Impulse/force in pounds for the time frame

[sophiecentaur]

How do you work that out ? What machine can lift say 80% up, and then lower it down using very little energy, and what energy is this ?

Wayne



Where and how does the machine get its energy back ? It will be powered by say diesel or electricity, let’s say diesel, so it uses, let’s just say a half a pint of diesel to lift the weight, you tell me where and how the machine gets that diesel back ? You know very well that when the half a pint of diesel is gone, has been used to lift the weight, you can “never” get it back.

And when it lowers the weight, it will have to use energy again, as in the diesel, a little less this time, but it has to use energy/diesel to move in any direction, as its using force, and this force is putting tension on the machine.



You and all here know physics far better than me, but I give you 7 real World practical points proving your theory does not fit, and as you know, a theory, is just a theory until you can prove it with a practical experiment, and I have proved it wrong and few times.

Just for now take the EMG, and the fact that you fail 50% faster.

Also, what have you proved ? I see no equations, what you did say that there is no such thing as total/overall force in physics, yet the EMG reads out a higher average reading on the faster, and the EMG work with the equations of physics, they are put in the EMG.

I thought is was the physics job to do the theory, and when the practical proves this wrong, the physics needs to be looked at.



I do see what you mean, but what about my points, like the EMG, and the fact you fail faster, they can only mean one thing, the fast is putting more tension on the muscle, and the only way to put more tension on the muscle is by putting out more force, and taking more force on the muscles.

Wayne

Here you go again - leaping in with both feet in the absence of knowledge. Do you know the difference between a Machine and an Engine? Of course a diesel engine has no energy return but a Machine, consisting of no more than a SPRING can lift and lower a weight without losing any energy at all (allowing for a minuscule amount, due to friction.

You have got it wrong when you say it is up to us to Disprove what you say. I'm afraid that it is up to you to Prove what you say because it goes against all known Physics. Just read any simple textbook to find out the meanings and derivations the various terms that you are using with such abandon.

There is not a single statement from any of us which denies the fact that you feel more knackered and your muscles ache more when you are doing exercise faster. Our issue it that you are trying to 'explain' this in 'physics' terms that just don't apply. You have a gut feeling that it should be straightforward but you don't seem to realize just how muscles actually work. If you read what douglis tells you, instead of giving all those "but surely" - type responses then you might learn something.

Most people come on this forum in order to learn something. You have breezed in and you're trying to tell us all how we should be able to do something with the Physics that we understand but that you do not. Do you ever consider that you might just be plain wrong in this?

 

[douglis]

Hi D. and all.

Are you trying to be sarcastic or something ? I mean we are on a physics forum, I have all ready proved this, ITS UP TO YOU TO “TRY” AND DISPROVE IT, the cards are in my hands, the EMG states you wrong.

Wayne

OMG you're really delusional.You don't have a clue about basic physics terms and you think have proved something!ALL your nonsesnse from 1-7 show NOTHING in terms of force.
I won't repeat them...it's a waste of time.
For your own good...quit your nonsense and just focus on DaleSpam's posts...he's really trying to help you.

 

[Dale]

Could anyone please answer this ?

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 ?

Yes. Newton's 3rd law guarantees that at all times the force of the mass on the person is equal and opposite to the force of the person on the mass. A MMMT would be seen in a sudden spike in the acceleration or deceleration of the mass.

Can you please respond to my questions of post 265?:

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.

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 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"?

 

[waynexk8]

Read the other posts later, just going to price some jobs up, and just thought of this, and again thank you for your help and time.

PLEASE let’s try this way. 1RM or maximum you can lift up one time = 100 pounds.

1,
I lift a 90 pounds and hold it half way up for 20 seconds, as I am first applying over 90% or/and 90 pounds of force, then hold it steady with 90% or/and 90 pounds of force and then lower.

2,
You as you are only applying 80% or/and 80 pounds of force, do not, cannot lift the weight, as your only apply 80% or/and 80 pounds of force.1a,
I have applied an average of 90% or/and 90 pounds of force for 20 seconds = 90F x 20S.

2b,
You have applied an average of 80% or/and 80 pounds of force for 20 seconds = 80F x 20S.

HOWEVER, the three of you here, are telling me that 80F = 90F and that we have both applied the same amount of force for the 20 seconds, EVEN thou we all agree that I use 90F and you use 80F, you turn around after agreeing that, and say different, and that we used the same force for the same time frame ?

Wayne

 

[douglis]

HOWEVER, the three of you here, are telling me that 80F = 90F and that we have both applied the same amount of force for the 20 seconds, EVEN thou we all agree that I use 90F and you use 80F, you turn around after agreeing that, and say different, and that we used the same force for the same time frame ?

Wayne

Who agrees with that?The three of us are telling you that we both apply 80 pounds on average for 20 sec but for some reason you're unable to understand it.Your above example does not represent what happens in dynamic lifting where ALWAYS force equal with the weight is applied for the duration of the set.Regardless the lifting speed.
Stop your nonsense and read carefully what we write.

 

[Dale]

Hi DaleSpam...if you have the time check the paragraph "2.1 Participants and experimental protocol" in http://jmbe.bme.ncku.edu.tw/index.php/bme/article/viewFile/635/839 .Do you think that the magnitude total muscle activation (TMA) can give a good estimation of the impulse?

Thanks for the paper, it was an interesting read. The TMA, by itself, is not an estimate of impulse, but scaled by the corresponding force data from the dynamometer, it would be. Of course, the estimate would be pretty inaccurate since the forces would vary with both joint position and speed for a given EMG reading.

However, it is probably good enough to make relative assessments. I.e. you couldn't use it to estimate that the impulse was X, but you could use it to estimate that the impulse was greater for the slow than for the fast (due to the longer time).

It's interesting that the TMA per second is greater for the slow puh ups(in contast of what Wayne claims).For example if you check the tables 1 and 3 for the pectoralis major:
for the slow push ups the TMA is 3121.81 for 101.2 sec.(TMA/t=30.85)
while for the fast push ups the TMA is 2114.22 for 84.2 sec.(TMA/t=25.11)

Yes, I found that interesting too. I am thinking of what properties Wayne should be looking for in selecting a measure. Here is what I came up with.

1) it should be physical, and not require biomechanical or physiological information
2) it should scale with weight
3) it should scale with time
4) for a fixed weight and measure decreasing the rep rate should increase the time
5) for a fixed weight and measure increasing the rep rate should increase the number of reps

I can't think of any more based on the data. Impulse is actually pretty close, it accomplishes all of those except 4).

 

[douglis]

Yes, I found that interesting too. I am thinking of what properties Wayne should be looking for in selecting a measure. Here is what I came up with.

1) it should be physical, and not require biomechanical or physiological information
2) it should scale with weight
3) it should scale with time
4) for a fixed weight and measure decreasing the rep rate should increase the time
5) for a fixed weight and measure increasing the rep rate should increase the number of reps

I can't think of any more based on the data. Impulse is actually pretty close, it accomplishes all of those except 4).

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.

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

 

[Dale]

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.

Note figure 6b. In that figure the EMG is lower during the descent compared to the sticking region, but the force is higher.

 

[waynexk8]

Wayne wrote;
Could anyone please answer this ?

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 ?

DaleSpam;3824653Yes. Newton's 3rd law guarantees that at all times the force of the mass on the person is equal and opposite to the force of the person on the mass. A MMMT would be seen in a sudden spike in the acceleration or deceleration of the mass.

Yes a sudden spike would be the MMMT’s.

But please, there “HAS” to be different force/s generated in both lifts, which one are you saying that you think is equal to the slow lift.

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, so this lift “will” generate more tension on the muscles, agreed ? if there is more tension on the muscles as in lift 2, and there is, as this can be proven practically quite easy, there must be more force.

Can you please respond to my questions of post 265?:

Ok will go back first thing tomorrow, sorry I missed, very glad you said.

Before you can prove your total/overall muscle force theory you need to define it, otherwise there is no theory to prove or disprove.

Right, agreed.

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.

We could ask, which is harder, more fatiguing on the muscle, this is the fast, so why is the fast harder and more fatiguing. First we know that you use far far far more energy on the fast in the same time frame, we all should be asking why is this, to find that out, maybe we should go a step further, the fast moves the weight 6 times the distance in the same time frame, to me if you move something further in the same frame, and 6 times further, you have to use more force, that equals the more energy used.

If not, you here seem to be saying you can move a weight 6 times further in the same time frame, using the exact same force that you only moved the weight 2m, as to 12m with the fast, please could you show and tell me how you can move the weight 6 times further using the exact same force as you used to move the weight just 2m with the slow rep ?

I as I said before, I try to use a 100 pounds of force for 6 seconds equals 100 pounds of force for 6 seconds, call it 100f x 6s, that’s why I move the weight further, as I use more force for the same time frame.

You use 80 pounds of force for 6 seconds call it 80f x 6s.

How can 80 force used for 6 seconds be as high as 100 force used for 6 seconds ?

You also seem to be saying the Second law is wrong, the acceleration a of a body is directly proportional to the net force F and inversely proportional to the mass, F = ma.

Please could someone answer this one.


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

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

Ok, great.

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"?

Yes, that’s perfect and exactly what I have been saying, at last I think we all agree on something statisticaly.

So as I said above, if I try to exert 100 lbs for 10 s and you exert 80 lbs for 10 s, have not I have exerted 20% more the impulse than you have ? As that’s why I use more energy and more the weight further, and also fail faster, as of my temporary force has been used up faster.

Wayne

 

[Dale]

You also seem to be saying the Second law is wrong, the acceleration a of a body is directly proportional to the net force F and inversely proportional to the mass, F = ma.

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.

Yes, that’s perfect and exactly what I have been saying, at last I think we all agree on something statisticaly.

So as I said above, if I try to exert 100 lbs for 10 s and you exert 80 lbs for 10 s, have not I have exerted 20% more the impulse than you have ?

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?

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?

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

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.)

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

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]

 

[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.