Originally Posted by
EvilV
LOL - you are still falsely drawing a link between the risk of brain injury in a variety of sedentary activities such as showering and sleeping and that of riding an unstable two wheeled device at likely speeds of 15 - 18 mph. Theses situations bear no comparison whatsoever.
Since force is increased exponentially with increases in speed, slipping in the shower will result in a much lower risk of cerebral injury than crashing a bicycle at 18 miles an hour. In the one case, your head might strike something at 5 feet per second and in the second at 26 fps. Lets round it down and say 25 fps. Five times faster.
Using the formula F=mv2, assuming a person weight of 170 pounds, falling in the shower onto your head might result in an impact of 5fps which translates to
170x25 or 4250 (v2 being 5fps x 5 fps)
Whereas in the second case of a 17mph fall onto the head from a bike it works out rather differently:
170x625 or 106250. (v2 being 25 fps x 25 fps)
The force is 25 times as great.
Therefore, I conclude that it is entirely specious to enter sedentary activities like slipping in the shower or falling out of bed into a discussion of the advisability of wearing a cycling helmet.
It is not I that is drawing the link, but the helmets.
Cycling helmets do not function as designed in the latter case (17mph fall). They fail, crack, as if a parachute tearing apart upon deployment. So the only cases where the helmet can possibly provide any benefit at all are those which are precisely comparable to the aforementioned sedentary activities. If, as you say, it bears no comparison then neither does the cycling helmet provide any benefit for cycling.
I doubt many people would pour 16 oz of steaming hot coffee into a cracked 8 oz styrofoam cup claiming, "at least I wasn't burned by the whole 16 oz". So why do they make these kinds of ridiculous gestures when it comes to their heads? You can't have it both ways, either cycling bears no comparison to the aforementioned sedentary activities and the helmet provides no benefit or it only provides benefit for situations comparable to slipping in the shower which begs the question: why aren't those cyclists wearing helmets while riding also wearing them in the shower?
In my case, rbrian hit the nail on the head: there's no sun or wind in the shower, which are the primary kinds of protection I seek from my bike helmet.