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Why Do Some People Sweat Buckets While Others Stay Dry? · So That's Why

• 0:04
  Jen Oliver: Welcome to the, so that's Why podcast, where we unpack the
• 0:08
  science behind everyday questions.
• 0:10
  I'm Jen.
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  Chris Smith: I'm Chris.
• 0:12
  Matt Edmundson: And I'm Matt.
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  Jen Oliver: Right.
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  Picture this, two people on treadmills next to each other.
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  Same pace, same incline, same duration.
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  One.
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  Looks like they stepped out of a magazine shoot, barely a bead of sweat visible
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  the other absolutely drenched, looking like they've run through a sprinkler.
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  Why do some people sweat buckets while others stay mysteriously
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  dry when they exercise?
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  Chris Smith: Well, did you know fact fans, when it comes to mammals,
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  we are the sweating champions.
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  So humans have the highest density of sweat glands of any mammal.
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  Jen Oliver: Feel like we need a certificate for that.
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  By the end of this episode, you'll discover your brain acts
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  as a sophisticated thermostat.
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  Your sweat glands operate like tiny factories with
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  different production capacities.
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  And of course there's genetics involved.
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  Matt Edmundson: And of course, we're gonna unpack whether being a heavy
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  sweater means you're actually fitter.
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  Chris Smith: And I think a good place to start is to let quantify how rates
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  of sweating vary between individuals.
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  So that variation can mean sweating between half a liter per hour and two and
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  a half liters per hour in some athletes.
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  So that's more than a five fold difference for, for a similar exercise.
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  Jen Oliver: Wait, two and a half liters, that's more than two large bottles
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  of water coming out of your skin.
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  Every hour I've had workouts where I thought I was sweating
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  buckets, but apparently I'm not even in the major leagues.
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  Chris Smith: Absolutely.
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  Yeah.
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  And sweating directly affects your performance and safety too.
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  So studies show even a 2% dehydration caused by sweating can
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  decrease performance by a fifth.
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  Jen Oliver: So if you are a high sweater and you don't know it, you could be
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  unknowingly compromising every workout.
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  Chris Smith: Totally.
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  And the stakes really are high.
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  Because 40 to 50% of athletes underestimate their sweat losses.
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  So this affects heart rate, perceived exertion and temperature regulation.
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  Matt Edmundson: So this is literally about whether your body
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  can perform the way you want.
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  Right?
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  I see people at the gym all the time chugging water, or some people don't
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  barely drink at all, and I wonder.
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  Actually how well we know our own sweatpants in all of this.
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  Chris Smith: Yeah, really good point.
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  And to make it even more complicated, apologies that we've gotta think
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  about environmental factors too.
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  'cause they do come into play.
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  So the same person can have around a 10% change in their sweat rate
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  just from a change in temperature.
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  Humidity or hydra, how hydrated they are going into exercise.
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  Jen Oliver: But this isn't random.
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  There's sophisticated biology determining whether you're a
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  light sweater or not, right?
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  Matt Edmundson: Absolutely.
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  And I guess once we understand it, we can actually work with our
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  bodies and understand them better.
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  Chris Smith: So the biology
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  Matt Edmundson: done, done,
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  Chris Smith: the hypothalamus is basically your body's thermostat and it's
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  monitoring core temperature and making split second cooling decisions for you.
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  So when your core temperature rises during exercise, even by half a degree.
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  Thermoreceptors sends signals to the hypothalamus and that triggers
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  activation of sweat glands automatically.
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  Clever, right?
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  Jen Oliver: It's brilliant.
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  So my brain decides how much to sweat without me having any say.
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  Chris Smith: Exactly.
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  Matt Edmundson: And that's why you see people struggling in hot gyms
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  or during summer workouts, right?
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  Their bodies are trying to manage this critical emergency
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  system, and if it can't keep up.
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  We all know it.
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  Performance tanks.
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  Jen Oliver: Well, if we've all got the same system, why do some
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  people's emergency systems set seem to set on gentle mist while
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  others are on like a fire hose mode?
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  Chris Smith: Well, yeah.
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  So this comes down to your individual sweat gland architecture,
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  for want of a better word.
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  So sweat gland density varies significantly across the body
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  and between different people.
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  So if you have sweaty palms or sweaty feet, it's no surprise really because
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  they have the highest concentration of sweat glands across the body.
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  Now, sweat gland density decreases with body surface area, meaning larger people
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  generally have lower gland densities.
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  Jen Oliver: So what you're saying is bigger people have
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  fewer sweat glands per area.
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  Chris Smith: That's right.
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  But.
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  They might compensate with, um, having higher output per gland.
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  So sweat glands are really clever in how they work.
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  Each gland produces fluid similar to blood plasma, but then a
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  duct reabsorbs, sodium chloride
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  Jen Oliver: like a factory with quality control.
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  Chris Smith: Exactly.
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  And the kind, these little kind of water treatment plants.
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  Um, and they include.
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  Like individual variations in reabsorption create differences
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  in both sweat rate and saltiness
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  Matt Edmundson: saltiness, which may explain why some people leave salt stains
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  in their workout gear and others don't.
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  Right?
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  Like I've, I've got that friend whose gym shirt looks like
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  it's been through a salt mine.
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  Uh, whilst mine don't always, thankfully.
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  Jen Oliver: Well, I'm curious about the genetic component here are some
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  people just born to be better sweaters.
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  Chris Smith: They are.
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  Yeah.
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  So the genes involved in sweat gland development come into
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  play while with still embryos.
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  Jen Oliver: So my DNA essentially predetermined my relationship with sweat.
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  Chris Smith: Absolutely.
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  Right?
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  Yeah.
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  And gender's also a factor.
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  So women have higher sweat gland densities due to smaller surface
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  area, but men produce higher absolute sweat rates during intense exercise.
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  Jen Oliver: And higher sweat rate means better cooling, right?
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  Chris Smith: Well, not necessarily.
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  So it's about efficiency.
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  So efficiency matters way more than volume.
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  If sweat isn't evaporating efficiently or causes excess
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  fluid loss, more isn't better.
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  Matt Edmundson: Right.
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  So you see this again and don't you, in the gym really humid days.
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  People are absolutely drenched, but still medically overheating because the sweat
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  just sits there instead of evaporating doing what it's supposed to do.
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  Jen Oliver: That's gross.
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  Matt Edmundson: It is.
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  But you know, welcome to the gym.
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  Jen Oliver: Yeah, but that's real life.
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  But what about age?
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  I noticed younger people seem to be able to handle a heat better.
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  Chris Smith: Yeah, it's true.
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  So older adults show reduced sweat gland responsiveness, like
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  compared to their younger people.
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  Jen Oliver: And how do these biological differences play out in real people then?
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  Chris Smith: So there was a study of over 1000 athletes and it found
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  that males averaged about 1.3 liter per hour of sweat loss, whereas
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  females just under one liter.
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  But the range still within these groups was enormous.
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  Jen Oliver: And what about fit?
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  People who sweat buckets?
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  I'm drenched after warmups, while others haven't even removed their jackets.
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  I mean, am I outta shape?
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  I didn't think I was.
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  Chris Smith: No.
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  So actually this busts a major myth.
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  So fitter individuals often sweat more at the same intensity.
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  Jen Oliver: Woo.
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  Matt Edmundson: Well that's good news.
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  Uh, so being a heavy sweater can actually then be a badge of honor.
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  Right.
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  Which changes everything for people who might feel
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  self-conscious about their sweating.
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  Jen Oliver: Yeah.
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  Chris Smith: Yeah.
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  Potentially.
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  If you look at people at their kind of peak fitness, they begin sweating within
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  one to two minutes, but whereas it's kind of five plus minutes for people
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  who are less trained, so your body learns to be proactive about cooling.
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  Jen Oliver: So sweating and waterfalls might actually mean my
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  cooling system is working better.
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  Chris Smith: Exactly.
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  So your body is anticipating the heat rather than just trying to react to it.
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  Jen Oliver: Yeah.
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  'cause I notice in the summer the heat often you deal with it better, don't you?
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  By August.
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  So does that mean my sweat system is adapting?
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  Chris Smith: It is, yeah.
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  So after about one to two weeks of.
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  Regular heat exposure while you're exercising, you acclimatize
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  and your sweat system adapts.
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  So it includes like leading to improved sodium conservation too.
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  Matt Edmundson: Sodium conservation.
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  Great phrase.
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  So my body then actually is just becomes better at dealing with salt.
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  Right.
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  Becomes more economical with salt, which is actually one of the incredible
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  things about our human bodies.
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  Jen Oliver: Mm-hmm.
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  Chris Smith: It is.
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  And heat acclimatized people produce.
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  Dilute sweat.
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  So about six times less sodium than un acclimatized people.
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  Jen Oliver: What about medical conditions that affect sweat?
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  Do they exist?
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  Chris Smith: Yeah, so the biggest is hyperhydrosis, and this is a condition
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  that affects about 3% of adults and it causes excess sweating within the body.
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  So the body's basically stuck in its cooling mode.
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  Matt Edmundson: Mm-hmm.
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  Yeah, I've heard of this, eh, and, and thankfully I don't suffer
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  with it, but imagine sweating even when air conditioning's on you.
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  I mean, that's gotta be hard.
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  Yeah.
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  Chris Smith: Yeah, absolutely.
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  And the opposite is another condition, it's called anhidrosis.
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  And anhidrosis is the inability to sweat and this, but this can lead
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  to like serious heat exposure risks and affected individuals often
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  can't rely on their body's natural cooling system during exercise.
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  So it can be very dangerous.
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  Jen Oliver: Okay.
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  So what can we do with all this information about sweat?
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  Chris Smith: So one thing you can do is calculate your personal sweat rate.
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  Sounds weird.
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  Jen Oliver: You're gonna totally do this, I'm sure.
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  Yeah,
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  Matt Edmundson: I'm, I'm doing it.
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  I'm totally doing it.
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  I'm taking notes.
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  Chris Smith: So here's the method.
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  First of all, weigh yourself before you exercise.
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  Then exercise for an hour without drinking and weigh yourself again.
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  And if you take that weight difference in kilograms, you can times that figure
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  by 1000 and it gives you the personal sweat rate in milliliter to per hour.
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  Jen Oliver: So if I lose a kilogram, which probably happens
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  regularly, 'cause I do sweat, that's a thousand milliliters hourly.
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  I do actually get really thirsty on workout days.
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  So that's probably why.
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  Chris Smith: Yeah, but many athletes actually, when it comes to like
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  dehydration, many, many athletes think they need a hundred percent replacement
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  during exercise, but that's not the case and can actually be dangerous 'cause it
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  can de deplete your electrolyte balance.
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  Mm-hmm.
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  Matt Edmundson: Yeah.
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  Now I've seen this a people forcing themselves to drink.
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  A lot of water rather than listening to their bodies.
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  And it used to be when I used to work on the ambos, as we say,
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  Jen Oliver: ambulances, for those that dunno.
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  Matt Edmundson: When we used to work on the ambos at marathons, there was this
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  real issue that you had with runners who would just drink water because they
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  felt they needed to hydrate, which they do, but it depleted their electrolytes
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  and over a long period of time.
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  They actually got really ill.
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  So current recommendations suggest replacing about 150% of losses over
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  time, not just during exercise.
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  Jen Oliver: So we don't need to constantly drink during water during our workouts.
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  Chris Smith: That's right.
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  Not necessarily, no.
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  So your body handles some dehydration during exercise.
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  Absolutely fine.
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  So up to 2% of body weight loss is acceptable.
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  The key is managing your hydration based on your individual routine.
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  Yeah.
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  Jen Oliver: So for those high sweaters out there, um, that are
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  losing over like one and a half liters an hour, what's the strategy?
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  Chris Smith: So I'd say pre-exercise, hydration is key, and then
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  moderate intake during exercise.
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  So don't overdo it.
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  And then really focusing on that post-exercise, rehydration,
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  potentially including electrolytes, electrolyte drinks and such like.
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  Jen Oliver: And I guess if we know we sweat a lot, we could be
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  proactive too and use some pre-cooling techniques to help ourselves.
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  Chris Smith: Yeah, definitely.
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  So cold towels, cooling vests, cold showers, they all help.
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  Um, but, and they genuinely do help, like high sweaters.
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  Jen Oliver: Mm-hmm.
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  Matt Edmundson: So even simple things can help us well, right.
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  So like run cold water over your wrist for, I don't know, 30 seconds.
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  The key areas I, you know, to run cold water over your forehead, palms, feet.
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  They're used for temperature regulation, aren't they?
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  Jen Oliver: Yeah.
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  And does when you exercise matter?
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  Chris Smith: Yeah.
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  So interestingly, when it comes to high sweaters, if they exercise in
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  the cooler parts of the day, that can cut their sweat losses by 30 to 40%.
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  Matt Edmundson: Yeah.
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  Early morning and evening workouts actually make a huge difference.
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  I found for me, working out in the morning is a big deal, right?
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  The best time to work out.
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  Um, plus obviously wearing, you know, the right gear, moisture, wicking fabrics.
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  Um, they help for high sweaters, cooling, headbands, neck wraps.
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  All these things can be real game changers.
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  Jen Oliver: And how does sweat differences connect to other
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  health, BA health aspects?
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  'cause we know, we think.
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  Everything connects.
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  Matt Edmundson: Everything connects.
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  You're right, I've read that your pattern, um, your sweat patterns
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  actually affect sleep quality.
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  So people who don't cool efficiently have disrupted sleep, uh, for a long,
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  prolonged elevated temperatures.
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  It impacts performance and recovery time between workouts.
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  Chris Smith: That's it.
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  It's all linked, and it comes down to mood and energy levels too.
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  So excess fluid loss affects blood volume, impacted circulation.
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  So even mild dehydration can cause a. Like decreasing cognitive function.
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  So it all comes down to your, your own personal health
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  and like diet and exercise.
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  There is no universal hydration strategy.
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  It's what's right for you.
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  Matt Edmundson: So what we are saying is understanding your sweat response
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  is foundational for effective routines.
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  Heat tolerance, even travel strategies.
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  You know, like if you are a high sweater, planning a tropical holiday,
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  uh, you need a completely different preparation, uh, perhaps than
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  someone who barely sweats at all.
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  Okay.
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  Jen Oliver: And sweating patterns.
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  Do they change as we get older?
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  Chris Smith: Yeah, they do.
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  So as we age, uh, sweat responses change.
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  So that affects our exercise capacity, of course.
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  So keeping on top of these changes, it can help like maintaining your active
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  lifestyle more effectively and safely.
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  Matt Edmundson: And For parents recognizing kids might have completely
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  different sweat patterns as well.
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  Right.
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  Is really important.
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  Even when the same family could prevent heat related problems
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  during sports or summer activities.
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  Chris Smith: Absolutely.
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  So that's why some people sweat buckets and some people stay mysteriously dry.
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  It's a combination of genetics, your sweat gland architecture, and how
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  your body reacts to exercise and conditions in the individual way.
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  Matt Edmundson: And when you see that park, one person sort of barely
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  misted whilst you are wrestling a garden sprinkler, um, you'll know
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  it's not about effort or fitness.
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  It's probably about biology.
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  Jen Oliver: So that's why some exercise for hours with minimal perspiration,
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  while others need industrial strength towels after warmups.
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  Okay.
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  That's it for this week.
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  Make sure you hit that subscribe button as we are gonna be unpacking the science
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  behind everyday questions each week.
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  And tell us in the comments what questions you'd like us to explore.
• 14:20
  Thanks so much for geeking out with us, but for now, that's it from me.
• 14:24
  Matt Edmundson: That's it from me,
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  Chris Smith: and that's it from me.
• 14:27
  Jen Oliver: Bye.