Deceleration etardation negative acceleration

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Could anyone please tell me which is right and why.

A person lifts 80pounds or 80% of his RM {one repetition maximum lift} for the last 40% of the concentric lift, the weight decelerates.

Which or can both of these be deceleration and why please.

1,
His RM = 100 pounds, so for the first 60% he will be roughly pushing with a force of 100 pounds, then at 60% he will be pushing with a force of 99 pounds, then at 62% he will be pushing with a force of 98 pounds, and so on until say 80% where he will use less force than the load and use 79% and less and less force to get to a very slow speed for the transition, then he will be lowering the weight on the eccentric.

2,
His RM = 100 pounds, so for the first 60% he will be roughly pushing with a force of 100 pounds, then at 60% he will be pushing with a force of less force than the weight which will be 79% for the deceleration. {retardation, negative acceleration}

As far as I know deceleration is of slowing down of the weight, thus, deceleration will still be the weight moving in the positive direction, up in this example, just on the deceleration it will be starting to move in the positive direction a little slower than it was before.

Wayne
 

Answers and Replies

  • #2
HallsofIvy
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The force necessary to hold something motionless is its weight. To accelerate something upward, you need to apply an additional force, proportional to the acceleration. The force necessary to hold a 100 pound weight at, say hip level, would be 100 pounds. The force neccessary to move a 100 pound weight upward would be slightly more than 100 pounds, to accelerate but then would decrease to 100 pounds as you decelerated to just holding it over your head.
 
  • #3
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The force necessary to hold something motionless is its weight. To accelerate something upward, you need to apply an additional force, proportional to the acceleration. The force necessary to hold a 100 pound weight at, say hip level, would be 100 pounds. The force neccessary to move a 100 pound weight upward would be slightly more than 100 pounds, to accelerate but then would decrease to 100 pounds as you decelerated to just holding it over your head.
Halls,
Basically, I agree with you.
I apologize, but it has been many years since I worked in physics.
So, my comments on your answer will have flaws.

But, I recall that the acceleration of the object will be along the lines of the square of the change of inertia.
I do not see a vertical position change as requiring a linear or geometrical change in energy applied.
The initial push on the weight will be more than some "slightly more than" the objects weight (linear).

It is difficult for me to frame a comment using the OP's scenario.
I recall having experimented with pushing barbells from my shoulders upward to arms' length.
The initial push was about 200 lb. on a 100 lb. barbell, to get it moving upward 24 inches.
My standard push upward was about 100 lb.
My push from the shoulders max, legging it up, was 200 lb, and it moved upward about 6 inches.
Those were near my max at that time.
It only shows that the increase in energy required is more than a linear relation.

But, from calculus I would say it this way.
My answer would be more along the lines of speed change from 10mph to 20mph.
This change in velocity (which is called acceleration) will take 4 times the energy.
We have not yet considered the time factor, and the momentum numbers.

We ALL need to check the books on Mechanical Physics to get the classical picture,
or work with calculus and the differential concepts involved in dealing with velocity and acceleration.

At any rate, YOUR answer GOES in the right direction.
And MY answer does NOT really get to what I think is a correct answer.
I hope these comments help the OP.
 
  • #4
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To Hall and the OP Wayne,

I found this excerp from Wikipedia and it shows that
a real explanation of the 'problem' is much more complicated than originally written.
There were links which led into calculus and that is where it got really interesting.

However, this quote begins to support Hall's answer:
"the acceleration of the body is proportional to the net force acting on it"

Thank you Hall, and I'll leave this quote for you, then return to my work.

/*Quote

Acceleration
From Wikipedia, the free encyclopedia

In physics, acceleration is the rate of change of velocity over time.[1] In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity.[2][3] Acceleration has the dimensions L T −2. In SI units, acceleration is measured in meters per second per second (m/s2).

Proper acceleration, the acceleration of a body relative to a free-fall condition, is measured by an instrument called an accelerometer.

In common speech, the term acceleration is used for an increase in speed (the magnitude of velocity); a decrease in speed is called deceleration. In physics, a change in the direction of velocity also is an acceleration: for rotary motion, the change in direction of velocity results in centripetal (toward the center) acceleration; where as the rate of change of speed is a tangential acceleration.

In classical mechanics, for a body with constant mass, the acceleration of the body is proportional to the net force acting on it (Newton's second law):

F = ma to a = F/m

where F is the resultant force acting on the body, m is the mass of the body, and a is its acceleration.

*/EndQuote
 
  • #5
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The force necessary to hold something motionless is its weight.
Hi all, and thx for your help and time, get back to the rerst tomorrow.

So if you try to hold 100 pounds, you need to exert 100 pounds, but I suppose more really, as you had to exert some force the hold the weight of your arm ???

To accelerate something upward, you need to apply an additional force, proportional to the acceleration. The force necessary to hold a 100 pound weight at, say hip level, would be 100 pounds. The force neccessary to move a 100 pound weight upward would be slightly more than 100 pounds, to accelerate but then would decrease to 100 pounds as you decelerated to just holding it over your head.
Yes I get that, additional force to accelerate the weight, but don’t get the other part, let’s keep it the same, RM, or the most force he can use = 100 pounds.

But let’s look at it another way, if he pushed on the weight with just over 80 pounds, say 81 pounds the weight would accelerate. Now let’s say a new lift, he pushed on the weight this time with a force of 100 pounds, the weight would now accelerate, but it would accelerate faster right ??? So why does this not happen in reverse as I asked ??? Question, when I use less force and less force, why does the weight not start to accelerate slower, or in other words why when I use less and less force does the weight not accelerate slower or in other words start to decelerate ??? How can something keep on accelerating faster and faster when you are using less and less force ???

As the study says that when using 81% that there is deceleration at 53% and someone says that means when using 81% that there is deceleration at 53% and someone says that means at 53% he will be using less force than the load, however as of the biomechanical disadvantages of the bench press, as say 70% of the ROM, the weaker triceps will take over more of the lift, however, the persons RM at this part of the ROM may well not be 100 pounds, but ??? 80 pounds, so the weight of the person RM at this part in the ROM, would be lower, thus he would still be using as much force at this part of the ROM than another part. But let’s forget that, and pretend the lift is down with a machine, with no disadvantages over the ROM, so I ask again;



So for the first 60% he/machine will be roughly pushing with a force of 100 pounds, then at 60% he/machine will be pushing with a force of 99 pounds, then at 62% he/machine will be pushing with a force of 98 pounds, and so on, until say 80% where he/machine will use less force than the load and use 79% and less and less force to get to a very slow speed for the transition, then he will be lowering the weight on the eccentric. How can something keep on accelerating faster and faster when you are using less and less force ???

Wayne
 
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  • #6
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Dear members,

There was one, yes I know I should not go on just one study, however the question means more that the %

The study stated that a person bench pressed 80% of his 1RM {repetition maxumun} and deceleration phase was at 52% of the upward movment.

Question,
Do you use less force than the weight on the deceleration phase ???





I was just thinking of this when doing bench press on my smith machine !!! For all new here, D. says that when I rep a weight up, and at a certain distance from the transition from the positive to the negative, that I will need a deceleration phase, and I also say that has to be true, but hes says on the decelerating phase that if I was using 320 pounds and my 1RM was 400 pounds, that on the deceleration phase I would be using less force than the weight, or less force than 320 pounds ??? How is this ??? as I would be trying to use all my 400 pounds of force up until the last say 10% of the lift !!!


When I press with say ??? 320 pounds for 10 reps, and that 80% so my 1RM = 400 pounds, too move the bar at different speeds/accelerations, I can use many difference forces, right ??? Anywhere from 320 to 400 pounds of force, right ??? And remember this is the human muscles pressing, thus there is n ever a full constant press with a constant force as of the biomechanical advantages and disadvantages of the Human muscles ??? Please keep that in mind.


So down press the 320 pounds to half way up, then hold it there, how much force does that take ??? Roughly 320 pounds right ??? But what would happen if as you are saying, in that you use less force than the weight, shall we say why ever is holding the weight half way starts to use just 300 pounds ??? The weight WILL start moving down again will it NOT ???


So when I am pressing up and using more force that the weight, the weight will move up in the positive direction, right ??? And if I start using any force less than the weight, the weight will stat moving back down again, in the negative direction right ???


But when I am pressing up in the positive direction until the transition, I am ALWAYS moving upwards in the positive direction, right ??? SO HOW IN THE WORLD CAN I USE LESS FORCE THAN THE BAR AND NOT MOVE THE BAR UPWARDS IN THE POSITIVE DIRECTION, WHEN AS YOU CLAIM, I AM ALSO USING LESS FORCE THAN THE WEIGHT, BUT LESS FORCE THAN THE WEIGHT WOULD MAKE THE BAR REVERSE ITS DIRECTION ???


Wayne
 
  • #7
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Dear members,

There was one, yes I know I should not go on just one study, however the question means more that the %

The study stated that a person bench pressed 80% of his 1RM {repetition maxumun} and deceleration phase was at 52% of the upward movment.

Question,
Do you use less force than the weight on the deceleration phase ???



Wayne
Hi Wayne....I really missed your threads here!

When you lift a weight there's an acceleration and a deceleration phase.In the acceleration phase you use greater force than the weight and in the deceleration phase you use less force than the weight.

Since the study found that the deceleration phase was for the last 52% of the lifting that means for that part you use less force than the weight.
 
  • #8
HallsofIvy
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Hi all, and thx for your help and time, get back to the rerst tomorrow.

So if you try to hold 100 pounds, you need to exert 100 pounds, but I suppose more really, as you had to exert some force the hold the weight of your arm ???



Yes I get that, additional force to accelerate the weight, but don’t get the other part, let’s keep it the same, RM, or the most force he can use = 100 pounds.

But let’s look at it another way, if he pushed on the weight with just over 80 pounds, say 81 pounds the weight would accelerate. Now let’s say a new lift, he pushed on the weight this time with a force of 100 pounds, the weight would now accelerate, but it would accelerate faster right ??? So why does this not happen in reverse as I asked ??? Question, when I use less force and less force, why does the weight not start to accelerate slower, or in other words why when I use less and less force does the weight not accelerate slower or in other words start to decelerate ??? How can something keep on accelerating faster and faster when you are using less and less force ???
??? It does accelerate slower with less force. Are you perhaps confusing "acceleration" and "velocity"? As long as the weight has any (positive) acceleration at all, its velocity will become greater.

As the study says that when using 81% that there is deceleration at 53% and someone says that means when using 81% that there is deceleration at 53% and someone says that means at 53% he will be using less force than the load, however as of the biomechanical disadvantages of the bench press, as say 70% of the ROM, the weaker triceps will take over more of the lift, however, the persons RM at this part of the ROM may well not be 100 pounds, but ??? 80 pounds, so the weight of the person RM at this part in the ROM, would be lower, thus he would still be using as much force at this part of the ROM than another part. But let’s forget that, and pretend the lift is down with a machine, with no disadvantages over the ROM, so I ask again;



So for the first 60% he/machine will be roughly pushing with a force of 100 pounds, then at 60% he/machine will be pushing with a force of 99 pounds, then at 62% he/machine will be pushing with a force of 98 pounds, and so on, until say 80% where he/machine will use less force than the load and use 79% and less and less force to get to a very slow speed for the transition, then he will be lowering the weight on the eccentric. How can something keep on accelerating faster and faster when you are using less and less force ???

Wayne
Again, it does not "accelerate faster and faster". The acceleration will be reduced (as glene77is said, the acceleration is proportional to the force- specifically, one of Newton's laws: F= ma or a= F/m.) However, as long as there is any acceleration at all, its velocity, or speed, will increase. It will move "faster and faster" even with lower acceleration.
 
  • #9
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So when I am pressing up and using more force that the weight, the weight will move up in the positive direction, right ??? And if I start using any force less than the weight, the weight will stat moving back down again, in the negative direction right ???


But when I am pressing up in the positive direction until the transition, I am ALWAYS moving upwards in the positive direction, right ??? SO HOW IN THE WORLD CAN I USE LESS FORCE THAN THE BAR AND NOT MOVE THE BAR UPWARDS IN THE POSITIVE DIRECTION, WHEN AS YOU CLAIM, I AM ALSO USING LESS FORCE THAN THE WEIGHT, BUT LESS FORCE THAN THE WEIGHT WOULD MAKE THE BAR REVERSE ITS DIRECTION ???


Wayne
No...when you use less force than the weight(hence the weight moves with negative acceleration or "deceleration") the speed will gradually decrease until it'll get zero and THEN the bar will start moving downwards.
 
  • #10
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??? It does accelerate slower with less force. Are you perhaps confusing "acceleration" and "velocity"? As long as the weight has any (positive) acceleration at all, its velocity will become greater.


Again, it does not "accelerate faster and faster". The acceleration will be reduced (as glene77is said, the acceleration is proportional to the force- specifically, one of Newton's laws: F= ma or a= F/m.) However, as long as there is any acceleration at all, its velocity, or speed, will increase. It will move "faster and faster" even with lower acceleration.
If I remember correct it's called negative http://en.wikipedia.org/wiki/Jerk_(physics)" [Broken] but the acceleration remains positive as long as the force is greater than the weight and of course the weight will keep moving "faster and faster".
 
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  • #11
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I did tell you to keep this in mind; the human muscles pressing, thus there is n ever a full constant press with a constant force as of the biomechanical advantages and disadvantages of the Human muscles ??? Please keep that in mind.

Therefore, this means that if you pressed 80 pounds on a machine and immediately stopped, the weight would carry on for 3 inches, BUT with the human body, the weight would not move out of your hands.

Hi Wayne....I really missed your threads here!

When you lift a weight there's an acceleration and a deceleration phase.
Right.

In the acceleration phase you use greater force than the weight and in the deceleration phase you use less force than the weight.
So you say with no explanation, proof, evidence or facts ???

We will split the rep up into five segments again, and the below numbers are made up just for simplicities sake.
So I accelerate the 80% or 80 pounds bar with a force from 81 to 100 pounds, and it accelerates, right ??? First segment I use from 81 to 86 pounds of force, and it moves 1mph, second segment I use from 87 to 91 pounds of force and it moves 2mph, third segment I use from 92 to 96 pounds of force and it moves 3mph. Now what happened to my mph if I at the forth segment use 81 to 86 pounds of force ??? Would not it decelerate from 3mph down ??? If not why and what would happen ???

HOW can you accelerate a weight, or should I say accelerate a weight slower, as in deceleration, if you are using less force than the weight ??? As far as I always understood if you use less force than the weight, then the weight not moves in the positive direction, the falls back on you in the negative direction.

Since the study found that the deceleration phase was for the last 52% of the lifting that means for that part you use less force than the weight.
D. its very unprofessional and scientific to just use one study, when we do not know how fast he lifted the weight, so please could you find some more.

Your trying to say, that I can only use 100% of my force for a quarter of a second ??? I mean you know as I said nothing about muscle fibers or to the point fast muscles fibers if you think that. When I rep I use full force until the exact moment I do the transition.




One more thing, this make no difference to that I use full force of a 100 pounds for the largest past of the rep, and you only use 80 pounds, as I keep on and on and on telling you, 100 = more than 80, and you medium force can and does not make this up when I am using less force, and here is proof evidence and facts proving that your forces can not balance out with mine in the long run as I move the weight in 6 seconds 12m to your 2m, so tell me now how you still think the forces balance out ??? They do not do they, as I said, 100 is higher than 80. Dont you get impulse. When a force is applied to a weight, it changes the movement of that body. A small force applied for a long time can produce the same movement change as a large force applied briefly, because it is the product of the force and the time for which it is applied that is important. BUT BOTH THESE FORCES ARE USED FOR THE SAME TIME, the only way your force could catch up if it went on longer, then it would move the weight the same disstance.

Wayne
 
  • #12
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Hi HallsofIvy,

HallsofIvy??? It does accelerate slower with less force.
Yes, that’s what I have been saying.

HallsofIvy Are you perhaps confusing "acceleration" and "velocity"? As long as the weight has any (positive) acceleration at all, its velocity will become greater.

Right.

However when moving 80% of your 1RM {one repetition maximum} which we will say is 80 pounds, if you use 100 pounds of force it will immediately accelerate to the speed a 100 pounds can take it to, then if you use 95 pounds, then 90 pounds then 85 pounds it will still be accelerating, just slower than it had been, thus decelerating, or slowing down.

My friend above I call D. seems to say that after I use 100 pounds of force, and then use 95, 90 and then 85 pounds of force, that the weight will still accelerate faster than when I was using more the, as in a 100 pounds of force. How can something like a barbell in say the bench press, accelerate faster when you use less force ???


HallsofIvy Again, it does not "accelerate faster and faster". The acceleration will be reduced (as glene77is said, the acceleration is proportional to the force- specifically, one of Newton's laws: F= ma or a= F/m.)
Right.

HallsofIvy However, as long as there is any acceleration at all, its velocity, or speed, will increase. It will move "faster and faster" even with lower acceleration.
Right.

Wayne
 
  • #13
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However when moving 80% of your 1RM {one repetition maximum} which we will say is 80 pounds, if you use 100 pounds of force it will immediately accelerate to the speed a 100 pounds can take it to, then if you use 95 pounds, then 90 pounds then 85 pounds it will still be accelerating, just slower than it had been, thus decelerating, or slowing down.
No....less acceleration does not mean "decelerating" or slowing down.As long as the force in your example is greater than 80 pounds the acceleration remains positive and the barbell will keep moving "faster and faster".
That's what HallsofIvy tried to explain to you.
 
  • #14
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No....less acceleration does not mean "decelerating" or slowing down.As long as the force in your example is greater than 80 pounds the acceleration remains positive and the barbell will keep moving "faster and faster".
That's what HallsofIvy tried to explain to you.
So if less acceleration is not deceleration, what do you think and say deceleration is/means ???

So you are saying that if I use less force, the weight will accelerate faster than if I use more force ??? And the less force I use the faster the weight will accelerate ??? Why and how do you think this ???

I am saying that if I use a 100 pounds of force, the weight will accelerate at {made up numbers} 4m a second, then 8m a second, but if I use just 85 pounds of force, the weight will accelerate slower, as in say 1m a second then 2m a second. In addition, in my calculations, you would accelerate at a slower pace if you used less force. So when I go from using a 100 pounds of force to 85 pounds of force, the acceleration will be slower, thus even thou the weight is still accelerating, its accelerating slower, thus decelerating as its acceleration.

Wayne
 
  • #15
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Look, your accelerating, thus going faster and faster, you can accelerate at different speeds, so if you start accelerating slower, your starting to decelerate, and if you keep on accelerating slower and slower, at one point you will be decelerating and going at slower and slower speeds.

What you did not note, is what I said about this is not a machine, as of the WEAK point in the bench press as of the triceps, the bar would slow down at say three quarters of the ROM, thats the biomechanical advantages and disadvantages of the muscles. BUT THE POINT WAS, I may STILL be pushing will as much force I could at this part of the ROM, but because the chest muscles have backed off, and the triceps muscles take far more of the load, the speed and acceleration will have to drop, but the point is the my muscles the Kinetic Chain, were still trying to push with as much force as they could, but as the triceps if you could measure their pushing force in the bench press only had say 30% of the pushing force in the bench press, and then as they do the chest muscles are hardily used in this portion of the lift, the speed acceleration would have to slow, as the weight was far too much for the triceps, BUT the triceps, and what was left { as of biomechanical advantages and disadvantages of the of the exercise} shoulders and chest muscles, were STILL trying to push with as much force as possible, so trying to measure thing like this with pure Physics does not work out, thats why we have to have Kinology and Biomechanics.

I like having three cars force pushing a lorry, you then measure the whole force of the three cars, then take 50% of two cars force away, even thou the force has dropped, the force is still as high as it could be. SO THAT MEANS, that even thou you think my force has dropped on the latter part of the ROM, it has not really, it just that the forces of some muscles have dropped slightly and other muscles have to try and take over, its the exact same with your slow rep, YOUR FORCE WILL ALSO DROP AT THIS PART OF THE ROM.


Wayne
 
  • #16
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So if less acceleration is not deceleration, what do you think and say deceleration is/means ???
''Deceleration'' is/means negative acceleration in your example(lifting a weight).
But less acceleration is still positive acceleration hence the velocity is still increasing(the barbell moves ''faster and faster'').It's not ''deceleration''.

You got to learn the basic terms if you want any kind of discussion.

So you are saying that if I use less force, the weight will accelerate faster than if I use more force ??? And the less force I use the faster the weight will accelerate ??? Why and how do you think this ???

Wayne
I'm saying that even though your force is reduced and you accelerate in less rate...the acceleration is still positive(velocity increases) as long as the force remains greater than the weight.The barbell doesn't ''decelerates''.
 
  • #17
cjl
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So if less acceleration is not deceleration, what do you think and say deceleration is/means ???
Deceleration means that it is accelerating in the opposite direction. As long as the force being used is larger than the weight, the acceleration will be upwards. The weight will continue to get faster (up) while the force is larger than the weight. The rate at which its speed will increase (the acceleration) will decrease, but the speed will still be increasing.

Only when the force being used is less than the weight will it start to slow down. That's when the deceleration will start to occur and the weight will begin to slow down.

So you are saying that if I use less force, the weight will accelerate faster than if I use more force ??? And the less force I use the faster the weight will accelerate ??? Why and how do you think this ???
No, nobody is saying that. They are saying that whenever the force is greater than the weight, it will continue to get faster. The rate at which it gets faster is dependent on the force, and if you use less force, the rate at which it gets faster will be less. Thus, the acceleration is decreasing.


I am saying that if I use a 100 pounds of force, the weight will accelerate at {made up numbers} 4m a second, then 8m a second, but if I use just 85 pounds of force, the weight will accelerate slower, as in say 1m a second then 2m a second. In addition, in my calculations, you would accelerate at a slower pace if you used less force. So when I go from using a 100 pounds of force to 85 pounds of force, the acceleration will be slower, thus even thou the weight is still accelerating, its accelerating slower, thus decelerating as its acceleration.

Wayne
Those numbers you are using are velocities. 4 meters per second is a velocity, as is 2 meters per second.
Acceleration has units of velocity per time, so an example of that would be 4 meters per second per second. That would mean that every second, the velocity would increase by an additional 4 meters per second.

Again, deceleration and decreased acceleration are not the same thing. For an object to be decelerating, the acceleration must be negative. A decreased positive acceleration is still an acceleration.
 
  • #18
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''Deceleration'' is/means negative acceleration in your example(lifting a weight).
But less acceleration is still positive acceleration hence the velocity is still increasing(the barbell moves ''faster and faster'').It's not ''deceleration''.
Right. Even thou I start accelerating slower, I still am gaining speed, I never said other ???

You got to learn the basic terms if you want any kind of discussion.
Thought I had them right ??? Where did I get them wrong ???

I'm saying that even though your force is reduced and you accelerate in less rate...the acceleration is still positive(velocity increases) as long as the force remains greater than the weight.The barbell doesn't ''decelerates''.
“Right” so your saying more of speed thats getting less. And your saying as of the initial push as of the force I am giving to the weight, thats 20% more than the weight of the weight, that, that force will have to make the weight accelerate, and when I use less force its still accelerating, but accelerating slower, but still speed is increasing, and when this weight is in motion, it can only decelerate, start moving at less speed, you have to use less force than the weight... As its in motion.

Right, get more what you have been on about now, wish you had said more on the speed slowing down.

Ok, now back to the study, the point is that first its “ONLY” one study, second, we did NOT know the time of the lift, was it lifted say 1m in .5 of a second, or 1m in 1.5 seconds ??? Third, as of the biomechanical advantages and disadvantages of the Human Muscles, and in this case the bench press, and as of the weaker triceps taking over more of the lift at say {and this will depend a lot on the lifters arm length triceps to chest muscles strength and many more thing} 60% You too will have this deceleration phase there at the same place also, thus you will also be decelerating at roughly 60% of the ROM and thus using less force than the weight !!! So lets sort your lift and the deceleration, and then its my questions like you promised.


Deceleration means that it is accelerating in the opposite direction. As long as the force being used is larger than the weight, the acceleration will be upwards. The weight will continue to get faster (up) while the force is larger than the weight. The rate at which its speed will increase (the acceleration) will decrease, but the speed will still be increasing.

Only when the force being used is less than the weight will it start to slow down. That's when the deceleration will start to occur and the weight will begin to slow down.


No, nobody is saying that. They are saying that whenever the force is greater than the weight, it will continue to get faster. The rate at which it gets faster is dependent on the force, and if you use less force, the rate at which it gets faster will be less. Thus, the acceleration is decreasing.



Those numbers you are using are velocities. 4 meters per second is a velocity, as is 2 meters per second.
Acceleration has units of velocity per time, so an example of that would be 4 meters per second per second. That would mean that every second, the velocity would increase by an additional 4 meters per second.

Again, deceleration and decreased acceleration are not the same thing. For an object to be decelerating, the acceleration must be negative. A decreased positive acceleration is still an acceleration.
Thank you cjl, that was very helpfull.

Wayne
 
  • #19
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“Right” so your saying more of speed thats getting less. And your saying as of the initial push as of the force I am giving to the weight, thats 20% more than the weight of the weight, that, that force will have to make the weight accelerate, and when I use less force its still accelerating, but accelerating slower, but still speed is increasing, and when this weight is in motion, it can only decelerate, start moving at less speed, you have to use less force than the weight... As its in motion.

Right, get more what you have been on about now, wish you had said more on the speed slowing down.
I was saying about "the speed slowing down" only when you use less force than the weight from the first time and you were keep saying that less acceleration also results in slowing down.
Don't make me look back at your posts.

Ok, now back to the study, the point is that first its “ONLY” one study, second, we did NOT know the time of the lift, was it lifted say 1m in .5 of a second, or 1m in 1.5 seconds ???
The study was about explosive lifting.When you try to lift explosively the 81% of 1RM the deceleration phase(where you use less force than the weight) is for the last 52% of ROM.

Third, as of the biomechanical advantages and disadvantages of the Human Muscles, and in this case the bench press, and as of the weaker triceps taking over more of the lift at say {and this will depend a lot on the lifters arm length triceps to chest muscles strength and many more thing} 60%
The biomechanical advantages and disadvantages of the Human Muscles are common either you lift fast or slow.

You too will have this deceleration phase there at the same place also, thus you will also be decelerating at roughly 60% of the ROM and thus using less force than the weight !!! So lets sort your lift and the deceleration, and then its my questions like you promised.

Wayne
When you lift a weight slowly practically there're no acceleration/deceleration phases.It's like lifting a weight with constant speed hence for almost the whole ROM you use force equal with the weight.
 
  • #20
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No time to read your post here right now, and have posted over at BB.com.
I hope you DO NOW understand this deceleration phase will depend on MANY things.

1,
The speed of the lift, the SLOWER the lift, the earlier, higher and longer deceleration phase.

2,
The length, size of the of the lifters limbs. For instance, if the lifter had short arms, and very strong triceps to his chest, AND moved the bar very fast, as he had very high RFD {Rate of Force Development} the deceleration phase would be much shorter, say the last 10%

3,
The lift in concern, as if your doing the squat for instance, you would have a acceleration, then a deceleration phase as say 40 to 50% then another acceleration, then another deceleration.

4,
All this deceleration goes in the faster lifter favour and in the slower lifter disfavour.

5,
And there is still something you have not thought of in the deceleration.




Just caught your last sentence, NOT TRUE, when you lift slow throughout the whole ROM, exercise or rep, there are CONSTANT accelerations and deceleration, will show you a graph.

Back later my friend D.

Wayne
 
  • #21
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No time to read your post here right now

Wayne
....but you had the time to write a long post where everything you write has already been answered in my last post.
 
  • #22
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....but you had the time to write a long post where everything you write has already been answered in my last post.
Yes I had to write that without reading what you wrote, or I may have had to write more if I had read what you wrote, and then been late, now I will read what you wrote above.

Wayne
 
  • #23
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I was saying about "the speed slowing down" only when you use less force than the weight from the first time and you were keep saying that less acceleration also results in slowing down.
Don't make me look back at your posts.
The thing is, we debated this months ago on BB.com, and I and you said that if your accelerating, and then accelerating slower, that your still going faster and faster, yes I agreed with what you were saying.

But then if you keep on and on accelerating slower and slower, there would be a point in which you could not accelerate, thus you would keep going at that speed, if that was a 100mph, and you then went down to 90mph, that means you have decelerated. I was thinking in more of the lines that when you accelerated slower you were decelerating.

The thing is I see the point your trying to make, I have know what your saying all along, BUT YOU CANT SEE WHAT I AM SAYING. Your saying that as I have to decelerate at some point in the ROM, that it will take more time than your decelerating. And that after I have used more force than you, I then have to use less force than you.

And for some strange reason you think as my force goes up and down that in the end we have used the same forces.

However as I have said over and over, and you have not replied AT ALL.

1,
How can 80 force every be as high as 140 force for the first fifth of the ROM, or how can 80 be as high as 100 force for the second fifth of the ROM, and how can 80 force be as high as 100 force for the third fifth of the ROM,

3,
My force is far far far higher than your force for more of the ROM, and thus time.

3,
As you also have a disadvantage in this exercise in this part of the ROM, you too will go from using 80 force to a FAR lower force, and far faster and quicker than me. The speed of the lift, the SLOWER the lift, the earlier, higher and longer deceleration phase.

4,
I WOULD LIKE THIS TO BE YOUR FIRST ONE TO TRY AND ANSWER PLEASE.
If you THINK you forcers even out, balance out in the long run, HOW, do you explain that I have moved the weight 10 more meters than you ??? JUST try to explain that. Forces are not linear, just like energy, the more energy you use, the more overall or total force you have to use.


5,
The length, size of the of the lifters limbs. For instance, if the lifter had short arms, and very strong triceps to his chest, AND moved the bar very fast, as he had very high RFD {Rate of Force Development} the deceleration phase would be much shorter, say the last 10%

6,
The lift in concern, as if your doing the squat for instance, you would have a acceleration, then a deceleration phase as say 40 to 50% then another acceleration, then another deceleration.


7,
All this deceleration goes in the faster lifter favour and in the slower lifter disfavour.

8,
What D. and K are trying to say {which is the opposite of Newtons Laws} for every action there is NOT an equal and opposite re-action.

As when I push up against gravity, moving at 1m ever 3 seconds, there is a reaction force that is equal in size, but opposite in direction to my push, and the FASTER I move at this constant speed, the HIGHER the force will be needed, and thus there is a HIGHER reaction force that is EQUAL in size, but opposite in direction to my push.

D. and K. Think the faster I move in accelerations or at constant speeds, that the opposite reaction force does not happen ??? But why ???

As whenever an object pushes another object it gets pushed back in the opposite direction with an equally hard force. THUS THAT MEANS THE MORE FORCE/SPEED, THE MORE OPPOSITE REACTION FORCE PUSHES BACK, THUS MORE TENSION ON THE MUSCLES THE MORE FORCE/SPEED. You seem to think that there is no G-force.

8,
Just TRY and tell me how I am using far far far more energy in the faster lifts, if its not more force used ??? How do you use more power then without more force ???

9,
Please note that the forces are higher in the faster reps for two fifths higher, thats 50% that means the forces overall in the 6 seconds are higher for 50% of the time.


10,
In the first segment 140 = 75% or 60 more than 80.


11,
In the second segment 100 = 25% or 20 more than 80.


12,
In the third segment 100 = 25% or 20 more than 80.


13,
In the forth segment 40 = 100% or 40 less than 80, BUT still its 80, in this forth segment, 80 is still not as high as 140 or a 100. So this means its still has not reached the higher forces of 140 or 100.


14,
In the fifth segment 20 = 300% or 60 less than 80, BUT still its 80, in this fifth segment, 80 is still not as high as 140 or a 100. So this means its still has not reached the higher forces of 140 or 100.


15,
D. does not seem to understand that he seems to think that when my forces are lower, that his forces somehow catch up, but as I have said over and over and over, 80 is still not as high as 140 or a 100. So this means its still has not reached the higher forces of 140 or 100. So the total or overall forces are still and will always be higher in the faster reps, that first fifth 140, second fifth 100, and third fifth 100, and as I have said these forces in the first three segments are a 100 higher and higher for 50% of the rep.

16,
Why is D. not able to answer the above ??? As hes wrong, if not why please ???

The study was about explosive lifting.When you try to lift explosively the 81% of 1RM the deceleration phase(where you use less force than the weight) is for the last 52% of ROM.
Yes, it seems so as I read more, however, this is for powerligting, and have you ever noticed how most bodybuilders train the bench press ??? Its in the shorter ROM rep range thus they want to train the chest muscles more, thus they leave out the last quarter or more, where because of the biomechanical disadvantages of the triceps taking over more of the weight of the lift from the chest muscles, as you pointed out, there is on this lift ONLY a deceleration at roughly where the triceps take over more of the weight. And as I have said, this will depend on the length of the persons arms, the strength ratios of the persons triceps to chest muscles and so on; this means that different people will have different points where they find the weight harder to move faster in certain parts of the ROM.

And as I said The lift in concern, as if your doing the squat for instance, you would have a acceleration, then a deceleration phase as say 40 to 50% then another acceleration, then another deceleration.

Also all this deceleration goes in the faster lifters favour and in the slower lifter disfavour, as of the faster lifter has a great acceleration, thus MORE force = speed/acceleration being used, as the slower you move at this weak point in the ROM, the faster or more the deceleration will be.

The best way to increase force is to rapidly accelerate, BUT with a heavier weight. Doing so increases the tension over the full range of the exercise and not just during the initial acceleration. AND WITH LIFTING THE FASTER REPS, YOU CAN AND DO USE HEAVER WEIGHTS THAN IN THE SLOWER REPS. As higher weight will result in great force, greater peak force, greater acceleration force. Power is ability of the muscular system to produce the GREATEST POSSIBLE FORCE in the shortest amount of time. Power is simply the product of muscle force multiplied by the velocity of movement: P = F x V. Any increase in power must be a result of improvements in either strength, speed or a combination of the two. Some people can possess a very large muscle mass and a tremendous amount of strength; however lack an ability to contract those strong muscles very quickly. To overcome this, power training that will result in improving the rate of force development.

Power = Force x Distance/Time

The biomechanical advantages and disadvantages of the Human Muscles are common either you lift fast or slow.

When you lift a weight slowly practically there're no acceleration/deceleration phases. It’s like lifting a weight with constant speed hence for almost the whole ROM you use force equal with the weight.
yOU JOKE RIGHT ???

Where did you get that information from, and how can you prove it with evidence and facts ???

How when the triceps take over a lot in the weight, do you still think you can keep this constant force going ??? thats very impossible.

When you lift a weight up, there are many biomechanical advantages and disadvantages thought-out the ROM, and the slower you go the more you will feel them. I you go very slow, the whole lift will be full of mini accelerations and decelerations.


Work you performed is equal to a force times a distance.The Law of Inertia; in the ABSENCE of an external force, {that means air resistance and gravity} a body in motion will continue to move at constant speed and direction, that is, at constant velocity. For a given body, the acceleration produced is proportional to the strength of the external force, so doubling the external force will cause the body to pick up speed twice as fast. To every action there is always opposed an equal and opposite reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts. Laws of the Vertical Motion.

Wayne
 

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