Impulse/force in pounds for the time frame

[waynexk8]

I have a PhD in biomedical engineering and did some coursework and research in functional electrical stimulation for neuro-prosthetic applications, so I know a thing or two about EMG, EEG, EKG, muscle recruitment, electrical stimulation, pacemakers, etc.

Wow, great. And that’s meant as a complement, as I am glad you also know about EMG.

Electrical muscle activity measures voltage changes due to the depolarization of the muscle cell membranes during the muscle's action potential, not the force exerted by the muscle.

Note, the key word "estimate". If you know the EMG and you know the tension v recruitment curve and you know the position of the limb and you know the force v tension curve for that position then you can use the EMG to make a good estimate as to what the force is. An estimate and a measurement are not the same thing. Force is measured with a force transducer, an EMG is a voltage transducer. The units of the EMG are μV, not N.

Before you can prove your total/overall muscle force theory you need to define it, otherwise there is no theory to prove or disprove. That is the purpose of teaching you about the standard physics concepts. I am hoping that as you learn what is meant by them you can express your concepts in the standard language, clearly define your theory, and then we can see the implications.

I have not the time tonight to give you a well deserved answer for the above, so will come back to this tomorrow.

So, let's talk a little more about impulse and see if it has the properties that you expect for "total/overall muscle force".

Impulse also has the property that if you exert the same force for twice as long you have doubled your impulse. So, for example if you exert 100 lbs for 10 s and I exert 100 lbs for 5 s you have exerted twice the impulse that I have. Does this also agree with your concept of "total/overall muscle force"?

As you know answered this in my last post.

Either we are all cross threaded, because I as I said, don’t get that when I say I am trying to use 100% strength for 6 seconds or 30 seconds, on a weight that is 80% of my 1RM {repetition maximum} and then you say you are only going to use 80% strength for 6 seconds or 30 seconds, on a weight that is 80% of your 1RM {repetition maximum} that you or some of the other here, turn around and say 80% strength/force is equal to 100% strength/force ?

And there is more than enough proof and evidence, as the 100% strength using person fails roughly 50% faster. So as I asked before,

1,
I fail at 30 seconds; you fail at 60 seconds, who puts the most tension on the muscles.

2,
I fail at 30 seconds, lift a lighter weight and fail at 30 seconds again; you fail at 60 seconds, who puts the most tension on the muscles.

3,
I lift for 30 seconds, and you lift for 30 seconds.

All can’t use the same force and have the same tension on the muscles.

Wayne

 

[Dale]

Either we are all cross threaded

Yes, we are cross threaded, I will give you the time to get caught up.

 

[douglis]

DaleSpam...I admire your effort to help Wayne but here's what I think that's the first thing that must be cleared out.
No matter what % of his force he deludes himself that he uses,he always uses force equal with the weight on average...regardless the lifting speed.In his example...he always uses force equal with 80% his 1RM for the lifting duration.

 

[waynexk8]

The numbers 1,2 and 3 are achieved with the "normalization" of the EMG data like it's described at the paragraph "analysis and treatment EMG data" at this http://www.scribd.com/coldstreamer/d/2528195-Elliot-et-al-A-biomechanical-analysis-of-the-sticking-during-the-bench-press.

http://www.scribd.com/coldstreamer/d/2528195-Elliot-et-al-A-biomechanical-analysis-of-the-sticking-during-the-bench-press

Why do you persist in WRONG data ? My concentric lift using 80% will take as close to .5 of a second, the study above you are showing is “not” close to this, it’s of a concentric, of 1.5 seconds, that’s 200% longer than my fast rep, or 1 second longer, WHY/WHAT are you bothering with this for ?

Of course there will be deceleration near the sticking point, as the force is SO low in this SLOW rep, that it has NOT the acceleration/force to move up at acceleration and thus more force than the weight for say the same as my lift, which accelerates for say ? 80/90% of the concentric. STOP using this false data please.

Wayne

You can also see many force-time graphs where the impulse can be easily calculated.

The average impulse is the same you say, for any lift using the same weight, using any rep speed and diffrent times, and we all know that if you lift a weight 1 time or a 100 times, if the average impulse is the same, the 100 times WILL put far far far MORE tension on the muscles, thus more total/overall force output.

Wayne

 

[waynexk8]

DaleSpam...I admire your effort to help Wayne but here's what I think that's the first thing that must be cleared out.
No matter what % of his force he deludes himself that he uses,he always uses force equal with the weight on average...regardless the lifting speed.In his example...he always uses force equal with 80% his 1RM for the lifting duration.

And you point ?

You are saying if I lift 80 pounds one time up and down = 1 second, and I lift 80 pounds up and down a 100 times that the average force is the same, right ? So answer this, too which proves average force means nothing.

Lift 1 = 1 second,
Lift 2 = 200 seconds.

Lift 2 puts more tension on the muscles thus puts out and on, more total/overall force from and on the muscles, right ? So as this IS the case, WHY are you brining in or talking about average force, when it means NOTHING to what we are talking about in this debate ? Just please explain why you talk or bring up someone as meaningless as this that has nothing to do with the debate at hand ? PLEASE STAY ON SUBJECT.

Wayne

 

[douglis]

The average impulse is the same you say, for any lift using the same weight, using any rep speed and diffrent times, and we all know that if you lift a weight 1 time or a 100 times, if the average impulse is the same, the 100 times WILL put far far far MORE tension on the muscles, thus more total/overall force output.

Wayne

For God's sake read carefully what we write if you want to learn something.How is it possible after so many pages to say a nonsense like that?

The average force will be the same either you lift the weight 1 or 100 times but the impulse will be 100 times greater if you lift the weight 100 times since the duration is 100 times greater.
Impulse=average force X time.

With 100N...either you do one rep with 5/5 or 10 reps with .5/.5 the impulse is always 100NX10s=1000Ns.
What exactly you can't understand?What's so hard at the above that required 18 pages?

 

[waynexk8]

One important point to emphasize in these types of discussions is the concept of slow and fast twitch muscle fibers. Unfortunately, this terminology is misleading because there are not two (or three) types of muscle fibers; rather, there is a continuous distribution in every muscle from the fibers with slow contractile kinetics through to those with fast kinetics.

Because there are not distinct types of muscle fibers, it is not possible to design an exercise program that stresses either "fiber type".

A more appropriate functional distinction between muscle fibers is the force at which the motor units are activated during a muscle contraction, which is known as recruitment threshold.

Motor units with low recruitment threshold can be either slow or fast twitch, whereas motor units with high recruitment thresholds are all fast twitch. But, recruitment thresholds decrease with contraction speed so that all motor units in a muscle are activated when rapid contractions are performed with loads 40% of maximum.

The force that a muscle must exert to move a load depends on two factors: the mass of the load and the amount of acceleration imparted to the load. The number of muscle fibers recruited during the lift increases with the speed the lift.

The rate at which any motor unit, low or high threshold, can discharge action potentials is not maximal during slow contractions. As contraction speed increases, so does discharge rate for all motor units.

Hi Roger,
The part on recruitment threshold, is a tricky one to get your head around. I think it means the faster you lift, the muscle fibers lowers their activation recruitment force, so that more can be recruited faster, and are thus recruited faster, as more are needed faster.

Am I right or half right or wrong ?

Hi Wayne,

You were right.

Cheers.

The number of muscle fibers activated to lift a weight depends on two factors:

(1) the amount of weight; and (2) the speed of the lift. Although more muscle fibers are activated during fast lifts, they are each generating MORE force. We know this because the rate at which the muscle fibers are activated by the nervous system increases with contraction speed.

Although your question seems relatively straight forward, it is not. Despite the popularization of the terms slow and fast muscle fibers, the characteristics of muscle fibers are not so black and white. Human muscle fibers are often classified as types I, IIa, and IIx.

This distinction is NOT based on contraction speed (slow or fast) but is based on the activity of an enzyme that is related to contraction speed. When the enzyme activity is assessed with an histochemical stain, the fiber types appear quite distinct: black, grey, and white.

When the enzyme activity is quantified, however, there is a continuous distribution of enzyme activity across the population. Furthermore, muscle fiber size (a measure of force capacity) varies continuously across the population and in some cases type I ("slow") fibers are actually the biggest.

I do not know how much work is performed by the different fiber types in the two scenarios you describe. I don't think this has been measured. The closest muscle physiologists have come to answering your question is to measure the size of muscle fibers in individuals who perform different types of training.

The most common finding is that it is the intermediate fiber type, the fast muscle fiber (type IIa) that experiences the biggest increase in size (strength) in individuals who perform conventional weight lifting (heavy loads,) and body building (lighter loads, fast/explosive reps) training. Neither type of training appears to have a significant effect on the size of types I and IIx fibers.

Cheers.

Per Aagaard Professor, PhD
Institute of Sports Science and Clinical Biomechanics
University of Southern Denmark

When a given load is lifted very fast, the acceleration component means that the forces exerted on the load (and thereby by the muscles) by far exceeds the nominal weight of the load.

For instance, a 120 kg squat can easily produce peak vertical ground reaction forces (beyond the body mass of the lifter) of 160-220 kg's when executed in a very fast manner! Same goes for all other resisted movements with unrestricted acceleration (i.e. isokinetic dynamometers (and in part also hydraulic loading devices) do not have this effect).

This means that higher forces will be exerted by MORE muscles fiber when a given load is moved at maximal high acceleration and speed - i.e. contractile stress (F/CSA) will be greater for the activated muscle fibers than when the load is lifted slowly...
best wishes
Per

Back later.

I have a PhD in biomedical engineering and did some coursework and research in functional electrical stimulation for neuro-prosthetic applications, so I know a thing or two about EMG, EEG, EKG, muscle recruitment, electrical stimulation, pacemakers, etc. Electrical muscle activity measures voltage changes due to the depolarization of the muscle cell membranes during the muscle's action potential, not the force exerted by the muscle.

As you will see, the muscle's action potential enables the muscles to produce force, the force produced by a muscle fiber “depends” on action potential rate, force and more force “is” and “depends” on the action potential rate.

When you lift a heaver weight, the EMG reads the average reading in the same time frame higher, thus more total/overall force is being used. When you lift the same weight with more velocity/accelerating, to create higher velocity/acceleration, you must create higher force, so the EMG reads the average reading in the same time frame higher for the faster reps, thus more total/overall force is being used. More muscle activity means more force, what else could it mean ? Less force ? No, more activity like it applies means more force, it’s impossible to move with more velocity/acceleration without more force, thus more force more muscle activity.

Back later in full.

The all-or-nothing principle only refers to the discharge of action potential by a motor neuron; either it discharges an action potential or it does not. This depends on the action potential-mediated level of calcium within the fiber.

Each muscle fiber action potential releases a certain amount of calcium from the storage site (sarcoplasmic reticulum) that enables the contractile proteins to interact and produce force. The amount of calcium released by a single action potential is less than that required to produce maximal muscle fiber force. Consequently, the force produced by a muscle fiber depends on action potential rate.

Cheers.

Roger M. Enoka, Ph.D.
Professor and Chair
Department of Integrative Physiology
University of Colorado

Wayne

 

[sophiecentaur]

This is all very interesting stuff but what's it doing on a General Physics Forum? The 'Physics' content is limited to the occasional use of words like Force and Acceleration. After acres and acres of talk about weight lifting - getting more and more Physiological with time there has emerged not a single paragraph to sum things up in strictly Physics terms - except for the very basics of Newton's Laws, which we were all taught when we were at School. Hardly surprising because Muscles are far too complex in their operation for simple analysis.

 

[Dale]

Muscles are far too complex in their operation for simple analysis.

I agree. I think that I can teach Wayne about impulse, average force, and work, but in the end none of those simple quantities are going to be a measure of muscle fatigue.

 

[waynexk8]

I have a PhD in biomedical engineering and did some coursework and research in functional electrical stimulation for neuro-prosthetic applications, so I know a thing or two about EMG, EEG, EKG, muscle recruitment, electrical stimulation, pacemakers, etc. Electrical muscle activity measures voltage changes due to the depolarization of the muscle cell membranes during the muscle's action potential, not the force exerted by the muscle.

Note, the key word "estimate". If you know the EMG and you know the tension v recruitment curve and you know the position of the limb and you know the force v tension curve for that position then you can use the EMG to make a good estimate as to what the force is.

Yes your right, however, when I did my tests on the fast and slow reps, I did 20 tests on the fast, and 20 tests on the slow, and the results were 100% for the faster reps by a big factor. Wow, this is very interesting, I added up the whole tests and averaged them out, and the faster EMG reading for the average muscle activation, or force/strength output for the given time, was 21% higher ! As I said, the force I also use is 20% higher on the faster reps, so for 10 seconds I said I use 20% more force/strength, and the EMG states 21% more on average after 40 tests.

All we need is a very good estimate, and that’s what we have.

An estimate and a measurement are not the same thing.

Right, but I don’t really think a machine as advanced as a EMG estimates, if it does, it’s very close at being right, as this machine is used Worldwide a 10,000 times a day all over the World for about 20 years.

=DaleSpam;3822934]Force is measured with a force transducer; an EMG is a voltage transducer. The units of the EMG are μV, not N.

All a force transducer does is converts measured forces.

What the EMG does is to take Symbol for the microvolt, an SI unit of electromotive force EMG is used to record muscle activity, it detects the electrical potential generated by the muscle.

EMG Introduction,
Small electrical currents are generated by muscle fibres prior to the production of muscle
force. These currents are generated by the exchange of ions across muscle fibre
membranes, a part of the signalling process for the muscle fibres to contract.

http://www.bortec.ca/Images/pdf/EMG measurement and recording.pdf

Muscle force estimation using a measure of muscle activation extracted from surface EMG (Citations: 1)




Rok ISTENIC, Ales HOLOBAR, Marco GAZZONI, Damjan ZAZULA
The aim of this paper is to introduce a new measure of muscle activation level that can be used for force prediction from surface EMG signals, or as an input into the biomechanical models as well. It is called activity index and its range is between 0 and 1, 0 meaning that no motor units are active in the observed muscle, while 1 stands for the maximal activity of all motor units in the muscle. The important property of activity index is that it increases and decreases in the same way as the force produced by the observed muscle does. It is a measure of global muscle activity and represents the summation of innervation pulse trains of all active motor units. Activity index is based on motor control information rather than EMG amplitude processing, which is the most common approach in muscle force estimation task nowadays. This estimator of the motor control information is obtained from multi-channel surface EMG signals. Our method was compared to the method known as MUAP rate, which estimates muscle force as the number of motor unit action potentials in a time epoch, so it uses the motor control information for the estimation purpose as well. Experimental data was obtained from biceps brachii muscle during elbow flexion task on 5 subjects using 2D matrix of surface electrodes (13 rows by 5 columns). Isometric constant force contractions at three different force levels were performed, i.e. at 5, 10 and 30 % of maximal voluntary contraction. Torque produced at the elbow joint was measured simultaneously with surface EMG. The performance of both methods was measured with root mean square error (RMSE) between real and estimated force. Average for all 3 contractions of 5 subjects (total 15 trials) produced the following results: activity index scored 13.46 % ± 6.26 % RMSE and MUAP rate scored 26.25 % ± 6.36 % RMSE. In all individual trials activity index was a better force estimator. This is due to the technique for extraction of motor control information out of surface EMG signals. However, the presented study is only preliminary and since the performance of the activity index can be enhanced in many ways, the activity index has vast potential to become the most commonly used muscle force estimation technique.

http://academic.research.microsoft.com/Paper/11760911

http://87.248.112.8/search/srpcache...8&icp=1&.intl=uk&sig=yq5UF5_NEa1ROJRGEcmu3A--

The purpose of this study was to evaluate three methods for predicting muscle forces of the shoulder by comparing calculated muscle parameters, which relate electromyographic activity to muscle forces.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258142/

Wayne

 

[waynexk8]

Back later in full, sorry for not getting back, and thank you for all the comments.

Two machines power up a very steep hill using force/energy, one goes at 100mph, and reaches a 100miles in 1 hour, the other goes at 80mph, and reaches an 80miles in 1 hour.

Seems like some here are turning around, and saying that the 100mph machine, did not actually go at 100mph, but we all first agreed on that, seems very contradictory.

Wayne

 

[sophiecentaur]

Two machines power up a very steep hill using force/energy, one goes at 100mph, and reaches a 100miles in 1 hour, the other goes at 80mph, and reaches an 80miles in 1 hour.

Seems like some here are turning around, and saying that the 100mph machine, did not actually go at 100mph, but we all first agreed on that, seems very contradictory.

Wayne

Seems like, once again, you haven't been thoroughly reading what's been written.
The actual Physics content of the whole of this thread could have been written on a Postage Stamp. All the rest of it has involved your getting hold of the wrong end of the stick and people trying to put you right. Occasionally, due to battle fatigue and sheer frustration, it is possible that some 'inappropriate' words may have been used. These seem to be the only ones that you bother to read and pick up on. You have ignored the seriously accurate Physics that is scattered all over the thread.
What a nerve - trying to point out inconsistencies in other peoples' posts.

 

[douglis]

Back later in full, sorry for not getting back, and thank you for all the comments.

Two machines power up a very steep hill using force/energy, one goes at 100mph, and reaches a 100miles in 1 hour, the other goes at 80mph, and reaches an 80miles in 1 hour.

Seems like some here are turning around, and saying that the 100mph machine, did not actually go at 100mph, but we all first agreed on that, seems very contradictory.

Wayne

So far you were confusing force and energy.Now speed also became a part of the confusion.
Great!Everyday you become better and better!

 

[waynexk8]

Originally Posted by waynexk8

6,
You fail with these variables, 50% faster in the fast = there MUST be more tension on the muscles per unit of time to make them fail faster, = more tension = there must be more total/overall force if there is more tension as on failing faster.

While I am sure that you do fail faster with fast reps I don't think that your conclusions follow. Something is exhausting the muscle's ability to function,

Ok this is fair, I ask you the same question, what is not exhausting the muscle's ability to function on the slow reps ?

Yes, something is exhausting the muscle's ability to function it’s the higher forces from the higher accelerations, “what” else could it be, this seems so obvious to me, it’s like if I hit a car with a hammer very slow, then very fast, on the very fast, it makes a far far far more huge dent then the slow, that’s because more force was used to make the acceleration.

And then in the end, this is why I fail faster, because the slow reps force, does, and cannot make up or balance out the fast reps total or overall force. Why else could I fail faster ?

Then don’t forget, we have in the fast, huge forces on the muscles, far far far higher than the forces on the muscles in the slow reps, not the forces from the muscles now, but the forces on the muscles from the transition from negative to positive. The forces on the muscles on the slow at this transition will be just 80 pounds, but on the fast you can have forces as high as ? 140 pounds.[/b]

but why MUST it be the tension/time.

Ok this is fair, I ask you the same question, why is it not the time/tension ? Why do you think the slow has the same time/tension ?

Because as I just said, the higher forces for the accelerations MUST make for higher tensions, and if the slows time/tension was the same, or did make up, both would fail at the same time, but the time/tension is not made up by the slow, as the muscles have not had the same time/tension on then, that’s why they are able to keep going longer.

Why couldn't it be the energy expenditure/time,

It is also the energy expenditure/time, but we should be asking why do you spend more energy expenditure/time, it can only be because the higher forces of the accelerations, do and are not made up or balanced out on the slow reps, as if they were they would use the same energy, but they don’t.

or the oxygen debt, or ATP depletion, or lactate build-up, or temperature rise?

It is all these as well, as these rise more, or deplete faster in the faster reps, because the total/overall forces must be higher. As I said, I try to use 100 pounds of force for 6 seconds, I accelerate and decelerate, use “ONLY” use 80 pounds of force for 6 seconds, you accelerate and decelerate. My question is, how and why can 80 pounds of total/overall force for 6 seconds, ever be as high me using as close to a 100 pounds of force ? How can 80 x 6 seconds be as high as 100 x 6 seconds ? I HONESTLY JUST DON’T GET HOW ANYONE COULD DEBATE AGAINST ME ?

It’s like me coming here, and you tell me 5 + 5 = 10 and 4 + 4 = 8, what “if” I turned around and said that 4 + 4 = 10 ? You would look at me a bit odd, please I am not being total sarcastic here, I just don’t get how when I say I am using 100 pounds of force for {yes I know I have to decelerate, but so does the slow} 6 seconds, and then someone else is using 80 pounds of force for 6 seconds, then someone like D. turns around and say 80 pounds of force for 6 seconds = 100 pounds of force.

I can think of lots of things that it could be, so the MUST just isn't true. Just because they fail faster does not imply that there is more tension/time.

Ok, you tell me why the fast uses more energy expenditure/time, oxygen debt, ATP depletion, lactate build-up, and temperature rise, if its not because of higher total/overall forces used, and remember I “have” moved the same weight 6 times further in the same time frame, I have produced more acceleration/velocity.

Question to all physicist here.

Fast trys to use 100 pounds of force moving 80 pounds object for 6 seconds = 100/6

Slow uses 80 pounds of force for 6 seconds = 80/6

How can 80/6 = or be as high as 100/6 ?

Wayne

 

[waynexk8]

Let’s look at the question from a different angle, mind you I have asked D. this before.

Fast rep moves the weight with acceleration and deceleration 1000mm in .5 of a second.

Slow rep moves the weight with acceleration and deceleration 166mm in .5 of a second.

“IF” and I am saying if, because I am saying that you don’t use the same force, so if you only move the weight 166mm in .5 of a second, and claim to use the exact same force as me moving the weight 1000mm in .5 of a seconds, HOW/WHY/WHERE does your exact same force used as me go ? As I know and can say where my forces was used.

1,
I moved the weight 6 times further in the same time frame, more physical work was done.

2,
I used higher velocities and accelerations,

3,
I “HAD” to use more energy,

But where did the same force per time used did your force go ? If as you claim you used the same total/overall force per same time as me, it should have been used somewhere, but where ?

Wayne

 

[waynexk8]

Seems like, once again, you haven't been thoroughly reading what's been written.
The actual Physics content of the whole of this thread could have been written on a Postage Stamp. All the rest of it has involved your getting hold of the wrong end of the stick and people trying to put you right. Occasionally, due to battle fatigue and sheer frustration, it is possible that some 'inappropriate' words may have been used. These seem to be the only ones that you bother to read and pick up on. You have ignored the seriously accurate Physics that is scattered all over the thread.
What a nerve - trying to point out inconsistencies in other peoples' posts.

But I have to point them out, unless you can explain this,

Question.


Fast trys to use 100 pounds of force moving 80 pounds object for 6 seconds = 100/6


Slow uses 80 pounds of force for 6 seconds = 80/6


How can 80/6 = or be as high as 100/6 ?

How do you think when we both agree that I use 100 pounds of force, or as near as I can force for say this time, .5 of a second, and then we both agree than you use a force 20% less of 80 pounds force .5 of a second, and then turn around to me and say you used the same force as me for .5 of a seconds, how can you turn around and say 80 is as high as 100 or/and 80 = a 100 ? how can 80 force used for .5 of a second be as high as a 100 force for .5 of a second ? I use a higher force than you, we both agree this, then when you use your lower force for .5 of a second, and I use my higher force for .5 of a second, you say to me, your lower force use for the same time frame was as high as your higher force !


Wayne

 

[waynexk8]

What you should do, is try and answer some questions

So far you were confusing force and energy.Now speed also became a part of the confusion.
Great!Everyday you become better and better!

How and where did I confuse ?

Two machines power up a very steep hill using force/energy, one goes at 100mph, and reaches a 100miles in 1 hour, the other goes at 80mph, and reaches an 80miles in 1 hour.

Seems like some here are turning around, and saying that the 100mph machine, did not actually go at 100mph, but we all first agreed on that, seems very contradictory.

Or I could have said, Seems like some here are turning around, and saying that the 80mph machine, did not actually go at 80mph, but we all first agreed on that, seems very contradictory.

I will ask you the same question, that is, “after” you try and tell me how I was confused above ?


Fast try’s to use 100 pounds of force moving 80 pounds object for 6 seconds = 100/6


Slow uses 80 pounds of force for 6 seconds = 80/6


How can 80/6 = or be as high as 100/6 ?

How do you think when we both agree that I use 100 pounds of force, or as near as I can force for say this time, .5 of a second, and then we both agree than you use a force 20% less of 80 pounds force .5 of a second, and then turn around to me and say you used the same force as me for .5 of a seconds, how can you turn around and say 80 is as high as 100 or/and 80 = a 100 ? how can 80 force used for .5 of a second be as high as a 100 force for .5 of a second ? I use a higher force than you, we both agree this, then when you use your lower force for .5 of a second, and I use my higher force for .5 of a second, you say to me, your lower force use for the same time frame was as high as your higher force !


Wayne

 

[waynexk8]

Seems like, once again, you haven't been thoroughly reading what's been written.
The actual Physics content of the whole of this thread could have been written on a Postage Stamp. All the rest of it has involved your getting hold of the wrong end of the stick and people trying to put you right. Occasionally, due to battle fatigue and sheer frustration, it is possible that some 'inappropriate' words may have been used. These seem to be the only ones that you bother to read and pick up on. You have ignored the seriously accurate Physics that is scattered all over the thread.
What a nerve - trying to point out inconsistencies in other peoples' posts.

Dalespam wrote;
Impulse has the property that if you exert twice the force for the same amount of time you have doubled your impulse. So, for example, if you exert 100 lbs for 10 s and I exert 50 lbs for 10 s you have exerted twice the impulse that I have. Does this agree with your concept of "total/overall muscle force"?

Impulse also has the property that if you exert the same force for twice as long you have doubled your impulse. So, for example if you exert 100 lbs for 10 s and I exert 100 lbs for 5 s you have exerted twice the impulse that I have. Does this also agree with your concept of "total/overall muscle force"?

This is what I have been saying all along, I use exert 100 lbs for 10 s and you exert 80 lbs for 10 s I have exerted 25% more the impulse that I have.

Why is that so hard to understand ?

Ok, could you please after the last question, could you answer these,
What forces do you think you have that can make up of balance out the higher propulsive forces of the fast in the studies ?

Let’s take the mean propulsive forces, slow 6.2mean in 10.9 seconds. Fast 45.3mean 2.8 seconds, now let’s divided the mean slow of 10.9 seconds by the fast 2.8 = 3.8, so now let’s divide the slow mean by 3.8 = 1.6.

Fast mean for 2.8 seconds = 45.3.

Slow mean for 2.8 seconds = 1.6.

The fast has nearly 3000% more mean propulsive force as in N's in the same time frame.

Please what forces have I left out that the slow has to make up or balance out these ?

http://www.jssm.org/vol7/n2/16/v7n2-16pdf.pdf

Which has the highest force, and which are you saying has the same force as the slow rep for the same time frame, 1 or 2 ?

I was just wondering and thinking, ARE you adding “all” the force, I mean with the fast there are NOT just force being exerted by the muscles, there are HUGE forces on them, for say .1 of a second x the 6 reps = high forces on the muscle for maybe .6 of a second. Have you added these in ?

I mean the peak force from the transition from negative to positive, the force on the muscle, NOT given out by the muscles ? We call them the MMMTs {Momentary Maximum Muscle Tensions} these forces “ON” the muscles can be as high as 140%

Have you added these on ?

Lift 1,
You lift 80% of the ground, up 1m and then down 1m all in 1 second, .5/.5

Lift 2,
You start at the top, lower the weight down 1m, and then lift it back up 1m all in 1 second, .5/.5

On lift 2, on the transition from negative to positive, there will be huge force on the muscles and coming from the muscles.

Wayne

 

[waynexk8]

I agree. I think that I can teach Wayne about impulse, average force, and work, but in the end none of those simple quantities are going to be a measure of muscle fatigue.

Thank you.

What I would like to learn more on is,

Impulse, yes,

Not average force ? Why do you and D. keep on mentioning average force ? If the average force is the same for 1 rep at 1/1 and 100 reps at 1/1, we all know that the tension will be 99% times more on the muscles than the 1 rep at 1/1 thus the total/overall force must be higher it the tension is higher. I just don’t understand why you mention this, could you explain please ?

Also we have a problem there, as the EMG states a higher average reading.

Work, yes.

I know quite a lot about the measure of muscle fatigue, that would be my department explaining to someone.

Have to say, as this seems a confusing and frustrating thread, big thank you for all your times and helps, its honestly more then appreciated.

Wayne

 

[K^2]

This is what I have been saying all along, I use exert 100 lbs for 10 s and you exert 80 lbs for 10 s I have exerted 25% more the impulse that I have.

Why is that so hard to understand ?

Yes, but it doesn't mean that you have done more work. I can exert less force over the same amount of time, which will mean that I transferred less impulse, but at the same time, do more work.

That's the only point that anyone (with a sense) have been trying to get across.

 

[waynexk8]

This is all very interesting stuff but what's it doing on a General Physics Forum? The 'Physics' content is limited to the occasional use of words like Force and Acceleration. After acres and acres of talk about weight lifting - getting more and more Physiological with time there has emerged not a single paragraph to sum things up in strictly Physics terms - except for the very basics of Newton's Laws, which we were all taught when we were at School. Hardly surprising because Muscles are far too complex in their operation for simple analysis.

Ok, if you think you are right, why does the EMG state a higher average reading ? How and why do I move the weight 6 times further ? How and why do I use more energy ? how and why do I fail roughly 50% faster ?

And what equastions give you any proff ?

Wayne

 

[K^2]

Ok, if you think you are right, why does the EMG state a higher average reading ? How and why do I move the weight 6 times further ? How and why do I use more energy ? how and why do I fail roughly 50% faster ?

Muscles are funny that way. They require ATP just to maintain constant position under stress. Add to that the fact that you get better circulation while muscles move, and it seems quite reasonable.

 

[Dale]

Hi waynexk8, don't forget to respond to post 281, especially the 4 questions.

 

[douglis]

Thank you.

What I would like to learn more on is,

So stop your endless rambling and try to learn something.

Impulse, yes,

Not average force ? Why do you and D. keep on mentioning average force ? If the average force is the same for 1 rep at 1/1 and 100 reps at 1/1, we all know that the tension will be 99% times more on the muscles than the 1 rep at 1/1 thus the total/overall force must be higher it the tension is higher. I just don’t understand why you mention this, could you explain please ?

Wayne

With 100N

1)you do 1 rep with .5/.5
What's the average force?What's the impulse?

2)you do 6 reps with .5/.5
What's the average force?What's the impulse?

3)you do 1 rep with 3/3
What's the average force?What's the impulse?

 

[sophiecentaur]

Ok, if you think you are right, why does the EMG state a higher average reading ? How and why do I move the weight 6 times further ? How and why do I use more energy ? how and why do I fail roughly 50% faster ?

And what equastions give you any proff ?

Wayne

The only way that I could ever believe that the EMG is giving you accurate 'Work Done' information is if you tell me that, when you are stationary, the EMG reading is Zero.
EMG tells you something about how hard your muscles are working but nothing reliable about the effective work they are doing on the weights.
I know you are devastated that your expensive machine could possibly not be doing what you think it is but you may just have to get over that. It is a useful tool, no doubt, but not in the way you seem to think it is.

 

[waynexk8]

Sophiecentaur and D.

Could you please say why you cannot answer my question on my last posts ? I will number them this time. And if you don’t understand them, or anything part please say, but as this is a physicist forum, I don’t really see how they are complicated ?

dalespan, if you have the time, could you please anser ?

Dalespam wrote;
Impulse has the property that if you exert twice the force for the same amount of time you have doubled your impulse. So, for example, if you exert 100 lbs for 10 s and I exert 50 lbs for 10 s you have exerted twice the impulse that I have. Does this agree with your concept of "total/overall muscle force"?

Impulse also has the property that if you exert the same force for twice as long you have doubled your impulse. So, for example if you exert 100 lbs for 10 s and I exert 100 lbs for 5 s you have exerted twice the impulse that I have. Does this also agree with your concept of "total/overall muscle force"?

Question 1,
This is what I have been saying all along, I use exert 100 lbs for 10 s and you exert 80 lbs for 10 s I have exerted 25% more the impulse that I have.

Why is that so hard to understand ?



Question 2,
What forces do you think you have that can make up of balance out the higher propulsive forces of the fast in the studies ?

Let’s take the mean propulsive forces, slow 6.2mean in 10.9 seconds. Fast 45.3mean 2.8 seconds, now let’s divided the mean slow of 10.9 seconds by the fast 2.8 = 3.8, so now let’s divide the slow mean by 3.8 = 1.6.

Fast mean for 2.8 seconds = 45.3.

Slow mean for 2.8 seconds = 1.6.

The fast has nearly 3000% more mean propulsive force as in N's in the same time frame.

Please what forces have I left out that the slow has to make up or balance out these ?

http://www.jssm.org/vol7/n2/16/v7n2-16pdf.pdf


Question 3,

Which has the highest force, and which are you saying has the same force as the slow rep for the same time frame, 1 or 2 ?

I was just wondering and thinking, ARE you adding “all” the force, I mean with the fast there are NOT just force being exerted by the muscles, there are HUGE forces on them, for say .1 of a second x the 6 reps = high forces on the muscle for maybe .6 of a second. Have you added these in ?

I mean the peak force from the transition from negative to positive, the force on the muscle, NOT given out by the muscles ? We call them the MMMTs {Momentary Maximum Muscle Tensions} these forces “ON” the muscles can be as high as 140%

Have you added these on ?

Lift 1,
You lift 80% of the ground, up 1m and then down 1m all in 1 second, .5/.5

Lift 2,
You start at the top, lower the weight down 1m, and then lift it back up 1m all in 1 second, .5/.5

On lift 2, on the transition from negative to positive, there will be huge force on the muscles and coming from the muscles.

Which of the 2 forces on the 2 faster reps are you saying that’s the same as the slow rep for the same time frame ? As lift 1 and 2 use a different amount of force.



Question 4,
Fast reps person trys to use 100 pounds of force moving 80 pounds object for 6 seconds = 100/6

Slow reps person uses 80 pounds of force for 6 seconds = 80/6

How can 80/6 = or be as high as 100/6 ?
How can you trying to use 80 pounds of force for 6 seconds, be as high or the same as me using 100 pounds of force for 6 seconds ? HOW can 80 foirce be as high as 100 force ? As I always thought a 100 was 20 more then 80, or/and 25% more than 80, but you are saying that 80 = 100 ? Please for once explain how 80 = 100 ?

Wayne

 

[Dale]

dalespam, if you have the time, could you please anser ?

Hi waynexk8, yes, I could answer, but I won't at this time. If you stick it out, I will answer when I think you are ready.

If I came into your gym, having never done weightlifting, and asked you to show me how to do an Olympic snatch at twice my weight, would you teach me that right away or would you try to teach me the basics first?

For question 1 you are correct, it is 25% more impulse. For the rest of the questions we need to lay some more groundwork. Question 4 will be the next one we can address with a little more work.

 

[waynexk8]

Hi waynexk8, yes, I could answer, but I won't at this time. If you stick it out, I will answer when I think you are ready.

Ok that’s sounds more than fair.

Thank you very much dalespam,

If I came into your gym, having never done weightlifting, and asked you to show me how to do an Olympic snatch at twice my weight, would you teach me that right away or would you try to teach me the basics first?

Your right, I would never let you do that, you would have to do the basics first.

For question 1 you are correct, it is 25% more impulse. For the rest of the questions we need to lay some more groundwork. Question 4 will be the next one we can address with a little more work.

The odd part about this, as D would never even answer this, and I still don’t get why, unless he knows he’s wrong.

So could we all stay on question 1 for a while please.

So D. and S. it seems you worked the fast reps out, from the lifted that started on the ground, and was lifted up in .5 of a second and lowered in .5 of a second, = 1 second for the total lift, you then multiplied this by 6 = 6 seconds of lifting, as this is the same time frame as the one slow lift, 3 seconds up and 3 seconds down.

But you forgot to add in the peak forces, or the peak acceleration forces, the MMMTs, {Momentary Maximum Muscle Tension} the huge forces from the transition from negative to positive, and in 6 reps or 6 seconds there are 5 of these.

So I think, that if you add in the peak acceleration forces, too which are 25% higher, you x 25% by 5 = in 6 seconds the faster reps used 125% more impulse/force then the 1 slow rep in the same time frame. Could you comment please dalespam.

This that D. left out the most important forces, the peak acceleration forces, fits in with what he left out before, as he did the exact same this.

https://www.physicsforums.com/showthread.php?t=472526&page=9

Originally Posted by jarednjames
All this average acceleration stuff is non-sense. You are ignoring the fact that to get a rocket to accelerate at 1m/s2 uses significantly less energy than to get it to accelerate at 2m/s2. To increase the acceleration by even such a small amount requires a drastic energy increase.


douglis wrote;
O.K...let's start from here.
We agree that acceleration requires more energy and also the greater the acceleration the greater the energy.
So in this rocket example let's say that the rocket used force that caused initial acceleration equal with 2g(if we assume that was accelerated for 30sec) and then since the engine shut down used zero force for the final deceleretion(the last 30sec).
On average the force that was used produced average acceleration equal with g or else the average force was mg for 1 minute.
Exactly like the force that was used by the rocket that was standing still in the air.

Since in both cases the average acceleretion that the engined produced was equal I can't see how the fuels can be different.The fuels that the moving rocket spent when using 2g for 30 sec are exactly equal with the fuels that the standing rocket spent by using g for 1min.



Originally Posted by jarednjames
They most certainly are not.

Average acceleration doesn't apply to the fuel use because it isn't linear.

As previously, fuel use is exponential. If you double your speed, the fuel use more than doubles.

So to double your speed may half your travel time but it more than doubles fuel use.

1g for a minute may use 1L of fuel. 2g for 30 seconds will use 4L. 4g for 15 seconds will use 15L etc.

Obviously, it's not as straight forward as that but that's the gist of it. 1g for a minute does not equal 2g for 30 seconds.



douglis wrote;
Look...I tried to make an equivalent with weight lifting and I assumed that fuel expenditure is linear.If we don't make that assumption the discussion goes too far.


Originally Posted by jarednjames
In no case, ever, is fuel consumption linear. Weight lifting and rockets alike.

To make that assumption would completely change the physics and make it so that twice the speed with double the distance would give you the same energy use. Complete non-sense.



douglis wrote;
I insist that speed and distance are irrelevant and keep the nonsense comments for youself.
Forget for a moment the acceleration phases.Two rockets with different constant speeds will spend identical fuels for the same duration if you exclude the air resistance.

Again at the acceleration part now...do you believe that double force will result in more than double fuel expenditure?



Originally Posted by jarednjames
Constant speed yes, but it has to get to that speed which involves acceleration which, depending on the required velocity is different (as you are aware). To accelerate to 50mph does not take half the fuel it takes to accelerate to 100mph.

For simplicity you can ignore constant speed and simply have acceleration and deceleration.

If deceleration is due to gravity the rocket expends no fuel.

Leaving you only acceleration to consider for fuel use and the values for different accelerations (1m/s2, 2m/s2, 4m/s2 etc) do not have the same fuel use and it is not simply double fuel as you double acceleration.



Note that D. is trying to leave out the peak acceleration forces, just like he is doing now, and S. seems to be doing the same thing, but as they said, you HAVE to get to that speed, which must involve acceleration, and acceleration, involves more force, thus the peak acceleration forces.

D. got the energy used wrong over a year ago, and now gets the forces involved wrong, but only because he was looking at it the wrong way, and not adding all the forces in, easy done I suppose.


Wayne

 

[sophiecentaur]

Could anyone explain to me just what this thread is trying to do?
Wayne will, clearly, never take on board the Physics and is only interested in pointing out any inconsistency he can find in the (mostly) good Science. I can't think just what he really wants out of this - certainly not to learn any Physics. Yet the thread drags on and on. Can't it just be put to rest?

 

[Dale]

So could we all stay on question 1 for a while please.

So D. and S. it seems you worked the fast reps out, from the lifted that started on the ground, and was lifted up in .5 of a second and lowered in .5 of a second, = 1 second for the total lift, you then multiplied this by 6 = 6 seconds of lifting, as this is the same time frame as the one slow lift, 3 seconds up and 3 seconds down.

But you forgot to add in the peak forces, or the peak acceleration forces, the MMMTs, {Momentary Maximum Muscle Tension} the huge forces from the transition from negative to positive, and in 6 reps or 6 seconds there are 5 of these.

So I think, that if you add in the peak acceleration forces, too which are 25% higher, you x 25% by 5 = in 6 seconds the faster reps used 125% more impulse/force then the 1 slow rep in the same time frame. Could you comment please dalespam.

OK, question 1 was about impulse for constant forces, I don't think we are quite ready to discuss changing forces. If you would please go ahead and answer the four questions I posed earlier in post 281 for non constant forces. That way I can see where you are in your conceptualization of impulse.

 

[douglis]

But you forgot to add in the peak forces, or the peak acceleration forces, the MMMTs, {Momentary Maximum Muscle Tension} the huge forces from the transition from negative to positive, and in 6 reps or 6 seconds there are 5 of these.

Wayne

What kind of nonsense is that?
We talk about the average value of force for the exact reason that we recongnise that there're peak high and low fluctuations of force.Otherwise we would only talk about a constant velue of force.
BTW...the MMMTs are exctly the peak high of force.Those two are the same thing.The MMMTs are not an exotic and mysterious additional force.

Anyway...if I were you...I would shut up right now and I would take advantage of DaleSpam's superhuman patience to help you learn basic physics.

 

[waynexk8]

So stop your endless rambling and try to learn something.



With 100N

1)you do 1 rep with .5/.5
What's the average force?What's the impulse?

2)you do 6 reps with .5/.5
What's the average force?What's the impulse?

3)you do 1 rep with 3/3
What's the average force?What's the impulse?

Tell me please D. ?

Wayne

 

[waynexk8]

This thread is not to try and mock. The only reason for the above, as it seems, 1, you don’t understand the questions, which I find odd. 2, You do understand the questions, but will not answer as it will prove you wrong, that’s why you are not answering and trying to spoil the thread.

Could anyone explain to me just what this thread is trying to do?

We are debating which person uses the most total/overall force per time.

Let me explain one more time one of the questions you will not answer.

I use or try and use a 100 pounds of force for 6 seconds, that = 100 force x 6 seconds of time, let’s call that 100f/6t. You use 80 pounds of force for 6 seconds, that = 80 force x 6 seconds of time, let’s call that 80f/6t.

Fast rep = 100f/6t

Slow rep = 80f/6t

Please tell me, when we all agree that I use 100 force for 6 seconds, and you use 80 force for 6 seconds, how/why you think 80 is as high as 100 ? When 100 = 25% more than 80 and/or 20 more units than 80 ? And yes we both accelerate, and decelerate.

It’s like saying, I used 100 Joules of energy in 6 seconds, and you used 80 Jules of energy in 6 seconds, then you turn around and say you used the same amount of energy, “please” just tell me why you think this ?

Wayne will, clearly, never take on board the Physics

I AM a Man of physics, you have to believe in physics, it’s how the universe and life works or is explained, I can here to ask questions and to have them answered, I showed you that a EMG machines shows that the average force is higher, I showed you that you fail roughly 50% faster with these variables, I showed you that I move the weight 12m to your 2m, I showed you that you use more energy in the fast reps, this is all physics.

All you do is not answer.

and is only interested in pointing out any inconsistency he can find

Of course I will point out inconsistencies, and I would in all walks of life, and “if” you find any in what I say is you think wrong, please say.

in the (mostly) good Science.

What science are you thinking of, what do you think I have been showed ?

I asked a question, you and D. did/could not answer, dalespam did, I was right in what I said ?
For question 1 you are correct, it is 25% more impulse. Please how do you say that I did not say good science when I was right, it was not even a hard question, it was quite obvious

I can't think just what he really wants out of this - certainly not to learn any Physics. Yet the thread drags on and on. Can't it just be put to rest?

An answer, why can't we just debate and stay frendely.

Wayne

 

[waynexk8]

OK, question 1 was about impulse for constant forces, I don't think we are quite ready to discuss changing forces. If you would please go ahead and answer the four questions I posed earlier in post 281 for non constant forces. That way I can see where you are in your conceptualization of impulse.

Sorry I m issed this one, well not missed forgot to get back to it.

I am not saying that at all. The second law is correct; you just have some misunderstandings. We will get to those in a bit. Right now we need to focus on the progress that we have made and flesh out the concept of impulse.

OK, so now that we have confirmed that your concept of "total force" is the same as the standard physics concept of "impulse" I expect you to not write the words "total force" any more and to use the correct term "impulse". You may think that this is nitpicky, but there is a very important reason for doing this. Impulse has units of momentum, and not units of force, so the term "total force" is not only non-standard but incorrect. Something that does not have units of force cannot be any kind of force, let alone a "total force". Do you agree to this?

Ok, total/overall force = impulse, question first before I use it, impulse is the integral/whole of a force with respect to time ? I am sure it is, but best ask.

So, if you exert a constant 100 lb for 10 s then you have exerted an impulse of 1000 lb*s. And if you exert a constant 80 lb for 10 s then you have exerted an impulse of 800 lb*s. If you drew a force v time curve as I did above then each of these would be a simple straight flat line. And in both cases we would get the impulse by calculating the area under the curve (area of a rectangle is base times height which in this case is the time times the force).

OK, so now let's work a couple of problems to solidify the concept of impulse. Please show your work:

1) What is the impulse if you exert a 100 lb force for 5 s and then 80 lb for an additional 5 s?

900lb/10s

2) What constant force would give the same impulse as in 1) if exerted over 10 s?

90lb. 90 x 10 = 900

3) What is the impulse for the attached force vs time graph? (Hint: remember that the impulse is the area under the graph which is shaded in this graph and also remember that the area of a triangle is 1/2 base times height.)

Not sure why it’s a triangle, or the force curve is going down as the time goes on, it seems to me as you start using a 100 force, and then the force you use goes down and down the more seconds you are trying to apply an force ? Or is it a 100 force for 10 seconds 1000lb/10s ?

4) What constant force would give the same impulse as in 3) if exerted over the same amount of time?

If its 1000/10s it would be 100.

The graph is plotted in Mathematica using the following code:

y[t_] := 100 - 10 t;
Plot[y[t], {t, 0, 10}, Frame -> True, 
 FrameLabel -> {Style["Time (s)", Larger], 
   Style["Force (lb)", Larger]}, 
 PlotLabel -> Style["Force vs Time", Larger], Filling -> 0]

Slow rep,
So if we used 80 force for 10 seconds – off 1 second for the deceleration and call that second zero, it would be 800f/9s.

Fast reps,
So if we used 100 force for 10 seconds – off 1 second for the deceleration and call that second zero, it would be 1000f/9s. 20 more impulse in 10 seconds, or/and 25% more impulse in 10 secondsHowever, now we have left out the forces “on” the muscles, the forces from the transition from negative to positive {can you work this out ?} these forces for say a quarter of a second, can be as high as say ? 140% or more, so as there are 9 of these in 10 seconds, that = so and so force that we have to add onish, for so and so time, as this will put far far far more tension on the muscles, and this is the crux of this debate.

Wayne

 

[Dale]

Ok, total/overall force = impulse, question first before I use it, impulse is the integral/whole of a force with respect to time ? I am sure it is, but best ask.

Yes, impulse is the integral of a force with respect to time.

900lb/10s

This is incorrect, but I can see that you are heading in the right direction. Remember that division and multiplication are different operations, so 900lb/10s = 90 lb/s. This is not even in the correct units for impulse which is in units of force*time (lb*s) not force/time (lb/s). Do you see the difference?

So the way you calculate this is as follows:
(100 lb * 5 s) + (80 lb * 5 s) = (500 lb*s) + (400 lb*s) = 900 lb*s

Do you see the difference between 900 lb*s and 900lb/10s?

90lb. 90 x 10 = 900

Correct, but be sure to always put the units in correctly. The impulse is 900 lb*s and the force was applied for 10 s total. The constant force that would produce the same impulse is 90 lb since, as you said, 90 lb * 10 s = 900 lb*s.

Not sure why it’s a triangle, or the force curve is going down as the time goes on, it seems to me as you start using a 100 force, and then the force you use goes down and down the more seconds you are trying to apply an force ?

Yes, the person is starting exerting 100 lb force, but over the course of 10 s the force decreases linearly to 0 lb. I.e. somebody steadily getting weaker over the 10 s, unable to sustain the inital force of 100 lb.

Or is it a 100 force for 10 seconds 1000lb/10s ?

Remember the area of a triangle is 1/2 * base * height. In this case the triangle has a height of 100 lb and a base of 10 s, so the area (impulse) is:
1/2 * 10 s * 100 lb = 500 lb*s

If its 1000/10s it would be 100.

Based on the above, why don't you try this one again?

Do you understand the corrections I have made above, particularly the difference between division and multiplication and the correct use of the units?