|
|
Thread Tools | Display Modes |
#31
|
|||
|
|||
Per David Damerell:
Why you think something that increases the lever arm won't hurt in torsional impacts. I'm more or less of a helmet zealot since undergoing a little attitude adjustment some years back. But in support of your observation, I'm pretty sure I messed up my neck a couple years back taking a header in the water at 20+ mph wearing a helmet (windsurfing). There was a definate sensation of the helmet catching water and twisting my neck. I'd extrapolate from that to believe that there's a risk factor in bike helmets around the helmet catching on something (i.e. MTB riding...). I still wear the things - but it's not a black-white issue with me. -- PeteCresswell |
Ads |
#32
|
|||
|
|||
These threads are all so tiresome. This subject has been beat to
death, and still no conclusion has been reached. You guys can go on all you want citing statistically insignificant personal events, but you are neither convincing anyone, nor proving anything. An issue like this needs scientific study, not the opinion of some random guy off rec.bicycles.misc. As for me, I'm taking no side, as both are as unconvincing as the other. |
#33
|
|||
|
|||
gym.gravity wrote:
Will wrote: gym.gravity wrote: gwhite wrote: Good thing he was wearing a helmet. **** off! Given the gentle response above, one might assume that it is too late for you to get much benefit from a helmet g. I was just trying to fast forward the thread to it's inevitable conclusion. Hitler! Nazis! There. Thread over. Move along folks, nothing to see here, go back to your homes. We now return you to your normally scheduled RBR, RBT, RBM programming. Mark |
#34
|
|||
|
|||
David Damerell wrote in
: Quoting Qui si parla Campagnolo : Jay Beattie wrote: Like, does the name Casartelli ring a bell? He actually hit more of his face than his upper head but I agree... Helmets-don't hurt, may help. What's so diffuclt to understand? Why you think something that increases the lever arm won't hurt in torsional impacts. Why you think something that dissapates and redistributes the point stresses that will inevitably also be present in the non-torsional part of the impact isn't a good thing? Compare and contrast the maybe 1" difference, allowing for the obviously different coefficient of friction of skin vs plastic along with the slip in the helmet suspension, with the abrasions and non-rotational trauma inflicted. I personally knew at least one child and one father who would be alive today if they had been wearing helmets after they died from the trauma of minor bicycle falls; I know of nobody who has died from a twisted neck. I also wish I had had a helmet on when I smashed my glass lens into my face on a fall and took 8 stitches to put the eyebrow and other skin back in place. It's nice to know you can duck and cover on a fall instead of trying to keep your cranium off the ground. |
#35
|
|||
|
|||
On Fri, 15 Jul 2005 23:07:35 -0400, wvantwiller
wrote: Why you think something that increases the lever arm won't hurt in torsional impacts. Why you think something that dissapates and redistributes the point stresses that will inevitably also be present in the non-torsional part of the impact isn't a good thing? But there is no known case where cyclist safety has improved with increasing helmet use, so obviously what goes on after the crash is only part of the story. I personally knew at least one child and one father who would be alive today if they had been wearing helmets after they died from the trauma of minor bicycle falls; I know of nobody who has died from a twisted neck. You think? I wonder why, then, there is no robust evidence that helmets actually save lives? Mind you, what would I know? I suffered a serious bicycle crash many years ago and wasn't wearing a helmet, so obviously I'm dead! But you misunderstand. The torsional force is important not because of its effect on the neck, but because of the differential movement it causes between the hemispheres of the brain. These torsional forces are reckoned to be a (some say the) major source of permanent disabling brain injury. Guy -- http://www.chapmancentral.co.uk "Let’s have a moment of silence for all those Americans who are stuck in traffic on their way to the gym to ride the stationary bicycle." - Earl Blumenauer |
#36
|
|||
|
|||
On Fri, 15 Jul 2005 23:07:35 -0400, wvantwiller
wrote: I personally knew at least one child and one father who would be alive today if they had been wearing helmets after they died from the trauma of minor bicycle falls; How do you know that? JT **************************** Remove "remove" to reply Visit http://www.jt10000.com **************************** |
#37
|
|||
|
|||
Just zis Guy, you know? wrote:
But you misunderstand. The torsional force is important not because of its effect on the neck, but because of the differential movement it causes between the hemispheres of the brain. These torsional forces are reckoned to be a (some say the) major source of permanent disabling brain injury. Total BS. |
#38
|
|||
|
|||
John Forrest Tomlinson wrote in
: On Fri, 15 Jul 2005 23:07:35 -0400, wvantwiller wrote: I personally knew at least one child and one father who would be alive today if they had been wearing helmets after they died from the trauma of minor bicycle falls; How do you know that? JT **************************** Remove "remove" to reply Visit http://www.jt10000.com **************************** Mostly the newspaper articles quoting the doctors that the internal trauma would probably been prevented if the riders had been wearing helmets. Both accidents were recent enough to have involved newer helmets, also. In neither case did the victim go to the hospital, but decided just to take a nap after the fall. And, as usual, I suppose your experience in your person medical practice, including all that trauma room experience during your internship and residence, give you better insights? Also, I suppose you were there and can vouch that my other example that I'd be a few stitch marks to the better if I had been wearing my helmet is ALSO false? Or do you only consider the evidence you want to? Must be a conspiracy. Go on wearing your aluminum skullcap. |
#39
|
|||
|
|||
I submit that on or about Sat, 16 Jul 2005 07:52:57 -0600, the person
known to the court as Rich made a statement in Your Honour's bundle) to the following effect: But you misunderstand. The torsional force is important not because of its effect on the neck, but because of the differential movement it causes between the hemispheres of the brain. These torsional forces are reckoned to be a (some say the) major source of permanent disabling brain injury. Total BS. Plenty of cites are available, but this will do as a quick layman's guide: http://www.emedicine.com/radio/topic216.htm Background: Diffuse axonal injury (DAI) is a frequent result of traumatic deceleration injuries and a frequent cause of persistent vegetative state in patients. DAI is the most significant cause of morbidity in patients with traumatic brain injuries, which most commonly are the result of high-speed motor vehicle accidents. DAI is a significant medical problem because of the high level of debilitation of the patient, the stress that the patient's family must endure when the patient is in a persistent vegetative state, and the staggering medical cost of sustaining an individual in this state. DAI typically consists of several focal white matter 1-15 mm lesions in a characteristic distribution (see below). Pathophysiology: The pathophysiology of DAI first was described by Holbourn in 1943 using 2-dimensional gelatin molds. His work led to the understanding that shear injury is not induced by linear or translational forces but rather by rotational forces. Sudden acceleration-deceleration impact can produce rotational forces that affect the brain. The injury to tissue is greatest in areas where the density difference is greatest. For this reason, approximately two thirds of DAI lesions occur at the gray-white matter junction. The result of shearing forces in areas of greater density differential is trauma to the axons, which results in edema and axoplasmic leakage that is most severe during the first 2 weeks after injury. The exact location of the shear-strain injury depends on the plane of rotation and is independent of the distance from the center of rotation. Conversely, the magnitude of injury depends on 3 factors, including (1) the distance from the center of rotation, (2) the arc of rotation, and (3) the duration and intensity of the force. The true extent of axonal injury typically is worse than visualized using current imaging techniques. On the microscopic level, the axon may not be torn completely by the initial force, but the trauma still can produce focal alteration of the axoplasmic membrane, resulting in subsequent impairment of axoplasmic transport. Axoplasmic swelling ensues, and the axon then splits in two. A retraction ball forms, which is a pathologic hallmark of shearing injury. The axon then undergoes wallerian degeneration. Dendritic restructuring may occur, with some regeneration possible in mild-to-moderate injury. Within the basal ganglia, the effect of DAI produces parenchymal atrophy brought on by shrinkage of astrocytes in the lateral and ventral nuclei, with sparing of the anterior and dorsomedial nuclei, the pulvinar, centromedian nuclei, and lateral geniculate bodies. Cholinergic neurons have been found to be slightly more susceptible to trauma than neurons belonging to other neurotransmitters. Peripheral lesions usually are smaller than central lesions. The lesions typically are ovoid or elliptical, with the long axis parallel to the direction of the involved axonal tracts. A high association is seen between thalamic injury and DAI. Both silver stains and beta-amyloid precursor protein immunohistochemical staining have proven useful in the pathologic identification of DAI lesions. DAI classically was believed to represent a primary injury (occurring at the instant of the trauma). Currently, however, it is apparent that the axoplasmic membrane alteration, transport impairment, and retraction ball formation may represent secondary (or delayed) components to the disease process. Guy -- May contain traces of irony. Contents liable to settle after posting. http://www.chapmancentral.co.uk 85% of helmet statistics are made up, 69% of them at CHS, Puget Sound |
#40
|
|||
|
|||
On Sat, 16 Jul 2005 10:08:38 -0400, wvantwiller
wrote: And, as usual, I suppose your experience in your person medical practice, including all that trauma room experience during your internship and residence, give you better insights? I'm not the one making claims so I have no need to back anything up. JT PS -- unless the medical people you're talking about are comparing people who fell and were uninjured, I don't see how they could come to conclusions about helmets. Think about it. **************************** Remove "remove" to reply Visit http://www.jt10000.com **************************** |
Thread Tools | |
Display Modes | |
|
|