Why we consume energy while holding something statically?

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In summary: It shows the heat production of an arm at rest (black line), an arm lifting a weight (grey line), and an arm holding a weight static (white line). As you can see, even when the arm is at rest (or lifting the weight very slowly), the muscle is still producing heat.
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Curiosity 1
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Hello.

When we are lifting up weight using arm, there is work done by us (we give energy for the weight to move upward and so we feel tired), and by law of conservation of energy, we can write mgΔh= mΔ(v^2)/2.

However, when we are holding the weight statically (arm does not move at all), we also feel tired some time later. It seems like we are still consuming energy even when we do not have any work done on the weight and our muscle does not move at all. Why? How a contracted muscle that is static consumes energy? Non-living things that support weight does not need energy but living things does! Why?

Your answer will be appreciated. Thanks!
 
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Curiosity 1 said:
Why? How a contracted muscle that is static consumes energy?

At the cellular level your muscles actually aren't static. The muscle fibers alternate between fully contracted and fully relaxed, which consumes energy even when your overall muscle is "static".
 
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Curiosity 1 said:
mgΔh= mΔ(v^2)/2.

Thanks for sharing knowledge!
I should've written E_used= mgΔh+mΔ(v^2)/2.
 
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Otoh, a table transfers no energy, internally or externally when it supports a brick. That's because there is no motion within it - apart from thermal motion and that will be in equilibrium with its surroundings
 
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Drakkith said:
At the cellular level your muscles actually aren't static. The muscle fibers alternate between fully contracted and fully relaxed, which consumes energy even when your overall muscle is "static".
I've heard that before, but I'm not sure if I've ever seen a good reference - do you have one?

In either case, it is worth noting that our bodies are so inefficient that even when in a dead sleep, we still put out about the same heat (about 70-80 watts) as when at rest and awake. Our muscles don't need to be vibrating to consume energy.
 
  • #8
russ_watters said:
I've heard that before, but I'm not sure if I've ever seen a good reference - do you have one?

I can't seem to find one that directly says that, but I swear I've seen one before, and everything I've read leads me to understand that this is the way it works. I'll let you know if I find a good reference.
 
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Figure 8 in that reference is interesting.
 

Why do we consume energy while holding something statically?

There are a few reasons why we consume energy while holding something statically. First, our muscles are constantly working to maintain a certain posture or position, which requires energy. Second, even though we may not be moving, our muscles are still contracting and relaxing in order to maintain our grip on the object. Third, there may be small movements or adjustments that we make without realizing it, which also require energy.

Does the amount of energy consumed while holding something statically depend on the weight of the object?

Yes, the amount of energy consumed while holding something statically does depend on the weight of the object. The heavier the object, the more force our muscles need to exert in order to hold it up, resulting in a higher energy consumption. Additionally, the longer we hold the object, the more energy we will use.

Why does holding something statically for a long period of time make our muscles tired?

Holding something statically for a long period of time can make our muscles tired because they are continuously contracting and relaxing to maintain the position. This continuous use of our muscles can lead to fatigue, which is the feeling of tiredness or weakness in our muscles.

Is there a difference in energy consumption between holding something statically with our dominant hand versus our non-dominant hand?

Yes, there may be a difference in energy consumption between holding something statically with our dominant hand versus our non-dominant hand. This is because our dominant hand is generally stronger and more coordinated, so it may require less energy to hold the object compared to our non-dominant hand.

Can holding something statically for a long time lead to muscle strain or injury?

Yes, holding something statically for a long time can lead to muscle strain or injury. When we hold something for an extended period of time, our muscles can become fatigued, which can increase the risk of strain or injury. It is important to take breaks and avoid holding heavy objects for too long in order to prevent muscle strain or injury.

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