Hot & Bothered Triathletes, Part 4: Getting Steamed About “Cooling Gear”

A Secret Weapon in the Palm of Your Hand?

cycling, cyclist, marathon, triathlon

We’ve done a lot of homework up to this point. By now, you are better educated on the matter of heat in endurance racing than 99% of your peers. Now that you understand the underlying science, we’re ready to cut to the chase.

What works and what doesn’t in the “extreme heat garment” market?

Let’s go down the line of a few products and assess their claims.

First is the idea of hand coolers, gadgets that propose to help keep you cool by allowing you to hold something very much like ice in your hand during your run. Among this group is DeSoto, who debuted a new and improved line of arm coolers this year just in time for the Ironman World Championships.

On their website, they claim that:

Backed by medical research proving that cooling the palms and wrists results slows the rising of core body temperature, reduces onset of fatigue, and accelerates recovery time…

The greatest advantage in palm cooling is running in heat. The purpose of this product is to keep your core body temperature from rising when “crossing that bridge” between aid stations that can provide ice, cold water, or cold sponges.hand cooling, hand coolers,

DeSoto then refers to three separate peer-reviewed studies to back up the validity of their technologies.

I dug up the three papers and read through them. There are some serious issues. Two of the three reports used a highly sophisticated unit to provide the hand cooling during testing. Priced at $800, it’s essentially a mini-fridge for your hands. Far from just inserting a few ice cubes into the palm, you actually immerse your whole hand up to the wrist in a sealed container that constantly circulates ice-cold water into it from a cooler. Therefore, the method in the research really isn’t the same thing that De Soto is offering. One report explicitly states that the device had an added advantage by sealing the hand in its own pressurized micro-environment, citing that “Hand cooling alone had little effect on exercise duration…”[1]

Given this information, it’s worth examining just how much extra heat you can remove from your body by putting an ice cube in your hands.

Let’s make some assumptions. First, let’s assume the ice is able to cover the entire surface area of an athlete’s palm, which gives the hand coolers the maximum possible chance. Second, let’s assume that an athlete wearing the arm coolers fills up on ice at every aid station on the run, and therefore never runs out of ice.

Now for a few numbers, which we’ll need for an equation.

Ice freezes at 32⁰F (274.15⁰K). We’ll assume our athlete’s skin surface temperature is 99⁰F (310⁰K).

Studies have found that the surface area of the palm of an adult human’s hand ranges between 132 and 146cm2, and a brief overview of anatomical literature indicates the maximum skin thickness on the palm of the hand is about 1.5mm. Our primary method of heat transfer is conduction (contact between skin and the ice). The equation for energy transfer via conduction, also known as Fourier’s Law, is:

palms, palm of the hand, handsRate of Heat Transfer (watts) = (conductivity of skin) x (surface area of palm) x (temperature of hand – temperature of ice) / (thickness of skin)

The thermal conductivity of human skin is estimated to be anywhere between 0.2 and 0.4 W/m⁰K.

Assuming the best possible skin conductivity, the largest hand, and that the ice is directly against the skin, the hand coolers would help you expel 280 watts of heat energy (140 watts from each hand). But if we go with less-than-ideal conditions, and assume a smaller hand and a more modest skin conductivity, our rate of heat dissipation drops to about 190 watts (95w from each hand).

Even 190 watts is actually pretty good!

It’s around 15% of your total heat production on the run. But one has to keep in mind that this requires ideal conditions. The ice is touching the entire palm of your hand and doesn’t melt. We are also not factoring the extra insulation of the hand fabric itself between your skin and the ice. In fact, these real world considerations will greatly reduce the product’s effectiveness. As the ice melts, it will approach your skin surface temperature and touch less skin. This means you will probably only experience the ideal heat dissipation rate for a few moments after each refill. You also have to consider that it will take some extra time and energy to grab ice and put it into the hand coolers at every aid station. In practice, it’s quite dubious as to whether any hand cooler product will yield a substantial benefit.

DeSoto’s product is a little more problematic, though, because it incorporates sleeves. According to their advertising, the company says that “the arm coolers do provide skin protection by blocking UVB rays to the arms and back of the hands and keeping you cool.” This is a claim made by manufacturers of several such products, but they all have one tiny problem in common—namely, choice of color. White is the go-to color for everyone’s “beat the heat” gear. Is that really the right choice? Science says not. That’s next.

1. Dennis A. Grahn, Vinh H. Cao, and H. Craig Heller, “Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment.” Journal of Applied Physiology 99: 972–978, 2005.

Does the science of speed interest you? You’ll be fascinated by Jim Gourley’s new book FASTER: Demystifying the Science of Triathlon Speed.

FASTER by Jim GourleyJim Gourley is an astronautical engineer and triathlon journalist. His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.

Hot & Bothered Triathletes, Part 3: Heat’s Toll on the Athlete’s Body

The heat’s toll on the human body and how you pay the price

In the last post, we looked at the four primary ways your body gets rid of heat as it converts food calories into energy and heat in the form of waste energy from exercise. Now we’re going to take a closer look at how much heat you naturally produce and expel during exercise. That will serve as our basis of comparison when determining if particular types of cooling garments actually live up to expectations.

runners, running, athletes, triathletes

When running, we can calculate your heat production based on the following formula:

Heat (in watts) = 4 x [your body mass (kg)] x [running speed (meters/second)]

Here’s a helpful little link to make the conversion from your mile split to that pesky metric speed. Just remember that time is decimals, so a 6:30/mile gets entered as “6.5.” Just to demonstrate, let’s get a hypothetical triathlete—yoink!

Say he’s a 145-pound (66kg) cyclist who will run a 7:00/mile split so long as it’s his local Olympic distance race.

His heat production would be: 4 x 66kg x 3.81m/s = 1,005 watts.

I have not yet been able to find a tidy equation relating an athlete’s cycling power output to heat generation. However, studies estimate comparable values, so for the sake of argument we’ll say that our hypothetical athlete is generating 1,000 watts of heat energy throughout the entire course of a triathlon. That’s 1,000 joules of heat energy every second. It only takes 4 joules to raise the temperature of 1 gram water one degree Celsius. So every four seconds, an athlete produces enough heat energy to raise the temperature of a liter (1,000g ≈ 1 L) of water one degree. That means if you could concentrate all the heat energy you produce while running and beam it into a 1-liter pot of water, you could bring it to boiling from room temperature in about five minutes. That’s some serious heat!

boiling water, boiling, hot Obviously, we don’t want to boil our blood or internal organs, so the body has to get rid of the heat like a sailor bailing water out of a sinking ship. How well can it do that? The answer is “it depends.” Let’s look at each of the four ways our bodies can get rid of heat to figure out how well each will work.

First, let’s try Radiation.

To determine the amount of heat our bodies can dump via radiation, we use the Stefan-Boltzman equation, which is:

Heat (watts) = (Emissivity of skin) x (Stefan-Boltzman constant) x (Surface area of skin) x [(Skin surface temperature in Kelvin)4 - (Air temperature in Kelvin)4]

Don’t get riled up by the math! It’s what the equation shows us that matters. (I generously do all the math for you in my book FASTER.) Using our hypothetical athlete on a 90⁰F day and assuming his skin temperature elevates to 100⁰F, we find:

Heat = .97 x 5.67×10-8 x 2 x [ 3104 - 3054] = 67 watts

1,005 watts minus a meager 67 watts = one very hot athlete!

Okay, so radiation isn’t going to help much in staying cool. (In fact, we actually radiate less heat when we race than when we just sit on the couch watching television.)

Did you notice in the formula how the rate of heat exchange depends on the outside temperature? When it gets hotter, the temperature difference totally kills your ability to vent the heat. We’ll have to try something else. Unfortunately, conduction is out the window because there’s nothing cool against our body (yet).

Next let’s try Convection.

cycling, cyclist, triathlete, triathlonWe’ll have to look at convection in two cases—running and biking—because your relative velocity changes the convection coefficient. For cycling, let’s say our cyclist can keep up a good 20mph speed into a 5mph headwind, giving him a 25mph relative wind velocity. We use the following equation to calculate the convection coefficient:

Convection coefficient = 10.45 – v + 10 x v1/2

(With thanks to http://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html)

After converting his speed to meters per second, we get

Convection coefficient = 10.45 – 11.2 + 10 x 11.21/2 = 32.7

For running at a speed of 7:00/mile into that same headwind, the coefficient is 29.

Our equation for convective heat transfer is:

Rate of convection = (Skin surface area) x (Convection coefficient) x (Skin temperature – Air Temperature)

This means our rate of heat dissipation by convection on the bike is 327 watts and on the run it’s 290 watts. Now we’re getting somewhere! So far, we’re up to getting rid of 394 joules of heat every second.

But we still have 606 joules left to deal with! This is a serious problem. So serious, in fact, the phrase “no sweat” no longer applies. It’s going to take a lot of perspiration if we want to avoid expiration.

Transpiration (aka sweating like a pig)

In hot conditions, the human body will sweat out between 1500-2000 grams of water per hour (http://www.ncbi.nlm.nih.gov/pubmed/9282540). But all that waterworks only helps if the water is evaporating.

waterfall, pouring water, Our bodies have no way to measure evaporation rates, so we keep pouring out the sweat regardless how much is already sitting on your skin waiting to be vaporized. While that puddle you make on the floor during spin class does serve to carry away some heat, it’s a negligible amount. What really counts is how much liquid gets sucked up into the air, and that depends on three factors:

  1. the speed of the air flowing over you,
  2. the ambient vapor pressure of the air,
  3. and the pressure at your skin.

Vapor pressure is a little complicated. It depends on the temperature and dew point outside. It would take too long to wander through a meteorological discussion, so instead I’ll simply provide you the link to a handy vapor pressure calculator, courtesy of the National Weather Service. For our purposes, we’ll assume a moderate dew point of 55⁰F (let’s say the outside temp is still 90⁰F). That gives us an ambient vapor pressure of 11mm Hg. For our athlete whose skin is 100⁰F, we assume a vapor pressure of 47mm Hg. Remember that our relative wind velocities while biking and running are 11.2m/s and 6m/s, respectively.

Given that, we can finally use the following equation to calculate the evaporative cooling rate.

E = 11.9vair0.6(Psk-Pa)

During cycling, that equates to 1,825 watts of heat. For running, we get 1,255 watts.

Suck it, heat! You’re dissipated!

Combined with radiation and convection, this evaporative cooling rate vastly exceeds our requirements to dissipate heat energy. Outstanding! Thanks to sweat, our hypothetical athlete doesn’t die.

This stands to reason, as the majority of athletes in the majority of races don’t keel over from heat exhaustion. But not all athletes and courses are built the same. For this overview of heat dissipation, we’ve used pretty favorable conditions. 90 degrees is about as hot as it will get at most races, but a 55-degree dew point is well within the “comfortable” region. In other words, it’s a dry heat.

lava, lava fields, hawaii, hot conditions, heatWhat happens when we turn the humidity up? As you might expect, it becomes much more difficult to get that sweat to vaporize. In conditions such as Hawaii in October, our hypothetical athlete’s heat losses due to evaporation drop to only 1200 watts (cycling) and 1000 watts (running), respectively. That’s barely keeping up with heat production, especially when you consider temperatures on certain roads through the lava fields can soar over 100⁰F.

That’s not the only place, either. Athletes can find extreme heat and humidity throughout the country during the summer, and depending on your conditions, it can cause a slow buildup of heat that will ultimately cramp your style, not to mention your legs. The question is at what point the environment overcomes our efforts, and what physiological penalties we start paying.

We’ll look at that in the next installment.

Does the science of speed interest you? You’ll be fascinated by Jim Gourley’s new book FASTER: Demystifying the Science of Triathlon Speed.

FASTER by Jim GourleyJim Gourley is an astronautical engineer and triathlon journalist. His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.

Hot & Bothered Triathletes, Part 2: Beat that Heat!

Welcome to 8th grade physics! Take a seat and we’ll talk about heat.

Last week, we talked about the problem of hot and bothered athletes. All other forces being equal, nothing slows an athlete down more than the gradual buildup of heat in the body. To avoid overheating (and death!), the body has a variety of ways to dissipate heat during exercise.

And here they are.

ice cube, cooling off, conductionConduction: This is the direct transfer of heat energy between two solid objects. It’s pretty intuitive that putting a cube of ice against your skin makes you feel cold, but for our purposes it’s important to understand why. The ice cube is cold because it has a low thermal energy state. When the energy is removed from those water molecules, they stop moving as quickly and assume the solid state of ice. Transferring thermal energy into it will increase the motion of the molecules and turn it back into water. Putting the ice against your leg creates an imbalance of heat energy between the two objects in contact (you and the ice). The laws of thermodynamics dictate that heat energy will naturally move from a high-energy area to a lower one. Your leg starts to feel cold because all the heat energy at your skin surface suddenly begins rushing into the cube. Once the heat energy of the entire leg-cube system is balanced, your skin will stop feeling cold and you’ll have a lukewarm puddle of water on your leg. This is important to understand because it means conduction is only effective as a thermoregulatory method so long as whatever object you place against your body is substantially cool enough to cause heat to leave your body faster than normal. We’ll discuss what constitutes a substantial rate later.

swimmer, swimming, swim, athlete, triathleteConvection: This is very similar to conduction, except the heat is transferred to a fluid (in the triathlete’s case, water or air) instead of a solid. Why the distinction? Because a fluid field like the atmosphere or your local pool is so large compared to your body that you can’t change its energy state the way you can with something small like an ice cube. The air and water around you is moving so much that you are also essentially “refreshing” its cooling properties on a constant basis. These are the two major aspects that make convection so effective. You have some conduction by transferring tiny amounts of heat to those air molecules directly in contact with your skin, but more important is the advection component, which is the flow of air sweeping heat off your skin surface like a hurricane blowing debris around.

The key point for athletes is that the motion of the air matters more than its temperature. For those who are curious and do a little digging, you may find sources that seem to contradict this. Here’s why. If you simply look up “convective heat transfer,” you’ll find equations and coefficients that deal with standard conditions, such as walking or running. But athletes on bikes are not working under standard conditions. The airflow around you on a bike is so great that it qualifies as “forced convection,” which means you are literally creating air conditioning for yourself. While the equations work the same, the coefficient of heat transfer is much larger, so you are working with completely different numbers. To see what this means in practical terms, try turning the A/C down in your house someday and riding your trainer at a race pace without a fan on you. You’ll quickly learn the power of cold wind vs. static cold air!

infrared, radiation, thermodynamicsRadiation: Ladies, gentleman—you are positively radiant! We all are, in fact. Heat doesn’t always need to transfer from your body into the molecules of the air or some object in contact with you. Sometimes, it just beams into space all by itself, just like light, which is also a form of energy. The difference is that heat energy beams at a wavelength that isn’t visible to the human eye, known as infrared. You may have heard of infrared (often called “IR”) devices used for night vision by the military. These sensors are uniquely adapted to detecting energy in this wavelength. The amount of heat you radiate depends primarily on the difference between your skin surface temperature and the outside air. All told, the average person emits about 100 watts of heat energy while standing still in room temperature conditions. By comparison, the average athlete generates between 900-1300 watts during exercise.

Transpiration (Evaporation): In other words, sweat. You might think that sweat needs no introduction to you as an athlete. You get hot, you sweat, it evaporates and you cool off. True enough, but there are a couple of subtleties in the process that make all the difference to you as an athlete. First of all, you don’t sweat because your skin gets hot. The physiological response that turns on the waterworks is actually a response to your core temperature. That means your body is building up heat all the way through. This has tremendous implications when you consider just how quickly you can start sweating in some situations like waiting in line for an amusement park ride or walking across a parking lot on an extremely hot day. That’s how quickly you start to cook inside!

transpiration, sweating, evaporation, thermodynamicsThe speed with which this happens once again relies heavily on air temperature. If the air around you is warmer than your skin, you no longer get rid of heat energy by way of radiation or convection. Instead, you take on heat from your surroundings! When the other three forms of heat transfer fail, evaporation is all you have left. Sweat beads up on your skin, absorbing heat from your body through conduction. Eventually, the little water droplets take on so much heat that they begin to turn into vapor. When those molecules float off of your skin, they take the heat energy with them. It’s literally our body’s last line of defense against dying in the heat, but anyone who’s ever crossed a finish line drenched in sweat understands how limited this mechanism is. Sweat only helps you when it’s evaporating. Any sweat still on your body isn’t moving heat energy off your body. Once again, the process of evaporation is dictated by the environmental conditions, namely the heat and a new enemy—humidity.

The laws of thermodynamics are harsh, indeed. That’s why the hot races are always the most punishing. Given that the proposition of heat dissipation relies so heavily on mother nature, is there really anything that clothing technology can do about it? Now that we have an understanding of the fundamentals, we can begin to answer that question.

Does the science of speed interest you? You’ll be fascinated by Jim Gourley’s new book FASTER: Demystifying the Science of Triathlon Speed.

FASTER by Jim GourleyJim Gourley is an astronautical engineer and triathlon journalist. His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.

Hot & Bothered Triathletes, Part 1: An Introduction to Heat Transfer

Conduction, Convection, Radiation, and Transpiration: An Introduction to Heat Transfer

With it becoming ever more difficult to gain performance edges in bike aerodynamics and nutritional supplements, technology is turning to a relatively unexplored realm of sports performance augmentation–the clothes on our backs. I’m going to spend the next several installments of this blog analyzing different claims about “beat the heat” garments. Before we start in earnest, it will help to go a little more in-depth about how the body deals with excess heat during competition. Some of this will be review from the book, and some of this will be new material.

ironman triathlete, triathlete, triathlons, cycling, cyclist

Substantial research on endurance sport clothing began ahead of the 2000 Summer Games in Sydney, which produced everything from body-length swimsuits to hooded track suits. Much of the research was then applied to time trial suits for professional cyclists. All of this was in the name of better aerodynamics (or hydrodynamics, in the case of the swimmers). This has some utility in long endurance events, but more concerning to long-course racers than cutting through the air is staying cool in it.

As discussed my book FASTER: Demystifying the Science of Triathlon Speed, heat dissipation is the predominant limiting factor on speed once you begin the run portion of any triathlon. That’s because your speed decreases significantly while maintaining the same level of physical exertion. Without all that airflow passing over your body, you lose a major resource for heat dissipation. And, depending on your local conditions, you could also suffer heat-induced injuries even while on the bike.

Drinking water and maintaining electrolytic balance is key to succeeding in extremely hot competitions. But beyond certain temperature, humidity, and exertion limits, there’s only so much hydration can do. Other forms of physiological damage become unavoidable as heat continues to accumulate in the body. The only remedy is to find a way to expel heat faster. Sports apparel manufacturers have taken note of this and are now pursuing methods to expedite heat transfer from the body.

Swimmers, triathlon, triathlete, swim

It’s not an easy problem to solve.

If you think the law of gravity can be a real pain while climbing up a hill, try the laws of thermodynamics on for size! They have been used to suggest everything from the cause of global warming to the theory that the entire universe will die someday. So, thermodynamics isn’t exactly the best field of research in which to find cheerful optimists.

Indeed, there are major limitations on staying cool. The body releases heat through every method of heat transfer possible, and they are still not enough to dissipate all the excess energy in hot conditions. Let’s quickly review those methods to establish a basis of comparison.

Next week, please join me back in 8th grade physics class for a refresher on how heat dissipates from the body.

Does the science of speed interest you? You’ll be fascinated by Jim Gourley’s new book FASTER: Demystifying the Science of Triathlon Speed.

FASTER by Jim GourleyJim Gourley is an astronautical engineer and triathlon journalist. His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.

Ask the Scientist: To Glide or Not to Glide, That Is the Question

FreeTriSpeed got this reader question from Ken V. on swim technique. Do you have a question on the science of triathlon? Ask the Scientist!

“Great website and book. Your work is both technical and entertaining (hard to do!) and much appreciated.

I have a question regarding the swim. I know there are many different schools of thought on “the best way” to swim. I just have a technical question about one portion of the swim stroke–the glide. Or more precisely, “to glide or not to glide” is the question.

There seem to be two popular swimming “systems” out there that oppose each other.

Pitch of hand, swimming, swim strokes, triathlons, triathlete
ITU world champion Sheila Taormina, now a triathlon swim coach

1. One school believes that incorporating the glide reduces energy expenditure, making it easier to complete the swim, and allowing a more efficient use of the body.

2. The other school says to eliminate the glide as much as possible, claiming it reduces your momentum, forcing you to expend more energy to resume your speed with each stroke before you started slowing down during the glide. They say to basically increase your stroke rate, thereby avoiding any loss of speed, which would overall result in a faster swim and less energy used. However the pro-glide people would say that such a high stroke rate would once again increase your overall energy expenditure, slowing you down.

So my question is: what’s more efficient in terms of energy expenditure per unit distance covered in a swim? Less total swim strokes but including a glide, or more total swim strokes but no glide? Triathletes looking to lower their “energy leaks” are ready and waiting.

The obvious follow-up question which begs to be answered for all the speedsters out there is much harder to answer for sure (maybe impossible): which would be more favorable in a race? Would you tire out with the high stroke rate and end up slowing down anyway (the old tortoise and the hare theme here)? Or is it beneficial, akin to the higher RPMs in cycling and increased cadence in running that coaches love to talk about? Would you really gain more distance per stroke if you use a glide, perhaps resulting in a slower swim time but less overall energy used, which could be used for the bike and run? Tough question, I know.

Thanks, Ken V.”

Jim Gourley’s reply:

Thanks for the question! As you rightly observed, this is a complicated issue. It involves competing requirements (speed and efficiency) and a good layout of the principles at work. You’ve pretty much done all the work for me in accurately defining the problem.

With the issues clearly defined and the variables placed in such opposition, there’s only one thing left to do: collect data. Thankfully, another group of researchers thought of our problem before you and I did, and went out to collect the very data we need.

http://www.feelforthewater.com/2012/12/the-data-on-stroke-rate-and-efficiency.html

The data in that report clearly indicates that there is in fact a higher energy cost associated with a lower stroke rate. This is due to the energy required to hold the body in correct position as the arms slow down. That’s not something that could be predicted without experimentation, which is why direct observation is so important.

swimming, swimming stroke rate, swim cadence, triathlon, triathlete

It’s also remarkable that trained swimmers’ preferred stroke rate seems to be almost the most efficient, or just a little less than the optimal condition. After accelerating their rate beyond a certain point, the energy cost increased again.

There are a few tri-specific conclusions we can draw from this:

  1. First, your energy cost will probably increase even more than the swimmers in this study due to open water conditions. A high stroke rate is even more important to you due to the turbulence and destabilizing obstacles (i.e., other people).
  2. Second, keep in mind that these are trained swimmers, and most triathletes (according to data) are not. Your personally-selected stroke may or may not be the most optimal for you due to technicalities in your form.
  3. Finally, we can reasonably conclude that training will increase your VO2 and therefore allow an increased stroke rate for greater speed with lower energy cost. This training does not necessarily have to be swimming.

Hope that helps and good luck in your training and racing going forward!

Do you have a question that’s always bugged you about swim-bike-run? Ask the Scientist!

FASTER by Jim Gourley

Jim Gourley is an astronautical engineer and triathlon journalist who has written on the science and technology of triathlon and cycling for Triathlete, Inside Triathlon, LAVA, USA Triathlon, and 3/GO magazines.

His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.

 

Evil Twins, Triathlon’s Draft Box, and Race Day Interval Workouts

In last week’s post, we learned that the triathlon rulebook specifies an unnecessarily wide gap between two triathletes riding their bicycles.

Science talks about things in terms of space and time, and so does the rulebook. To avoid penalties in a no-draft race, you have to overtake your competitor within 15 seconds of initiating a pass. Otherwise, you’re compelled to give up the chase and back off 7 meters again. Let’s examine what happens.

Consider the following example. Two triathletes, a competitor and her evil clone, are racing down the road on identical bikes. They start out of the transition area with exactly seven meters between them per USA Triathlon regulations on a totally windless, flat stretch of road, travelling at 20mph. Evil clone is leading and our friendly, law-abiding triathlete is second out of transition. Our law-abiding triathlete’s immediate desire is to pass her doppelganger.

Triathletes, triathlon, race, draft-box, passing

At 20mph, the evil twin will cover 134.1 meters in 15 seconds (sorry for the unit-swapping, aerodynamics works best in metric). To put her front wheel ahead in that same time, our heroine will have to travel 141.1 meters. When you back out from that number, you find that she has to move at 21mph to get ahead. In fact, no matter what initial speed the two competitors start at, the passing athlete has to put in an extra mile per hour to be legal according the USA Triathlon’s drafting rules. Simple enough, right?

Not quite. Our law-abiding triathlete needs to put out the necessary power to pass her leading evil clone, but she can’t accelerate to that speed instantaneously. So the question becomes how much more power is required to pass legally? To figure that out, we use a rather complicated equation.Faster Jim Gourley passing formulaWhat this essentially says is that power is based on acceleration, velocity, mass of rider and bike, the coefficients of both air and rolling resistance, and the gradient of the road.

(There is actually a much more enjoyable and informative way to experiment with this and other physical factors of cycling. Check out the website www.analyticcycling.com for great “calculators” that graph performance and offer invaluable nuggets of wisdom about aerodynamics.)

Courtesy of math, we learn that at 20mph our 130-pound triathletes riding 17-pound bikes need to sustain an approximate output of 138 Watts. But to accelerate and cover the greater distance necessary to legally pass in fifteen seconds, our fearless rider will have to ramp up to around 185 Watts! That’s an extra 47 Watts.

And 47 Watts is kind of a big deal.

For heavier athletes at higher speeds, the increase is even more dramatic. But when you allow the trailing rider to close the gap by those two-and-a-half meters that don’t give any draft advantage, it reduces the power output needed to pass to only 168 Watts. That’s a major savings in terms of effort.

triathlon, triathletes, passing, draft box, cycling

The USA Triathlon drafting rule requires triathletes to put forth gargantuan exertions to bypass a non-existent “cheating zone.”

We’ve all felt the consequences. What should be endurance races are at times turned into fitful sprint intervals workouts coming out of transition followed by an exercise in mind-over-lactate buildup.

Race officials could still make the argument that the draft box promotes safety by avoiding collisions, but my counterpoint would be that safety would be improved if races had more course marshals to better enforce the rules.

It’s my suspicion that accidents often happen as a result of someone trying to “equalize” what they view as someone else’s cheating. In the meantime, cutting the draft box would at least put those who play by the rules on a more equal footing with those that don’t. It’s simple math and common sense.

Does the science of speed interest you? You’ll be fascinated by Jim Gourley’s new book FASTER: Demystifying the Science of Triathlon Speed.

FASTER by Jim GourleyJim Gourley is an astronautical engineer and triathlon journalist. His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.

Thinking Inside a Smaller Box: How Current No-Draft Rules Penalize Honest Triathletes

In my last post I discussed the advantages of riding close to someone else’s rear wheel and how such considerations influence strategy in draft-legal races. Those aerodynamic benefits are also the source of much anger in races that don’t allow drafting.

triathlon cyclist, triathlons, triathletes, cyclists, cycling

Cheating is an often-discussed problem in long-course racing and the popular consensus is that illegal drafting is epidemic even at the top levels of the most sacred racecourses in the world. This post will probably do little to assuage the hurt feelings, because it reveals an underappreciated benefit of cheating:

Not only are cheaters getting an unfair advantage, law-abiding triathletes actually get penalized for obeying the rules. You get punished for doing the right thing not once, but twice.

Let’s start by setting up the problem.

Here is USA Triathlon’s “draft box,” which is used as the standard in all USAT-sanctioned races that don’t allow drafting. The rules state that the closest legal distance between two athletes is a 7-meter space between the front wheel of the lead rider to the front wheel of the trailing rider. This is problematic enough in the first place, as any sensible cyclist would gauge their distance off the rear wheel of the person they’re following. Because that’s the wheel they can see! But it doesn’t make sense when you look at it from a scientific standpoint, either.

Faster Jim Gourley USA Triathlon draft boxWe’ve already analyzed the merit of this box in our last post, coming at it from the viewpoint of a draft-legal situation. The 7-meter rule certainly keeps the pursuing athlete from cheating. But our analysis in this post showed that you don’t actually start drafting until you get much closer than that. There’s no aerodynamic benefit until the distance between athletes is less than 3 meters (this is distance between rear wheel of the leading rider and front wheel of the following rider, see diagram). Estimating the length of a bicycle to be 1.5 meters, it doesn’t take a geometry whiz to realize that USA Triathlon’s draft box is keeping triathletes much farther back than is really necessary. You could debate exact measurements, but approximately 2.5 meters could be chopped off the draft box without giving anyone an unfair advantage. That’s just a little over 8 feet.

How big a difference can that really make for people who obey the rules?

As it turns out, a very big one when you consider the other half of the problem. Join us next week as we explore: Evil Twins, Triathlon’s Draft Box, and Race Day Interval Workouts.

Does the science of speed interest you? You’ll be fascinated by Jim Gourley’s new book FASTER: Demystifying the Science of Triathlon Speed.

FASTER by Jim GourleyJim Gourley is an astronautical engineer and triathlon journalist. His new book FASTER takes a scientific look at triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and race times. With science on your side, you’ll make the smart calls that will make you a better, faster triathlete.

FASTER is now available in your local tri shop or from these retailers:

FASTER is published by VeloPress, leading publisher of books about triathlon. See more books for triathletes at www.velopress.com/category/triathlon.