Sprinting in high G

August 25, 2008 9:52 AM

If the earth's gravity was increased by 10%, would sprint runners be slower or faster?

Argument that they would be slower: It would be harder to run, duh.

Arguments that they would be faster: Moonmen move as if in slow motion. The runner would spend less time in the air. The runner would be able to "push off" with more force, similar to the reason Indy cars find it advantageous to generate downforce.

posted by IvyMike to science & nature (49 comments total)

Faster but tire quicker?
posted by ian1977 at 9:57 AM on August 25, 2008

Indy cars only find it advantageous at high speeds, and that's really only for cornering. While I don't know the specific answer -- they would tire much more quickly, so for marathon runners, they would be slower overall :).
posted by SirStan at 9:58 AM on August 25, 2008

Astronauts on the moon moved in slow motion to avoid damaging their suits, which would have killed them. I'd argue that the same sprinter in 10% less gravity would move faster because their muscles are resisting less weight and can therefore apply more force towards forward motion. Runners would also likely alter their movements to avoid leaping in bounds (where air resistance would slow them down).
posted by Mapes at 10:02 AM on August 25, 2008

Slower. A runner carrying 20 pounds on his back runs slower than without, because in every stride, there's a component of motion pushing the body off the ground, which is more difficult with the extra weight. Basically, carrying that extra weight is the equivalent of increasing gravity by a small percentage.

"Moonmen" are were not trying to go fast, and they had extra weight in their space suits and air tanks.
posted by beagle at 10:03 AM on August 25, 2008

I want to modify my answer...

The runner would use more energy to get up in the air, but then fall 10% faster than 9.8m/s squared. I can almost imagine the runner taking more time to go 'up' and then plumetting down with each step...sorta like a frog. plop, plop, plop. Well, maybe not at a 10% increase.
posted by ian1977 at 10:03 AM on August 25, 2008

but then fall 10% faster than 9.8m/s squared

Actually, 9.8 m/s² is the acceleration, not the speed. It means that in 1 second, in a vacuum, you accelerate by 9.8 m/s. In this scenario, you'd accelerate by 10.8 m/s, approximately, in a vacuum.
posted by signal at 10:18 AM on August 25, 2008

Slower. The extra weight would be a burden. I don't think sprinters spend any time "in the air". If you look at their hips there is almost zero vertical motion.
posted by rocket88 at 10:18 AM on August 25, 2008

If gravity were increased, wouldn't the air be denser at sea level as well, which would mean (I'm guessing) more oxygen to breathe thus providing further fuel for the "they would run faster" group?

Also, it would depend on what time frame you're using. If they ran the 100m dash immediately after the 10% increase, then it would most certainly be slower, as they might have to change techniques and/or their muscles wouldn't be adapted to it. But if it was 20 years after the gravity increase, I imagine someone who grew up and trained with the change might be able to run faster since there would be less time in the air between strides, and any time that a runner is not physically touching the ground he should be slowing down due to air resistance/lack of force pushing him forward.

However, it would be tough to tell even then, because world records are being broken at every olympics it seems, so unless they beat the times by a full second, it might be hard to determine whether it was due to increased gravity or just the natural speed increases that seem to happen at every olympics....

/IANAD, IANAP, IANAO (doctor, physicist, Olympian)
posted by Grither at 10:21 AM on August 25, 2008

I don't think sprinters spend any time "in the air". If you look at their hips there is almost zero vertical motion.

The difference between running and walking quickly is whether or not you spend any time in the air.
posted by recoveringsophist at 10:23 AM on August 25, 2008

Speed on the moon was a factor of many things, but Gene Cernan famously worked out the "Bunny Hop" as the fastest way around.

SirStan is referring to downforce which is a function of speed, hence why they can only use it at high speeds. The question of downforce at lower speeds for straightaways seems to be don't bother, as far as I've seen so far. Instead they focus on tire composition and the like, so grip is important, but not being pushed into the ground as much.

In otherwords - animals and machines make the most efficient use of the materials at hand in the given situation. At 2Gs a runner would grow larger muscles to cope with the greater gravity. So I don't think you'd see any difference at all if they grew up with it, and if they didn't... they aren't made for it. They'd be slower. However, if given time to refine technique I'm sure the runner would do what humans do best - we'd figure something out and get back up to speed. Heel striking might be more efficient since it'd have more gravity to convert to forward momentum, etc.
posted by jwells at 10:25 AM on August 25, 2008

If gravity were increased, wouldn't the air be denser at sea level as well, which would mean (I'm guessing) more oxygen to breathe thus providing further fuel for the "they would run faster" group?

Air would also be harder to move through. In the hour record in cycling, attempts are often made at high altitude to get the aerodynamic benefit of thinner air. Surprising, yes. Riders will acclimate for a couple months prior to the attempt.

But if it was 20 years after the gravity increase, I imagine someone who grew up and trained with the change might be able to run faster since there would be less time in the air between strides, and any time that a runner is not physically touching the ground he should be slowing down due to air resistance/lack of force pushing him forward.

If we strapped a 15-lb weight to the back of a runner and had him train for a few seasons, we could simulate this effect today. Once he was acclimated, we could enter him in a race and see how he performed against unencumbered runners. I believe he would lose. If there were a benefit to being 15 lb heavier, runners would be doing it already.
posted by adamrice at 10:32 AM on August 25, 2008

A runner carrying 20 pounds on his back runs slower [...] carrying that extra weight is the equivalent of increasing gravity by a small percentage.

But 20 pounds on the back increases the overall mass, which would not be the case for the runner on the high-G earth. On the high-G earth there would be no additional mass impeding horizontal acceleration.

I don't think sprinters spend any time "in the air"

The old "unsupported transit" debate. Fortunately for us, there are plenty of readily available photos of sprinters in the air
posted by IvyMike at 10:33 AM on August 25, 2008

Yeah... you could test this just by adding more weight to a runner, 10% of their bodyweight. What do you think would happen?

(yeah, the acceleration would be a little different, but other then that, the effect would be about the same)
posted by delmoi at 10:34 AM on August 25, 2008

No, I wasn't referring to unsupported transit. Sprinters don't move like astronauts on the moon, so there is no rising and falling motion that would be affected by higher gravity.
Also, downforce in cars is only beneficial to prevent losses from tire slippage. Beyond that, downforce robs a car of speed. Unless sprinters are skidding their feet under current gravity, more won't help them at all.
posted by rocket88 at 10:46 AM on August 25, 2008

Gravity is a function of mass, not weight. Further, gravity plays no role in horizontal motion: friction does. The runner might accelerate slower vertically under higher gravity, but why would he or she run at a slower peak velocity horizontally?
posted by Blazecock Pileon at 10:49 AM on August 25, 2008

Also, keep in mind that people estimate that humans would be able to run 2 or 3 times faster on mars, although I can't find a cite at the moment. this abstract seems to indicate that people would take longer to speed up to running, but that it would take much less energy to do so.
posted by delmoi at 10:56 AM on August 25, 2008

Gravity is a function of mass, not weight. Further, gravity plays no role in horizontal motion: friction does. The runner might accelerate slower vertically under higher gravity, but why would he or she run at a slower peak velocity horizontally?

And weight is a function of gravity. Mass -> Gravity -> Weight. They would run at a slower peak velocity because they have to do more work per step, and because the wind resistance would be higher (due to higher pressure air being pulled down by the increased gravity)
posted by delmoi at 10:59 AM on August 25, 2008

Because he or she weighs more?

Is the question asking what would happen if earth's gravity suddenly increased by 10%, or asking what would happen if earth's gravity was always 10% higher? As in, the earth massed more?
posted by Justinian at 11:00 AM on August 25, 2008

I don't think sprinters spend any time "in the air". If you look at their hips there is almost zero vertical motion.

Any decent sprinter will tell you they're training to minimize their ground contact. It's all about the the short sharp pulse forwards, and the immediate relaxation of the muscles afterwards. The best sprinters are the ones who can to stay as relaxed as possible, which may be be staying in the air as a long as possible.

The earth's gravity already varies from place to place --- races at an altitude tend to be faster --- and the wind resistance will surely change from moment to moment, because of all the natural variations in the air pressure. However, these effects measured are tiny compared to the 10% increase given in the question.

Let's answer this differently. I reckon a 10% increase of the gravity will make either make humans tinier in the run long, which gives them smaller limbs and less speed; or it will make their limbs bulkier, more elephant like, which makes them slower as well.
posted by ijsbrand at 11:04 AM on August 25, 2008

Does the 10% increase occur overnight, such that sprinters who trained in the lesser gravity must now perform in the greater gravity? This is the only scenario where we can reasonable answer the question without piling variables upon each other.

If this is the scenario you're thinking about, then it seems obvious that the runners will be slower.
posted by pmbuko at 11:21 AM on August 25, 2008

A very interesting question - and fair arguments on both sides.

I have to say slower (IANAS) - but only if they haven't had the chance to train in the 'new' gravity. If sprinter A grew up in 10% heavier gravity and sprinter B didn't, the seemingly infinitesimal differences in things like stride, familiarity with the 'new' gravity, etc.. would probably cause sprinter A to win handily.

If we use the current world record, THEN change the gravity... Assuming sprinter A wasn't doping and was in peak physical condition, I suspect he'd come close, but wouldn't quite match the world record time. Perhaps an anatomy specialist could chime in, but I doubt the human's muscular adaption would quite match the gravity increase in a short time. But then again that depends on the time span we're talking about here :)
posted by chrisinseoul at 11:21 AM on August 25, 2008

Any decent sprinter will tell you they're training to minimize their ground contact.

While I am not a world class sprinter, this seems untrue just by going outside and taking giant bouncy steps.
posted by IvyMike at 11:22 AM on August 25, 2008

Slower.

Here's why. Everyone above me discussing how downforce is a function of aerodynamics, and thus a function of speed, is only partially correct. Aero grip (downforce) is only one component of why race cars stick to the track. The other component is mechanical grip, ie how sticky your tires are. NASCAR cars are less reliant upon aero grip, and more reliant on mechanical grip; this is why they're able to race right behind each other without any big problems. Formula One cars are much, MUCH more reliant on aero grip; this is why they could hypothetically race upside down (!!!) once they hit 80 mph. This is also why, as soon as a Formula One car gets into the slipstream of another car, a la NASCAR, they find it absolutely impossible to turn; they have almost no grip at that point.

Anyways, back to the hypothetical Earth-is-ten-percent-larger question. People who run for a living have almost no reliance on aero grip, instead they create propulsion by the friction of their shoes against the track; this is entirely "mechanical" grip. If you had super-sticky shoes, would you be able to race faster? It would generate more friction, but a runner actually has to then overcome that stickiness in order to get their foot back in front of them. That is to say: more force sticking you to the ground won't make you go faster because you'll expend more energy overall in lifting your leg, placing it in front of you, and then pushing again.

Now, here's the curious thing about the games: were you to ask this question about a cyclist racing in the Velodrome, the answer might be yes. Combined with bike rigidity (allowing the rider to transfer as much force as possible from the pedals to the wheels) and increased stickiness of the tires (assuming cyclists don't use other tire compounds; do they? I don't know) then a bicycle, given all other factors being equal (equality of weight penalty, increased muscle mass from having to train on supersized-Earth, etc), would benefit from the increased mechanical grip.
posted by mark242 at 11:23 AM on August 25, 2008 [2 favorites has favorites]

Moonmen move as if in slow motion.

A lot of the footage you've seen was in slow motion. Then you look at this footage, and the shots from this footage, and while it looks awkward as hell, it's looks pretty normal for guys in bulky suits.
posted by Cool Papa Bell at 11:24 AM on August 25, 2008

They would run at a slower peak velocity because they have to do more work per step

The majority of the work runners have to do is to overcome frictional resistance with the ground, which is the same whether gravity is increased or decreased. In a 1G or 1.1G world, I would argue that frictional resistance is the same.

Wind resistance might be a factor, but how much does gravity increase air pressure, to the extent that drag is increased enough to show a significant mean speed decrease?

Further, why do we assume that the runner in this 1.1G world is not still running at 1 atm of air pressure, which eliminates that difference?

Further still, if increased gravity creates a selection pressure for smaller organisms, that means less surface area that causes drag, which means less air resistance and potentially faster sprinting -- assuming muscles have evolved to deliver the same impulse in both worlds.

I think this question is complicated by its assumptions, which make a correct answer somewhat difficult. In any case, gravity plays no role in motion normal to the Earth's surface.
posted by Blazecock Pileon at 11:27 AM on August 25, 2008

I'd say faster. You spend a lot of time falling when you sprint, and assuming as a first approximation that the motion of sprinters would be the same with a 10% increase in g, that time would be reduced between 5 and 6%.

A natural experiment bearing on this question was done at the 1968 Olympics in Mexico City, which is at 7349 ft-- meaning less gravity. Bob Beamon bettered his previous best in the long jump (and the world record) by nearly two feet! (air resistance was probably much more of a factor than gravity). If the medal winning sprinters did not match their previous bests, I would count that as weak confirmation.
posted by jamjam at 11:41 AM on August 25, 2008

Oops, actually a little less than 5%.
posted by jamjam at 11:51 AM on August 25, 2008

If you had super-sticky shoes, would you be able to race faster? [...] It would generate more friction, but a runner actually has to then overcome that stickiness in order to get their foot back in front of them.

Don't the sprinters already have super-sticky shoes? And unless you are dragging your foot on the ground to get your foot back in front, how does friction affect that segment of motion?

To take the friction to the other extreme, super-unsticky shoes would clearly not work well.
posted by IvyMike at 12:03 PM on August 25, 2008

Im voting slower. If we take today's best runners and drop them off on a planet which has 10% higher gravity pull then they would be at huge disadvantage because every part of the body and all the mechanics of running evolved on a planet that had 10% less gravity. The change would be much worse than just strapping on a 20lbs weight or gaining 20lbs.

I can see some hypothetical technique-based advantages but those advantages need to overcome all the real disadvantages (extra work, extra weight, general weirdness of suddenly being 10% heavier, etc). I dont think they do.
posted by damn dirty ape at 12:06 PM on August 25, 2008

Great question!

I'm voting for slower. I don't think friction is the limiting factor here since they sprinters never seem to skid when they're accelerating. I don't think they rely on gravity to bring their feet down either: I think they use their muscles to push their feet downwards against their centre of mass, which is balanced overall since one leg rises as the other falls. So, no advantage there.

However, they are pumping their legs up and down to move, and the upward move now takes more energy. So overall, I think they'd be slower.
posted by TheophileEscargot at 12:24 PM on August 25, 2008

I don't think friction is the limiting factor here since they sprinters never seem to skid when they're accelerating.

Then why do they start off of blocks? And wouldn't more G force let them have the same effect on every step?
posted by IvyMike at 12:53 PM on August 25, 2008

While I am not a world class sprinter, this seems untrue just by going outside and taking giant bouncy steps.

The best way to think about sprinting is as gliding as closely to the ground as possible without touching it. When your foot is down, its stationary. You don't want that. You want to have the shortest, hardest burst against the ground as you can, and then you want to be back in the air. Sprinters (and other runners) train like hell to not bounce, to keep their hips steady, and to really just glide along the top.

Don't the sprinters already have super-sticky shoes? And unless you are dragging your foot on the ground to get your foot back in front, how does friction affect that segment of motion?

Sprinters have spikes. Spikes are not sticky. Spikes let you touch the ground and not slip backwards, so you can start pushing back (and not down) the moment your toe touches the track. Pushing down, as you already pointed out, makes you bounce, which you don't want. Pushing back is only possible if there's something pushing against it, and the spikes prevent your shoe from sliding.

And, with regard to the original question, my guess would be the air density and extra work needed to stay off the ground would far outweigh the benefit of increased oxygen, so my vote would be for slower.

IANAS, but I did run track.
posted by devilsbrigade at 1:04 PM on August 25, 2008

Oops, didn't see that last one. They start off blocks because they want the most horizontal acceleration possible. The first few steps are very powerful because your quads can direct most of their force backwards. Starting off of blocks well is incredibly difficult, and requires a massive amount of strength to not just fall on your face. The spikes keep them from slipping backwards when they run.
posted by devilsbrigade at 1:07 PM on August 25, 2008

Note the placement of the spikes.
posted by devilsbrigade at 1:10 PM on August 25, 2008

They start off blocks because they want the most horizontal acceleration possible.

I guess what I am saying is that if it's advantageous to provide more horizontal "pushing force" on the first step, why not on the second, third, and fourth steps? With greater G, there's a greater force normal, and Ff = μFn.

Are you saying that that the spikes provide adequate friction to supply the maximum amount of horizontal force except on the first step?
posted by IvyMike at 1:31 PM on August 25, 2008

I voted slower, up near the beginning.

I'm now thinking about another way to conceptualize this. If you take the problem to logical extremes -- say gravity went to 10 Gs overnight. Runners not bred and evolved for that environment would clearly run much slower, if they could even move at all, because they'd weigh a ton.

Now take the other extreme: gravity almost disappears overnight, to .01G. Now, a sprinter is so light that with one kick out of the starting block, or maybe a couple of big steps, he's at the finish line.

So it's a continuum from very fast at very low Gs, and very slow at very high Gs. Therefore clearly, any increase in gravity slows the sprinter down, and any decrease speeds him up.

A natural experiment bearing on this question was done at the 1968 Olympics in Mexico City, which is at 7349 ft-- meaning less gravity. Bob Beamon bettered his previous best in the long jump (and the world record) by nearly two feet! (air resistance was probably much more of a factor than gravity). If the medal winning sprinters did not match their previous bests, I would count that as weak confirmation.

I seriously doubt if you can draw conclusions from his. Gravity is only 0.28% diminished by the altitude at the top of Mt Everest, (according to this Wikipedia page), so at Mexico City it would be only about 0.07% less (or less than 1/1000th).
posted by beagle at 1:54 PM on August 25, 2008 [1 favorite has favorites]

Yes, the spikes provide more than enough friction on a track. Its incredibly hard to run bent over, even though you get the most explosive power that way, and I imagine after you get some speed you get more acceleration from the upright posture rather than bent over.
posted by devilsbrigade at 1:57 PM on August 25, 2008

Are you saying that that the spikes provide adequate friction to supply the maximum amount of horizontal force except on the first step?

Blocks have to with the direction of the force exerted by the leg, not friction.

Have you ever seen a sprinter with spikes whose legs slipped out from under him? It doesn't happen, because friction between the shoe and the track is simply not a limiting factor for sprinters.
posted by ssg at 2:10 PM on August 25, 2008

And unless you are dragging your foot on the ground to get your foot back in front, how does friction affect that segment of motion?

The plane does take off from the conveyor, because... oh, different thread, sorry.

Think of this from the most optimal solution: a sprinter generates a certain amount of (let's call it) torque with her legs. That torque gets converted to propulsion by the friction between her shoes and the track, and in a perfect world, the shoes are only sticky enough to provide just enough friction so as not to slip, and no more. Why no more? Because when our sprinter is picking her leg up, she has to overcome the friction between the shoes and the track, albeit in a different vector than the horizontal propulsion, and she has to overcome the force of gravity upon her leg.

Moving on, in our perfect world, the sprinter keeps her foot mere millimeters above the surface of the Earth, all the way until she has her foot back in the original position, when she places it back down on the ground and provides more force to propel her forward. (Alternatively, if you want to be really sci-fi, her shoe turns from a spiked shoe into an instantaneous frictionless surface) Again, if this were a perfect world, her opposite foot would be providing propulsion at the exact moment when she picks her first foot up.

So where does gravity come into play in the optimal scenario? The friction of the shoe and the track only. Again, back to my original comment, this is "mechanical grip" in racing. Because sprinters don't need to turn, there's no need to have any excess grip over and above the amount which will keep their foot from slipping; think of it as squealing the tires in a drag race. Increasing the amount of gravity only serves to increase that friction; once you're past the "traction control" point, that increased friction serves no purpose but to slow down the lift after a step.
posted by mark242 at 2:19 PM on August 25, 2008

Now, a sprinter is so light that with one kick out of the starting block, or maybe a couple of big steps, he's at the finish line.

But just because he only pushed off once doesn't mean he got there fast. Do you think the runner can get to ~25mph in one push? That's what he would have to do to beat the world record.
posted by IvyMike at 3:14 PM on August 25, 2008

You seem to already know the answer, so why are you asking?
posted by ten pounds of inedita at 3:20 PM on August 25, 2008

You're right, beagle. I've been hearing about Bob Beamon and the lesser gravitation thing since I was a kid and never bothered to do the calculation to check it out, even though it's quite simple. The gravitational difference is far too small to attribute any differences to. How embarrassing.

Thanks for the correction.
posted by jamjam at 5:05 PM on August 25, 2008

Moonmen move as if in slow motion.

A lot of the footage you've seen was in slow motion.

WTF? You're claiming NASA slowed it down in tranmission?
posted by A189Nut at 5:36 PM on August 25, 2008

But just because he only pushed off once doesn't mean he got there fast. Do you think the runner can get to ~25mph in one push? That's what he would have to do to beat the world record.

Yes, absolutely. In my example, I was pushing this to the extreme of 0.01G, which means the sprinter weighs 2 pounds or so, but still has normal human muscles. If a baseball pitcher can throw a ball 95 miles per hour, a 2-pound sprinter with normal muscles can push himself off the blocks at 25 mph or better. Its the same as scaling a grasshopper up to human size - it would jump 100 meters with no problem.

My point is, you have to imagine how this works out over a curve from near-zero G to infinite G. And what you'll see is that the closer to zero G you get (with your existing 1G muscles), the faster you'll cover 100 meters. And as you go up the scale, obviously at infinite G you can't move at all.

You keep jumping in here and wondering if the curve goes the other way, but it simply doesn't and can't.
posted by beagle at 6:10 PM on August 25, 2008

Definitely slower. Running speed depends on two factors:

Running speed (m/sec) = Stride length (m/stride) x Stride frequency (stride/sec)

The reason running is faster than walking is that there is an "aerial phase" in which both feet are off the ground, so that the stride length can exceed the maximum reach of the legs. When walking, one foot is in contact with the ground at all times, so that stride length is limited by reach. With higher gravity, the hang time will be reduced which means a shorter aerial phase and therefore a shorter stride length.

Assuming the anatomy and muscle physiology are the same, the stride frequency should also be reduced, because this depends on the acceleration & deceleration of the legs at the beginning & end of each stride. Assuming the muscle force is the same, the greater body weight will result in slower acceleration of the leg at the beginning of each stride and thus a slower frequency.

So both stride length and stride frequency will be lower with increased gravity, therefore the running speed must be slower.
posted by wps98 at 8:19 PM on August 25, 2008

the work done against gravity is a red herring. compare numbers: the max power output of a top athlete over a 10-20 second sprint is something on the order of 2 kW. assume an average up-down motion of the body's center of mass of 10 cm per stride. given 50 or so strides in a sprint, the amount of power devoted to work against gravity 10cm * 50 strides * 70kg / 20 seconds = 17.5 watts. that's a fraction of a percent. negligible.

friction on the track is a red herring too - sprinters' shoes don't slip as it is, so it's not like more friction will help or hurt, as there's no energy loss either way, and runners don't push so hard on the track that they're at the traction limit.

during the acceleration phase of a sprint from blocks, most of the available power is used for horizontal acceleration. however, at each stride, the muscles must spend some energy overcoming the inertia of the runner's own limbs. the legs have to be slowed, reversed, brought forward, slowed, and reversed again. so do the arms, to conserve angular momentum. all of this takes work, because limbs aren't like springs, they do not conserve energy in doing a complete cycle.

during the acceleration phase, the motion of the limbs is short, and not so fast, so more work can be put into accelerating the runner. as the runner speeds up, the limbs move faster, and less work is available to accelerate. eventually this situation saturates, and the sprinters running at max speed are spending almost all of their energy internally, working against the inertia of their own body.

do an experiment: hold your hand out, and wiggle it back and forth as fast as you can by bending at the wrist. there's a maximum frequency you'll be able to do it, which is determined by the moment of inertia of your hand and the torque your muscles can apply.

now do the same thing but this time wiggle at the shoulder. slower, right, because you have a lot more inertia to overcome, despite having more torque available.

by extension, top speed of a runner is given by the rate at which he or she can turn their legs over at maximum extension. a runner a top speed is hardly pushing horizontally on the track at all, just enough to overcome air friction or whatever. he's going at whatever speed he can where his stride frequency, as determined by inertia, times his leg extension will keep up.

what's the point? none of this shit has anything at all to do with gravity. its' a function of all the available torques at each joint and their respective moments of inertia, which has to do with muscle mass and its distribution along the limbs.

so, my thing is that unless gravity were increased by a humongous amount, it would have essentially zero effect on the results of a sprint, as it has a negligible effect on where the power output goes compared to all other factors of variability, like the runner's mental state, or whether they ate their wheaties that day.
posted by sergeant sandwich at 9:43 PM on August 25, 2008

Thank christ that's over.
posted by theyexpectresults at 9:53 PM on August 25, 2008

oh, maybe not.
posted by theyexpectresults at 9:53 PM on August 25, 2008

I dont see what is so confusing about this, it seems very straightforward to me that the answer would be

SLOWER

First, assuming that we "drop off" the runner on a planet with +10% gravity as compared to earth

doesn't mass + the effect of gravity = weight?!

If there is more gravity, (and the mass of the runner remains the same), wouldnt the extra gravity make the person weigh more?

So if all other things remain equal (like, the power output capability of the runners muscles), if a person weighs ~30 pounds more, they have more inertia to compete with during the acceleration phase, taking them longer to accelerate to the same speed, and therefore will take longer to complete the race. I.e. running slower



BUT, if you change the situation and assume that the runner has lived and trained on this +10% gravity planet, I think the muscles would have conditioned themselves and become stronger than the person with normal gravity. Exactly opposite of what happens to astronauts' muscles under zero gravity conditions. Maybe the more powerfully developed muscles will compensate, and the two runners would be about equal in the race.
posted by Ryaske at 3:23 PM on August 26, 2008