Studied by 49 People4 factors that affect force production in a muscle
Looks like no one added any tags here yet for you.
4 factors that affect force production in a muscle
size of motor units 3)# of fibers in activated motor units 4)relation between stimulation and inhibition in force production
Most common inhibitor
Gamma amino butyric acid (GABA)
Most common stimulant
Acetylcholine (ACH)
Stimulus threshold
Amount of stimulant needed in order to cause an action potential ( all or nothing )
How can you increase force production in a motor unit
By increasing the frequency of stimulation
What is tetanus
The plateau of stimulation of a muscle fiber when a motor unit is stimulated frequently
Task dependency model of fatigue
The cause of fatigue depends on the activity you are doing
Increase in motor unit recruitment and stimulation frequency will
increase force
relationship between recruitment and firing rate is concurrent until
80-90% of max force
after 80-90% of max force what happens
Firing rate increases
in order to avoid exhaustion, what percentage of motor units does the hand allow to be recruited
about 50%
Accumulation Hypothesis
Build up of metabolic byproducts cause fatigue
Examples of metabolic by products
Lactate, inorganic phosphate, ammonia
Depletion hypothesis (neuro fatigue)
The depletion of ACH at the myoneural junction causes fatigue
Depletion hypothesis (energy substrates)
The depletion of energy substrates causes fatigue
Example of energy substrates
Phosphagen, ATP, Glycogen
Under what conditions does the accumulation hypotheses cause us to fatigue
85-95% of max, maintained for 30 seconds - 3 minutes Ex: 200, 400, 800m run
Primary energy pathway in accumulation hypothesis and why
Anaerobic glycolysis Lactic acid build-up causes fatigue
Why lactate may not be the bad guy
Lactate can be used as an energy source for other cells
The dissociated hydrogen from lactic acid is what causes fatigue due to pH increasing
four ways lactate can cause fatigue
Interference with the release of calcium from the SR
Lactate build-up interferes directly with actin/myosin bonding strength
Lactic acid interferes with ATP breakdown
Lactic acid interferes with ATP production
How to effect lactic acid build up
Exercise training Increasing the buffering capacity of the cell Sodium Bicarbonate supplements
4 ways inorganic phosphate interferes with force production
interferes with actin-myosin binding affinity
interferes with calcium-troponin binding affinity
interferes with calcium release by the SR
interferes with calcium reuptake by SR
Ammonia is a byproduct of what reaction
ADP+ADP->Adenylate kinase->AMP+ATP AMP-->AMP deaminase-->Ammonia + IMP
How does ammonia build-up effect fatigue
It effects action potential propagation along the SR
At what intensity is ATP-PC system used
High-max intensity
What increases creatine phosphagen storage
Exercise training and creatine supplementation
What naturally forms creatine
Arginine glycine and thymine
Explain creatine loading phase
20 g of creatine a day for 5-7 days or 3-5 g a day for 30 days it boosts your creatine phosphate storage by about 20%
Where do we store ATP
The only place is bound to the myosin Head
This is only enough for about 3-4 seconds of exercise.
Primary ATP production pathway in a marathon
Aerobic oxidation of carbohydrates
When is the Aerobic oxidation of carbohydrates depleted
when glycogen stores run out
How long does Aerobic oxidation of carbohydrates last when running
about 20 miles
What happens when a runner "hits the wall"
Glycogen stores are depleted and they are using fats as energy
Fatigue from fats is from the accumulation theory
Glycogen supercompensation
Also known as carbo-loading
Deplete glycogen stores a week before the race Eat low or zero carbs until three days before the race then eat about 80% carbs Your body will super compensate causing glycogen stores to be nearly doubled.
3 muscle fiber types
Slow twitch Oxidative, Fast twitch glycolytic, and Fast twitch oxidative glycolytic
3 types of muscle
cardiac, smooth muscle, and skeletal muscle
what causes cardiac muscle to contract
SA Node
What NS influences heart rate
Autonomic nervous system (sympathetic and parasympathetic)
What muscle is striated
cardiac and skeletal
What muscle is not striated
smooth muscle
What NS innervates skeletal muscle
Somatic nervous system
What is the outer layer of skeletal muscle that connects to tendon
Epimysium
What surrounds the Fasciculus
Perimysium
What surrounds the muscle fibers
endomysium
What is a fasciculus
it is what houses muscle fibers
What is the function of connective tissue outside of muscles
energy transfer and protection
Force of a muscle fiber is directly proportional to
Size
cell membrane of muscle fibers is the
sarcolemma
Cytoplasm of muscle cells
Sarcoplasm