Elbow Flexion Joint Reaction Force

In summary: Can you upload a sketch of your scenario please? The more info you...Attach files: Attached Files:In summary, Berkeman is asking how to minimize injury from physics calculations. He is specifically interested in acute injuries, not chronic ones. He does not want to consider muscle strains or tendon sprains.
  • #1
ziywang50
10
0
Homework Statement:: This is not a homework, but I want to know how to find the joint reaction force of the 2d elbow flexion, if I know the angular acceleration of the forearm, and the mass of elbow with a known weight on hand. I assume the forearm is a simple cylinder. Suppose the angular acceleration is 0.6m/s^2. The mass of forearm is 10kg, and the mass of weight is 20kg. Suppose length of forearm is 30cm. Now 1) assume the upper arm is the same direction as gravity and hand is downward to the shoulder 2) assume the upper arm is 45 degrees to gravity and hand is downward to the shoulder I am confused with how to draw the free body diagram, since I read one introductory textbook but it only gives the stationary case and the arm is perpenticular to the force of gravity, and I am unclear about how to find the joint reaction force on the elbow joint. I want to find this force because I heard the joint reaction force is the major force to cause elbow injury.
Relevant Equations:: F=ma

I am guessing that the direction of the joint reaction force is just perpendicular to the forearm, but I am really uncertain about this. Can somebody help?
 
Biology news on Phys.org
  • #2
Welcome to PF. :smile:

Can you upload a sketch of diagram of the system? Use the "Attach files" link below the Edit window to upload a PDF or JPEG version of rthe sketch. That would help a lot, IMO. Also include the muscle/tendon attachments that are generating the torque that results in the angular acceleration. Thanks.

ziywang50 said:
I heard the joint reaction force is the major force to cause elbow injury.
Also, can you post a link to where you read this? And specifically what type of "elbow injury" are you concened with?
 
Last edited:
  • #3
I read frm here. The diagram, maybe I will draw it later.
 

Attachments

  • ijbet.2016.081223.pdf
    818.2 KB · Views: 98
  • #4
ziywang50 said:
I read frm here. The diagram, maybe I will draw it later.
That helps a little. Still, what kind of injuries are you primarily concerned with? If you are wanting to calculate the worst-case reaction forces, why are you not considering the case where the forearm is horizontal and the upper arm is vertical?

1667517852863.png
 
  • #5
[Thread moved from the schoolwork forums to the Biology/Medical forums]
 
  • #6
@berkeman I am asking because I am not sure how to calculate the reaction force, and I do not know when the arm is horizontal it maximizes the reaction force. I mean it is shown on the paper but it is not really based on any theory and I am not going to use that simulation software they used. I am not sure what is the direction of that reaction force.
 
  • #7
berkeman said:
That helps a little. Still, what kind of injuries are you primarily concerned with? If you are wanting to calculate the worst-case reaction forces, why are you not considering the case where the forearm is horizontal and the upper arm is vertical?

View attachment 316680
Honestly any injury. But the paper gives elbow injury so I am considering elbow injury now
 
  • #8
ziywang50 said:
Honestly any injury. But the paper gives elbow injury so I am considering elbow injury now

That doesn't really help. What is the overall purpose of your question? Do you have a medical worry, or is this for schoolwork after all?

There are a number of joint injury modalities, including chronic issues and acute injuries. Tendonitis is very different from compression fracture, for example.
 
  • #9
@berkeman I just want to decide how to minimize the elbow injury from physics calculations.
 
  • #10
ziywang50 said:
@berkeman I just want to decide how to minimize the elbow injury from physics calculations.
Like an example would be which pose or which weight
 
  • #11
ziywang50 said:
@berkeman I just want to decide how to minimize the elbow injury from physics calculations.
ziywang50 said:
Like an example would be which pose or which weight
Sorry, still no help and too wide-ranging.

In addition to my EE full-time work, I work part-time in EMS and have actually used physical therapy for a couple joint injuries. So if you want help, you will need to say more please.

It sounds like you are wanting to avoid chronic elbow joint injuries (as opposed to acute injuries), possibly like tennis elbow and baseball throwing injuries? Or more weight lifter related injuries? I'm not the most patient medic in the world, so you have one or two chances left to explain what you want out of this thread...

(well, okay, I am the most patient medic in the world, but I'm still losing my patience)...
 
  • Like
Likes BillTre
  • #12
@berkeman I mean acute injuries, because I am looking at a weight lifting problem. Not chronic injuries.
 
  • #13
ziywang50 said:
@berkeman I mean acute injuries, because I am looking at a weight lifting problem. Not chronic injuries.
So muscle strains and tendon sprains?

Can you upload a sketch of your scenario please? The more info you can provide us, the better we can try to address your questions.

Are you a weight lifter? Which lifts are you most concerned about? Should we assume bicept curls on a standard machine (Bowflex, etc.)?
 
  • #14
berkeman said:
So muscle strains and tendon sprains?

Can you upload a sketch of your scenario please? The more info you can provide us, the better we can try to address your questions.

Are you a weight lifter? Which lifts are you most concerned about? Should we assume bicept curls on a standard machine (Bowflex, etc.)?
Thank you for answering my post in detail. Yes, we can assume normal bicep curl for now. I am not a weight lifter, but I want to use code developed by other developers to find pose of a person then find if the weight is too heavy for that person by some physics calculation. The input should be a video, and my goal is to find which pose to minimize the chance of injury, given the weights are known. But I am not sure which force I should calculate and how to determine if the weight is too heavy to avoid acute injuries like tendon injuries and muscle strains as you mentioned.
 
  • #15
  • #16
CF556820-0D3F-414D-AF7A-8B48AD166B4E.jpeg

Here is my friend lifting, as an example
 
  • #17
I have seen some phone apps that are used to analyze body movements from videos, which you can take with your phone.
Did this with my daughter when she was doing track and field.
They can do a lot of analyses.
There might be some that do force calculations.
 
  • #18
ziywang50 said:
[...]I assume the forearm is a simple cylinder. Suppose the angular acceleration is 0.6m/s^2. The mass of forearm is 10kg, and the mass of weight is 20kg. Suppose length of forearm is 30cm. [...]
...not based in reality.

The mass of the forearm is 3kg-ish, and the length is 40cm-ish.
 
  • #19
ziywang50 said:
The input should be a video, and my goal is to find which pose to minimize the chance of injury, given the weights are known. But I am not sure which force I should calculate and how to determine if the weight is too heavy to avoid acute injuries like tendon injuries and muscle strains as you mentioned.
It sounds like you should be talking with a Physical Trainer or Physical Therapist about these questions. The mechanisms of injury (both for chronic and acute injuries) are not as straightforward as calculating reaction forces in joints. For example, when doing deltoid lifts with dumbbells, the degree of pronation of the hands makes a big difference in the likelihood of developing chronic injuries in certain muscle groups. PTs know this, and most people who don't use a PT do not know this.
 
Last edited:
  • Like
Likes pinball1970, Fra, ziywang50 and 2 others
  • #20
I agree with previous speaker. Its the job of the senior trainer, sensei or whatever to make sure beginner dont start training the wrong way. Angles of limbs, knees and joints should be aligned to allow the intended muscles to take main load and minimize torque om joints. This goes also for training with hard punches and kicks. Different techniques may also be advised for speed vs force. I think after training you should have just normal sore muscles, not joint pain or overstretching something.

I learned this the hard way as well. Now i see i need to learn tecnique before going all in with power as the reactiona forces comes back to you when even hitting a heany bag. But thet may not tell you on first lesson.

/Fredrik
 
  • #21
ziywang50 said:
View attachment 316684
Here is my friend lifting, as an example
As per #19 & #20 Gyms usually give you a tour when you join for insurance purposes. This is not only to give you heads up on how best to avoid injuries but also to get the most out of your work outs in terms of muscle simulation.
They will also give recommendations on things like intensity and number of reps and sets, as well as best techniques.
Not just for your elbow but your back, shoulders and knees too (all important to you!)
Based on your age and weight they should be able to give recommendations on diet too, depends what you want to get out of it.
 

1. What is the elbow flexion joint reaction force?

The elbow flexion joint reaction force is the force generated at the elbow joint in response to the contraction of muscles that flex the elbow. It is a measure of the resistance that the joint experiences during movement.

2. How is the elbow flexion joint reaction force calculated?

The elbow flexion joint reaction force can be calculated using the equation F = ma, where F is the force, m is the mass of the body segment being moved, and a is the acceleration of the body segment. In this case, the acceleration is the angular acceleration of the elbow joint.

3. What factors affect the elbow flexion joint reaction force?

The elbow flexion joint reaction force is affected by several factors, including the amount of weight being lifted, the length of the lever arm (distance between the elbow joint and the weight), the angle of the elbow joint, and the strength and coordination of the muscles involved in elbow flexion.

4. Why is the elbow flexion joint reaction force important to understand?

The elbow flexion joint reaction force is important to understand because it can help in the diagnosis and treatment of elbow injuries and disorders. It can also be used to assess the effectiveness of rehabilitation programs and to design exercises that specifically target the muscles involved in elbow flexion.

5. How can the elbow flexion joint reaction force be reduced?

The elbow flexion joint reaction force can be reduced by using proper form and technique during exercises, avoiding overloading the elbow joint with excessive weight, and gradually increasing the intensity and duration of training to allow the muscles to adapt and become stronger. It is also important to properly warm up and stretch the muscles before engaging in activities that require a high elbow flexion joint reaction force.

Similar threads

  • Mechanical Engineering
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
24
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
3K
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
3
Views
2K
  • Introductory Physics Homework Help
Replies
10
Views
8K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
1K
Replies
9
Views
1K
Back
Top