is less than optimal?

Answer 6

because the thin filaments will overlap, limiting the number of active sites available for crossbridge formation

Question 7

what is muscle tension?

Answer 7

the force exerted by a muscle contraction on an object
- lifting an object steadily

Question 8

what is muscle load?

Answer 8

the force exerted on a muscle by an object
- the object weighing your hand down

Question 9

what is going to dictate what type of muscle contraction you are going to produce?

Answer 9

the relative balance between muscle tension and muscle load
- dictate whether the muscle shortens or lenghens

Question 10

is the muscle going to lengthen or shorten if the tension is greater than the load?

Answer 10

shortening contraction

Question 11

is the muscle going to lengthen or shorten if the tension is less than the load?

Answer 11

lengthening contraction

Question 12

what is it called when a muscle contracts without any shortening?

Answer 12

isometric contraction
- constant length contraction

Question 13

what is it called when a contraction involves constant load/tension?

Answer 13

an isotonic contraction

Question 14

which isotonic contraction involves an increase in muscle length?

Answer 14

lengthening / eccentric contraction

Question 15

which isotonic contraction involves a decrease in muscle length?

Answer 15

shortening / concentric contraction

Question 16

during what type of contraction can you produce the most amount of force?

Answer 16

during an isometric contraction
- maximal force can be produced when velocity is zero

Question 17

the greater the load, the ______ the velocity of shortening.

Answer 17

lower

Question 18

is there such thing as an unloaded shortening velocity in real life?

Answer 18

no
- only in lab

Question 19

as the velocity of the contraction increases, the amount of force you can generate rapidly _________.

Answer 19

decreases

Question 20

what is power a combination of?

Answer 20

force x velocity

Question 21

when is maximal power produced during muscle shortening?

Answer 21

when optimal load and velocity relationship is determined

Question 22

what are the three fibre types in human skeletal muscle?

Answer 22

1. Type I –> slow twitch
2. Type IIA –> fast twitch
3. Type IIX –> fast twitch

Question 23

which fibre type is our fast fatigable?

Answer 23

Type IIX

Question 24

which fibre type is our fast fatigue-resistant?

Answer 24

Type IIA

Question 25

what do our slow twitch fibers predominantly rely on?

Answer 25

oxidative metabolism within the mitochondria for ATP generation
- slow oxidative

Question 26

which fibre type is our fast oxidative glycolytic?

Answer 26

Type IIA

Question 27

the larger the diameter of the fiber, the more _____ and _____ that are going to be packed within that area, the more _____ that can generate.

Answer 27

• actin and myosin
• force

Question 28

what are the muscle fibre diameters for each fibre type? what about motor units per muscle?

Answer 28

Muscle fibre diameter
T1- Small
TIIA - Large
TIIX - Large

Motor units per muscle
T1 - More, smaller
TIIA - Fewer, larger
TIIX - Fewer, larger

Question 29

what is the force production of each fibre type?

Answer 29

T1 - low
TIIA - intermediate
TIIX - High

Question 30

which fibre type is the most fatigable? least fatigable?

Answer 30

most - TIIX
least - TI

Question 31

what is TIIX fibres sensitivity to recruitment?

Answer 31

low

Question 32

is someone given more slow twitch or fast twitch fibers by genetics or training?

Answer 32

more genetics related
- extreme examples will give the shift of fibre type

Question 33

what are the determinants of whole-muscle tension in skeletal muscle?

Answer 33

1. changing the numbers of fibers contracting
2. tension developed by each contracting fibre

Question 34

how do we determine the number of fibres contracting?

Answer 34

take into consideration:
- number of motor units recruited
- number of muscle fibres available to contract
- number of muscle fibres available to contract
- size of muscle
- presence of disease
- extent of recovery from traumatic losses

Question 35

how do we determine the tension developed by each contracting fibre?

Answer 35

• frequency of stimulation
• length of fibre at onset of contraction
• extent of fatigue
  
  • duration of activity
  • amount of asynchronous recruitments of motor units
  • type of fibre (fatigue-resistant oxidative or fatigue-prone glycolytic)
• thickness of fibre
  - pattern of neuron activity (hypertrophy, atrophy)
  - amount of testosterone