Let’s start by describing the issue. The human body generates a great deal of heat [...]]]>

How do we stay cool when running in hot weather? In my last post, I challenged race directors to reconsider the growing practice of including moisture-wicking technical shirts as race “swag.” That resulted in a slew of questions and comments ranging from skepticism to recommendations on staying cool when running in hot weather. I’m going to address all these issues here.

Let’s start by describing the issue. The human body generates a great deal of heat when running. Our bodies are only about 25% efficient, meaning the metabolic processes that keep us alive and keep us moving down the trail (or Shiva forbid- a road) results in 75% of all energy burned being wasted as excess heat. We’re basically a big furnace.

In cold weather, this is a good thing. As long as we fuel the furnace, that generated heat will keep us warm. Even though the outside temperature is lower, our body still has to shed the excess heat. We do this via four mechanisms: Radiation, conduction, convection, and evaporation. All four mechanisms move heat from the hotter human body to the cooler area outside the body.

In hot weather, things get a little dicey. We begin to lose the ability to shed heat, which increases the danger of hyperthermia, which can lead to heat stroke and death. Let’s look at each in detail.

Heat Transfer

• Radiation: Radiation occurs when infrared energy is emitted from an object to surrounding objects when no physical contact exists. This is how the sun heats the Earth. Your body sheds some heat via radiation. If you’re wearing any sort of clothing, some of that radiated heat will be reflected back to the body.
• Conduction: Conduction occurs when two objects come in contact with each other. The second law of thermodynamics explains how heat is transferred from the warmer to the cooler object until they are the same temperature. This is how a heating pad works. Or why your cold water in your handheld water bottle quickly warms up even on cool days. Our body normally transfers heat to our clothing and surrounding air via conduction. This is also why we can cool down faster when swimming- water is more efficient at transferring heat than air. It’s also why we thaw our Thanksgiving turkey in a sink full of water instead of just leaving it on the counter. This idea plays a role in the mechanism behind the “soaking-wet-shirt phenomenon I’ll discuss later.
• Convection: Convection involves the loss of heat through the movement of molecules of air, water, or other such “stuff” across a surface (such as our skin.) The greater the movement of a substance across a surface, the greater the heat loss. My friends in the north are familiar with this idea in the winter when we experience wind chill. This is also why we use fans in warm weather. For our purposes, we just need to know that moving air cools faster than stagnant air.
• Evaporation: When a liquid is converted (evaporates) to a gas, heat is lost which produces a cooling effect. This is the purpose of sweat- our body emits the liquid to our skin, then it evaporates into the surrounding air. This mechanical process produces a cooling effect, which in turn cools the skin. For those folks living in the desert, this is the principle behind a swamp cooler- the evaporation of water will cool the air, which can then be circulated to cool a living space.

Bodily Mechanisms

Okay, so those are the mechanisms our body uses to cool itself. Our body employs a few strategies to maximize these processes, including:

• Sweating: Our body produces sweat which is evaporated on the skin, thus cooling our skin. Some people seem to believe sweat cools by mechanically eliminating heat from the body, which is false. Sweat cools because it evaporates. We consume water to replace the water lost via sweat to prevent dehydration. In an environment where evaporation is difficult (high humidity), evaporative cooling is less efficient. It’s important to note that sweating has a finite cooling potential. Many runners believe they can combat any heat as long as they drink enough, which is NOT the case.
• Vasodialaton: the small capillaries near our skin widen allowing more blood to circulate near the surface of our skin. Our skin is cooled via evaporative cooling from sweat, which cools the blood via radiation, convection, and conduction. The cooler blood is then routed to our body core to help cool our organs… much like the radiator in a car.
• Our body hairs flatten. The tiny hairs that cover our bodies relax via tiny muscles, which increases air flow over the skin (and heat loss via convection.)

Environment

All of these systems work together to allow us to exercise in hot weather. At some point, the environmental conditions will become harsh enough where we begin to lose a few of these cooling options.

For example, when the ambient air temperature is above the temperature of our skin, our body can no longer shed excess heat via via radiation and conduction. In fact, our body absorbs heat from the environment.

Humidity is an issue, too. When the air is saturated with water vapor (100% relative humidity), sweat no longer evaporates, thus eliminating the evaporative cooling effect.

Radiation from the sun is a rather obvious environmental issue, but still worth mentioning. Direct sunlight is going to increase solar gain whereas shade from clouds, trees, or a hat are going to decrease solar gain.

Finally, a lack of air movement can be problematic because we lose the ability to shed heat via convection. A nice breeze will keep you cooler than perfect calm.

Before we get into the discussion of clothing choice, we need to consider the role of insulation. Here in the U.S. we measure this with r-value, which is an expression of a substance or object’s ability to reduce the rate of heat flow. Any clothing will produce an insulation effect by disrupting radiation, conducton, convection, and/or evaporation.

Effects of Clothing

Clothing can either enhance or disrupt each of our body’s cooling mechanisms. Many clothing choices have both pros and cons. Some are dependent on the environment. A few choices may be made based on perceived comfort over actual thermal regulation properties. Needless to say, there’s a lot of personal preferences involved.

All clothing is going to create a radiant barrier that will reflect the radiant heat given off by the body. The lighter the color of the interior of the material, the more pronounced the effect. Think of those silver foil emergency blankets- they work because they reflect a great deal of radiant heat (they also greatly reduce convection because they’re non-porous.) Clothing can also reflect radiant heat from the sun. A hat can shade the upper body, for example.

Speaking of convection- any clothing that prevents air from penetrating will greatly reduce convective cooling. No air flow = no convective cooling. This is usually the goal of outer shells for cold weather activities. In addition to convective cooling, fabrics that prevent airflow also prevent sweat from evaporating which further reduces their cooling potential.

The more air a fabric traps, the greater the r-value (the more it prevents heat transfer.) This is usually why thicker fabrics keep you warmer. When a fabric becomes saturated with sweat (or water), the water is much better at transferring heat than the trapped air. As a result, saturated clothing won’t keep you as warm (or will keep you cooler depending on your goal) as dry fabrics.

It all seems pretty logical, doesn’t it? How about this riddle- the goat-herding Bedouins of the Sinai Peninsula live in a desert where temps routinely top 100 degrees F. Their preferred clothing?

Thick black robes.

At first it seems to defy logic because black absorbs solar radiation from the sun and the thick robe inhibits conduction, convection, and evaporation, right?

Wrong.

Since it’s a loose-fitting robe, air can flow freely inside. The sun heats up the fabric, which heats the air inside. Hotter air rises which pulls cooler air from the bottom as the hottest air escapes the top. This airflow promotes convective and evaporative cooling, which keeps them cool.

If you understand the science of heat transfer, the mechanisms the body uses to cool itself, and how various clothing affects both, you can begin to make educated clothing choices.

So What Do We Wear When Running to Keep Us Cool?

Should we all run in thick black robes?

Probably not. The Bedouins aren’t running around. They’re not producing as much heat as a runner would, so there’s less excess to shed.

A better option is to use a method that utilizes as many principles discussed above as possible.

Naked (or minimally-clothed) is among the best options. If there’s no clothing to interfere with radiation, convection, conduction, or evaporation, we should be able to stay cooler longer.

We may still outrun our cooling capacity. In that case, we have to stop generating as much heat by slowing down, stopping, and/or utilizing an external cooling mechanism like sitting in a cool stream.

Some clothing items may help, like a wide-brimmed hat in sunny environments. It will provide shade for our head and upper torso which reduces solar gain. A straw hat that allows airflow would be ideal.

If clothing must be worn, loose-fitting options would be ideal because they allow air to pass (promoting evaporative and conductive cooling.)

Fabric type does matter… which is the crux of my anti-tech shirt rant. In hot, dry conditions, a tech shirt mechanically moves sweat from the skin to the surface of the shirt. In theory, the sweat would then evaporate from the surface of the shirt which cools the shirt (evaporative cooling) then cools the skin via conductive cooling (heat moves from hotter skin to the cooler shirt.)

There’s two significant problems with this theory. First, sweat evaporating on the skin is going to have more “cooling potential” than sweat evaporating off the shirt then cooling the skin via conduction. Second, the shirt fabric itself acts as an insulator to heat transfer because it traps air.

These problems disappear if the tech shirt is hydrophllic (the fabric absorbs water) and becomes saturated. The wet shirt clings to the skin. Since water is a better conductor of heat than air, the cooling on the surface of the shirt cools the underlying skin much more efficiently. It’s not as good as naked skin, but a lot better than a non-saturated shirt.

Materials like cotton, which become saturated much easier, will keep you cooler because this effect occurs sooner. Unfortunately, clingy, drenched clothing is uncomfortable and usually chafe underlying skin easier. Many people prefer tech shirts because they stay drier. That’s an entirely valid reason to use them… as long as the other principles are understood.

So What Should You Use?

Experiment. Test out a variety of fabrics. Figure out what conditions require specific types of clothing. Don’t disregard bare skin. In the event you’re overheating in hot weather, consider the effects of your clothing choice. If you’re interfering with even one of your body’s natural mechanisms, you may be handcuffing your cooling capacity.

Also remember your body can only cool itself so much. When the ambient air temperature rises above your skin temperature, you lose a lot of cooling potential. Same deal with high humidity. Drinking more water won’t help because you’re already sweating at capacity. Walk a bit. Sit in the shade. Place an ice-filled bandana around your neck. Train for heat acclimation.

A thorough understanding the science behind heat transfer and thermoregulation helps immensely. It helps you become a better consumer of products that supposedly “keep you cool.” It also helps you improve your self-experimentation abilities.

Good luck and stay cool!

 ###

Like the idea of self-experimentation and running? You’d probably love the Squirrel Wipe book! Check it out here!

                          

I understand you have undertaken a thankless job. You put in countless hours to assure your event is well-organized. I also understand you receive a slew of dumbass requests. Hopefully some of you will consider this request even though it directly contradicts the accepted logic most runners ascribe to.

Please stop distributing moisture-wicking tech shirts.

Why you ask?

Quite simply, they’re endangering the lives of runners that falsely believe their [...]]]>

Dear race director friends:

I understand you have undertaken a thankless job. You put in countless hours to assure your event is well-organized. I also understand you receive a slew of dumbass requests. Hopefully some of you will consider this request even though it directly contradicts the accepted logic most runners ascribe to.

Please stop distributing moisture-wicking tech shirts.

Why you ask?

Quite simply, they’re endangering the lives of runners that falsely believe their clothing will help keep them cool in hot weather. Many runners believe the tech fabric’s ability to transport sweat away from the skin helps cool the underlying skin.

In reality, it robs their bodies of the evaporative cooling effect, thus raising their body temperature instead of lowering it. Sweat evaporating off the surface of the shirt doesn’t cool the skin under the shirt with nearly as much efficiency as naked skin.

In short, most runners don’t understand how their body thermoregulates.

To combat this overheating, many runners will attempt to drink more water or sports drink which increases the danger of hyponatremia.

I touched on the topic in this post here and here last year, and is a major topic in the Squirrel Wipe trail and ultra book.

I’ve done several reviews of the literature to find any empirical evidence that moisture-wicking fabric actually lowers core body temperature. Not surprisingly, none apparently exists.

There are studies measuring perceived comfort where tech clothing is rated as more comfortable than natural fibers like cotton, but the research is silent on the issue of thermoregulation. Yet clothing manufacturers continue to churn out moisture-wicking clothing with the implied or expressed promise it will “keep you cool.”

In reality, moisture-wicking clothing was developed for low-intensity cold weather activities that required frequent stops (i.e., hiking.) For that purpose, it works wonderfully. It also works well for areas that remain covered, thus preventing air circulation (think socks and underwear.) For hot-weather exercise, it’s flat-out dangerous. Not only will hyperthermia reduce performance, it can lead to heat stroke and eventual death.

Race directors can help correct this deception by refraining from distributing moisture-wicking clothing, especially in hot-weather races. Please stop contributing to the idea that this clothing will keep you cool. You could potentially save the lives of your fellow runners.

Thank you for your time, I know it is valuable.

Appreciatively yours,

-Jason Robillard

###

Runner friends: Please help me spread this important message and forward this post to any race directors you may know.

                          

The situation also produced a hint of personal responsibility, much like a teacher feels when a former student drops [...]]]>

Yesterday a friend posted a rather cryptic status in Facebook. Their spouse had left for a trail run hours earlier and was not responding to texts. It produced one of those sinking feelings you feel when bad shit starts to unfold. Based on the comments, it was obvious the friend had little information to relay to the authorities.

The situation also produced a hint of personal responsibility, much like a teacher feels when a former student drops out of school or commits a heinous crime.  That “I could be doing more to change the world for the better” feeling is what once motivated me to write The Barefoot Running Book and set out to change how we perceive running shoes and gait.

Despite the flippant title and not-so-serious tone, Never Wipe Your Ass with a Squirrel had a similar goal- teach trail runners and ultrarunners some very basic knowledge that may someday save their lives. The following excerpt is the most important part of the book. Every trail runner should always follow these steps.

Oh, and the friend’s spouse? They were fine. It seems they were running in an area that did not receive phone reception. Anyway…

Preparing For Trouble

What happens if you get lost? Or hurt? For anyone venturing into the wilderness, this is a real possibility. Preparing for trouble can help keep you safe. The more remote the area, the more important good preparation becomes. Follow these simple tips.

Before you leave for your run

ALWAYS tell someone where you are going, when you plan on returning, and who to contact should you fail to return. Exact information could include the trailhead where you will start, the number of people in your running group, gear (food, water, fire-starting equipment, clothing, shelter, etc.), your experience level, maps and compass, and your planned route. All of this information can be used by search and rescue to help plan a search effort.

Give the person an exact time you plan on returning. Give yourself some wiggle room in case you’re delayed. Instruct them to attempt to call you first in case you forget to call them. If they don’t get a response, give them an emergency contact number based on the area you’re running. They will forward all your information to the authorities, which will forward it to the search and rescue agency.

In the event this isn’t possible, you can leave a note with the same information in your car at the trailhead. If you don’t return, search and rescue will locate and search your car. I’ve never been a fan of this because I don’t want to advertise my whereabouts and return time to prospective thieves. If you do this, leave the note folded on the dashboard.

If the trailhead has a register, fill it out. Search and rescue will also use this to locate you.

Don’t pull an Aron Ralston.

If you do get lost or hurt

Knowing how search and rescue operates is useful to maximize their efforts to find you. First, stabilize any injuries and move to a safe place. For example, if you’re bleeding, stop it. If you’re on top of a summit during a thunderstorm, move to lower ground. If you’re in a floodplain during a rain storm, move to higher ground.

Second, assess the situation. If there’s a very good chance of finding your way out of trouble in a timely manner, a storm is closing in and you don’t have a means of building a shelter, or you didn’t tell anyone where you’re running, try navigating out. If not, stay put. If people are searching for you, moving makes it much more difficult to locate you. Understanding how search and rescue works will greatly increase the chances of being found. This is the process search and rescue (SAR) usually uses to locate lost runners.

Search and rescue efforts usually start with teams checking obvious locations in the event you’re not really lost, like your tent, car, or home. This is done in the event you didn’t have a means (or forgot) to contact the person that reported you missing.

The SAR team begins the actual search by determining your last-known location. They calculate the time that has elapsed since you were last seen and how fast you were likely traveling. Using this data, they can determine the size of the search area.

Before beginning the actual search, the SAR team will post people on roads, trails, and streams or rivers around the boundary of the search area. This serves two purposes. If you’re moving, there’s a chance you will run into one of the SAR team members. This also helps assure the search area doesn’t enlarge over time since it will be unlikely you’ll pass by one of the containment team members. This is the reason staying in one place is important- moving out of this search zone will dramatically increase the time it takes to find you, since the initial search zone will be thoroughly searched first.

The search team will then dispatch small teams to quickly search the zone. They will check any place people may go when lost or injured such as shelters or caves, or check obviously dangerous places like cliffs. The goal of this stage is to end the search quickly, so the searchers aren’t especially thorough.

Shortly after, SAR may dispatch helicopters or airplanes to search from the air. They will look for signs like fires, shelters, or signals and notes left on the ground. They may or may not use heat detecting technology.

SAR may also use signaling methods like whistles, car horns, or yelling. If you hear any of these, attempt to respond. If possible, head toward the signals. It’s a good idea to mark your path in some way. This allows you to return to your shelter if needed and creates a series of clues if SAR stumbled upon your path.

If the initial search is unsuccessful, the SAR team may expand the search zone or, more likely, use a grid search of the area. The team will section off the area, then have searchers thoroughly search each section of the grid for any clue they can find. This is a very slow, manpower-intensive process and usually reserved for times when they are searching for an incapacitated person or a body.

You can greatly increase your chances of being found by following a few guidelines that will assist SAR.

Step one: Get safe. If you’re in a dangerous place (possible rock slides, avalanche zone, ridge or summit during a thunderstorm, a flood plane, etc.), move to a safe location. If you’re injured, administer appropriate first aid.

Step two: Protect yourself from the elements. The greatest danger in a survival situation is exposure. Heat or cold can kill a human surprisingly fast. If you are close to a known shelter, take refuge there. SAR will likely search those first, so it increases your odds of being found. If not, use whatever you have at your disposal to build a makeshift shelter. If you are prepared, you should have an emergency blanket and some cord. This can be combined with trees, sticks, or other natural elements to build a simple lean-to shelter.

Shelter placement is a tradeoff between visibility and protection. If you built the shelter in an open area, it is more likely to be seen from above. However it also exposes you to the elements. It’s probably a better idea to build the shelter near a bare hilltop or clearing, then construct signaling devices in the open areas.

This step should also include building a fire if the weather is colder. A small fire build near the open side to a lean-to with a reflector on the opposite side will provide plenty of warmth.

Step three: Build signals for SAR. Make your presence known. The universal distress signal in the United States is a grouping of three. It may be three signal fires built in a triangle, three piles of rocks or clothing, three blasts from a whistle, etc. The ideal location is an open area that can be seen from a distance such as a bare hilltop or large clearing. Here are a few options for signaling:

• Signal fires. The smoke from a fire can be seen in the daytime and the flames can be seen at night. To increase the smokiness, add green pine needles or leaves.

• Clothing arranged in an “X.” Bright clothing can be seen from a long distance. If you have an abundance, leave a clothing “X” in a clearing near your shelter.

• Signal mirror. I don’t usually carry a mirror when running, but they are a great signal device.

• Rocks, logs, or dirt arranged in the shape of messages. Use whatever you have available to create notes in open areas. Write the letters “SOS” if possible, otherwise arrange three piles in a straight line or a triangle. If you move, also include an arrow pointing toward your direction of travel.

• If you see or hear an aircraft, find an open area and lie flat on the ground with your arms and legs spread. The goal is to be as noticeable as possible.

Step four: Procure water. After exposure, dehydration is the next danger. Humans can live about three days without water. If you have water, use that. Some people recommend rationing, others suggest drinking normally. There are merits to both approaches. I prefer to ration because it’s psychologically demoralizing to run out of water. Regardless of the approach, it’s important to avoid heavy exertion. Sweating wastes water.

I discuss methods to find water in an earlier section, including methods to purify potentially dangerous water. Drinking untreated water has risks ranging from illness to death. If you’ve exhausted your water and are in danger of dehydration, it may be worth the risk of drinking untreated water. Most illnesses may take a week or more before symptoms show up. If people are searching for you and you followed all the advice in here, you’ll be found before it becomes an issue.

Step five: Find food. Food is the last step because humans can survive for weeks without food. While it may seem like an immediate concern, the other steps are FAR more important. If you’re trapped in the wilderness long enough to starve, you probably didn’t tell someone when or where you were running. Even then, it’s unlikely that you would have remained missing.

If you DO need food, being familiar with local flora and fauna will help. As a general rule of thumb, most furry mammals can be eaten. So can snakes (cut the head off far enough back to remove poison sacs on poisonous species), fish, and insects that aren’t furry, brightly colored, or sting. Plants are more of a mixed bag. Some are okay, others will make you sick. Some will kill. It’s best to consult a field guide specific to your area for better information. Or use Google. It’s quicker.

These steps constitute the most basic of survival tactics. Nothing can replace field experience. If you plan on spending a lot of time in the backcountry, a survival course taught by qualified instructors can be an awesome addition to your knowledge base.

                          

And I like the nomenclature because it’s mildly antagonistic.

It perfectly explains the parenting strategy Shelly and I use. We let them play unsupervised, which often involves wandering around [...]]]>

While doing some research for a new project, I came across the term “benign neglect.” As a parenting style, it involves allowing your kids freedom to well, be kids. Let them explore their world. Solve their own problems. Take their lumps when things don’t go so well.

And I like the nomenclature because it’s mildly antagonistic.

It perfectly explains the parenting strategy Shelly and I use. We let them play unsupervised, which often involves wandering around our campground without us in tow. We let them interact with people of all ages in every imaginable setting. We let them make messes and get dirty. We give them the freedom to try new things even if we know they can’t (they often surprise us.) We let them fight their own battles.

We’re here for support if needed, but otherwise let our kids do their own thing. If they encounter a problem, we make them solve  it. Our kids have heard the phrase “Work it out” thousands of times. If they absolutely can’t, we may offer advice. We’re the safety net that assures there’s no lasting harm.

The purpose is simple- we want our kids to develop the skills needed to successfully navigate adulthood. A day will come when we’ll kick them out of the nest. I’ll be damned if I want them flying back home.

But what about boundaries and responsibility?

Our kids have clear boundaries, but they also have the freedom to more or less do as they please within those boundaries. And responsibility? That’s developed through the make a “decision and face the consequences of your actions” process.

[Edit: This section was added after Becky's comment.]

What about safety?

This is the number one question I receive. Parents worry about the safety of their kids… that’s a given. How do you give kids freedom in this great big evil world we find ourselves in today?

First, by pretty much every objective measure, our world is safer than it was when we were kids (or our parents were kids.) The difference is one of perception. We’re no inundated with news of murder, rape, kidnappings… whatever. If anything, we should feel better about our kids having more freedom than our parents did. Unfortunately, too many parents buy into the notion that would world is a scary, dangerous place.

Second, if our world really were so scary and dangerous, wouldn’t that be an even better reason for kids to learn to survive without parental protection? Greater adversity requires better coping skills.

[end of edit]

The strategy is the exact opposite of the helicopter “I have to protect my kid from everything or else I will feel insanely guilty” approach so many parents use today. These parents want to give their kid every advantage, which ironically leaves them completely unprepared for life outside the womb… er, I mean watchful eye of the parent.

As a teacher, I routinely saw the results of helicopter parenting… and it wasn’t pretty. Kids were on the brink of adulthood but couldn’t do much of anything without parental intervention. Kid failed a test? I could expect an angry call from mom. Shiva forbid she tell her lazy-ass kid to deal with it himself. It was a sad sight.

Give your kids freedom, even if it means they may get hurt, fail, or face other adversity. Bruce Lee said it best:

“Do not pray for an easy life, pray for the strength to endure a difficult one.”

As a parent, there’s no need to rely on prayer for your kids to develop strength. Giving them freedom to live their lives will give them the strength to endure a difficult life.

Many of my readers are parents. What do you think? Share your comments!

###

                          

This universal question is always at the forefront of my curiosity about others. Why do we make the decisions we make? What is the fuel that motivates us? I love seeking these answers n others because it helps understand my own self.

Runners are even more fascinating. Why do we run? In the case of ultrarunners, this question becomes even more pertinent. What drives us to run for [...]]]>

Why do we do the things we do?

This universal question is always at the forefront of my curiosity about others. Why do we make the decisions we make? What is the fuel that motivates us? I love seeking these answers n others because it helps understand my own self.

Runners are even more fascinating. Why do we run? In the case of ultrarunners, this question becomes even more pertinent. What drives us to run for hours and hours, often in solitude?

What about those that make radical life changes? For example, packing up and moving 3000 miles? Or quitting your job, moving into an RV, and traveling the country seeking running adventures?

Vanessa Rodriguez answers all of these questions in her book The Summit Seeker. Vanessa provides a behind-the-scenes glimpse into her fascinating life via a series of stories beginning with her childhood through the present day.

I’ve known Vanessa for a number of years. Back when barefoot running was all the rage, a bunch of us regularly posted on the Runner’s World barefoot running forum. Many of us have remained friends after we moved on to other things. Vanessa is one of those friends.

Vanessa’s life story had always fascinated me, and The Summit Seeker fills in many of the captivating details. It’s not a book about running, though many of her stores revolve around the sport. It’s more of a book about living.

There are many lessons to be learned as she takes us on a journey through her life, including her decision to start embracing life and doing what makes her happy. All too often, we trudge through our lives suffering from one day to the next. After experiencing Vanessa’s story, it is nearly impossible to make excuses. She motivates us to start living.

This is a book you need to read. Trust me on this one.

I know many of the people reading this have already read the book- what lessons did you learn? What was your favorite story? Share in the comments!

###