Leah.J
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Leah.J
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I dont understand how both the flexor and the extensor muscle could contract together at the same time. Shouldn't the muscles be antagonistic and shouldnt the answer be Flexor muscle contracts when lifting and the extensor muscle contracts when holding steady
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nexttime
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Why would extensor muscles alone hold a weight steady?
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Dunya
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https://www.youtube.com/watch?v=VCminz-X52I

I just spent 10 minutes lifting a mug up and down trying to understand it. To lift upwards, the biceps contracts and the triceps relaxes. To straighten the elbow, the triceps contract and the biceps relax.

I don't get it, I guess mark schemes can be wrong. I'll ask my teacher on Monday and see if they can figure it out.
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(Original post by Dunya)
https://www.youtube.com/watch?v=VCminz-X52I

I just spent 10 minutes lifting a mug up and down trying to understand it. To lift upwards, the biceps contracts and the triceps relaxes. To straighten the elbow, the triceps contract and the biceps relax.

I don't get it, I guess mark schemes can be wrong. I'll ask my teacher on Monday and see if they can figure it out.
I don't understand what you don't understand
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Leah.J
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(Original post by nexttime)
I don't understand what you don't understand
How can two antagonistic muscles contract together at the same time ? Isn't that contradicting the whole point of an antagonistic pair
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(Original post by Leah.J)
How can two antagonistic muscles contract together at the same time ? Isn't that contradicting the whole point of an antagonistic pair
How can they? Easily - that's what flexing your muscles is! Why would they is perhaps a better question

So, its obvious that lifting a weight is going to be mainly biceps.

When you're holding a weight steady the main force is still downwards right? So its still going to be mainly biceps.

It is technically both though - holding something still is a fine motor task that your body will have to work hard to maintain, and you would expect a small amount of extensor force to help with small adjustments. I would say the mark scheme is correct, although both are mainly flexors.

Even if you were lowering the weight - if it were at all controlled most of the work would still be biceps. If you only contracted extensors you'd be throwing the weight hard (stronger than gravity) to the ground!
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Leah.J
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(Original post by nexttime)
How can they? Easily - that's what flexing your muscles is! Why would they is perhaps a better question

So, its obvious that lifting a weight is going to be mainly biceps.

When you're holding a weight steady the main force is still downwards right? So its still going to be mainly biceps.

It is technically both though - holding something still is a fine motor task that your body will have to work hard to maintain, and you would expect a small amount of extensor force to help with small adjustments. I would say the mark scheme is correct, although both are mainly flexors.

Even if you were lowering the weight - if it were at all controlled most of the work would still be biceps. If you only contracted extensors you'd be throwing the weight hard (stronger than gravity) to the ground!
I'm sorry but I'm not sure I get it, if I was in an exam, how would I decide that everything that my teacher and book said about biceps and triceps isn't entirely true ?
My revision guide says : The biceps and triceps work together to move your arm - as one contracts, the other relaxes.

But you're now saying, that they can both contract together at the same time .. and apparently most (if not all) of the times
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F_r_a_z
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If you think of it as an equilibrium, to hold something steady you need equal forces in opposite direction otherwise the object will move in one direction over the other. Hence, when you hold something steady, your tricep works as hard as your bicep to ensure that the contraction of your bicep does not cause the object to be lifted upwards. They're still working antagonistically because your tricep is essentially counteracting the upward force exerted by your bicep with an equal downward force to reach equilibrium. If your tricep was relaxed but your bicep still contracted, the object will move up because there's no counteracting force.
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(Original post by Leah.J)
I'm sorry but I'm not sure I get it, if I was in an exam, how would I decide that everything that my teacher and book said about biceps and triceps isn't entirely true ?
My revision guide says : The biceps and triceps work together to move your arm - as one contracts, the other relaxes.

But you're now saying, that they can both contract together at the same time .. and apparently most (if not all) of the times
So my main problem with your (and the other person's) answer which I keep saying is that you said that extensors alone would hold it steady. How?! You understand that extensors would extent the arm right? So how would it hold it steady?

The other main problem is that you both seem to think that its impossible for both to contract at the same time. But just flex your arm muscles now like you're showing them off - what do you think that is? Its both contracting together!

Indeed unconscious muscle contraction is literally happening constantly - its generally referred to as your muscle's 'tone' - and its really only suppressed when you need to do an active movement the opposite direction to what that muscle pulls. So for instance I would expect the triceps to completely relax when doing a bicep curl. That particular question is kind of hard as when holding steady you'd still need a good amount of force in the biceps would still expect a bit of muscle tone ongoing, especially if the person has been specifically instructed to 'hold it steady'. Its an awkward question and if someone answered biceps flexing for both I'd forgive them (even if they still wouldn't get the mark!)

Your textbook is focusing on the basics - when doing active movements what it is saying is correct. My advice to you is to also focus on the basics first, because as I say: saying the triceps alone are needed to hold the weight steady is absolutely wrong and makes me think you don't understand this topic at all!
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(Original post by F_r_a_z)
If you think of it as an equilibrium, to hold something steady you need equal forces in opposite direction otherwise the object will move in one direction over the other. Hence, when you hold something steady, your tricep works as hard as your bicep to ensure that the contraction of your bicep does not cause the object to be lifted upwards. They're still working antagonistically because your tricep is essentially counteracting the upward force exerted by your bicep with an equal downward force to reach equilibrium. If your tricep was relaxed but your bicep still contracted, the object will move up because there's no counteracting force.
I can see some teachers choosing to explain it that way... but its not really true. Muscles aren't 'all or nothing' - you can contract your biceps hard or you can contract them less - that should be common sense!

Its more about your body wanting having more control over movements (and more resistance to sudden unexpected forces) when you've got a bit of tone covering both directions of movement.
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The Korean girl
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it's easy, the arms above in the question holding 'steady' contracts both flexors and extensors. Focus on the word 'steady', that arm is going to hold that mug for a while, not lifting or put it down, unless the arms are put onto the object for support, both flexor and extensor muscles would be contracting to maintain the posture.
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The Korean girl
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it's easy, the arms above in the question holding 'steady' contracts both flexors and extensors. Focus on the word 'steady', that arm is going to hold that mug for a while, not lifting or put it down, unless the arms are put onto the object for support, both flexor and extensor muscles would be contracting to maintain the posture.

When lifting the mug, the flexor contracts to bring the mug UP and so the extensor relaxes here
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F_r_a_z
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(Original post by nexttime)
So my main problem with your (and the other person's) answer which I keep saying is that you said that extensors alone would hold it steady. How?! You understand that extensors would extent the arm right? So how would it hold it steady?

The other main problem is that you both seem to think that its impossible for both to contract at the same time. But just flex your arm muscles now like you're showing them off - what do you think that is? Its both contracting together!

Indeed unconscious muscle contraction is literally happening constantly - its generally referred to as your muscle's 'tone' - and its really only suppressed when you need to do an active movement the opposite direction to what that muscle pulls. So for instance I would expect the triceps to completely relax when doing a bicep curl. That particular question is kind of hard as when holding steady you'd still need a good amount of force in the biceps would still expect a bit of muscle tone ongoing, especially if the person has been specifically instructed to 'hold it steady'. Its an awkward question and if someone answered biceps flexing for both I'd forgive them (even if they still wouldn't get the mark!)

Your textbook is focusing on the basics - when doing active movements what it is saying is correct. My advice to you is to also focus on the basics first, because as I say: saying the triceps alone are needed to hold the weight steady is absolutely wrong and makes me think you don't understand this topic at all!
I didn't say just the tricep was contracting. I said both muscles must be contracting. You're over complicating such an easy question worth 2 marks.
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F_r_a_z
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(Original post by nexttime)
I can see some teachers choosing to explain it that way... but its not really true. Muscles aren't 'all or nothing' - you can contract your biceps hard or you can contract them less - that should be common sense!

Its more about your body wanting having more control over movements (and more resistance to sudden unexpected forces) when you've got a bit of tone covering both directions of movement.
This is a GCSE question. They don't learn about fine motor skills. You only learn about that in a level biology when you start learning about different parts of the brain. It's easier to think of it as an equilibrium at GCSE. I think your just over thinking it bro. There's bigger harder questions in the test to get more marks from
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(Original post by F_r_a_z)
It's easier to think of it as an equilibrium at GCSE. I think your just over thinking it bro. There's bigger harder questions in the test to get more marks from
Ok but the way you explained it was not just factually wrong, but against common sense. I also thought you believed it was true, given you'd posted it.

I agree it is a simple question at heart - principles of flexion, extension, and muscle tone. I've recommended focusing on the basics.


I didn't say just the tricep was contracting. I said both muscles must be contracting. You're over complicating such an easy question worth 2 marks.
I wasn't referring to you.
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Leah.J
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(Original post by nexttime)
Ok but the way you explained it was not just factually wrong, but against common sense. I also thought you believed it was true, given you'd posted it.

I agree it is a simple question at heart - principles of flexion, extension, and muscle tone. I've recommended focusing on the basics.




I wasn't referring to you.
What are the basics you want me to focus on ? I'm not that best at bio (more of a physics person) and my basics aren't the best so I'd appreciate it if you specify
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(Original post by Leah.J)
What are the basics you want me to focus on ? I'm not that best at bio (more of a physics person) and my basics aren't the best so I'd appreciate it if you specify
As in: biceps flexes the arm (so lifting the weight), triceps extends the arm (so would be throwing the weight to the ground), when holding steady you have small amount of muscle tone in both groups. That's it really.
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