Nueromuscular system Part 2

Question 1

Can motor units be converted?

Answer 1

Motor units cannot completely convert in humans with normal training
there is some shift of the contractile properties and metabolic profile can occur

Question 2

Can fiber type be converted?

Answer 2

Can modify their expression of myosin heavy chain content

Can co-express types of MHC of the same fiber type (after intense exercise training)

Question 3

What is shifting?

Answer 3

Shifting is when the fiber type moves up to the next position
Type I moves to Type IC but cannot move to type II
Type IIX is fastest in humans and type II b occurs only in animals

Question 4

What happens to the muscle during immobilization?

Answer 4

The muscle atrophies
Fiber type profile shifts from ST to FT
Muscle oxidative capacity reduces
General weakness

Question 5

When stressors on muscle are taken off

Answer 5

fibers will convert to type II

Question 6

What happens to muscle when we age?

Answer 6

Motor neuron apoptosis(natural death) = muscle fiber necrosis especially FT(not natural death)
40% loss of FT
Loss of muscle mass
Decrease MF size
Increase muscle connectivity tissue content
Increase grouping due to reduced number of MU
Decrease in overall metabolic activity

Question 7

How does muscle increase in size?

Answer 7

Hypertrophy = increase size of fibers
Hyperplasia = increase number of fibers

Question 8

Does muscle increase through hypertrophy, hyperplasia or both?

Answer 8

MacDougall - showed same number of fibers in bicep muscle of body builders and the untrained (hypertrophy)

Sjostrom- showed that dominant tibialis anterior had greater muscle fiber compared to non-dominant (hyperplasia or genetic?)

Question 9

What is the possible hyperplasia mechanism?

Answer 9

Muscle fiber splitting
Muscle satellite cell incorporation
(replicate cells to create a new muscle fiber)

Question 10

What are the effects of training on the neuromuscular system?

Answer 10

1) Change in neural properties

2) Change in muscle fiber properties

Question 11

1)Changes in neural properties

Answer 11

Increase CNS drive
Increase the synchronization of MU
Increase MU recruitment
Decrease less inhibition due to resetting of neural tension limiting mechanisms)
Increase in size and number of NMJ

Question 12

What is asynchronous MU firing?

Answer 12

Allows for some MU to fire while other “relax” which increase all MU efficiency

Question 13

What is asynchronous MU firing?

Answer 13

Allows for some MU to fire while other “relax” which increase all MU efficiency

Question 14

2) changes in muscle fiber properties

Answer 14

2A) Increase size of muscle fiber with strength trainigng
2B) Angle of pennation is less in vastus lateralis and gastroc of sprinters then endurance
2C) Increase anaerobic potential/aerobic potential of FT and ST (Type I become more like type II)

Question 15

What causes pain and soreness?

Answer 15

When nociceptors are stimulated by:
1) Mechanical damage to muscle or connective tissue
2) Stretch due to swelling
3) Muscle spasm
4) Inflammatory chemical
5) Ion accumulation
(Brain mediates the peripheral neural stimulation)

Question 16

What is short term pain?

Answer 16

Immediate during or after exercise usually a dull ache, burn or throb the subsides with recovery

Question 17

What causes short term pain?

Answer 17

Ionic imbalance within the muscle
Muscle edema (fluid in the muscle) that causes stretch during high intensity

Question 18

How long doe short term pain last?

Answer 18

Subsides relatively quickly during recovery

pH in muscle restored within 20min

Question 19

What is long term pain?

Answer 19

Muscle soreness ecperienced over several hrs/day

Delayed Onset Muscle Soreness (DOMS)

Question 20

What causes long term pain?

Answer 20

Actual muscle damage caused by mechanical stress

Question 21

What are the results of DOMS?

Answer 21

Tearing of the sarcomere and muscle tendon
Release of chemicals that continue to stimulate nerve ending that results in prolonged sensation
Swelling/muscle edema
Disruption of Ca2+ regulation
Inflammation

Question 22

What types of exercises cause DOMS?

Answer 22

1) Eccentric forms of muscular contractions and training

2) Unaccustomed forms of exercise

Question 23

How long does DOMS last?

Answer 23

2-3 days
Peaks at 48hrs
Severs can last several days

Question 24

What can you do about DOMS?

Answer 24

Training will reduce it by:
Increase connective tissue
Increase muscle fiber size
Increase suppleness and flexibility through greater ROM

Others
Warm up/cool down
Stretch
Antioxidant supplements
Pharmaceuticals