Seated Chest Press vs Smith Machine Bench Press

External Since: May 02, 2006 Posts: 297

On Fri, 8 Feb 2008, rev wrote:

> Tom Anderson wrote:
>> On Wed, 6 Feb 2008, Prisoner at War wrote:
>>
>>> Your arms really isn't the point, see. Yes, in a sense, we do agree, but
>>> it's really got nothing to do with the weight of one's arms. That's just
>>> "total weight" to be pushed, regardless of the direction of the push.
>>> What makes the two directions of pushing feel so different (i.e., one
>>> harder to perform than the other) is that one is going 100% against
>>> gravity while laying down and pushing up, while maybe only 70% against
>>> gravity while seated upright and pushing out, forward.
>>
>> I'm getting the impression that you don't know how a chest press machine
>> works. You push forward, horizontally, on some levers. The levers are
>> connected by a spooky mechanism to a stack of weights - and they move
>> *vertically* (told you the mechanism was spooky!). So when you're doing a
>> machine chest press, you're lifting the weights 100% against gravity. So
>> the direction of push doesn't affect the way the weights relate to gravity
>> - but it does affect the way the weight of your arms relates to gravity,
>> since those aren't on the other end of the mechanism.
>
> While I am no engineer, I am puzzled why nobody has brought up the
> *spooky* mechanism in the chest press machine before . The use of and
> number of pulleys used in the spooky mechanism could well create a
> mechanical advantage and hence reduce the force needed to move the
> weight for any given distance.

This point gets made here occasionally, but i think it's misplaced. It
would be absolute madness to build a machine where to lift the 100 lb
weight, you didn't have to exert 100 lb of force. If there is mechanical
advantage, wouldn't the designer adjust the weights (or the labelling on
them) to compensate for it?

We need to go and take measurements of distances moved at the handles and
weight stack on our chest press machines, and then weigh the weights, to
see if this is happening or not.

tom

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External Since: May 02, 2006 Posts: 297

On Thu, 7 Feb 2008, Prisoner at War wrote:

> On Feb 7, 7:29 am, Tom Anderson <t... DeleteThis @urchin.earth.li> wrote:
>
>> I'm getting the impression that you don't know how a chest press
>> machine works. You push forward, horizontally, on some levers. The
>> levers are connected by a spooky mechanism to a stack of weights - and
>> they move *vertically* (told you the mechanism was spooky!). So when
>> you're doing a machine chest press, you're lifting the weights 100%
>> against gravity. So the direction of push doesn't affect the way the
>> weights relate to gravity - but it does affect the way the weight of
>> your arms relates to gravity, since those aren't on the other end of
>> the mechanism.
>
> Can you show me a picture of what you mean, then? I'm pretty sure we
> have the same things in mind...there are a few different seated chest
> press machines in my gym, and thought their structural design is
> different, they all seem to work the same way.

Here is a lissom young lady doing a chest press (although they call it a
machine bench press):

http://www.bodybuilding.com/fun/exercises.php?Name=Machine+Bench+Press

As you can see (especially with the videos or the zoomed-in pics), she
moves the handles roughly horizontally, but causes a weight stack to move
vertically.

She seems to be a bit of a chest exercise specialist:

http://www.bodybuilding.com/fun/exercises.php?Name=Flat+Bench+Cable+Flyes
http://www.bodybuilding.com/fun/exercises.php?Name=Incline+Cable+Flye
http://www.bodybuilding.com/fun/exercises.php?Name=Cable+Crossover

And hey, it's working for her o_O.

This, incidentally, is not a chest press:

http://www.youngwomenshealth.org/fitness/ti_chest_press.html

That's not anything. I see people doing that sometimes, and i want to slap
them in the head for wasting their time and my oxygen.

> Look, all I'm saying is is: you jump farther when jumping horizontally
> than vertically (basically my shot put example). Weight of the legs (or
> arms, what you'd noted) doesn't matter 'cause it's factored in in both
> situations.

That analogy is no good, because when you do a horizontal chest press,
you're still lifting the weight vertically. It's like doing a long jump
with a rope tied to you that goes to a pulley and a weight stack. Or
something.

>> Oh, and for itto be 70% against gravity, you'd have to be pushing at 45
>> degrees.
>
> Whatever the exact percentage is; my point was that it's much less,
> which is why it's easier. Again, jumping straight up isn't going to
> take you further than jumping straight across. Why not? You're
> working against much more gravity in one case than the other...same
> thing with the seated chest press.

No, not the same at all.

tom

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Next issue - Nigel and the slavegirls ... or, why capitalism can never
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