I've recently found out I perspire excessively during physical activities, and this seems to account for my struggles in running.
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"Yo, kinda curious, are you a sweaty salt bucket?" queries Emily Arrell, a team member from Precision Hydration, as she hooks me up with a couple of wires for a good ol' fashioned sweat test.
I'm on my 53rd lap around the sun, and this is a first for me – I never even imagined people could sweat differently! I mean, I know some sweat more than others, but I figured the salty consistency was the same across the board. Boy was I wrong.
Darn humans, we're complex critters – different from one another in so many ways that aren't immediately apparent, and it turns out our sweat varies massively too. And considering the trauma our bodies endure during activities like marathons, let alone ultra marathons through deserts, this tucked-away difference becomes a major player.
Lab Time
Find myself in the lab with a couple of cool cats – Dave, a fellow journalist, and Pierre Meslet, an elite athlete who's twice tackled the Marathon Des Sables (MDS) and placed 9th overall in 2021 and 6th in 2023 as part of Team France, who took home the team category win. After recently returning from Costa Rica where he won the Coastal Challenge, a grueling multi-stage 157-mile/252km ultra marathon that shivered through tropical jungles, beaches, and mountains, you could say Pierre knows a thing or two about running in harsh conditions.
The test Emily administers kicks off an imperceptible electrical current through our bodies, triggering our autonomic nervous systems to let loose with some sweat in a designated arm area, where a vial is waiting to collect it. This sample is then examined for sodium content.
The results don't lie – I take the top prize with an outrageous 1740mg of sodium per liter of sweat. I'm practically a salt mine – hey, in Roman times, salt was a form of currency, and I'd have been a fortune unto myself! And if I needed any more confirmation, the email I received immediately on my phone seals the deal: "Patrick, you, my friend, are a seriously salty sweater." Cheers for that.
Tuning In to the Newsletter
Apparently, my zest for sodium isn't a new development – there are plenty of signs I could have picked up on earlier. Do I see white residue on my running gear following extended, toasty outings? You bet. Does sweat in my eyes cause burning issues if I don't wear the proper headgear? Yup – life's pretty much a blur during the summer months. Do I crave salty snacks post-workout? Like, who doesn't, right? (Allegedly, not everyone at my level.) So, obviously, my track record speaks volumes.
But what does it mean? Emily and sports scientists Dr. Lindsey Hunt and Dr. Sam Shepherd are all giggly about my monstrous sodium count, but I can't help feeling sweaty palms. Does this mean I'm headed for a heart attack or that my diet's going to kill me?
Calm down, mate, Lindsey assures me. "Nothing to worry about," she says. "Your scores are high, sure, but it's just how your body's made. It's nothing to do with lifestyle and it's not a problem, so long as you're aware of it and adjust your intake of minerals during periods of high-intensity exercise."
Phew, that's a relief! But if I've been oblivious to this up until now, I can't say I've been managing it all that well. I usually chow down on some runnin' gels during longer events and grab bars and other nutritional supplements if I think I need 'em, but that's about as scientific as it gets.
"And do you ever suffer from cramps?" Lindsey inquires? Yep, that's me all day, every day! Again, though – doesn't everyone? (Not if they know their sodium-sweat game-strong and stay on top of their intake, apparently.)
Sweatin' It Out
Turns out I'm not the only super-salty drip in the bunch. Andy Blow, founder of Precision Fuel & Hydration, has even higher levels than me. An accomplished triathlete in years gone by, Andy struggled in long-distance, hot triathlons despite adhering to a nutrition plan. Naturally, it took a sweat test to enlighten him as to the cause.
"I discovered that I lose a crazy amount of sodium in my sweat," he explains. "And this, combined with a lack of awareness of sodium's importance at the time, meant that I was a higher risk of issues like cramping and low blood sodium, resulting from sweating out too much sodium, overdrinking plain fluids, or usually a combo of the two."
Though the insight came late in his athletic career, Andy realized how life-changing this info could've been for his performance, and in 2011 he founded a company to help runners, cyclists, and triathletes up their game by customizing their mineral intake to match the conditions they're racing under.
Buckling Under the Heat
There's more to this process than simply running a sweat test and establishing sodium levels. To genuinely prep for an event, especially one under extreme conditions, you need to know just how much you will sweat and tailor your intake accordingly. Precision Fuel owns a lab in Dorset where they run athletes on treadmills and stationary bikes in a specially crafted heat chamber, allowing them to get the precise sweat stats required to formulate a thorough hydration plan.
During an event like the MDS, where temperatures consistently climb north of 104°F and competitors are running for over five hours a day, managing your electrolyte intake correctly can be a matter of life or death. It's impossible to consume as much liquid as you're losing through sweat in such harsh conditions, but even if you could, if you don't replace electrolytes – specifically sodium – you're looking at a potential hyponatremia diagnosis.
"At one point during the MDS, my urine was a browny red," Pierre shares. "It was freaky, but the race doctors said as long as it returned to normal, I'd be in the clear. And luckily it did."
Sure, there was some luck involved, but there's more to it than that. Before racing off to places like Costa Rica and Morocco to tackle ultra events, Pierre spends weeks training in heat chambers to pre-acclimatize his body, and uses stats gathered from facilities like this one to work out a tailored nutrition plan for the challenge ahead.
"During the MDS, I was guzzling water loaded with this stuff all the time," he tells us, brandishing a tube of PH1500 electrolyte tablets. "I'd double dose my bottles before setting off, and each night I just kept sipping the solution. I even used it in my morning oats."
Before donning our shorts and running shoes, we're instructed to weigh ourselves in the buff. Once ensconced in the heat chamber, where the average temperature is set at 96.6°F and relative humidity is 34%, we're allowed to drink water (packed with electrolytes) but everything we consume is weighed. Pierre sets a blistering pace on one treadmill, running for a full hour, while Dave and I spend 40 minutes each on the second machine, with sports scientists Lindsey and Sam keeping tabs on our heart rates and ensuring we feel comfortable. Within a couple of minutes, I start to feel beads of sweat trickling down my back, and by the end of the session, I'm drenched.
A second weigh-in and some calculations reveal that I sweat at a rate of 1.4L an hour, which, to my relief, is slightly below average. I've had enough of being a unique snowflake for one day, and if my sweat rate was high in addition to my sodium being off the charts, I'd really be struggling.
The leaderboard on the heat chamber wall shows some folks sweat at double that rate, with the record standing at an impressive 3.2L per hour. Of course, those folks might've been running faster than me – Pierre's pace was much faster than mine, and he was sweatin' at a rate of 1.88L per hour, despite being much fitter and retaining some lingering acclimatization from his Costa Rican adventure.
"Despite Pierre running 4 km/h faster [than you] and for 20 minutes longer, his peak core temperature and yours were quite similar," Lindsey notes. "This suggests that Pierre is much more tolerant of hot conditions than the average Joe."
However, Lindsey continues: "Both you and Pierre still lost more fluid per hour than it's generally feasible to replace during prolonged exercise. Most individuals who are accustomed to drinking high amounts of fluid may be able to tolerate up to 1L per hour, but generally beyond that rate of fluid intake, it becomes quite challenging without extensive practice."
"The challenge that comes with a high sweat rate is that fluid and sodium losses can accumulate quickly, and, if not properly replenished, can lead to a variety of issues such as cramping, low blood sodium, and even more severe health problems," Lindsey concludes. "For these reasons, it's crucial to monitor and manage electrolyte levels carefully during races."
The strategy I walk away with, designed to carry me through a marathon in regular conditions, is to guzzle 600ml of liquid each hour, with a minimum of 1000mg of sodium per liter, plus 60g per hour of carbs. I'm not gunning for the MDS just yet, but I do have a 20-mile multi-terrain event on the horizon that I've completed ten times before, and I've frequently cramped towards the end. This time around, I'm going in armed with the knowledge that I'm a super high-sodium sweater, and I have a plan to stick to – let's see if it makes a difference.
- Given the high sodium content of Patrick's sweat (1740mg per liter), it is essential for him to pay close attention to his mineral intake during periods of high-intensity exercise, as the sports scientists suggest, to avoid potential issues like cramping and low blood sodium.
- And as shown in the tests run by Precision Fuel & Hydration, understanding one's unique sweat profile can be vital in improving performance, especially during events under extreme conditions such as marathons or ultra marathons, where managing electrolyte intake correctly can be a matter of life or death, as Pierre's experience with the MDS illustrates.
