| Mild dehydration won’t slow you down

You’ve heard the warning: By the time you notice you’re thirsty, you’re already (cue ominous music) dehydrated – and that will slow you down.

So it’s worth considering the counterintuitive results of a 2009 experiment. French researchers weighed 643 runners before and after a marathon to estimate how much fluid they’d lost.

The fastest runners, it turned out, were the most dehydrated: Sub-3:00 finishers lost an average of 3.1% of their starting weight, those between 3:00 and 4:00 lost 2.5%, and those slower than 4:00 lost just 1.8%.

This effect is even more pronounced at the elite level: When Haile Gebrselassie became the first sub-2:04 marathoner in 2008, he lost 10% of his starting weight – far more than the 2% loss that the American College of Sports Medicine says “degrades aerobic exercise”.

So what explains this apparent contradiction?

The key is to understand the difference between dehydration (the physiological state of having lost fluid) and thirst (the desire to drink).

For decades, researchers lumped the two together, conducting studies in which volunteers were denied water for hours before undergoing exercise tests.

Those subjects were both thirsty and dehydrated – and their endurance suffered even with 2% dehydration.

Read more: 5 hydration mistakes you are probably making

But as the familiar warning implies, it’s also possible to be dehydrated, at least temporarily, without feeling thirsty. Does this matter? In a 2016 study, athletes completed a 20K trail run while either drinking an amount chosen to replace their expected sweat losses or simply drinking when they felt like it – a plan that, in the latter case, left them dehydrated by 2.6%.

The finishing times in the two conditions were essentially identical.

One theory is that the disconnect between dehydration and thirst isn’t an evolutionary bug – it’s a feature. As you sweat out water, you also sweat out electrolytes like sodium, which keeps your blood concentration relatively constant.

That disconnect, the theory goes, allowed our ancestors to keep hunting without constantly needing to stop for water.

This rethink has two practical consequences: You can trust your sense of thirst during a run, but you have to repay that fluid debt after you finish – otherwise, the next day, you’ll have nothing left to borrow.

This article was originally published on

Image credit: iStock

NEXT ON HEALTH24X | The cycling coach you didn’t know you had

Many moons ago, I had the pleasure of interviewing endurance mountain bike racing legend John Stamstad for a feature story on the topic of pain.

Stamstad, who had racked up five consecutive victories at Iditasport in Alaska, as well as bested all comers at many a 24-hour race, knew something of the subject. He once raced 23 hours of the 24 Hours of Canaan with a compressed vertebrae following a crash; another time, he rode the final 130km of a 160km race with a collarbone break.

How did he so expertly handle the typical hurt that racing doles out, let alone manage the monster doses of agony of racing injured? I had to know.

Broken bones aside, he told me that he’d actually sought out pain in his training so he could get to know it better, like a friend of sorts. He actually kind of said just that.

“It took me a long time to stop treating pain like some horrible villain to be avoided,” he told me. “Pain is a positive thing in my training. Getting to know suffering is important because it helps me know what it takes to win.”

He went on in great detail about how he hones in on how he’s hurting at any given time.

“The worst thing to do is get emotional about your pain, because that heightens your sensations. Take it as a signal from your nervous system that you’re working hard. And when you work hard, you do well.”

He suggested using pain as just another metric, like heart rate or power. If you’re labouring like a rented mule with your heart rate at 190 while cranking out 375 watts, well, of course you’re going to be in pain. But if you’re hurting the same way at 145 bpm and 150 watts? You need to listen to that.

Read more: Troubleshooting your common cycling pains

“It’s a cue that you need something like food or hydration. If you listen to your pain unemotionally, it will help you,” he said.

I’ve made no secret over the years about how I hate to suffer, specifically and kind of ironically, during races. It’s not something I’m particularly proud of, especially in a sport that prides itself on the ability to handle pain, heralding riders who can go deep into the “pain cave” and have the best “pain faces.” I’m not particularly fond of spelunking and I prefer to smile.

Unlike Stamstad who approaches his agony with the detachment of an errant bungee jumper’s retina, I have a tendency to get all Hallmark-y with mine.

“Why? This is awful. How many more hours? Why do I do this? Why? Why? Why?” It’s all kind of a problem when the going gets hard and it’s supposed to hurt. So as I revisited this topic recently for an upcoming book, I pinged Rebecca Rusch – you know, the Queen of Pain – and asked for her take. Did she consciously work on building her pain tolerance, or was a bigass hurt locker just part of her DNA?

Read more: 4 bike fit tips to knock out knee pain

“Oh you can definitely practice suffering. I do it all the time,” she told me. “I try to embrace the pain and tell myself that I’m better at managing pain than my competitors. This comes with relaxing and accepting instead of fighting against it. I know that the sooner I get to the finish, the sooner the pain will stop. I remind myself that everything that’s been worthwhile in my life has involved pain, suffering and hard work. It makes the reward that much sweeter. Discovering that is powerful and addictive. I know that I can excel by just putting my head down and pushing through.”

You know what? She’s right.

Last week I was out doing some Godforsaken threshold efforts – something I really don’t enjoy – and I started getting that insides-squeezing total body hurt that comes with them.

My pain devil immediately sounded the alarm, rousing the internal chorus of demons, “You suck. You can’t do this. This hurts. Another season huh? You’re out of your mind.” And something clicked. I felt like Dorothy in the Wizard of Oz who had just had enough of being bullied by some evil, unseen demagogue behind some fortress and pulled back the curtain on my pain to discover nothing but a little gremlin with a megaphone. I decided to talk back.

“This? Please. Yes my legs are burning. No kidding. Am I dying? No. Actually I’m riding strong and feeling pretty good. How many years have I been doing this now? I know this kind of hurt won’t last forever. And I know if I’m suffering, chances are everyone is suffering. And really, it’s not that bad, nothing I can’t live with for a while, especially since I know pain has rewards. Heck, this pain itself is kind of rewarding.”

I kept pedalling, suddenly feeling lighter and calmer. Did the intervals still hurt? You bet. Was I happy when they were over? Absolutely.

But they didn’t bury, intimidate, or rattle me. They elevated me. They showed me in stark relief what I’m capable of, how far I’ve come, and the work I’ve yet to do. A few days later during another hard ride, the gremlin tried to pipe up numerous times. Each time, I put him in his place.

The final attempt was harder to quell. So like Stamstad advised, I listened, quickly realising that I was probably suffering unduly because my fuel stores were dipping. I popped some food in my mouth and was able to silence the gremlin’s shouting once again.

Have I become some sort of pain master? Nah. I won’t be dethroning Reba anytime in the near or distant future. But in learning to reframe my pain as a thing of beauty rather than a beast, I have tamed it into something far less savage, and occasionally even something perhaps a little bit sweet. And that’s enough for me.

This article was originally published on

Images credit: iStock