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# Thread: For the physics/biomechanics experts out there, I have some confusion....

1. ## For the physics/biomechanics experts out there, I have some confusion....

I've recently started the resistance training specialist dvd's and text.

Most of the examples early on relating to moment arms, force, lines of force, axis related terms, etc.....are shown with lateral raises and bicep curls. I'm trying to take these examples and related them to other exercises.....

So someone help me understand the pushup. Your bodyweight is going to be the resistance. Is your shoulder joint supposed to be the axis for the movement? What is the toe or knee (in a knee pushup) in this movement?

How do I determine the moment arm...the shortest distance from the axis to the line of force. I'm thinking the line of force is perpendicular to your torso, in line with your arms in the pushup position? It's hard for me to see all these in exercises for which i'm not shown an example.

I think this RTS course is going to help me a ton but its hard to grasp it.

2. Good on you for taking that, you will find it helps a lot. I'm going to do my RTSm in the summer starting in July.

One thing you need to think about is a bit more of the bigger picture - for example, in a push-up, there are several axes of movement. Your shoulders, but also your elbows, wrists and hands and how your body relates to the floor are all factors into the overall movement. Therefore, if you are considering your shoulder as the axis you are looking at, the moment arm will be different than the one for your elbow, one for your feet, etc.

The moment arm is actually perpendicular from the axis (point of rotation) to the line of force. So for example if you were pushing straight up from the floor and the axis is your shoulder, the moment arm is one way. However, if you push your hands out while pushing up, then your line of force is slightly different and causes a different moment arm. Our instructor actually had us push our hands up, down, in and out while doing a push-up and note how different it feels through the shoulder. It's really awesome stuff when you break it down.

3. Originally Posted by WoofieNugget

The moment arm is actually perpendicular from the axis (point of rotation) to the line of force. So for example if you were pushing straight up from the floor and the axis is your shoulder, the moment arm is one way. However, if you push your hands out while pushing up, then your line of force is slightly different and causes a different moment arm. Our instructor actually had us push our hands up, down, in and out while doing a push-up and note how different it feels through the shoulder. It's really awesome stuff when you break it down.
by pushing your hands up do you mean your are flexing your shoulders where your hands are more underneath your face opposed to underneath your shoulders/chest?

in a pushup would the line of force (assuming your axis is at the shoulder) be in line with the hands vertically from the ground up? Would the line of force always be through the hands in a pushup position regardless of the axis you're looking at?

it doesn't seem like the moment arm would change to much when you drop eccentrically into the pushup. Just confuses me.

I'm trying to watch the lecture videos and read the book before i go to the rts1 module, i don't want to be lost when i go and have all the material go over my head.

I never took physics in school, and really science in general was my weakest subject. The language just kind've bored me to be honest cause "moment arm" is not typically in my regular vocab.

Did you have any RTS study aids, notes, etc? All i have is the text/dvd's....i wish they had a study guide or flashcards or something. Those help me a lot.

4. Yes, in the pushup the line of force is through the hands - however, you also have to take into consideration the line of force that your hands have from the floor. So, for example if your hands are under your shoulders or spaced wide it changes the line of force through the shoulder. It really doesn't change that much, but if you change something by an angle of even 10 degrees then it can affect the movement and what muscles are either emphasized or not.

All I had was the texts - but I did buy the series Joint Structure and Function (3 books) which really helped because they are awesome at explaining proper joint movement and breaking down everything. Plus the guy teaching the course was amazing. Once you really learn to think at that higher level you will be much better off as a trainer.

5. Originally Posted by WoofieNugget
Yes, in the pushup the line of force is through the hands - however, you also have to take into consideration the line of force that your hands have from the floor. So, for example if your hands are under your shoulders or spaced wide it changes the line of force through the shoulder. It really doesn't change that much, but if you change something by an angle of even 10 degrees then it can affect the movement and what muscles are either emphasized or not.

All I had was the texts - but I did buy the series Joint Structure and Function (3 books) which really helped because they are awesome at explaining proper joint movement and breaking down everything. Plus the guy teaching the course was amazing. Once you really learn to think at that higher level you will be much better off as a trainer.
i just got one of the joint structure and function books in the mail, i didn't know there were 3?

http://www.valorebooks.com/textbooks.../9780803611917
thats the one i just bought.

also been looking for the supertraining book that purvis recommends.

6. Sorry - the books I was talking about are Physiology of the Joints Volume 1-3 by Kapandji. I also have Joint Structure and Function and you might also want to pick up Muscle Testing and Function with Posture and Pain, which is a great detail book that also allows you to learn muscle testing if you are going to get into the MAT stream, which I highly recommend.

7. Originally Posted by WoofieNugget
Sorry - the books I was talking about are Physiology of the Joints Volume 1-3 by Kapandji. I also have Joint Structure and Function and you might also want to pick up Muscle Testing and Function with Posture and Pain, which is a great detail book that also allows you to learn muscle testing if you are going to get into the MAT stream, which I highly recommend.
the guy that got me into rts has been through the mat internship and passed those exams....thats like 95% what he does know is mat, he rarely trains people anymore.

I'm still overwhelmed by rts. the whole theory is backwards compared to all the certifications. Learning from the inside of the body first towards the outside.

i'm just trying to get through the video lectures, read along w/ in the book....then go to the modules. We'll see what i learn from there, i'm still very much in the definition phases of rts, haven't gotten to the goodies yet.

It might not be till i attend the module that i can fully understand the whole moment arm thing. It's still very confusing to me in everything other than lat raises and bicep curls lol. I'm only 3 videos in tho, 8.5 more to go.

8. Originally Posted by CharlottePT

I'm still overwhelmed by rts. the whole theory is backwards compared to all the certifications. Learning from the inside of the body first towards the outside.
The funny thing is once you get into it you'll realize how much garbage is taught by most certifications. That which is backwards is all relative, but when it's based on simple physics and proven engineering principles you really can't debate it. That's what I love about it.

9. I will be starting Muscle Activation Techniques in May, so I will be following this thread. I am currently reading/experiencing the Trail Guide to the Body by Andrew Biel.

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