Lecture Exam 1 (part 3) Flashcards
How fatigue affects force production in a muscle (model)
task dependency model of fatigue
Task dependency model of fatigue says this
what causes fatigue is dependent on the activity in which we are participating
two hypothesis of the task dependency model of fatigue
accumulation hypothesis
depletion hypothesis
accumulation hypothesis says this
build up of metabolic byproducts cause fatigue
es. lactate, Pi, ammonia
depletion hypothesis says this
we run low on NT, or energy substrate and that causes fatigue
This hypothesis is said to come into play in exercises that last 20-30 sec to 2-3 min
accumulation hypothesis
by products in the accumulation hypothesis are these
substances produced while making ATP
lactate, Pi, ammonia
average exhurtion for the accumulation hypothesis
70-80% max
in the accumulation hypothesis ATP mostly comes from here
anaerobic glycolysis
carbohydrates are broken down to produce ATP and lactate
Things that ties all the metabolic byproducts together in the accumulation hypothesis
build up of materials lowers the intracellular pH
Lactate build up can cause fatigue in this ways (4)
Decrease in pH interfers with Ca++ from SR
Bond between Actin/Myosin is not as strong in low pH leading to less force production
Interfers with ATP breakdown due to low pH interfering with ATPase activity
interfers with ATP production, acidic pH interfers with rate of enzyme activity in glycolysis
How Pi can cause fatigue (4)
Pi build up interfers with actin/myosin affinity
Pi interfers with Ca++ release from SR
Troponin-Ca++ binding affinity inhibitied
Interfers with Ca++ reuptake
Where does Pi come from
ATP breakdown produces ADP + Pi + energy
How Ammonia can cause fatigue
Reduces AP propagation along the sacrolema
Where does ammonia come from
ADP builds up during exercise
ADP + AK -> ATP + AMP
AMP acted on by AMP deaminase
AMP + AMPdeaminase -> IMP + Ammonia
THis is the largest factor affecting fatigue in the accumulation hypothesis
change in pH
T/F: all of the accumulated substrates work together to cause fatigue
T
How to modify acid/base chemistry to reduce fatigue
Sodium bicarb loading
exercise training
how does sodium bicarb loading affect acid/base chemistry
increases proformance by acting as additional blood buffer
increases the bloods ability to buffer the acidic byproducts of metabolism
how does exercise training affect acid/base chemistry
causes physiological shift to tolerate the added acidic stress placed on the body during training
Two branches of depletion hypothesis
neural fatigue
energy substrate depletion
caused by a total depletion of ACh at NMJ end bulbs
neural fatigue
after enough constant contraction this will occur in a lab setting
neural fatigue
depletion of the fuels used to produce ATP is an example of this
energy substrate depletion
Fuels that can in theory be depleted
phosphogens
carbohydrates
proteins
fats
We cannot exercise enough to deplete these in energy substrate depletion
proteins
fats
Phosphogen depletion describes the depeletion of
ATP and creatine phosphate
These are used as the primary energy substrate for high intensity exercise
ATP and creatine phosphate
How much activity do we have (time) with initial ATP resting stores
2-4 seconds
where is ATP stored in the muscle
bound to myosin head
T/F: ATP in the muscle can be fully depleted
F, but can reach a level low enough where it is not available for muscle contraction
This energy substrate is stored in the cell and starts recharging process of ATP
phosphocreatine
The stores of this in the muslce are the limiting factor of the duration of high intensity exercise
phosphocreatine
also ATP to a lesser degree
depeletion of PC and ATp causes this
fatigue
At max/near max exertion fatigue is caused by this
depletion theory (ATP, CP)
at approx. 80% exertion, fatigue is caused by this
accumulation theory
At lower exertion lvls fatigue is caused by this
depletion theory (glycogen)
Benefit of enhancing PC stores increases this
duration of max intensity
Two ways to increase PC stores in the body
high intensity exercise training
suppliment w/creatine
this is the best form of supplimental creatine
creatine monohydrate
directions on creatine loading
20g/day for 5-7 days
4-5g, 5-4x/day
3-5g/day after load
also works at lower dose over longer period
this percent of what we eat has PC
50-70%
this AA combine to form creatine naturally
Gly
Arg
Met
If PEG creatine you can do this
take half as much
Some negative side effects of creatine may include
increase cramping or damage to organs
how scientific evidence to prove negative side effects
Supplimentation of creatine does this
increases anaerobic exercise in repeated bouts
increase bone and muscle mass
Mid intensity long term exercise causes fatigue thorugh this
glycogen depletion
glycogen
polymer of glucose stored in muscle
glycogen is primarily used as
an aerobic breakdown of carbs in endurance exercise
This term is used when glycogen stores run out
hitting the wall
this much energy is stored as glycogen in SM, and this much kcal will get you 1 mile
2000 kcal
100 kcal
this can increase glycogen stores
aerobic training
glycogen super compensation
after glycogen is used up you use this for energy
aerobically burn FA
