Concept2 and lower back pain

[johnlvs2run]

By raising or lowering the feet -- which is what you suggested -- it makes no difference because that does not change the angle from the line of force to the railing.

exactly we agree. This is why I said the slope and axle height were independent parameters. You are agreeing with me.

Agreeing with you? ... No, I am saying they are not independent parameters.

Lift the erg up and down, move it around, twist and shout, the angle stays the same.

In a boat the oar handle moves in the direction that force is applied to it. This is a physical law.
The handle does not move in the plane defined by the line between the shoulders and the arms.

The line of force is from the shoulders, to the hands, to the ends of the oars in the water.

The oars are not horizontal. The oars are in the water.

I was not suggesting it makes no difference. I was saying a horizontal line is the correct one.
Putting the axle significantly lower or higher then it is would be different from rowing a boat.

You row otw by holding the oars out horizontally from your shoulders?

The line of force otw is from the shoulders, to the hands, to the end of the oars in the water.

The line of force is horizontal on the erg, like if you were holding the oars out horizontally from your shoulders otw.

[El Caballo]

The line of force is from the shoulders, to the hands, to the ends of the oars in the water.

John, you obviously don't have any comprehension of simple physics. For the line of force from the shoulder to extend to the ends of the oars in the water, you would have to be swimming and holding onto the blades, not the handles. I don't know how this could be done unless both oars were on the same side of the boat...

or maybe there isn't a boat, just John swimming with the oars.

[Nosmo]

The line of force is from the shoulders, to the hands, to the ends of the oars in the water.

This is your basic misunderstanding. A line of force is a straight line, it does not have bends in it. (Technically it should be a force vector, but calling it a line avoids having to specify if it the force of the hands on the oar or the reaction force of the oar on the hands)

The oars are not horizontal. The oars are in the water.

The oar handles move in a (more or less) horizontal plane.

What matters is the force applied by the hands to the oar. This force is applied at the oar handle.
Since the oar handle moves back more or less horizontally this is the direction of the applied force. The oar is simply a lever.

You row otw by holding the oars out horizontally from your shoulders?

Again this is the basic misunderstanding. The force on the oar handle is not along the arm. One does not row on the erg or on the water with the arms horizontal from the shoulder. If you look at the pictures Nav posted you will see the movement of the hands is very similar OTW and OTE. If the hand movement is the same, the direction of force is the same. Since you don't understand this, I suggest getting a basic college entry physics or mechanics book and working through the first several chapters.

We have argued over this in the past. Perhaps I am just a bad teacher.

[snowleopard]

Perhaps I am just a bad teacher.

Not at all.

Mr Rupp seems to think that one rows a boat in much the same manner as a bird trying to swim with outstretched wings. Ouch!

A rower's hands move roughly parallel to the sides of the shell. The oar pin provides a means to lever the shell past the blades and the resulting movement of the shell is horizontal.

The erg is a rowing simulator and is called such because it works the body of a rower in much the same way as rowing a boat.

Newton's 3rd law tells us all we need to know. I suggest Mr Rupp starts there.

[NavigationHazard]

Sorry, inadvertently deleted the evidence:

Tom Kay at the catch on an erg:



Xeno at the catch in a boat:



Tom Kay mid-drive on an erg:



Xeno mid-drive in a boat:



Tom Kay at the finish on an erg:



Xeno at the finish in a boat:

[johnlvs2run]

Tom Kay at the catch on an erg

You are simply proving my point, that people with tall torsos have less of a problem on the erg.
Also it looks like you are suggesting Nosmo is wrong, because Tom Kay's line of force is downward on the erg, not horizontal.
Here is the photo of a woman on the erg for comparison, notice the horizontal line from her shoulders to the axle.



Whether the line of force is horizontal or downward on the erg, depends on the torso length of the rower.

All of the boat photos show exactly what I've been saying too, that the line of force is downward to the water.

In fact the water in every photo is about 2 feet lower than the shoulders.

[johnlvs2run]

For the line of force from the shoulder to extend to the ends of the oars in the water, you would have to be swimming

All the photos on this page show that the ends of the oars are in the water.

I challenge anyone here to show someone making progress otw by holding the oars horizontally.

[johnlvs2run]

What matters is the force applied by the hands to the oar. This force is applied at the oar handle.

To the other ends of the oars in the water.

If that were not the case, then just hold the oars horizontally, as you keep suggesting.

It would certainly be much easier, since then the oars would not be in the water.

But of course that makes no difference, right?

[johnlvs2run]

Mr Rupp seems to think that one rows a boat in much the same manner as a bird trying to swim with outstretched wings.

No, because then the oars would be horizontal.

[Nosmo]

Whether the line of force is horizontal or downward on the erg, depends on the torso length of the rower.

Lets go back to basics to make sure we understand where we disagree:

First: Forget about the force. Look at Nav's pictures. Do you agree that on the erg and on the water the hands move more or less horizontally?
I think that much we can agree on, but I want to be sure.

Second: Basic physics is F=ma. Where F and a are vectors. Biomechanically what matters is what the rower is doing. The direction of force applied to the handles is 100% determined by the direction of hand movement*. It is not from the shoulder to the arm.

I assume our disagreement is with the second statement not the first. Correct?

*before someone gets overly pedantic, I know I'm neglecting gravity.

[Bob S.]

*before someone gets overly pedantic, I know I'm neglecting gravity.

Aha! There is my cue!

Gravity was long ago replaced by hilarity on this thread (and others).

Bob S.

[johnlvs2run]

Do you agree that on the erg and on the water the hands move more or less horizontally

The shoulders are at shoulder level, the water is at water level, the hands are in between the shoulders and the water.
The hands are not horizontal to shoulder level otw and they are not horizontal to the water.

On the erg, the shoulders, hands, and axle vary from horizontal to downward, depending the on torso height of the rower.

Biomechanically what matters is what the rower is doing. The direction of force applied to the handles is 100% determined by the direction of hand movement

If what mattered were only the rower, then you wouldn't need oars - you could just move your hands back and forth horizontally.
But it is the rowers who put the oars in the water. And the rowers do cause the oars to move in the water.

The line of force is from the shoulders, through the arms, through the hands, through the oars, to the water.

[Nosmo]

Do you agree that on the erg and on the water the hands move more or less horizontally

The shoulders are at shoulder level, the water is at water level, the hands are in between the shoulders and the water.
The hands are not horizontal to shoulder level otw and they are not horizontal to the water.

On the erg, the shoulders, hands, and axle vary from horizontal to downward, depending the on torso height of the rower.

Try again: The question is about the movement of the hands period. You did not answer the question. Do the hands move horizontally or not?

Start there then we can go on to the rest of it.

[johnlvs2run]

The question is about the movement of the hands period. You did not answer the question. Do the hands move horizontally or not?

The line of force is from the shoulders to the water.

[bloomp]

John, you really aren't thinking about what you're saying. Which is what I drew in on that piss poor force-body diagram.