Question

exactly why does our muscles get tired?

Answer 1

It was once believed that lactic acid build-up was the cause of muscle fatigue.[24] The assumption was lactic acid had a "pickling" effect on muscles, inhibiting their ability to contract. The impact of lactic acid on performance is now uncertain, it may assist or hinder muscle fatigue.
Produced as a by-product of fermentation, lactic acid can increase intracellular acidity of muscles. This can lower the sensitivity of contractile apparatus to calcium ions (Ca2+) but also has the effect of increasing cytoplasmic Ca2+ concentration through an inhibition of the chemical pump that actively transports calcium out of the cell. This counters inhibiting effects of potassium ions (K+) on muscular action potentials. Lactic acid also has a negating effect on the chloride ions in the muscles, reducing their inhibition of contraction and leaving K+ as the only restricting influence on muscle contractions, though the effects of potassium are much less than if there were no lactic acid to remove the chloride ions. Ultimately, it is uncertain if lactic acid reduces fatigue through increased intracellular calcium or increases fatigue through reduced sensitivity of contractile proteins to Ca2+.

Answer 2

Muscle cells work by detecting a flow of electrical impulses from the brain which signals them to contract through the release of calcium by the sarcoplasmic reticulum. Fatigue (reduced ability to generate force) may occur due to the nerve, or within the muscle cells themselves. New research from scientists at Columbia University suggests that muscle fatigue is caused by calcium leaking out of the muscle cell. This causes there to be less calcium available for the muscle cell. In addition an enzyme is proposed to be activated by this released calcium which eats away at muscle fibers.[25]
Substrates within the muscle generally serve to power muscular contractions. They include molecules such as adenosine triphosphate (ATP), glycogen and creatine phosphate. ATP binds to the myosin head and causes the ‘ratchetting’ that results in contraction according to the sliding filament model. Creatine phosphate stores energy so ATP can be rapidly regenerated within the muscle cells from adenosine diphosphate (ADP) and inorganic phosphate ions, allowing for sustained powerful contractions that last between 5–7 seconds. Glycogen is the intramuscular storage form of glucose, used to generate energy quickly once intramuscular creatine stores are exhausted, producing lactic acid as a metabolic byproduct. Contrary to common belief, lactic acid accumulation doesn't actually cause the burning sensation we feel when we exhaust our oxygen and oxidative metabolism, but in actuality, lactic acid in presence of oxygen recycles to produce pyruvate in the liver which is known as the Cori cycle.
Substrates produce metabolic fatigue by being depleted during exercise, resulting in a lack of intracellular energy sources to fuel contractions. In essence, the muscle stops contracting because it lacks the energy to do so.

Answer 3

This guy copied this text from http://en.wikipedia.org/wiki/Muscle_fatigue .
It sucks that this plagiarism happened with even crediting the source. But anyways.

Answer 4

it doesn't matter. i asked you biologists because you'd know it better where to look directly for the concerned questions not that you'd come up with your own hypothesis.

Answer 5

lol ?
but he could have cited it.
and it does matter.

Answer 6

http://openstudy.com/code-of-conduct

Answer 7

yeah i've read the code, we all will be careful next time

Answer 8

ya.
np.
Just you said it didn't matter... and it sorta does ;p

Answer 9

just idk, if people think this is cool, it could lead to worst plagiarism

Answer 10

wow, ok dude, i does matter, sorry about that.

Answer 11

'it'

Answer 12

Np. :)

Answer 13

so, now to the question. if we keep a constant supply of energy and maintenance we wouldn't get tired???

Answer 14

Even with unlimited supply of energy we would still get tired because our muscles lack the oxygen. When we do physical activity like running our muscles start anaerobic respiration (Aerobic = oxygen; this is the opposite) basically: WE NEED O2! :D

Answer 15

suppose we take care of that too......

Answer 16

or is there anything else? i was trying to use the muscle fibers for the motion agent in a system so is it possible ?
@sraone88 @dumbsearch2 @IvantheBear

Answer 17

explain ?

Answer 18

under the light of your knowledge, what things should i take care of to carryout this system? for the simplest just take a system of contraction and expansion of the muscles

Answer 19

if your system does not require oxygen. No matter if its a muscle or not there must be a force in order to create energy that allow the 'muscle' to move.