Weight Lifting & Cycling - Fuel to the Fire (Off Topic)

[octagon]

a quick thought, fuel to the fire, the notion that the physiognomy of sprinters and climbers is differnt is fallacious. essentially both represent the same task, that is applying a foprce to pedals in order to change momentum. in either instance being heavier makes it harder to change speed and direction (or to resist any forces applied constantly to you). galilleo proved thatt he force of gravity is not significantly different for bodies of different mass of humanish size. (oh yeah, and the notion that heavier bikes go downhill faster is guff as well, lighter bikes go faster, because they have less inertia at the top. gravity is constant (enough) for anything)

 

[Roadie_scum]

Originally posted by octagon
a quick thought, fuel to the fire, the notion that the physiognomy of sprinters and climbers is differnt is fallacious. essentially both represent the same task, that is applying a foprce to pedals in order to change momentum.

1. If I employ similar logic, cyclists, car racers, rowers, distance runners and 100m sprinters are identical physiologically - everyone is just trying to complete the course as fast as possible. Just because a task is similar in some way doesn't make the physiology the same.

2. They are trying to change momentum? Which would be why they take on water bottles huh? So they can weigh more and win by having greater momentum? (p=mv, for anyone who's wondering, momentum is mass by velocity)

They are trying to change speed or velocity, not momentum (though these are equivalent for objects of the same mass, using momentum seems to show a lack of understanding on your part).

3. A sprinter needs a short burst of power (say 2-10 minutes fighting for position almost flat out with a 20-30 second punch at the end to kick and win), and enough baseline endurance (or teammates to push) to get him there with his sprint intact (or her/hers). A climber needs to maintain a constant power for a long time, say 30 minutes plus. They do need to accelerate to follow the occassional attack, or make an attack, but this is very different to what a sprinter does.

Also, a climber can differ (by being much smaller) from a rolleur, time trialler or good flatland domestique (who does maintain a high constant power for 30 mins plus). This is because the primary force opposing motion when riding on a flat is air resistance, not weight. When ascending, weight becomes much more important.

And yes, I know a=f/m (acceleration is force divided by mass), and that does mean that for a given force, someone with a lower mass accelerates quicker even on a flat, but more muscle mass allows sprinters to generate much higher forces, and this higher force massively outweighs the gain of mass.

Perhaps you can provide a coherent explanation why Chechu Rubeira isn't leading out Heras out at the end of the flat stages in the tour? I don't think it's just Postal's one for Lance, all for Lance attitude. Or why pettachi needs to be pushed up hills?

The physiology of a sprinter is hugely different to that of a climber - that's why they train different, look different and race different.

in either instance being heavier makes it harder to change speed and direction (or to resist any forces applied constantly to you). galilleo proved thatt he force of gravity is not significantly different for bodies of different mass of humanish size.

4. Galileo expressed it a lot more elegantly than you - and he didn't misapply physics to try to explain physiology.

(oh yeah, and the notion that heavier bikes go downhill faster is guff as well, lighter bikes go faster, because they have less inertia at the top. gravity is constant (enough) for anything)

5. If gravity is constant (enough) for everything, then how did you decide lighter bikes go faster down hills? Less inertia at the top? What are you talking about?

The force of gravity is EXACTLY THE SAME on any object on earth in a newtonian system (give or take a few decimal points for where you are on Earth and a few other variables). I don't think my computer goes to enough decimal places to detect or express the error in a newtonian system when we're talking about things the size of bikes and people. The only change between similarly shaped objects of different masses is caused by the force of air resistance opposing the force of gravity.

If two objects are the same size and shape, the heavier falls quicker because the air resistance opposing it is the same, while the force on the object is greater. (force from gravity=constantXmass)

Do the maths. It's high school physics, and you either don't understand it or can't express it. Either way, it doesn't prove your point. Sprinters and climbers are different beasts.

6. To get the physics right, try punching some numbers into the calculators at http://www.analyticcycling.com/

7. To work out the physiology, keep thinking and learning, and keep simplistic analyses of physiology based on other random facts you might know out of it.

 

[octagon]

2. They are trying to change momentum? Which would be why they take on water bottles huh? So they can weigh more and win by having greater momentum? (p=mv, for anyone who's wondering, momentum is mass by velocity)

thanks, glad to ahve started something interseting. actually, what you should consider is that the critical factor for both spriniting and climbing is acceleration. in sprinting this is applied to go forward faster than the next fellow, and in climbing to go uphill faster than the next fellow but with a counteracting force (gravity) acting against that. acceleration, i am sure you will agree, is defined as the rate of change of momentum, measured as either a change in mass at a constant speed (something of a nonsense for cyclists) or a change in speed at a constant mass. either way the change in velocity is related both to the mass of the object and the forces acting upon it. this applies both uphill and in a horizontal line. i do not dispute that this might be greater for a heavier object, but do dispute that it has greater impact related to the incline.

you may have a point about the nonsense of heavier bikes going downhill faster. they will have greater inertia, as they have greater mass and inertia is simply a term for momentum in a static object, relating the need to apply greater forces to produce a similar change in velocity (back to the accelertion concept above, try pushing a floating supertanker by hand and then try pushing a floating inflatable to see what i mean, the heavier things accelerate much more slowly for a constant force (f=ma)) so, according to galilleo, as for his cannon ball and his melon, they both go down at the same speed. of course, that counts on the forces slowing them being equal. however, it is worth considering that, other than windage, the main force slowing a descending bicycle is friction on the road. the friction of an object over another is related to the mass of that object, in direct proportion. it is reasonable to say, therefore, that a heavier object will lose more energy as heat through this means, and therefore accelerate more slowly. (i know this is miniscule and that mostly rolling wheels don't generate lots of friction but...)

all this is rubbish, of course, anyone aquainted with zeno's (?xeno's) paradoxes will know that i can cycle faster, both up and down hill, than anyone else, however fat i am, provided i have a small headstart.

 

[2LAP]

Originally posted by Roadie_scum
3. A sprinter needs a short burst of power (say 2-10 minutes fighting for position almost flat out with a 20-30 second punch at the end to kick and win), and enough baseline endurance (or teammates to push) to get him there with his sprint intact (or her/hers).

Try a burst of power for <20 seconds for a sprinter on the track in matched sprint. Another different beast from the 'endurance sprinter' you describe.

 

[Budarz]

Octagon,
to start with, let me say that the modeling of a cyclist or any other physical sytem via physics laws is a hobby of mine as I am a theoretical physicist.
You say that "what you should consider is that the critical factor for both spriniting and climbing is acceleration". Why do you say this? Acceleration is defined strictly and without compromise as a change in VELOCITY over a time interval. The fact that it takes a force both to climb and to accelerate is certainly a connection, but in one case the effort is to counter the force of gravity that would otherwise pull you down the hill, and in the other case it's to increase the speed of the bike quickly.
You also said "acceleration, i am sure you will agree, is defined as the rate of change of momentum". The rate of change of momentum is defined by Newton's second law as Force.
Now, about what matters to us. What's the difference between sprinters and climbers from a physics standpoint? To climb long hills, two things are important, and one thing is not so important. Low mass is important since gravity is tugging on it. A high CONSTANT rate of power output is important also. Air resistance is not so important on a climb due to low speeds.
Peak power output means nothing to a climber. Going at 380W for 20 minutes with very low body mass= a good climber.
What about a good sprinter? It is quite likely that any sprinter will have a much higher power to weight ratio than a good climber, and at first glance this would seem to indicate that a sprinter should also climb better. This is true (as I've often proven to local clubbies since I'm a track sprinter) so long as the climb is short enough to be anaerobic (roughly 1 km or less). The problem to the sprinter arises because the sustainable aerobic power to weight ratio will not be as high for a sprinter as for a climber. This has much to do with the fact that upper body (which is useful for yanking on the handlebars during quick starts or sprints) only acts as dead weight during an aerobic climb. The ideal climber physique has no excess upper body mass. Also, the sprinter's type IIb muscle fibers are dead weight while climbing aerobically since they only function anaerobically.
In the end they are both very good cyclists, but the massive, fast twitch muscle laden sprinter is tuned to perform short bouts of great power output against nothing but air resistance and their own mass. The climber has minimized their excess musculature only to maintain the necessary muscle to produce moderate, long-term power against as little gravitational resistance as possible under circumstances where air resistance is also not so important.
THe case where air resistance and long-term sustainable power are important is time trialing - yet another cycling specialty.
Hope this helps.

 

[discobean7]

Well said Budarz. Thank you for one of the few fact-based discussions of physics on this website. Keep the good info coming.

 

[BtonRider]

a quick thought, fuel to the fire, the notion that the physiognomy of sprinters and climbers is differnt is fallacious. essentially both represent the same task, that is applying a foprce to pedals in order to change momentum. in either instance being heavier makes it harder to change speed and direction (or to resist any forces applied constantly to you). galilleo proved thatt he force of gravity is not significantly different for bodies of different mass of humanish size. (oh yeah, and the notion that heavier bikes go downhill faster is guff as well, lighter bikes go faster, because they have less inertia at the top. gravity is constant (enough) for anything)

Roadie Scum is right. Your understanding of applied physics is the problem here.


Assuming both riders have the same cross section and initial speed. The heavier biker goes faster because he has greater inertia. It takes more force to stop him. Since the wind exerts the same force on both riders, the bigger rider goes faster (i.e. the wind doesn’t slow him down as much). The only reason a lighter bike would go faster is if heavier bike is built with really poor quality components (i.e. the bearings don’t roll smoothly and friction is greater).



The heavier biker goes up hill slower because it takes more work (i.e. power performed over a given distance). It takes more work to move a heavier object at the same speed. If you need a simple demonstration of this ride up a steep hill as fast as you can and record your average speed and time. Then do it again (starting from the same point at the same speed) wearing a backpack with 30-40Lbs in it. Try to get the same average speed and I’m sure you’ll realize you worked harder. In fact I doubt you’ll be able to do it in the same time if you put an honest effort into the first attempt. For the purpose of science (and learning the lesson well) you should perform this test 5 times to get reasonably reliable statistics.

 

[SolarEnergy]

essentially both represent the same task, that is applying a foprce to pedals in order to change momentum.

Isn't it the case for all cyclists, road and track?

in either instance being heavier makes it harder to change speed and direction (or to resist any forces applied constantly to you).

Yes, same goes with time trialists.

How can I disagree with your statements... However, the training regiment of a sprinter should be different than that of a climber, for reasons other than that you mentionned.

 

[Billsworld]

Octagon,
to start with, let me say that the modeling of a cyclist or any other physical sytem via physics laws is a hobby of mine as I am a theoretical physicist.
You say that "what you should consider is that the critical factor for both spriniting and climbing is acceleration". Why do you say this? Acceleration is defined strictly and without compromise as a change in VELOCITY over a time interval. The fact that it takes a force both to climb and to accelerate is certainly a connection, but in one case the effort is to counter the force of gravity that would otherwise pull you down the hill, and in the other case it's to increase the speed of the bike quickly.
You also said "acceleration, i am sure you will agree, is defined as the rate of change of momentum". The rate of change of momentum is defined by Newton's second law as Force.
Now, about what matters to us. What's the difference between sprinters and climbers from a physics standpoint? To climb long hills, two things are important, and one thing is not so important. Low mass is important since gravity is tugging on it. A high CONSTANT rate of power output is important also. Air resistance is not so important on a climb due to low speeds.
Peak power output means nothing to a climber. Going at 380W for 20 minutes with very low body mass= a good climber.
What about a good sprinter? It is quite likely that any sprinter will have a much higher power to weight ratio than a good climber, and at first glance this would seem to indicate that a sprinter should also climb better. This is true (as I've often proven to local clubbies since I'm a track sprinter) so long as the climb is short enough to be anaerobic (roughly 1 km or less). The problem to the sprinter arises because the sustainable aerobic power to weight ratio will not be as high for a sprinter as for a climber. This has much to do with the fact that upper body (which is useful for yanking on the handlebars during quick starts or sprints) only acts as dead weight during an aerobic climb. The ideal climber physique has no excess upper body mass. Also, the sprinter's type IIb muscle fibers are dead weight while climbing aerobically since they only function anaerobically.
In the end they are both very good cyclists, but the massive, fast twitch muscle laden sprinter is tuned to perform short bouts of great power output against nothing but air resistance and their own mass. The climber has minimized their excess musculature only to maintain the necessary muscle to produce moderate, long-term power against as little gravitational resistance as possible under circumstances where air resistance is also not so important.
THe case where air resistance and long-term sustainable power are important is time trialing - yet another cycling specialty.
Hope this helps.

That darn air resistance!!

 

[Alex Simmons]

Sounds like an eight sided debate to me....