Can We Measure Deceleration in Weightlifting Without Specialized Equipment?

[sophiecentaur]

Dalepam, will get back as soon as I can. Would like to see the proof on say YouTube, that proves you right in the practical as well, not sure what you meant by that.



I have not come here to mock, but for a serous scientific debate; I know you are a very intelligent person, in your field of intelligence. It's NOT that I have to say anything diffrent, it's you who have first to prove the below in your favor.

So if you want to prove yourself right, you need to say in a scientific way, why I use more energy/calories if as you think both impulses are the same. Then why a very bit of sophisticated computer, to which can add up more and faster than many humans put together states you wrong. Then you need to say why I fail faster in the faster reps.

Wayne

Not really. I /we are saying that the problem is too basic on the one hand yet too complex on the other. We have been over all this time after time but the definitions of work, force, energy etc etc are all well established. The problem with your request (demand??!) is that the system has just not been characterised properly. Your gizmo tells you about muscle activity and it could be very 'accurate' but muscles aren't springs and motors. They are far too complex and work to their own agenda. The very fact that you get tired just stand holding something tells you that there is no simple answer.
The reason that you fail faster at faster reps is the way that your muscles respire the food. It's nothing to do with the simple mechanics of the situation so you just can't expect an answer in those terms. However many times you come back with this question, the answer will always be the same from PF.
It is possible that a biochemist could give you some answers to some of this but I guess those answers could be above both of our heads. I can guarantee that any full answer to this would be a biological one, so complicated that you are unlikely even to recognise it as the right one.

 

[Dale]

Dalepam, will get back as soon as I can. Would like to see the proof on say YouTube, that proves you right in the practical as well, not sure what you meant by that.

No. I will not do that for you under any rational conditions. YouTube is not a valid scientific resource. If you will not accept the scientific evidence that is in every introductory physics textbook and repeated in introductory physics labs countless times worldwide every semester then you have no business posting questions on Physics Forums.

I need a clear yes/no answer: do you accept Newton's 2nd law as valid here?

Please answer this before responding to any additional posts.

 

[douglis]

So if you want to prove yourself right, you need to say in a scientific way, why I use more energy/calories if as you think both impulses are the same. Then why a very bit of sophisticated computer, to which can add up more and faster than many humans put together states you wrong. Then you need to say why I fail faster in the faster reps.

Wayne

This is total madness!

For God sake...you have the scientific proof and you admitted that you can't understand it!
It's YOUR claims that faster failure and greater energy usage equates greater impulse so it's YOUR job to prove it somehow.
You're obviously unable to do that(that would violate many known laws anyway) so the least thing you should do is to accept the 'authority' and stop bothering us with nonsensical scenarios.

 

[waynexk8]

Let look at the MMMTs, {Momentary Maximum Muscle tensions} the impact/impulse forces of the weight + velocity + distance + time from the transition from negative to positive, these are the highest force that will come from the muscles and will be on the muscles.

The weight will be lowered under control at 2m/s, and just before the transition, the velocity will be at 1.8m/s, we will say the contact/transition {as we are doing equations for a mass dropping and coming into contact with the floor, some little things in my rep transition will have to be change, but here goes my go now} will be for 0.20s and the mass of the weight = 35kg.

What would happen on the every action there is an opposite reaction force/impulse ? 6 balls weighing 35kg are lowered under control at 2m/s {repping the weight up and down, let’s say 1m in .5 of a second this time} into clay, this represents the tension displayed by the muscles, contact with the clay {peak time of tension on the muscles} for 0.20. Then you lower under control, 35kg at .3m/s, do not all agree that the fast = a far far far deeper hole made into the clay than the slow ? This will also be true for the every action there is an opposite reaction force/impulse, when lifting the weights at different velocities, the faster you move the weight up the opposite reaction force/impulse. So lift 80kg up at 2m/s for 6 times, then lift 80kg up at .3m/s for 1 time, contact with the clay {peak time of tension on the muscles} for 0.40, and the opposite reaction force/impulse, “will” be far far far larger for the rep speed of 2m/s.

Fast,
Impulse will = mass x change in velocity/time

{1.8m/s will represent the change in direction}

I = 35kg {2m/s – {-1.8m/s} / 0.20 s

I = 1N.

X this by 2 for the positive and negative = 2N, then x it by 6 for 6 reps = 12N.

Impact force will be roughly 70N.

Slow,
Impulse will = mass x change in velocity/time

{.2m/s will represent the change in direction}

I = 35kg {.3m/s – {-.2m/s} / 0.40 s

I = .25N.
X this by 2 for the positive and negative = .50N.

Impact force will be roughly 10N

So the fast rep in 6 seconds has an impulse of 2300% more than the slow.

Suppose I have done several things wrong there, {however drop 6 balls into a piece of clay like I said 6 times at 2m/s and then drop 1 ball at .3m/s and you will see what I mean about the peak forces from the transition from negative to positive will/are like. then you also have the higher impulse on the muscles for the fast 6 reps up} but at least I am having a go, like a lot have asked me.

Wayne

 

[waynexk8]

I have stated so many times why I think your examples are irrelevant that I'm sure it would be a waste of time to do it once again.But what the hell...

I showed you studies that found that the greater fluctuations of the same average muscle force are more energy demanding.

Where ? Which one was that. HOWEVER that is NOT an answer, the question was “WHY” is more energy/calories used in the faster rep. Please answer my questions directly, and not with answer that have nothing to do with an actual answer to my question.

For example,if the applied force varies from 0 to 10N in a second requires more energy than an applied force that varies from 4 to 6N in a second.Despite the fact that impulse and the average force is identical.

Yes but why, yet again you give no answer, you are basically saying the same question as me, your just say the fast uses more energy in the same time frame, I know that, look in a nutritionist or kinology book and it will tell you that, and why. What I ask is why the faster uses more energy.

That's the ONLY reason that fast reps lead to failure faster.They're more energy demanding(due to their greater fluctuations of force) even though their average force per second is identical with slow reps.

If it was because of greater fluctuations of force, than as these forces are you say average out over the same time frame, then fluctuations of force, must have nothing to do with it. And yet again, you did not actually say why you think greater/more or/and different amounts of fluctuations of force need to use more energy ?

Your example proves that you didn't even read or you didn't understand(most probably) the assumptions that DaleSpam is talking about.

Let me rephrase, you hit a Snooker ball {move a weight as in repping it up}with a force of 10N, the cue {arm/hand/muscles} comes in contact with the ball {weight} for .1 of a second, it moves 1m {arm moves the weight up 1M} hits another Snooker ball, {the weight goes full ROM, and that jolt goes on the muscles as tension} the original Snooker ball stops, and the second Snooker ball goes 1m. You hit a Snooker ball with a force of 5N, the cue comes in contact with the ball for .1 of a second, it moves 1m hits another Snooker ball, the original Snooker ball stops, and the second Snooker ball goes 500mm. This will be the same as your muscles moving a weight, as the reaction, reaction, will then be the muscles moving the weight, and the reaction, reaction from the force and impulse will be the tension on the muscles.

All you did above is again get out of answering the question, how can you say that a force of 5N is equal to 10N.

We're talking about cases where the load starts and stops at rest hence there's zero change in momentum.

By momentum do you mean movement ? If so there is a change, it’s about 1m

In your example,in the first case the one ball hits the other with double speed than the second case(I assume that the 10N and 5N are average values) and in .1sec the balls stop in both cases.
So the first case has double change in momentum than the second.Nothing like our weight lifting example where the change in momentum is always zero.

Not sure why you say there is no momentum/movement ? Let me show you on the fast, it starts still, then has momentum/movement for 1m then it changes direction and has momentum/movement for 1m, this happens 6 times in 6 seconds, the slow just goes up once and down once in the same time frame.

Please try and think other than you must use more impulse as you fail faster, or something else, it can only be this I think ? If as you think it is more fluctuations of force, then why would that be ? It is because the impulses do not even out at the end ?

Wayne

 

[Dale]

Please answer my question of post 37.

 

[douglis]

If it was because of greater fluctuations of force, than as these forces are you say average out over the same time frame, then fluctuations of force, must have nothing to do with it. And yet again, you did not actually say why you think greater/more or/and different amounts of fluctuations of force need to use more energy ?

The force and the impulse "average out"...not the energy usage.Are you able to understand the difference?
The fact is that fluctuations of the SAME force are more energy demanding.Why?I don't know and I don't care.The answer is irrelevant because is purely biological.
I could search at the discussion page of the studies to see the opinion of the biologists but I won't waste a minute of my life for something irrelevant.

By momentum do you mean movement ? If so there is a change, it’s about 1m

Wayne

Oh God...No...I don't have patience to deal with this!

 

[Dale]

I need a clear yes/no answer: do you accept Newton's 2nd law as valid here?

Hi waynexk8, since your name is crossed out, I assume that you answered this question in the negative and therefore got banned. I am sorry to see that, but if you do not accept basic physics principles like Newton's 2nd law then there is nothing that can or should be done to answer you in terms that you will accept. In fact, with that outlook, I have no idea why you are even bothering to ask your questions on Physics Forums. Any answer you receive here will obviously be based on experimentally validated physical laws like Newton's 2nd.

 

[Dale]

As one final follow-up, let me simply list the take-home messages.

1) Impulse over any number of reps depends only on the weight and the total time, not the speed of the rep.
2) Reps start and stop at rest, the above does not apply to scenarios where the weight does not start and stop at rest.
3) Reps involve only the lifting force and gravity, the above does not apply to scenarios involving another force on the weight.
4) The force from the muscles is always equal and opposite to the force on the muscles.
5) Energy consumption has no unique relationship to impulse.
6) More energy is consumed in the faster rep because the human is less efficient at higher speeds.
7) 6 does not contradict 1 because of 5
8) Fatigue has no unique relationship to impulse.
9) Fatigue occurs sooner in the faster rep for biological reasons (unknown to me).
10) 9 does not contradict 1 because of 8

I think that is a pretty complete characterization of the things I had hoped you would learn.