Thread: The physics of muscle mass...

It's nothing to do with the force or weight in the way you describe but how the body reacts.

There are 4 main ways muscle is built, hormonal, the intensity of stress (weight), the time under stress ("TUT") and the frequency, along with elevated blood-flow. At least that's the best you're going to get out of me this late at night anyway.

We haven't really touched on speed either, the same weight over the same distance lifted with explosive speed is different than when lifted slowly, likewise the weight could be lifted at the same speed but lowered very slowly, which is a completely different type of stress (micro-tearing based rather than multiple motor-unit activation and muscle-fiber type based).

In a more direct answer to your question, lifting heavy stimulates the muscle more and also more of the muscle (lighter weights don't use all of the muscle fibers). However go too heavy and you restrict growth, as flooding the tissue with nutrients, stretching the enclosing sheaths, stimulating hormonal responses and other such stuff doesn't really come into play on trained muscles until around 7 reps or so. So heaving really heavy at 5 reps will boost strength but do little for gaining extra mass or shape.

You may think your question is simple, or were perhaps hoping for a more complex answer, I'm not sure, but in essence you're asking for The Answer.

Everyone's genetics are different, plus different form, bone structure and anchor points, different diet and so on. Finding the exact rep range that gives you the best results is the never-ending quest of many bodybuilders, confounded by the fact that having found it your body will get used to it and adapt over time...

So in essence you can get as complicated as you want and you can also get person-specific but bottom line, 'it just does', alright?




B.

Originally Posted by etan

Ok, so this is a bit of a science geek question:

In physics, the equation for net force is Force = Mass * Acceleration... in other words, from a physics perspective, there is no difference between lifting 50kg at 1 m/s than lifting 25kg at 2 m/s... Both have a net force of about 500 Newtons (N)...

Also, the equation for the amount of work done is Work = Force * Displacement... so if you lift 500 N for 1 metre 10 times, it is the same as lifting 250 N for 1 metre 20 times (or 500 N for 0.5m 20 times, for that matter). In either case you have done 5000 Joules of work...

I can understand that lifting different distances (half lift vs full lift) works different parts of the muscle, but can someone explain what it is specifically about high weight/low reps that makes it more beneficial for adding muscle mass than low weight/high reps? (other than, "it just does!" hehehe)...

Sorry, long post...

High weight requires recruitment of a greater number of muscle fibres in the target muscles to move the increased load, as well as greater neural activity, as well as much more muscle in terms of stabilizers.

Basically it requires more effort to lift something heavier than something lighter, and more effort results in a greater need for adaptation by the body, hence the stimulation of muscle growth if you are in a large enough caloric surplus to fuel that.

Though i've built muscle using less weight and more volume, and also with something in between.

Not only do you have all that to take into account (and in FAR more detail than can be fit into a post) but you have your body's total adaptation to a certain 'configuration' of the stimulus you are using.

I.e. - your body can adapt to high weight/low reps and you wont gain any muscle from it. The body likes homeostasis and will do its best to achieve it.

I wouldn't call that a science geek question, i would call that a stupid question. You can't explain something as complex and varied as the human body with a simple GCSE physics equation.

What you're saying up there is that if i can lift a 10lb weight 100 times, i could lift a 1000lb weight once? Thats not gonna happen, mate. And even if i COULD lift 1000lbs, i guarantee it would use a lot more energy than the former.

Its not just about the amount of work you have done in basic energy expenditure. That IS a part of it, but its not as simple as A + B = C.

Also, welcome to IM

Hehehe... when in doubt, "it just does" is a good answer...

But i think

...lifting heavy stimulates the muscle more and also more of the muscle (lighter weights don't use all of the muscle fibers)...

sounds like the kind of simplified answer i was after... as you say, it can get as complicated as you like!

...Hmm... Just thinking about this answer...

As muscle exhaustion sets in, using lower weights, won't the surrounding fibres take up the slack so that after many reps the effect is the same as high weight/low reps? Even low strain causes micro-tearing doesn't it?

As an example: i have huge legs in proportion to my upper body, but i didn't get that way by focusing on my legs in the gym - i just walked up a long steep hill to my home every day when i was younger... it seems to me that this would be the equivalent of low weight/high rep (extremely high rep) in the gym... what do you think?

As an example: i have huge legs in proportion to my upper body, but i didn't get that way by focusing on my legs in the gym - i just walked up a long steep hill to my home every day when i was younger... it seems to me that this would be the equivalent of low weight/high rep (extremely high rep) in the gym... what do you think?

adaptations are adaptations. as i have said before, if you are eating enough calories to promote and facilitate an anabolic environment then you will grown, provided you are placing necessary stress on your system to illicit the adaptation you seek (strength, size, cardiovascular, power, etc).

What you're saying up there is that if i can lift a 10lb weight 100 times, i could lift a 1000lb weight once? Thats not gonna happen, mate. And even if i COULD lift 1000lbs, i guarantee it would use a lot more energy than the former.

But that's exactly what i am saying... the reason you can't lift 1000lb isn't because you don't have enough energy, but because you don't have the capacity (ie. strength, stability, etc). A car might be able to travel to the top of a hill with a slope of 15 degrees, but increase the slope of the same hill to 30 degrees and the energy it expends would be increased, but the distance that it travels would be shortened... the total energy expended (work) would be exactly the same... Now increase the slope to 45 degrees, and the capacity of the car would be inhibited to the point where energy is being uselessly wasted on "maintaining" its position, rather than its propulsion... The work would remain the same - as the work to the muscles in your example - but the difference in energy expended wouldn't be contributing towards the goal (the top of the hill, or muscle growth), it would be wasted on other things...

Thanks for the welcome!

Originally Posted by Gazhole

High weight requires recruitment of a greater number of muscle fibres in the target muscles to move the increased load, as well as greater neural activity, as well as much more muscle in terms of stabilizers.

Basically it requires more effort to lift something heavier than something lighter, and more effort results in a greater need for adaptation by the body, hence the stimulation of muscle growth if you are in a large enough caloric surplus to fuel that.

Though i've built muscle using less weight and more volume, and also with something in between.

Not only do you have all that to take into account (and in FAR more detail than can be fit into a post) but you have your body's total adaptation to a certain 'configuration' of the stimulus you are using.

I.e. - your body can adapt to high weight/low reps and you wont gain any muscle from it. The body likes homeostasis and will do its best to achieve it.

I wouldn't call that a science geek question, i would call that a stupid question. You can't explain something as complex and varied as the human body with a simple GCSE physics equation.

What you're saying up there is that if i can lift a 10lb weight 100 times, i could lift a 1000lb weight once? Thats not gonna happen, mate. And even if i COULD lift 1000lbs, i guarantee it would use a lot more energy than the former.

Its not just about the amount of work you have done in basic energy expenditure. That IS a part of it, but its not as simple as A + B = C.

Also, welcome to IM

From what I understand, doing less reps of a high-weight isn't the best way to accomplish hypertrophy anyways. I mean, powerlifters focus on huge weights that they can only do for a few, intense reps. Bodybuilders want more TUT.

Lifting a 10lb weight 100 times WOULD require the same amount of physical energy as lifting a 1000lb weight once, all other things (i.e. the path along which the weight is lifted, etc.)being equal. The problem is, most people can't exert enough force to even lift the 1000lb weight once, so they CAN'T exert that kind of work over one rep. In essence, most people can't exert the kind of power needed to lift the 1000lb weight once, but they can exert the kind of power needed to lift the 10lb weight 100 times. It requires A LOT more force to lift the 1000lb weight, and it's being exerted over a shorter period of time. This means the amount of power is huge in comparison with the smaller amount of force and longer period of time over which the 10lb weight is lifted.

I will agree with you, however, that this is really hard to understand. Building mass isn't simple science - there are a ton of factors involved. First of all, the movements are complex (i.e. there is bending, torsion, stress/strain, rotation, etc.) and involve multiple muscle groups. Secondly, the actual muscle building doesn't take place during training anyways and it involves various factors such as motor neurons, nutrition, respiration, etc.

Basically, there are too many variables involved to boil this down to something simple. (Also, 2m/s is not an acceleration, but rather a velocity.)

Originally Posted by oneovercabin

From what I understand, doing less reps of a high-weight isn't the best way to accomplish hypertrophy anyways. I mean, powerlifters focus on huge weights that they can only do for a few, intense reps. Bodybuilders want more TUT.

I dont think there is a best way to get hypertrophy going. Variation is the key to consistent results. Like P-Funk said, if you provide a unique stimulus and are in a caloric surplus you'll gain

Originally Posted by oneovercabin

Lifting a 10lb weight 100 times WOULD require the same amount of physical energy as lifting a 1000lb weight once, all other things (i.e. the path along which the weight is lifted, etc.)being equal. The problem is, most people can't exert enough force to even lift the 1000lb weight once, so they CAN'T exert that kind of work over one rep. In essence, most people can't exert the kind of power needed to lift the 1000lb weight once, but they can exert the kind of power needed to lift the 10lb weight 100 times. It requires A LOT more force to lift the 1000lb weight, and it's being exerted over a shorter period of time. This means the amount of power is huge in comparison with the smaller amount of force and longer period of time over which the 10lb weight is lifted.

Not sure i agree with this, but it doesnt really matter. I cant lift 1000lbs anyways :P.

Originally Posted by oneovercabin

I will agree with you, however, that this is really hard to understand. Building mass isn't simple science - there are a ton of factors involved. First of all, the movements are complex (i.e. there is bending, torsion, stress/strain, rotation, etc.) and involve multiple muscle groups. Secondly, the actual muscle building doesn't take place during training anyways and it involves various factors such as motor neurons, nutrition, respiration, etc.

Basically, there are too many variables involved to boil this down to something simple. (Also, 2m/s is not an acceleration, but rather a velocity.)

I think the basic precepts (variation, stimulus, intensity, diet) CAN be boiled down simplicity (train, eat) but when trying to apply the physical equation the OP was talking about to something as complicated as the human body it just doesnt work.

S'all relative yo'.

But yeah, i agree. You cant really simplify things as much as he was trying to.

Originally Posted by Gazhole

Not sure i agree with this, but it doesnt really matter. I cant lift 1000lbs anyways :P.

That's because your connotation of "energy" is completely different than the physical definition of energy. In the end, work done is exerting a force over a distance. If you exert 1/10 the force over 10 times the distance, you'll be doing the same amount of work and thus require the same amount of energy.

But that's not what you think of when you think of lifting 1000 lbs. You think of struggling to even hold that kind of weight. It's because you can't exert enough force to lift that weight, so your muscles tense up as much as they can to try and do so, but they don't move it. You struggle because the tension in your muscles requires chemical energy. The truth is, however, that you are doing no "work" on the weight.

Like I said, it boils down to force output. It's easy to output a small amount of force, but much harder to output enough to lift 1000 lbs. Think of it as 2 cyclists going up a hill: regardless of speed, if they go up the same hill along the same path, the work they do is the same. However, if one goes up the hill much faster, his workout is more intense. That's because he has to output more power than the guy who is going slower (the same amount of energy in a shorter time span).

i thought the other one hurt my head damn.

Guys, there is a reason why Physiology and Physics, while sharing certain concepts, are very different fields of study.

The human body is not a block sliding down a slope and cannot be neatly calculated to find an answer.

This thread gives me a headache.

Originally Posted by Yanick

Guys, there is a reason why Physiology and Physics, while sharing certain concepts, are very different fields of study.

The human body is not a block sliding down a slope and cannot be neatly calculated to find an answer.

This thread gives me a headache.

Exactly my point!

Thats why i hate the questions i so often get. "Well if i take creatine, how much will i gain?"

"I ate three donuts today, do you think i'll gain a lot of weight?"

I stopped giving people advice because of it, they look for concrete answers which do not exist.

Think of it as 2 cyclists going up a hill: regardless of speed, if they go up the same hill along the same path, the work they do is the same. However, if one goes up the hill much faster, his workout is more intense. That's because he has to output more power than the guy who is going slower (the same amount of energy in a shorter time span).

Sorry to be picky but no. Going up the hill with more speed would involve more energy, all other things being equal.

Of course if the guy going slower were pedalling furiously in a very low gear he might be using more energy than the guy just riding up a slight hill normally...

Your general point is correct and the same one I made, the human body is very complex and you cannot define muscle-growth stimulus with such a formula - but no, pedalling faster is a more intense workout because it is using more energy. The kinetic energy of the faster cyclist is greater, where did that extra energy come from? Yep, the greater "power" input but that is energy, same thing.

Yeah I'm just being picky

Totally off-topic but it amuses me how few people get this basic point - brakes work by converting kinetic energy (movement basically) into heat energy, via the process of friction. This is why brakes get hot and cars stop - and it's why trucks often can't stop down a hill. The brakes get too hot and once very hot they cannot absorb any more heat, hence no friction, no braking.

The result of that is glazed brake surfaces - trucks don't lose braking because the brakes are glazed, the brakes are glazed because the truck lost braking.

You can tell I haven't had my coffee yet, or I wouldn't be so damn picky. Sorry.


This useless trivia was brought to you by Biggly.


B.

Originally Posted by Biggly

Sorry to be picky but no. Going up the hill with more speed would involve more energy, all other things being equal.

Of course if the guy going slower were pedalling furiously in a very low gear he might be using more energy than the guy just riding up a slight hill normally...

B.

Actually, you're wrong. If they go up the same hill, they exert the same amount of total energy. Why? Well, the cyclist moving at a faster speed exhibits a higher rate of energy (i.e. POWER), but he moves up the hill in a shorter period of time. The cyclist moving at a slower speed exhibits a lower rate of energy for a longer period of time. If they move along the same path with everything else equal, the change in energy for both is the exact same (i.e. the work done by both cyclists is the same).

Why? Because work can be boiled down to a change in energy. In this case, it is a change in gravitational potential energy, which is only dependant on the mass of the cyclist, the acceleration due to gravity, and the height. If both riders move from point A to point B, their change in height is the same. Assuming their masses are the same, the change in energy they exhibit is the exact same.

Sure, just throw inertia, friction and air resistance clean out the window why doncha?

Take 2 identical cars, everything exactly the same, in the same highest gear, one doing 56mph, the other doing 104mph - which is using the most fuel, ie will get fewer miles per gallon?

The 104mph car, as it's fighting wind resistance and general friction (yes, wind resistance IS friction, OK call it mechanical friction) to a greater extent.

Heck we already know this effect is seen with the human body by comparing HIIT to steady plodding in the FBZ. You can technically perform the same "Work" but one burns a heck of a lot more calories than the other.

Shooting is one of my hobbies and one thing any self-loader will tell you is that to double the velocity you need 4 times the power/energy. You can see the same thing with a pump-up air rifle. You may have say 10ft/lbs of muzzle energy at 500 feet per second but you need 40ft/lbs of muzzle energy and a lot more pumping to propel the same slug at 1000fps. Even if you keep it simple and cartoony, to travel 500 feet the first slug takes 1 second, the 2nd slug half a second - but uses 4x more energy. In reality as a percentage of its velocity it also slows down a lot quicker.

So even with simple mechanics like a car or bullet we know things are not a simple linear matter of twice the speed meaning twice the energy but half the time. It's a matter of math that it takes a lot more energy to halve the time.

Now throw in the fact the human body is not a conventional machine but a specialised biological entity that is designed to function at 20% or so most of the time. We can stroll for hours but only sprint for a few seconds, as all sorts of different systems kick in or behave differently at higher energy outputs.

Put simply we're long lasting but inefficent, with many of our calories needed just to stay alive and digest our fuel - we then waste much of our energy as heat when performing work and more energy to shed that heat. We're nothing remotely resembling a machine that can just do more work for more calories. Actual mechanical movement for the most part is just a tiny fraction of energy expenditure, though obviously more for weight lifters in comparison to normal.

To peddle up the same hill but twice as fast as the other guy would take at least 4x more energy, in fact I wouldn't be surprised if it were 5, even 6x.



B.

Actually it's 8 times - I forgot how aerodynamic bullets are:

Power is work per time or the energy conversion rate. The higher the power (measured in Watt) of a car is, the more energy can be converted per time. This allows for example a higher acceleration but also increases the fuel consumption significantly.

If going on high speed we should consider, that the energy needed to accelerate the car quadruples with a doubling of the velocity and also the air drag quadruples with double velocity. Therefore, a car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). Twice the speed requires eight times the power.
Velocity & air drag


I rest my case.



B.

Totally agree with Biggly here, the HIIT vs hours of steady state was a great point.

*grins @ Gaz*

Actually right at the start the OP gets it wrong:

In physics, the equation for net force is Force = Mass * Acceleration... in other words, from a physics perspective, there is no difference between lifting 50kg at 1 m/s than lifting 25kg at 2 m/s... Both have a net force of about 500 Newtons (N)...

Yes but that's just boring old Newtons innit?

In the link I already posted they describe it thus:

Since energy needed increases with the square of the velocity more energy is required to bring a car of the same mass to the twofold speed than to bring a car of the double mass to the same speed.

In bodybuilding English, lifting a 25kg weight twice as fast as you lifted a 50kg weight requires more energy/effort that "performing the work of lifting 50kg" at half the 25kg speed. This is so evident in weight training we have our own little pet name for it as a training variable - 'tempo', expressed in the rather bizarre manner of for example 4/0/2, with the 4 being the rate of descent in seconds. Why on Earth it starts with the descent instead of the lift I dunno?

Anyone?




B.

Originally Posted by Biggly

Sure, just throw inertia, friction and air resistance clean out the window why doncha?

Take 2 identical cars, everything exactly the same, in the same highest gear, one doing 56mph, the other doing 104mph - which is using the most fuel, ie will get fewer miles per gallon?

The 104mph car, as it's fighting wind resistance and general friction (yes, wind resistance IS friction, OK call it mechanical friction) to a greater extent.

Heck we already know this effect is seen with the human body by comparing HIIT to steady plodding in the FBZ. You can technically perform the same "Work" but one burns a heck of a lot more calories than the other.

Shooting is one of my hobbies and one thing any self-loader will tell you is that to double the velocity you need 4 times the power/energy. You can see the same thing with a pump-up air rifle. You may have say 10ft/lbs of muzzle energy at 500 feet per second but you need 40ft/lbs of muzzle energy and a lot more pumping to propel the same slug at 1000fps. Even if you keep it simple and cartoony, to travel 500 feet the first slug takes 1 second, the 2nd slug half a second - but uses 4x more energy. In reality as a percentage of its velocity it also slows down a lot quicker.

So even with simple mechanics like a car or bullet we know things are not a simple linear matter of twice the speed meaning twice the energy but half the time. It's a matter of math that it takes a lot more energy to halve the time.

Now throw in the fact the human body is not a conventional machine but a specialised biological entity that is designed to function at 20% or so most of the time. We can stroll for hours but only sprint for a few seconds, as all sorts of different systems kick in or behave differently at higher energy outputs.

Put simply we're long lasting but inefficent, with many of our calories needed just to stay alive and digest our fuel - we then waste much of our energy as heat when performing work and more energy to shed that heat. We're nothing remotely resembling a machine that can just do more work for more calories. Actual mechanical movement for the most part is just a tiny fraction of energy expenditure, though obviously more for weight lifters in comparison to normal.

To peddle up the same hill but twice as fast as the other guy would take at least 4x more energy, in fact I wouldn't be surprised if it were 5, even 6x.



B.

Air resistance isn't all too valid here. Sure, it has SOME effect on the situation, but air resistance really only takes effect when objects are moving at very high speeds (i.e. a bullet or a jet). For a cyclist travelling up a hill, air resistance isn't that large.

Friction, that's a different story. The biker travelling faster isn't working more against friction, that's assinine. Friction is ONLY dependent on the amount of normal force between the surfaces and the two surfaces in contact. Thus, no matter how fast you're moving in your car, the force of friction is the same (assuming your tires are the same). Not to mention, friction PROPELS things that have wheels, it doesn't impede them. In this case, friction does POSITIVE WORK on the bicycle (and the car). If there were a smaller amount of friction, the bicycle wouldn't move as fast.

The reason a car gets less MPG at higher speeds has to do with energy conversion in a gasoline engine. The power output of an internal combustion engine can't keep up with the amount of RPMs you're giving it at 85 MPH, so your engine is essentially using a lot more fuel because you're asking it for a lot more fuel.

And the fact that you compared this to HIIT on a stationary bike is laughable because none of the things you talked about factor into someone on a stationary bicycle. The reason HIIT burns more calories is because you have to output energy at a higher rate (i.e. more POWER). Your body has to supply more force than it would at steady state and so it feels it has to convert stored energy (glycogen, fat, etc.) faster than it would at steady state. In the end, this has nothing to do with my example of the 2 cyclists on a hill 1) because you're talking about a stationary bike and 2) because you're talking about something completely different than my point. You're talking about the amount of stored energy a person uses, whereas I'm talking about the change in energy of the person/bicycle as a system. They're completely different things.

Why do you think you heat up more when you do HIIT v. steady state cardio? Your body starts to convert stored energy at a really fast rate, but soon that rate becomes way too fast. The amount of energy you're releasing by breaking chemical bonds is much greater than the amount you're using to do the exercise. The other energy is released as heat. Not to mention, at some point your body starts going anaerobic and you can't respirate as efficiently, so you're sending yourself into a much less efficient form of energy release.

I'll say this again as the last thing I'll say in regards to this topic: the biker travelling up the hill twice as fast may not use the same amount of energy as the other, but the total change in energy for both is THE SAME. There's nothing that will change that fact (unless you'd like to argue energy conservation).

Where did I mention stationary bike? You can do HIIT on a normal bike.

I think we all agree that the human body reacts differently to different stimulus but again you're ignoring energy expended for work produced.

This is schoolboy stuff and I've already supplied examples and a link - if you double the speed you expend a great deal more energy getting the same mass of cyclist to the top of the hill than you would do pushing him up there more slowly.

As for friction being a positive, try it with a rusty chain, flat tyres or jammed bearings, or just put the fucking brakes on while you're pedalling. Why do you think people oil their bikes, to slow them down? Likewise with air resistance, there is a reason why pro cyclists have low handlebars, arse in the air and very expensive and freaky-looking aerodynamic helmets - air resistance.

Here,

"A PROFESSIONAL BICYCLE RACER'S STREAMLINED HELMET AND CROUCHED POSITION HELP TO IMPROVE AIR-FLOW, THUS INCREASING SPEED"

Google Image Result for http://www.scienceclarified.com/everyday/images/scet_02_img0137.jpg

http://www.scienceclarified.com/ever...02_img0137.jpg






B.

Originally Posted by etan

Ok, so this is a bit of a science geek question:

In physics, the equation for net force is Force = Mass * Acceleration... in other words, from a physics perspective, there is no difference between lifting 50kg at 1 m/s than lifting 25kg at 2 m/s... Both have a net force of about 500 Newtons (N)...

Also, the equation for the amount of work done is Work = Force * Displacement... so if you lift 500 N for 1 metre 10 times, it is the same as lifting 250 N for 1 metre 20 times (or 500 N for 0.5m 20 times, for that matter). In either case you have done 5000 Joules of work...

I can understand that lifting different distances (half lift vs full lift) works different parts of the muscle, but can someone explain what it is specifically about high weight/low reps that makes it more beneficial for adding muscle mass than low weight/high reps? (other than, "it just does!" hehehe)...

Sorry, long post...

as you said force = mass * acceleration since the acceleration here is constant (gravity) = 9.8 m/s^2 then force is directly proportional to the weight being lifted ...

if you can change the acceleration of the same mass being moved from 1 - 2 m/s2 than you are lifting a very light weight that you could probably lift for 100 reps .. because doubling the acceleration is even a lot harder than doubling the speed or velocity ..... in case of lifting your 10 rep max for example there will be even no acceleration at all and the velocity will be constant , your muscle can't handle lifting your 10 rep max for example by twice the acceleration even for 1 rep ... go ahead and try it , if you could double the acceleration then your muscle can handle a lot heavier weight already so no need for growth ...