I’m sure many of us know the feeling that you get after a tough workout, or even just a long day on your feet. You muscles start to ache and feel tired. This feeling can go from merely being a little uncomfortable, to absolute exhaustion depending on how much energy you’ve expended. What you’re experiencing is called muscle fatigue. In this post, we’re going to discuss exactly how your muscles work, and what might be causing them to fatigue.
How Do Your Muscles Function?
Before we can understand what causes muscle fatigue, we first must understand the biomechanics of how they work.
Just like the rest of the human body, our muscles are made up of cells. Cells within the muscle work by detecting electrical impulses that are sent out by the brain. When the electrical impulse reaches the muscle cells, calcium gets released from the endoplasmic reticulum, a component of the cell, which causes the muscle to contract.
These contractions are the only reason that we’re able to do any sort of physical activity. Whether it’s lifting some heavy weight in the gym, carrying your groceries home from the supermarket, or simply taking a walk down the street.
Muscle Fatigue
What is muscle fatigue? The short answer is, that muscle fatigue is when your muscles become too tired to efficiently contract. There are many ways that this can happen, which we’ll talk about in the following paragraphs.
If you push your muscles too far, there is going to be a point where they can no longer support whatever activity you are doing. In a sense, they shut down, which will force your body to stop whatever it’s doing to prevent yourself from becoming injured.
Strenuous activity is the primary cause of muscle fatigue, and it can occur in a couple different ways which we’ll cover below:
Nervous Fatigue
As we stated earlier in the article, the brain (an important part of your nervous system) is responsible for sending out electrical impulses to the muscles to make them contract. Therefore, the brain is responsible for all contractions within the body. Overworking the nervous system is a big reason why one might experience muscle fatigue.
Although nervous fatigue is the more uncommon reason for muscle fatigue, it can occur when you put a large amount of stress on your muscles.
To explain, your body is often operating well below its max capacity when sending electrical impulses to the muscles to cause a contraction. Going about your day, and doing daily tasks is well within the limits of your brain, and should be accomplished with ease.
Problems start to arise when you put a large amount of strain on your body (example: heavy weight lifting). This forces the nervous system to send out electrical impulses more frequently, and if this goes on for too long, your nervous system can become fatigued and eventually your muscles will fail.
However, as mentioned earlier in the article, nervous fatigue is extremely rare and is not an issue for most people. Nervous fatigue is most common in body builders, and athletes who put huge amounts of stress on their muscles daily.
Symptoms that you might be experiencing nervous muscle fatigue can be a lack of pain or discomfort during activity. Your muscles will refuse to work, and you’ll feel weak and even light headed. Nervous fatigue happens gradually during the periods of high stress.
For most people, nervous fatigue isn’t the thing you need to concern yourself with. Metabolic fatigue is much more likely.
Metabolic Fatigue
Metabolic fatigue is much more complicated than nervous fatigue. Metabolic fatigue can be caused by two things:
Muscles lack the proper fuel that they need.
Buildup of elements in the muscle.
Either one of these two reasons can cause metabolic fatigue.
Lack of Proper Fuel
To properly contract, your muscles need what’s called substrates to be present within the cell. Substrates are a key part of a muscle contraction. Think of your body as a very efficient machine, if the machine doesn’t have enough fuel to continue to function, it will stop working. Your muscles are exactly the same, they require a good source of energy in order to operate as efficiently as possible.
These sources of energy are called ATP (adenosine triphosphate), glycogen, and creatine phosphate. Below we’ll go over how these energy sources work together to make your muscle contract.
A muscle fiber is comprised of two key protein filaments: Myosin, and Actin. When these two proteins slide over each other, a muscle contraction occurs. For this process to occur, your muscles require energy.
ATP is the primary energy source for the human body, and is very important for our very survival. ATP functions by attaching to the head of the myosin cell, which causes the myosin cell to contract over the actin cell. Without ATP, our muscles would not contract, and we would die.
Creatine phosphate also plays a large role in the body. Creating phosphate helps conserve energy, which allows ATP to regenerate faster than usual within the cell. If energy ATP doesn’t regenerate fast enough, the muscle won’t contract.
Glycogen is a cell that’s used to store energy. Glycogen stores glucose, a key component to the production of ATP. If there’s no glucose, there’s no ATP, and without ATP, there’s no muscle contractions.
Buildup of Matter in the Muscle
This is the second way that metabolic muscle fatigue can occur. The “matter” that we’re referring too, is called metabolites. Metabolites are byproducts of our muscle metabolism.
As our muscles use up energy via contractions, the byproduct of the used up energy can decrease the efficiency of the muscle.
There’s too many byproducts that can cause this to happen, and going over each of them would be far too much to go over in one article. But needless to say, these byproducts do interfere with muscle contractions.
How to Avoid Muscle Fatigue
The answer is actually quite simple: don’t push yourself too hard. Breaking down the muscle fibers is the only way to make them grow bigger and stronger, but taking that too far can do more damage than good.
If needed, take a few days off to rest between workouts. Let your muscles repair the damage before you push them to their limits again. In order to get ripped and in the best shape of your life, you need to take care of your body.
SOURCES:
http://www.webmd.com/a-to-z-guides/tc/weakness-and-fatigue-topic-overview
https://www.ncbi.nlm.nih.gov/books/NBK9961/
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