Apparently when one leg round kicks another leg in a shin guard, if a leg is to break it is the kicking leg. See this video from 4:37 to see what i mean - but not if you're squeamish, lots of nasty leg breaks.

I'm assuming that factors like bone density aren't a major factor as these are all highly trained athletes. I'm also thinking about the lower leg as a single pole rather than the two bones it actually is, just to keep it simple. 

So why would the moving poll break upon impact with the static pole and not vice versa? I can only imagine it has something to do with the momentum contained in the distal end of the pole, above the contact point, which means there is more force acting on the point of contact on the moving pole - like the inertia of a rotating body.

50 minutes ago, Prometheus said:

Apparently when one leg round kicks another leg in a shin guard, if a leg is to break it is the kicking leg. See this video from 4:37 to see what i mean - but not if you're squeamish, lots of nasty leg breaks.

I'm assuming that factors like bone density aren't a major factor as these are all highly trained athletes. I'm also thinking about the lower leg as a single pole rather than the two bones it actually is, just to keep it simple. 

So why would the moving poll break upon impact with the static pole and not vice versa? I can only imagine it has something to do with the momentum contained in the distal end of the pole, above the contact point, which means there is more force acting on the point of contact on the moving pole - like the inertia of a rotating body.

Just a guess. Could it be that the striking leg, being free to vibrate, keeps more of the energy that it's trying to apply to the anchored leg. Basically, I'm saying the kicking leg does a whipping action around the opponents leg and bends, with the foot acting as a weight on the end. The power really is in the swinging foot but the contact is higher up in a weaker spot, besides being illegal. If you get a stick with a metal ball on the end and whack a pole, with the ball making contact with the pole, the pole will break but get closer,  such that the stick makes contact instead, the stick will break because the stick is not strong enough to stop the ball which wants to carry on.

Edited June 3, 20187 yr by StringJunky

54 minutes ago, StringJunky said:

Just a guess. Could it be that the striking leg, being free to vibrate, keeps more of the energy that it's trying to apply to the anchored leg.

It's not always the anchored leg that's being kicked.

56 minutes ago, StringJunky said:

Basically, I'm saying the kicking leg does a whipping action around the opponents leg and bends, with the foot acting as a weight on the end. The power really is in the swinging foot but the contact is higher up in a weaker spot, besides being illegal. If you get a stick with a metal ball on the end and whack a pole, with the ball making contact with the pole, the pole will break but get closer,  such that the stick makes contact instead, the stick will break because the stick is not strong enough to stop the ball which wants to carry on.

Just to add, it's the kicking leg that has the momentum so the impact is absorbed at one point while the leg being kicked can absorb the impact over the whole leg.

1 hour ago, Prometheus said:

Apparently when one leg round kicks another leg in a shin guard, if a leg is to break it is the kicking leg. See this video from 4:37 to see what i mean - but not if you're squeamish, lots of nasty leg breaks.

I'm assuming that factors like bone density aren't a major factor as these are all highly trained athletes. I'm also thinking about the lower leg as a single pole rather than the two bones it actually is, just to keep it simple. 

So why would the moving poll break upon impact with the static pole and not vice versa? I can only imagine it has something to do with the momentum contained in the distal end of the pole, above the contact point, which means there is more force acting on the point of contact on the moving pole - like the inertia of a rotating body.

It depends on the dimensions and material properties of the poles and any external influences (like being anchored). You can find plenty of example where the moving pole will break, and plenty where the stationary one would. 

 

1 minute ago, swansont said:

It depends on the dimensions and material properties of the poles. You can find plenty of example where the moving pole will break, and plenty where the stationary one would. 

Probably best to say "everything being equal".

1 minute ago, swansont said:

It depends on the dimensions and material properties of the poles and any external influences (like being anchored). You can find plenty of example where the moving pole will break, and plenty where the stationary one would. 

Indeed, when the contact is close to foot the break happens the other way round.

 

As in the video.

 

19 minutes ago, StringJunky said:

Probably best to say "everything being equal".

Agree.

The leg in shin guard is always raised so it is not anchored. It is also either stationary upon impact or moving up, perpendicular to the incoming leg.

I tried to examine the video more closer to determine the relative points of contact on the legs but couldn't get much data due to low video quality. At least one leg broke distal to the point of contact. Most breaks seem to be to the lower half of the shin.