Why the faster we run we bounce less? If I look at sprinters there’s almost no vertical movement, but when we jog we bounce more up and down.
Why the faster we run we bounce less? If I look at sprinters there’s almost no vertical movement, but when we jog we bounce more up and down.
Because the less we bounce, the faster we go.
bouncing is boring
To go your fastest, you can't waste energy on irrelevant motion. Your goal is in the horizontal direction, so vertical motion is wasteful.
Tgg wrote:
To go your fastest, you can't waste energy on irrelevant motion. Your goal is in the horizontal direction, so vertical motion is wasteful.
Yea but that’s half the answer. Why waste that energy the slower you go?
Ever ridden a horse?
At a walk it is relatively smooth and rhythmic.
At a gallop it is relatively smooth and rhythmic.
But at a trot, the mid speed, it is pounding a lot of wasted energy into the ground and is a jolting ride.
This can be seen in the calories per mile used when charted by pace
From 13 minute miles to about 8 minute miles the calories burned per mile increase.
But starting at about 8 minute miles the calories burned per mile actually go down because you are more efficient - less energy pounded into the ground.
(you actually burn more calories per minute, but because it takes fewer minutes to cover a mile the calories per mile are less)
Bounce less = better efficiency
Whyfastnobounce wrote:
Why the faster we run we bounce less? If I look at sprinters there’s almost no vertical movement, but when we jog we bounce more up and down.
Walk through a doorway in an old house and then turn round and run back through.
Come back to me when you've got the stitches on your head sorted.
As Galileo would tell you, everything experiences the same gravitational acceleration and thus fall at the same rate. The vertical motion is purely a function of how much time you spend in the air.
This means that a higher cadence leads to less vertical movement because you spend less time in the air between steps. The faster you run the higher cadence, at least when comparing jogging to sprinting.
Because the faster you go a smaller amount of your foot touches the ground and your foot stays on the ground for less times which means less energy return because as you probably learned in high school sometime every reaction has an equal and opposite reaction. When you run faster more of that energy is directed forward rather than up.
wfbeewaw wrote:
Because the faster you go a smaller amount of your foot touches the ground and your foot stays on the ground for less times which means less energy return because as you probably learned in high school sometime every reaction has an equal and opposite reaction. When you run faster more of that energy is directed forward rather than up.
This seems the most correct answer. Within a pretty wide range, the cadence does not really change that much between fast and slow running, what changes the most is the length of the stride and the contact time.
But why "wasting" energy on vertical motion at low speed? Shouldn't there be a more efficient way to run slow?
Hop on a treadmill with a mirror and try to minimize your vertical displacement while jogging: you'll probably notice that, at slow speeds, the running form seed to be altered quite a bit and a different set of muscles is engaged, that are not as powerful/efficient. Less energy is spent, in an absolute term, but these muscles will get fatigued a lot earlier. As the speed is increased, it becomes progressively easier to eliminate vertical displacement while keeping a natural running form.
Mid D Guy wrote:
wfbeewaw wrote:
Because the faster you go a smaller amount of your foot touches the ground and your foot stays on the ground for less times which means less energy return because as you probably learned in high school sometime every reaction has an equal and opposite reaction. When you run faster more of that energy is directed forward rather than up.
This seems the most correct answer. Within a pretty wide range, the cadence does not really change that much between fast and slow running, what changes the most is the length of the stride and the contact time.
But why "wasting" energy on vertical motion at low speed? Shouldn't there be a more efficient way to run slow?
Hop on a treadmill with a mirror and try to minimize your vertical displacement while jogging: you'll probably notice that, at slow speeds, the running form seed to be altered quite a bit and a different set of muscles is engaged, that are not as powerful/efficient. Less energy is spent, in an absolute term, but these muscles will get fatigued a lot earlier. As the speed is increased, it becomes progressively easier to eliminate vertical displacement while keeping a natural running form.
You have more forward momentum while running fast. Picture a ball thrown hard vs a ball tossed lightly. One loses height much more quickly than the other.
Muffin bottoms wrote:
Mid D Guy wrote:
This seems the most correct answer. Within a pretty wide range, the cadence does not really change that much between fast and slow running, what changes the most is the length of the stride and the contact time.
But why "wasting" energy on vertical motion at low speed? Shouldn't there be a more efficient way to run slow?
Hop on a treadmill with a mirror and try to minimize your vertical displacement while jogging: you'll probably notice that, at slow speeds, the running form seed to be altered quite a bit and a different set of muscles is engaged, that are not as powerful/efficient. Less energy is spent, in an absolute term, but these muscles will get fatigued a lot earlier. As the speed is increased, it becomes progressively easier to eliminate vertical displacement while keeping a natural running form.
You have more forward momentum while running fast. Picture a ball thrown hard vs a ball tossed lightly. One loses height much more quickly than the other.
What? The ball loses height at exactly the same speed. The difference is that the slow ball has to be thrown higher to cover the same distance as a fast ball because it is not moving forward as quickly.
The faster your cadence is, the less time you're in the air per stride thus the 'arc' of your stride is smaller. Sprinters go about 240 steps per second.
There's no "wasting" motion vertically. Gravity pulls downward 9.8 N/kg so you will always average 9.8 N/kg of upward force no matter what.
kadoo wrote:
Muffin bottoms wrote:
You have more forward momentum while running fast. Picture a ball thrown hard vs a ball tossed lightly. One loses height much more quickly than the other.
What? The ball loses height at exactly the same speed. The difference is that the slow ball has to be thrown higher to cover the same distance as a fast ball because it is not moving forward as quickly.
Should have clarified I guess. The ball moving faster loses less height over the same amount of distance. Obviously you cover more ground at a faster pace but you still lose less height per step. Also, at a faster pace you strike the ground with a larger forward force so that, combined with gravity, your net force on the ground when you strike is at less of an angle with the ground meaning you leave the ground at less of an angle as well.
Hardloper wrote:
The faster your cadence is, the less time you're in the air per stride thus the 'arc' of your stride is smaller. Sprinters go about 240 steps per second.
240 per second is a heck of a cadence...
Cadence is faster for sprinters, but most people will keep pretty much the same cadence going from 8 to 5 minutes/mile; what changes dramatically is the length of the stride. A sprinter can cover up to 2.5 meters per step, while a jogger covers less than half that distance.
By the way, the analogy of the ball is misleading. We do not bounce up and down like a ball while running. The center of mass (or the head) of a runner with good form moves in pretty much straight line, with almost 0 vertical displacement.
Mid D Guy wrote:
By the way, the analogy of the ball is misleading. We do not bounce up and down like a ball while running. The center of mass (or the head) of a runner with good form moves in pretty much straight line, with almost 0 vertical displacement.
There was no bounce at all in the analogy and it was only meant to convey the idea that your body moves through a more horizontal path while moving faster as opposed to slower over the same amount of distance. And yes, you do bounce, that's the whole premise of this thread... You wouldn't have used the word almost if that weren't the case.
Mid D Guy wrote:
By the way, the analogy of the ball is misleading. We do not bounce up and down like a ball while running. The center of mass (or the head) of a runner with good form moves in pretty much straight line, with almost 0 vertical displacement.
The center of mass of a runner while in the air follows a parabola like any other object on this planet (also a bouncing ball).
Eventually the only way to overcome braking force and accelerate more is to increase cadence, and that can only be achieved by spending less time in the air on each stride.
You don't push the ground down! That's not how it's done. You use your trailing foot as a platform from which the rest of your body launches itself forward. Before it even leaves the ground, your center of mass should already be at just about its highest point and ready to descend to the next footstrike.
Look at the leaping cat. Its body accelerates itself nearly uniformly, like an uncompressing spring.
Muffin bottoms wrote:
kadoo wrote:
What? The ball loses height at exactly the same speed. The difference is that the slow ball has to be thrown higher to cover the same distance as a fast ball because it is not moving forward as quickly.
Should have clarified I guess. The ball moving faster loses less height over the same amount of distance. Obviously you cover more ground at a faster pace but you still lose less height per step. Also, at a faster pace you strike the ground with a larger forward force so that, combined with gravity, your net force on the ground when you strike is at less of an angle with the ground meaning you leave the ground at less of an angle as well.
But, will the plane take off or not????