Wednesday, September 23, 2015

Should You Change Your Bike’s Tire Pressure? Flying? At Races?


Should You Change Your Bike’s Tire Pressure?  Flying?  At Races?



               Let's have a look at the conundrum surrounding suggestions of tire pressure alteration in the low pressure environment of modern jet travel or at bike check in locales where the “afternoon sun will get the tires so hot they’ll burst.”


“Sir, you’d better take some air out those tires if you rack your bike early,” is heard frequently at venues like Kona, Hawaii for fear that one’s expensive tires may spontaneously explode.  Or, more worrisome, that they may blow up and damage one’s even more expensive race wheels.  Also heard at bike shops across the country, the time honored advice that reducing the air in one’s tires will reduce the potential of having them detonate in the reduced atmospheric pressure of that jet en route the your race site.

I was first confronted with this issue at Ironman Hawaii.  My local bike shop had taught me their philosophy years before and in my experience I had no reason to doubt them.  Inflate tires at purchase and “leave ‘em”, except to perhaps add air from time to time to correct for leakage.  These guys raced a lot, all over the country, and in a tradition that works well in triathlon, if it works for them it will work for me.  But here I am 6,000 miles from home, in what is likely the most important athletic event of my life, being advised to change my behavior or suffer dire consequences.  Yep, dire consequences.  By a volunteer no less.  And it seems to make sense.   Sort of.  What, if anything, should I do?

Well does it make sense?  No, not really.  If you think back to high school chemistry class you might, if you were paying attention (no, I guess not), or might not remember that there are relationships between the temperature and pressure of a gas explained by Boyle’s and Charles’s laws.  Basically they’re proportional.  In other words, as temperature rises so does pressure but it’s the amount of change that concerns us.  How much does the temperature have to go up before the tire goes kaplooey?  We know that bike tires like many other aspects of our lives are regulated and have to meet a standard.  That standard is blow off pressure, the force required to blow a tire off it’s rim. If the tire is Japanese made it’s governed by the J.I.S., the Japanese Industrial Standard.  If it’s from Germany, the D.I.N., etc.   This standard is typically double the recommended maximum inflation pressure.  It tells you that the manufacturer will test an adequate number tires, correctly mounted on recommended rims, inflated to double the maximum printed on the tire itself, and the test tires won’t explode.  If we can figure out the temperature needed to raise the tire on your bike to that pressure and stay below it, we’re golden.

Here’s where it gets complicated and some of you might want to skim to the next paragraph.  Beginning with the equation of the ideal gas law, pV=nRT, where p is the pressure of the gas, V is the volume occupied by the gas, n is the absolute quantity of gas present, R is the universal gas constant, and T is the temperature of the gas, if we constrain the system of interest to have a constant n and V, the ideal law can be redefined and we are able to compare the impact of a change in temperature on pressure. I’ll be happy to share the calculations but suffice it to say that if we assume a 70 degree day when we rack the bike, and tires set at 110 psi, we calculate the temperature needed to bring the tire to 220 psi, the blow off rating.  Still awake?

The answer is…..536.993 degrees Fahrenheit*, an unreachable result. That value is, of course, above the auto-ignition points of both gasoline and paper, and there are greater issues at hand if it is reached!  Or, as the Chemistry Phd. I pestered for the math help here pointed out, “based on these values, it is unlikely the required temperature will be reached under the conditions of ambient sunlight.”  An understatement if there ever were one.

There might be compelling reasons not to mess with your tires at the race, however.  The relationship between a wheel, tube and tire is a complex one.  I’ve been in T1 more than 30 times for Iron distance races and the biggest thing people fool with is their tires.  Some folks know a lot less about their equipment than others and when there’s a misstep in this process they’re lost.  We’ve all seen more than one racer come unglued in this situation. If the competitor has relatively new tires, has broken them in at home and is satisfied with their performance, does deflating/inflating them change their relationship with the wheel?  Does this action allow even the smallest portion of the tube to get stuck between the tire bead and wheel leading to a predictable outcome once re-pressurized?  According to Scott Paisley, owner of Blue Wheel Bike and Virginia Masters State Champion, regardless of flying or environmental temps, the only reason to ever reduce tire pressure is when packing the bike for shipment, “And it won’t fit into the box.”

So, when you say “Well I got my information from the Internet, it must be right” or you see the viral Jeff Gordon video on line (http://bit.ly/1bP0d1X) and wonder if it’s real – it’s not by the way – and it tells you that you need to be conscious of the late day sun cooking your tires into an explosion, it doesn’t hold air.




Thursday, September 17, 2015

Open Water Swimming and Jelly Fish


"Believe half of what you see and none of what you hear."

                                                       Grapevine, Marvin Gaye


"Dig Me Beach" Kailua-Kona, Hawaii

"There I was, half way thru the run in the (fill in the blank) Ironman when all of a sudden I took off like a jet!  And that's why I'm standing here on this pier a qualified athlete."  

                                                             Overheard on the Kailua pier in 2014

Triathletes are nice enough folks.  They pay their taxes, work hard, help old ladies across the street (if it doesn't get in the way of today's track workout that is.)  But when it comes to taper time before a big race like Ironman, things can get pretty deep.  I guess it's like this in any sport.  Some gal, your chief rival the year before, starts with, "you know my back is still sore despite the chiropractic care...and my shoulder, from that crash a couple months ago, still slows me in the water.  Why there are some days I trouble just getting dressed it hurts so much."  And then once the gun sounds, all you see is her tail lights.



You're not the only one (only thing?) in the water 

 I can't tell you how many times I've been "nipped" by jellyfish during an open water ocean swim.  More than 20 times I'd bet.  Kona, Boston, Chesapeake Bay, Florida, SC, come to mind quickly.  Many of us have run into a jellyfish or two either training or racing in ocean water. More of an inconvenience than anything for most of us, some poor souls have a more significant reaction. I received a note from an athlete a while back who stated a jellyfish sting allergy and she wondered about the legality of wetsuits in an important ocean swim she has in her future, I suppose thinking the wetsuit a shield of sorts.  Triathletes understand the significant differences between events held in a pool or lake and those in sea water.  Currents, waves, sighting,  etc., all are a little different and the triathlete who shows up event morning for their first effort trying to race in an ocean environment is not only stupid but risks both success and physical harm.  It's one of those times where the old adage of practice makes perfect has never been more true.

Well, our allergy athlete in question's race is the Ironman World Championship in Hawaii where wetsuits are not permitted. I've been stung in Kailua Bay a number of times, but it's always more like little needles that hurt/itch a little that day and then, like most of us anyway, it's gone. I've never even seen the ones that got me. If you're lucky, and looking ahead while you swim, which I know most of us don't do, and there's a big Portuguese man-o-war ahead, you can try and swim around it. Remember, it's tentacles can be 5-8 feet in length and have 100's of stinging cells on each. It's not uncommon after a stinging that some swimmers experience nausea, headache, muscle pain, etc., and after the initial welts subside a few are left with permanent scars.

In some locations, primarily around Australia, some jellyfish stings are so powerful that those who encounter them may need hospitalization with intravenous anti venom without which they suffer respiratory failure and and die.

So, if this fall you are stung by one, first (with gloves) peel off any left over tentacles and apply vinegar, straight from the kitchen. More involved stings may require medical attention and support from a cardiopulmonary perspective. And, always be aware of the signs of an allergic reaction - difficulty swallowing/breathing/swelling of hands, face or tongue, etc.

And how do we advise our lady with jellyfish allergy? Well, first, I told her to contact the race director and race medical team well before the event. I'm assuming that her condition has already been thoroughly worked up by a board certified Allergy Specialist.  The race medical guys need to know of the possibilities here. Second, there's a high likelihood that she can be "premedicated" before the race such that should a stinging event occur that she's covered. Sadly, in this day and age, I wouldn't be surprised if a special legal document isn't drawn up for her signature noting the risks she faces and accepts. Hey, it's 2015.

But, the take home here is that most of us, when hit by that odd jelly or two in our morning swim, simply complain about it at breakfast - maybe lunch, a little - and then it's chalked up to triathlon experience.  They might even brag about it one day. 

"Dig Me Beach," a different perspective





Photo credit: Photo 1. This was an aerial shot from race morning a couple years ago but I don't know the photographer to credit 

Friday, September 11, 2015

What Do You Break in a Bike Crash?


"I felt so good, like anything was possible."  Tom Petty

Or, 4 weeks till Kona.







Hawaii 2011-STPT 308



 We hear and read a good deal about broken collar bones be it from the Tour de France announcers Phil Liggett and Paul Sherwen describing a crash in the peleton to perhaps one of our kids Saturday soccer games.



The clavicle is the first bone in the body to ossify (turn to bone) and among the most commonly fractured, particularly in children. It can be fractured via several mechanisms including the classical fall on an outstretched arm as well as striking the point of the shoulder. It's not uncommon to also suffer rib, scapula and/or simultaneous cervical spine fractures and is seen repeatedly in cyclists.

Frequently a patient will tell me they actually heard the bone crack when the fracture occurred. This injury can be confused with an AC separation, a rupture of the ligaments at the end of the clavicle. They're treated differently as you'd suspect.. 

Displaced fractures are pretty easy to diagnose as the whole shoulder seems to fall forward and the patient describes a crunchy sound/feel. Xrays will define the specifics of the break and help guide treatment options. One also checks carefully for any accompanying nerve or vascular damage.  

For non-displaced fractures, immobilization without surgery has been the norm and usually gives good results in a short period of time. The athlete can ride the stationery bike indoors as pain permits (but not outdoors - there's no value in copying Tyler Hamilton - TdF 2003) and you should be back astride the bike by 5-6 weeks post injury. When the fracture is displaced, consideration of surgery to achieve the best long term outcome is undertaken.

In the not too distant past, collar bone surgery was considered both unnecessary as well as unwise. The old adage was "if both ends of the fracture are in the same room it will heal." Well, while a little silly, for the most part it's true.  But definitely not always.  In many displaced fractures of the midshaft of the clavicle, the separation is so great that a non-union (lack of healing) may develop or the fractures heals with a noticeable deformity (malunion.)  While frequently this is not a functional issue, anytime a male athlete is shirtless or female athlete clothed in a shoulder exposing garment like spaghetti straps, the appearance can be strikingly asymmetric.

According to a study in the 2012 Journal of Bone and Joint Surgery where a systematic search of the literature was performed on operative vs nonoperative care of displaced clavicle fractures, there can be a role for surgery in a higher percentage of patients than previously thought.  Their conclusions were, "Operative treatment provided a significantly lower rate of nonunion...and an earlier functional return when compared with nonoperative treatment.  However, there is little evidence at present to show that the long term functional outcome of operative intervention is significantly superior to nonoperative care."

So what does this mean to you?  Well, that there's still a significant role for not having an operation when you break your clavicle for one.  In fact, three quarters of the time, a completely displaced clavicle fracture treated with out surgery will heal with few, if any, long term consequences . However, "It is clear that there is a specific subset of individuals with a completely displaced midshaft clavicle fracture who will benefit from fixation."  This is especially true in the early period after the injury.  They will likely see  more rapid return to function, a decreased complication rate (particularly with regard to the serious negative out come of nonunion.)

Pete Jacobs, Lance Armstrong and Frank Schleck are three good examples of success with surgery in this setting.  But simply because a professional triathlete or bike racer makes a certain choice when given a set of facts, you don't necessarily have to do the same. Although a very successful ad campaign in the early 90's would have you "Be like Mike" referring to Michael Jordan, you have the wisdom to make up your own mind in this setting. Hey, you're a triathlete! 

So, should you find yourself with a displaced mid shaft clavicle fracture, sitting on a gurney in your Emergency Room waiting to talk with the Orthopedic surgeon on call, this may help you make the decision to go for a simple sling or the potential for repair.