7 ms·

I was maybe 10 or younger and I was speedbombing downhill with my younger sister. We were fearless and very, very fast. Of course we weren't wearing any helmet

I was maybe 10 or younger and I was speedbombing downhill with my younger sister. We were fearless and very, very fast. Of course we weren't wearing any helmet or whatever. One time as we were racing, she was winning, she shifted her bike toward my direction and slowed down. I ran into her bike and flew out of my bike. Next thing I know I'm in the air, falling down towards the hill. When I finally hit the ground, I uncontrollably rolled downhill another maybe 10 meters. All my face and body was covered in blood and soil. My mom, seeing this incident from far away, ran for help. She told me, when I grew up, that when she was close enough to see me she was sure I was dead because of all the blood on the asphalt and what not. But thanks to the gods of probability, I didn't even break a bone. I don't understand how can human body can be so resilient that a 10 year old kid can survive such an accident without any damage other than his skin (and it wasn't permenant, I forgot about this event until now). I was stupid and I probably did that again and again, possibly even the next day. Now 15 years later, I bike everyday, but I bike very cautiously. I was lucky once, I don't wanna try my luck again.

jacquesm 8y ago
The big factor is that you simply weigh less.
- TheSpiceIsLife 8y ago
  Also, as far as I understand, growing bones impart a bit more flexiblity to the skeleton due to epiphyseal plates at either end of long bones. Or is this a myth?
  - MaxfordAndSons 8y ago
    I believe that's true, but I doubt it's really a factor in this phenomenon of kids surviving high speed crashes that would likely be fatal to adults. It's really just a matter of a less massive body generating (exponentially) less force on impact.
- p1necone 8y ago
  The inverse square law is a powerful thing.
- a1369209993 8y ago
  Square-cube law; someone twice the size has eight times the mass and eight times the force, with only four times cross-sectional area to support it. A ten-year-old's bones and other tissues suffer half[1] the force per unit area in a crash, so require only half the material strength to avoid whatever level of damage. 1: spherical cow/fermi estimate
  - Gravityloss 8y ago
    Actually ... force is proportional to the cross section of the muscle. You can probably produce more power approximated by the volume of the muscle though.
    - hfdgiutdryg 8y ago
      force is proportional to the cross section of the muscle. This never made any sense to me. Muscles are made up of groups of fibers, which are made up of chains of sarcomeres. How could strength be proportional to cross sectional area rather than volume of the muscle?
      - dragonwriter 8y ago
        > How could strength be proportional to cross sectional area rather than volume of the muscle? The same reason that's true of strength of passive members; the limiting factor is the force that will cause shearing, which is basically the strength of one bond in the lengthwise direction times the number of them supporting in parallel in the cross section. So, given the same material, cross sectional area determines strength.
        hfdgiutdryg 8y ago
        But, by my understanding, the sarcomeres, which are the source of the actual movement, don't run end to end, they're chains. The entire line of reasoning seems to rest on the idea that the smallest unit we consider runs from one end all the way to the other.
- FlyMoreRockets 8y ago
  That is indeed a big factor, but another important factor is that the bones of children are less brittle than adults. I retired from being an EMT last year and it's amazing what kids literally bounce back from while adults break a hip from just falling in the yard.
skookumchuck 8y ago
My father always said that God looked out for boys, because it was a miracle they survived being a boy.
- 3chelon 8y ago
  I'm atheist but I like that saying. I'm amazed I survived my 1970s childhood intact. Plenty didn't.
  - lb1lf 8y ago
    I have come to realise that there's quite a survivor bias in childhood experience, too, whenever someone suggest that today's kids are pampered and parents are hysterical and after all, when we were kids we did all these fun things you cannot do anymore because safety - but yet we survived just fine, didn't we? I looked up the stats going back a few decades - in the sixties, an average hundred kids died in traffic each year here in Norway. Now? Two or three. Yet we drive more and the population is significantly larger, too. Drowning (the other biggie) is down by a similar factor. Generic accidents? Also down by at least an order of magnitude. We may sigh all we want that kids today are glued to their playstations while we were out building tree huts, conducting -ahem- applied pyrotechnics experiments and similar - but the fact of the matter is that kids today survive childhood. We didn't. :/
    - AstralStorm 8y ago
      They don't have to be glued to anything ever. The main difference is being supervised by a reasonable adult or not and how streets near homes have changed. Kids can only be left to free roam in a very safe environment - and even that is not entirely without risks. Alternatively only kids who are shown to be reasonable can do that - it takes parental sensitivity.
GreeniFi 8y ago
I didn’t know there was a name for this. Speedbombing...Like another commenter, aged 10 I took on the biggest hill in the area. 30 years later, I still bare the scars and memories of the pain at being cleaned up by a very unsympathetic nurse at the hospital. Which was more painful than the crash, as I remember it.
- jchrisa 8y ago
  In Portland we call it Zoobombing, because you can ride light rail to the zoo and zoom back downtown: http://www.zoobombpdx.org/ http://www.zoobombpdx.org/
kwhitefoot 8y ago
You might find Haldane's essay on the subject interesting: https://irl.cs.ucla.edu/papers/right-size.html https://irl.cs.ucla.edu/papers/right-size.html
fian 8y ago
Cyclists tend to break bones at slower speeds. Pro-cyclists racing down mountains will lose a lot of skin in a fall but unless they hit something hard (rock, pole, wall) they don't tend to break bones. At walking speeds, a sideways fall often results in broken collar bones and wrists. It is all about the angular momentum of the cyclist wrt to the road.
- nickjj 8y ago
  > At walking speeds, a sideways fall often results in broken collar bones That's pretty much what happened to me. I was going walking speed on a bike, popped a wheelie, handle bars came off, I tumbled forward and landed collar bone first onto a curb. Hairline fracture at about age 14.
  - gnulinux 8y ago
    > handle bars came off That sounds very concerning. I didn't know that could even happen...
    - nickjj 8y ago
      > That sounds very concerning. I didn't know that could even happen... I don't know too much about bikes, but the one I had used some type of bolt to connect the handlebars to the main frame. I was adjusting the height of the handlebars and I guess I didn't tighten it enough in the end. User error in all its glory.
  - johnvanommen 8y ago
    > handle bars came off I pulled the brake lever on my road bike once, and it FELL OFF. Went right into the front spokes and launched me over the handlebars like a cannonball. It was like putting a metal rod right into the front spokes.
- TheOtherHobbes 8y ago
  Interesting. I've moved to a warmer country and it's normal here for moped riders and motor cyclists to wear a helmet with shorts and a t-shirt. I'm used to motor cyclists wearing leathers. Bare skin in an accident looks terrifyingly abrasive.
linalgmixer 8y ago
I remember doing stuff like this as well when I was younger. I think it should be a collective responsibility of parents to instill in their children that safety is important. I don't let my children ride their bikes without helmets and that's the norm where I live, not the exception, and I think a great deal of it has to do with the fact that the parents around here are very involved in their children.

jacquesm 8y ago

The big factor is that you simply weigh less.

TheSpiceIsLife 8y ago
Also, as far as I understand, growing bones impart a bit more flexiblity to the skeleton due to epiphyseal plates at either end of long bones. Or is this a myth?
- MaxfordAndSons 8y ago
  I believe that's true, but I doubt it's really a factor in this phenomenon of kids surviving high speed crashes that would likely be fatal to adults. It's really just a matter of a less massive body generating (exponentially) less force on impact.
p1necone 8y ago
The inverse square law is a powerful thing.
a1369209993 8y ago
Square-cube law; someone twice the size has eight times the mass and eight times the force, with only four times cross-sectional area to support it. A ten-year-old's bones and other tissues suffer half[1] the force per unit area in a crash, so require only half the material strength to avoid whatever level of damage. 1: spherical cow/fermi estimate
- Gravityloss 8y ago
  Actually ... force is proportional to the cross section of the muscle. You can probably produce more power approximated by the volume of the muscle though.
  - hfdgiutdryg 8y ago
    force is proportional to the cross section of the muscle. This never made any sense to me. Muscles are made up of groups of fibers, which are made up of chains of sarcomeres. How could strength be proportional to cross sectional area rather than volume of the muscle?
    - dragonwriter 8y ago
      > How could strength be proportional to cross sectional area rather than volume of the muscle? The same reason that's true of strength of passive members; the limiting factor is the force that will cause shearing, which is basically the strength of one bond in the lengthwise direction times the number of them supporting in parallel in the cross section. So, given the same material, cross sectional area determines strength.
      - hfdgiutdryg 8y ago
        But, by my understanding, the sarcomeres, which are the source of the actual movement, don't run end to end, they're chains. The entire line of reasoning seems to rest on the idea that the smallest unit we consider runs from one end all the way to the other.
FlyMoreRockets 8y ago
That is indeed a big factor, but another important factor is that the bones of children are less brittle than adults. I retired from being an EMT last year and it's amazing what kids literally bounce back from while adults break a hip from just falling in the yard.

skookumchuck 8y ago

My father always said that God looked out for boys, because it was a miracle they survived being a boy.

3chelon 8y ago
I'm atheist but I like that saying. I'm amazed I survived my 1970s childhood intact. Plenty didn't.
- lb1lf 8y ago
  I have come to realise that there's quite a survivor bias in childhood experience, too, whenever someone suggest that today's kids are pampered and parents are hysterical and after all, when we were kids we did all these fun things you cannot do anymore because safety - but yet we survived just fine, didn't we? I looked up the stats going back a few decades - in the sixties, an average hundred kids died in traffic each year here in Norway. Now? Two or three. Yet we drive more and the population is significantly larger, too. Drowning (the other biggie) is down by a similar factor. Generic accidents? Also down by at least an order of magnitude. We may sigh all we want that kids today are glued to their playstations while we were out building tree huts, conducting -ahem- applied pyrotechnics experiments and similar - but the fact of the matter is that kids today survive childhood. We didn't. :/
  - AstralStorm 8y ago
    They don't have to be glued to anything ever. The main difference is being supervised by a reasonable adult or not and how streets near homes have changed. Kids can only be left to free roam in a very safe environment - and even that is not entirely without risks. Alternatively only kids who are shown to be reasonable can do that - it takes parental sensitivity.

GreeniFi 8y ago

I didn’t know there was a name for this. Speedbombing...Like another commenter, aged 10 I took on the biggest hill in the area. 30 years later, I still bare the scars and memories of the pain at being cleaned up by a very unsympathetic nurse at the hospital. Which was more painful than the crash, as I remember it.

jchrisa 8y ago
In Portland we call it Zoobombing, because you can ride light rail to the zoo and zoom back downtown: http://www.zoobombpdx.org/ http://www.zoobombpdx.org/

kwhitefoot 8y ago

You might find Haldane's essay on the subject interesting: https://irl.cs.ucla.edu/papers/right-size.html https://irl.cs.ucla.edu/papers/right-size.html

fian 8y ago

Cyclists tend to break bones at slower speeds. Pro-cyclists racing down mountains will lose a lot of skin in a fall but unless they hit something hard (rock, pole, wall) they don't tend to break bones. At walking speeds, a sideways fall often results in broken collar bones and wrists. It is all about the angular momentum of the cyclist wrt to the road.

nickjj 8y ago
> At walking speeds, a sideways fall often results in broken collar bones That's pretty much what happened to me. I was going walking speed on a bike, popped a wheelie, handle bars came off, I tumbled forward and landed collar bone first onto a curb. Hairline fracture at about age 14.
- gnulinux 8y ago
  > handle bars came off That sounds very concerning. I didn't know that could even happen...
  - nickjj 8y ago
    > That sounds very concerning. I didn't know that could even happen... I don't know too much about bikes, but the one I had used some type of bolt to connect the handlebars to the main frame. I was adjusting the height of the handlebars and I guess I didn't tighten it enough in the end. User error in all its glory.
- johnvanommen 8y ago
  > handle bars came off I pulled the brake lever on my road bike once, and it FELL OFF. Went right into the front spokes and launched me over the handlebars like a cannonball. It was like putting a metal rod right into the front spokes.
TheOtherHobbes 8y ago
Interesting. I've moved to a warmer country and it's normal here for moped riders and motor cyclists to wear a helmet with shorts and a t-shirt. I'm used to motor cyclists wearing leathers. Bare skin in an accident looks terrifyingly abrasive.

linalgmixer 8y ago

I remember doing stuff like this as well when I was younger. I think it should be a collective responsibility of parents to instill in their children that safety is important. I don't let my children ride their bikes without helmets and that's the norm where I live, not the exception, and I think a great deal of it has to do with the fact that the parents around here are very involved in their children.