Cycling Stuff Cycling Wed Exercise

CW: A summer’s cauldron of inflammation

People who exercise outdoors face a new threat.

It’s unrelenting.

Dehydrated, cramped, limping? on a bike. Road nationals 2010.



Perhaps, even more dangerous than distracted or mean motorists.

It’s the heat. Gosh, is it hot. If only I had a dollar for every time I heard someone say, “Doctor M, you aren’t riding in this heat; are you?”

Well…Other than the fortunate souls smart (or lucky) enough to live in cooler climates, most of us are facing an extreme wave of hotness. As a Kentuckian, I live in the epicenter of this summer’s cauldron. Louisville sits in a wind-protected valley alongside the heat sink that is the Ohio River. Think hot and steamy.

The excessive heat smacked me hard last evening. Normally, my highly-veined skin and northern European heritage serves me well in the heat. But last night, while riding in sight of our city’s skyline, it started: My mouth grew dry and my breathing labored. And why was that helmet feeling so tight? Next came the sensation of tingles—not the pleasant kind of tingles, like when your teenager hugs you. And then came the deal-breaker: chills. I stopped, swallowed my pride and called for a ride home. (Here’s an always for you all: When it’s ninety degrees out and you feel cold–stop exercising, immediately.)

After last night’s brush with heat exhaustion, I thought it reasonable to ramble on about the dangers of exercising in the heat. And of course, I will offer some nuggets of wisdom for beating the heat.

First, here’s some basic biology of exercising in the heat:

Heart rates run higher. To cool the body, the heart needs to send more blood to the skin. Since our vital organs malfunction at high temperatures, the body possesses exquisitely sensitive heat management systems. My heart rate runs about 10 beats per minute higher—at the same watt output–in extreme heat. Yours probably does too. As a beating muscle that requires energy, the heart will fatigue more rapidly at higher rates.

–Fluid losses in the form of sweat are greater. This means the body will ‘dehydrate’ much sooner. Lower blood volumes results in less nutrient transport to vital organs and muscles.

–Increased sweating risks electrolyte depletion. Sodium, potassium and magnesium levels can run dangerously low while exercising in the heat. These electrically charged ions are vital for normal heart function, especially the heart rhythm.

Blood thickness may increase. As the fluid part of the blood decreases, its viscosity increases. Thicker blood may increase the risk of clots. Think of molasses traveling though a pipe. Now there’s an incentive to drink more fluids.

Here are a few tips for beating the heat.

Of course, I like to start with the big picture items. Theorems if you will.

Theorem 1: Avoiding exercise because of bad weather is not a good option. Regular exercise represents one of the three components of health—good nutrition and sleep are the other two. A good friend and teammate once remarked, “there’s no such thing as bad weather, only inadequate gear.” He was speaking of preparing to ride in cold temperatures, but the same logic applies to hot extremes.

Theorem 2: We are humans; we can overcome challenges by reasoning, and applying common sense.

Theorem 3: The three ‘Ps’–planning, preparation and priority—can guide us in overcoming the heat.

Now let’s move to some specifics pointers:

  • Prioritize your day around exercising when it’s cooler. This means the early morning or evening–but not at night because of the risk of disrupting sleep. Never disrupt sleep. Early morning exercise, for example, requires performing some evening rituals; things like charging the bike light, pumping the tires and placing your exercise clothes in another room so that you don’t wake your spouse at 0500. That last one is really important. Plan, prepare, prioritize.
  • Stay hydrated. Many years ago, I underwent an ultrasound of the kidneys. To make them more echodense, I had to drink thirty ounces of water beforehand. It was a lot of fluid to get down, but it was amazing how good I felt the rest of the day. I had great sensations later that day on a ride. Starting the day topped-off with fluids surely lessens the chance of dehydration later. Along these lines, it’s also helpful to chug down yet another full bottle just before heading out in the heat. Prepare. Plan. Drink.
  • Modestly increase salt intake: For those athletes without salt-sensitive high blood pressure, it’s helpful to liberalize salt intake in the warm weather months. Taking in salt helps the body hold onto fluid. Salted almonds are a pre-ride favorite of mine.
  • Beware of drugs that stimulate. The most common offenders in this class are the “eenes.” Caffeine is legendary for its (perceived?) performance-enhancing effects; another common example includes the OTC decongestant, pseudoephedrine. More sinister examples of stimulants are the diet-suppressants and amphetamines. What makes these drugs dangerous in the heat are that they work by raising the metabolic rate. In other words, they cause the body to run hotter. Though caffeine is clearly not as dangerous as amphetamines, it could be argued that coffee’s heat-raising effects  negate any of its benefit on hot days.
  • Avoid diuretics. Another reason to limit caffeine intake before going out in the heat is that caffeine works as a diuretic. Diuresis—increasing urine output–only enhances the risk of dehydration, or electrolyte depletion. Plan.
  • Lower expectations:  Do not look for personal bests in the heat. In fact, I would argue it’s never good to look for personal bests. Rather, I would recommend just letting them happen. But that’s another post: #obviousness.
  • Plan more water breaks. When I was a runner, I would loop my long runs around the location of water fountains. Smart cyclists often add an extra store stop on hot days.
  • Don’t push through the warning signs of heat exhaustion. Enough said. In the heat, more pain is definitely not more gain.
  • Take a buddy along. They may see the warning signs before you do.

This quote from another of my teammates is highly relevant to exercising in the heat. He frequently hollers this sage advice whenever it gets dangerous on the bike:

“Arrive alive.”


One reply on “CW: A summer’s cauldron of inflammation”

I very much enjoy following your blog. An old retired Army colonel instructor of mine in dental school taught me something in my first week of dental school. He taught me the six P’s. I can remember him to this day, looking down at me at my cubicle while I was trying to find something and saying: “Young doctor, I can see you don’t know the 6 P’s”….Wait for it…..”Prior planning prevents piss-poor performance”.

That may have been the single most important thing I learned in school. It has served me well in everything I do.

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