Art,

I think the energy goes to several places:

1. Isotonics. In order to control the motion of the legs, opposing
muscles often need to work at the same time. I was amazed to study
some of the muscles and see that they often perform in groups, and
often in such a way as to counter each other. The reason they do this
is to stabilise the joints. The net effect is that there is much more
muscle force through the range of motion than relates to the actual net work
that is being done. (Picture a tug of war, where effort is expended, and
yet because of the balance the work done is minimal! Our bodies are
more efficient than this, but not perfect.)

2. Overcoming inertia. The leg is heavy, and must be driven backward
and then driven forward, over and over.

3. Overcoming gravity. We need to drive ourselves into the air to hop
to the next footfall, then absorb the downcoming energy upon impact.
Whatever is not taken up by elastic tissue (nor non-elastic, in the
case of damage!) is muscular work.

Add the energy your heart and respiratory muscles are using to provide oxygenated blood flow to the working muscles (as well as the rest of you major organs), and you've got even more energy drain. There is even friction in the working muscle itself. Then there is the fact that humans aren't very efficient at using energy (compared to machines) and you use up local energy stores and must mobilize stored energy sources (taking more blood flow resources), and, like the old saying...a billion dollars (few Calories) here and a billion dollars (few Calories) there, and soon you're talking about a lot of money (energy overhead)!

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Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)

That is all true, ktalon, but doesn't explain why running is slower
than cycling. Why are we pathetic sweaty messes if we try to run 10
mph, and yet that is a breeze on a bicycle? (Same respiratory system,
etc).

One point I didn't mention clearly: the battle against inertia may be
easier on a bike because the mechanical circle of the pedals help
accelerate your feet around. I'm not totally convinced myself, and
someone like Frank Day who has studied it may be able to shed some
light.

I once read an article about why kangaroos move the way they do. Bottom line was that they do it because they are hungry. It turns out that their motion is very efficient since very little energy is lost as the springs (tendons) compress and expand.

Once you take a few strides the center of mass doesn't accelerate. I can see how a proper running style would reduce braking and accelerating, use the muscles and tendons as springs and reduce friction. I guess that is what the Pose method attempts to do. I have no idea if it succeeds.

It is simply a matter of physics. One method uses the very efficient wheel while the other one requires bouncing and, frequently, foot strike is very inefficient, slowing the runner.

Frank

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Frank,
An original Ironman and the Inventor of PowerCranks

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"Du or Du not-there is no Tri" - Yoda

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"Du or Du not-there is no Tri" - Yoda

To AJ Franke, don't forget that as you become more efficient in converting potential energy (that stored in your muscles), to mechanical energy (forward motion), you will actually sweat less etc. This is because the energy used to contract your muscles is turning into mechanical energy and not a whole whack of heat. As you increase your running economy, you should sweat less and go faster for the same energy consumption.

By the way, once you "get" the pose method, it is actually less work on your calves and tendons. As one of the posters responded, your tendons will become like those of a knagaroo, momentary storing energy on initial impact and then releasing as you cycle through a stride. By the way folks, don't underestimate the amount of energy being used in pushing wind aside while running. Although not as fast as biking, your frontal area is much more substantial and the profile less aero. Anyone trying to run even a sub 40 min 10K pace knows the value of drafting a competitor.

Why, mechanical advantage, of course!!! The force exerted by your legs pedalling is multiplied by its trasmission through the chainring and sprocket much like lifting force is multiplied in a two-pulley block and tackle. Thus, if you imagine a 180 degree movement of the right crank (170mm), that's roughly a 13 inch 'stride' (from furthest rearward position of crank parallel to ground to furthest forward position parallel to ground). Running, you only move forward that 13 inches you have strode; cycling that 'stride' gets multipled by the gearing and becomes a number of rotations of the rear wheel. My math is totally breaking down at this point, but clearly the circumference of the rear wheel of a bike is greater than 13 inches. Thus, if your rear wheel rotated even only once for that 13 inch 'stride' you'd be moving further ahead on the bke for that same leg distance travelled than if you were just running.

But, that's enough sketchy bs science out of me for one week. I'm confident there's at least a kernel of truth in there somewhere. :-)

Mechanical advantage means that force is exchanged for velocity; power
is not affected by mechanical advantage. But you do raise a good
point, that the battle against inertia (getting the legs to change
direction as they move back and forth) is less on a bike due to
mechanical advantage; and, that being the case, some more power is
available for locomotion.

sorry, but most of you guys are way off base here. turns out the explanation is relatively simple. almost the entire energy cost of running is associated with supporting your body weight. in cycling, your weight is supported, so the energy output can be used to generate propulsive force.

Where does all the energy we put out go?

I cant recall the exact figures from my exercise physiology lectures about 200 years ago. I remember that mostly the energy developed by the body is wasted as heat. The internal efficiency of the working muscles I think was about 30% at best.

The rest of the energy generated is disipated as heat to the environment. If you are moving fast on a bike or through water there is obviously a much greater cooling effect than running.

Makes me hot just thinking about it.

brentl, it is easy to dismiss and assert. But tell me, if it costs so
much energy to hold the body up, why standing for an hour doesn't make
us sweat and fatigue our muscles?

pedaller, it is easy to dismiss and assert when the science backs you up. anyone studying the bioenergetics of locomotion will back me on this one. most on this forum probably don't have a science background and i wouldn't expect that. but in this case, the question has been studied and the answer is fairly clear. i'll have to do some digging and see what references i can find.

anyway, perhaps i should have been a little clearer. in running, you are not just supporting the weight (like when standing), but lifting it off the ground to move it forward. this obviously requires more force from the muscles, increasing the metabolic demands of which you speak. running is a spring like motion so each step requires a push off. but the main idea is that the majority of the energy cost is supporting the mass, not moving it forward. in cycling, the mass is supported by the bicycle, and energy can be spent providing propulsive force.



brent

brentl, thank you for the clarification. When you stepped in and said
'it turns out' without explaining, I was wondering what was behind it.
Now it seems you are much closer to what we have been saying (so we
are not all 'way off base'). Agreed that push off and upward thrust
consume energy; the question at hand is how to minimise this. The fact
of holding the body up alone does not cost a lot of energy, as is
evidenced by standing. The fact that forward thrust alone is minimal
at running speeds is evident on the bicycle (despite differences in
frontal area and Cd, it is still plain to me). The point is that in
running there is a tradeoff between minimising the explosive push and
getting the cadence so high that it costs energy to get the legs back
in place. I gladly confess my ignorance of how much we can 'spring' to
make these things happen, instead of using muscular energy. I think
there would be general agreement that you are right -- that this is
what costs so much energy. The question now is, does it *have* to cost
so much? Granted, we are all at different levels of understanding
science. Any links you can provide to related articles would be
welcome.

Ach! I tried so hard to not stick my nose in here and geek out on this one. Oh, well!
Muscles are not springs. Springs are much, much more efficient and are governed by totally different equations. Tendons and ligaments are much, much more like muscles than springs. The viscoelastic nature of body tissues makes them horrible springs. While, when you pull on a muscle is does automatically pull back initially, that autonomic function is quick reflex and cannot be used to effectively cause long range motion. It's a protective effect attempting to disallow immediate joint injury.
Hang a weight on a spring and let it go, it will happily bounce along until heat and friction within the spring eat up the energy needed for motion. Hang a weight on a muscle (try it with a strip of steak or thick bacon, for example) and let it go, it will drop and hang if it doesn't tear the muscle and fall. Look at the energy needed to perform a typical pull-up. If your muscles, tendons, and ligaments could store up internal energy like springs, after you pulled yourself up the first time, you could let go and with little energy expended at the right times, you could rack up hundreds of pull-ups. That is not going to happen.
As others have noted, "bouncing" is one of the biggest wastes of energy in running. The other major concern is your own footfall slowing you down. If you can get your center of gravity to move in a perfectly straight line and get your net driving force to equal your gross driving force, you've become more efficient than humanly possible. The key to the former is simply muscle control and often will translate immediately into gains in the latter. The latter is "simply" caused by using your muscles to only push rearward and down. After your next running workout, try 10x100m repeats on a slight downgrade to really exagerate the effect. Practice rolling your stride under you without slowing down until the bottom. You get right to that point of feeling out of control when you're running most efficiently. It's hard to keep up when your legs are tired, so please try it on a grass hill first! I don't want to get flamed when someone has roadrash from their favorite gravel or asphalt running trail!

i never claimed that muscles were springs. i said that the mechanics of running were a spring like motion and this is correct. the action of a spring is the best model for the biomechanics of running. depending on materials and other properties, springs will have different characteristics. clearly, the theoretical spring used to model running action does not return much of the force of impact to the following push off. this does not, however, mean that the motion cannot be modeled on a spring, which it quite clearly can.

brent

Hey, no offense intended. I was voicing my opinion on some of the statements of the Pose method, as much as replying to you post.
Maybe I'm making a mountain out of a molehill and being nitpicky about the details of the system (more than likely), but you could only model the motion as spring-like if you also added in a *huge* dashpot-type dampening coefficient. I think I would tend to model the system as a hydraulic system of pistons, since, as I previously noted, you don't get a stored energy effect out of muscles the way you do out of springs. You could also model the travelling motion by a series of sinusoids to make the math easier to swallow, but looking at at most a single stride, if not a single step, you could optimize your model to an actual human condition. It all depends on how you want to define your system.

While one may model a motion analysis on springs, it is flawed to analyze energy expenditure of running on springs. Nothing in the body is springlike in the sense it can convert significant amounts of mechanical energy to potential energy which it can then return to the system. The body only appears spring like because of the constant generation of energy by the muscles appears as absorbtion and return of potential energy.

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Frank,
An original Ironman and the Inventor of PowerCranks

it is very well established in the scientific literature that human running can be accurately modeled as a spring system. i will try and find some references but doing a medline search should yield plenty of results. like i said before, this does not imply that muscles are springs, etc. however, the characteristics of the motion fit such a model. as a side note, walking does not. this motion is better modeled using a pendulum.

brent

I agree that the motion can be modeled on a spring but the original question is where does the running energy go. A spring keeps total system energy constant, allowing changes from kinetic to potential and so forth. It is in no way related to how energy is expended in running.

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Frank,
An original Ironman and the Inventor of PowerCranks

How much spring can be in the shoes? Negligible?

I agree although this post reminded me of some of the high tech stuff now being used by amputees for running that really are springs.

Frank

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Frank,
An original Ironman and the Inventor of PowerCranks