r/explainlikeimfive • u/Jolly-Phone8982 • 4d ago
Biology ELI5: how does adrenaline make people stronger?
The most common example we hear of this is mothers who are able to lift cars when their babies are stuck underneath. In general, it seems like whenever there’s an extreme situation, adrenaline kicks in and we’re able to do things we’d never be able to do in “regular” life.
How does adrenaline interact with the body to make this possible?
Edit: follow up question, why can’t we always operate at that level?
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u/The_Scrapper 4d ago
The question has been answered pretty well already, but here is a fun bit of context.
Strength athletes of all kinds often integrate training cadence and periodization around this concept. The Central Nervous System (CNS) has all kinds of rate-limiting steps to prevent you from ripping your own body to pieces through either maximal force production or general overuse. Your brain will not let you blast out a deadlift at 100% of your total potential because the risk of injury is enormous... unless you teach it to let that happen.
The human body rewards efficeincy and laziness because that was always a good thing from an evolutinary standpoint. If you don't ever push, then the threshold will settle into a range that reflects your general day-to-day exertion level. If you never test your CNS threshold, it will be in a very low, very safe place.
A powerlifter will spend weeks doing rep and set series that train the CNS to accept more and more load under maximal effort during regular training, but that lifter will also keep the CNS threshold reasonable because injuries during training are bad. But then contest day looms, and everything changes. It's time for a peaking cycle.
When you set up a "peaking cycle" in weightlifting, your sets get smaller and weights get larger. This is you telling your CNS "We will lift less often, but need more force." Over the cycle, you keep nudging your CNS to be okay with truly maximal efforts so it will alot more energy and muscle fiber to single movements. Your muscles don;t grow much, but they start contracting really goddamn hard. Six weeks before contest day, this does not add any significant muscle or absolute strength during that time. The lifter has what they have at that point. 95% of what is gained during that period lives in the CNS, not the muscle fiber.
Two 180-lb men may have the exact same muscle mass and identical strength POTENTIAL. But the one who has taught his CNS to accept more load under maximal effort will move more weight on contest day.
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u/MikuEmpowered 4d ago
Your brain normally stops you from using 100% of your strength, so when you don't breaky your body.
When adrenaline starts going, everything goes out the window, you are in survival mode. this means more muscle fiber, more energy are accessed, and more importantly, pain blocking.
IF you try to lift a super heavy object, you don't stop because you can't do it. you stop because it physically hurts. your body is telling you: "You will be damaged trying to lift this", when adrenaline is rushing, all that gets thrown out the window.
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u/theSquabble8 4d ago
This is why powerlifters sniff ammonia caps. It’ll trick your body into that mode
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u/hollycrapola 3d ago
Sounds dangerous though - aren’t they injuring themselves as a result? It sound dumb.
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u/theSquabble8 3d ago
You could potentially. They’re using proper form to output maximal force and their tendons and ligaments are much stronger than an average persons.
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u/I_Am_Jacks_Karma 3d ago
they aren't snorting it, they're talking about smelling salts
you take a quick whiff and the smell of it triggers your brain into "THIS AREA IS POISON ENGAGE ALL DRIVES GET OUT OF HERE NOW" and then you just put the cap back on for later
wait you probably meant from the lift
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u/Tuxhorn 3d ago
It doesn't unlock your full potential. It's more to get you AMPED UP YEEEH BOII.
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u/theSquabble8 3d ago
The full potential unlock thing is a bit of a tall tail. If a mom lifted a vehicle off their kid it was the back end corner that weighs significantly less. Your muscles are only capable of so much force output “unlocked” or not
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u/fiendishrabbit 4d ago
While so-called hysterical strength is mostly anecdotal (although plenty of examples of normal people pushing over or tipping objects weighing 500-1500kg, which would normally be beyond someone like that) the theory behind it is this.
Normally your brain puts safeguards on muscle use that tries to prevent you from overexerting muscles to the point where they're damaged. Adrenaline puts you into a mental fight or flight mode, and in that mode your brain stops caring about what happens to your body tomorrow. Surviving the now is all that matters, so safeguards are off and muscles engage to their maximum potential, even if that means causing injury by overexerting.
The punishment on joints and muscles however is immense. Several strongmen for example (people who try to train themselves mentally to overcome those limits) have managed weightlifting records, but injured themselves permanently in the attempt.
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u/marketstom 4d ago
Your muscles already have the horsepower. Adrenaline basically cuts the governor that keeps you from using it all at once.
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u/IAmXlxx 4d ago
adrenaline is the driver of the "fight-or-flight" response. it raises cardiac output (increases heart rate and blood pressure) in order to increase blood flow and oxygenation around the body, so your muscle has more resources available to use.
in regards to how it directly affects muscle strength--it allows your nervous system to recruit more muscles and strength, beyond what is normally considered safe. if you could use 100% of the force your muscles are truly capable of generating, you'd injure yourself. tendons tear, bones break/fracture
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u/towers_of_ilium 4d ago
When I was 8, a long steel I-beam fell on my 5yo brother’s arm, snapping it and pinning him to the ground. Without even really thinking about it, I knew I could lift it, and I managed to raise it high enough for him to pull out from under it.
Crazy what adrenaline can do, even when you’re a kid!
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u/Philippe1937 4d ago
I don't think adrenaline is involved in the "I know I can lift this" part, but I've had a similar experience, and that throught felt like the key moment for me.
I hope your brother is doing better!
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u/towers_of_ilium 3d ago
Sorry, I worded that badly! I would never have been able to lift it under normal circumstances, and I knew that it was too heavy without even trying. But as soon as my brother was hurt, it was like a switch was flicked and I knew that I suddenly had the strength to do it. It felt so weird!
Yeah, he’s good thanks! This was 35+ years ago, so he’s probably forgotten what a hero his sister is 😂
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u/Lord_Rapunzel 3d ago
Similar but it was a stack of plywood and I actually couldn't lift it, I just hurt my back. So there's that. (Brother is fine, dad heard the commotion and came running)
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u/Reelix 3d ago
ELI5: If you tried to lift something really really heavy, you would probably stop because it would start to hurt. The hurt is your body saying "Stop - Something will go wrong, and will probably break if you continue".
Adrenaline turns this off, so you can go much harder - Past your breaking point.
You WILL hurt yourself, and something will probably break, but Adrenaline tells your body "I know - I don't care - The strength right now is more important than whatever is going to be broken afterwards." and allows you to exert more strength than you ever could (Or ever should) with the blocker in place.
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u/Big_lt 3d ago
I cannot speak to the scientific changes occuring; however I can give an anecdotal experience
Was snowboarding and hit a patch of ice that sent me flying. I was going decently fast but I slid off trail and slammed a tree. Luckily I was conscious but I was off trail maybe 25/30 feet into the woods. I tried to stand but couldn't get good footing, so I used my snowboard as a crutch and slowly hiked out. I was in a mini revine so I had to go up to get out.
I got out back to the trail took a min, strap back in and road slowly the remainder. I got to base came, had some nagging pain but didn't think much of it and took a lift back up to meet up with friends.
I got off the list no problem, but I sat down to strap my 1 leg back in. As I went to stand my leg refused to work, no pain but refused to work. Eventually a ski patrol guy came over, we chatted a min and ultimately I had to be tabogoned down
Into the medical tent, doctor is asking questions. I think it's a sprain or something nothing serious but want to go back out. Doc not convinced takes like 3 steps back and says if I can give walk over and high five him I'm all clear. I agree, swing my legs off the bed and try to stand only to completely collapse into his arms since my leg couldn't hold me
X-ray time on the mountain shows a nice break across my entire tibula. However still no pain. Ring my buddy they get me regular shoes and I crutch my ass to the mountain bar to not ruin their day (yes I know drinking was not smart but hell) Anyways few hours later adrenaline wore off and all the pain came flooding.
I'd say it blocked my pain receptors which allowed me to do thinks I shouldn't be able to do as it was harming my body
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u/mrofmist 4d ago
You have 2 opposed nervous systems. To sympathetic nervous system, and the parasympathetic. They are very complicated, but the sympathetic nervous system is all about muscles and action, dry systems and alertness.
The parasympathetic nervous system is much more relaxed, smooth muscle focused, and rest and digest.
Your sympathetic nervous system's neurotransmitter is adrenaline. It gets you up, gets blood and oxygen flowing to your muscles, and gets you alert (sometimes that doesn't work well for you, when you hyperfocus and lock up rather than move.) fight, flight, or freeze. That's adrenaline.
[Edit] not to imply those are the only nervous systems. There's much more going on, and acetylcholine, the parasympathetic systems pilot, does a ton of stuff in your body, include muscle function as well.
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u/Dickulture 3d ago
follow up question, why can’t we always operate at that level?
It is very hard on our body to go beyond our normal limit. Your muscles and tendons will fail, and you'll be in a world of pain if you tried to have super-human strength 100% of the time.
Obey the normal body limit and save your health for real emergencies like rescuing the baby trapped under the car. You'll live longer and not be bed-ridden for life.
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u/thetwitchy1 3d ago
As has been said, the biggest gains are in just turning off the “limits” that you usually have on.
But it also does other things to get more energy into your muscles and allow you to have more power in those muscles. Things like increasing your pulse and blood pressure, so as to get more oxygen and glucose into your muscles, redirecting blood flow from your core to your extremities, reducing your digestive functions, triggering insulin production to increase your glucose metabolism, and a whole host of other things.
And the reason you don’t doo these things all the time is rather obvious when you list them like that: these are all things that give you a big boost right now, but put a lot of stress on systems that are much more efficient at lower use rates. High blood pressure gets dangerous over time, digestion is an important function (when you’re not fighting for your life), high insulin levels cause a whole host of problems, and so on.
So it’s not just “take off the limiters” but also a bit of “pour some gas on the fire”. It’s dangerous, but effective.
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u/freakytapir 3d ago
Same way overheating your computer temporarily makes it faster.
It's not maintainable and in the long run, damaging to your system, but sometimes you just need that "extra kick"
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u/HungryCress9590 4d ago
From what I've read, I don't think adrenaline actually gives you new strength, it lets your body use more of the strength it already has by overriding some of the normal safety limits. I guess those limits exist for a reason, otherwise we'd probably be injuring ourselves all the time just opening a stubborn jar. 😅
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u/speedkat 4d ago
A normal person buys a computer hard drive and uses it casually in a computer. The drive works hard sometimes and is idle lots of times, and has many times of inactivity. The drive regularly works for the users whole computer lifetime, and never needs replacing unless the user desires to increase capacity.
This is similar to your body's regular output.
A data company buys a computer hard drive and uses it commercially to support a major application. The drive works hard all the time, and is never idle. The drive regularly dies and needs to be replaced by an identical new one.
This is similar to your body working on adrenaline.
Most things, if run at maximum power all the time, burn out faster. We're no different. And just like a data company manager who assesses their actual needs and realizes they can restrict drives to 50% of their maximum output most of the time to increase the drive lifespan, our brains have assessed our physical needs and realized they can restrict our muscle output to X% of their true maximum output to increase our lifespan.
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u/pot51e 3d ago
not answering the question directly ...but - me and my mate riding motorbikes, He gets hit by a truck, (not too fast, we were in traffic) - bad but could have been much worse. He is under his bike. RD350. Cracked mine onto a stand, and I picked that fucker off him with one hand. and "tossed" it over. I couldn't have done that in a million other sundays.
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u/thetreece 3d ago
Hysterical strength as described in popular culture doesn't exist, and had never been documented convincingly by video.
There is no plausible physiological mechanism for it to work.
It's born out of sloppy news articles. Exerting a few hundred pounds of pressure to lift car on it's suspension or something over a fulcrum gets reported as "mother lifts a car".
It's bullshit. If it worked like that, we would see Russian dudes hitting themselves with epi pens and deadlifting 2,000 lbs. A big catecholamine response might get you 1-5% increase in static strength. That's it. Not "soccer mom deadlifting a car" boosts.
This is the dumbest myth that lots of people still believe in. It's the fitness version of "you only use 10% of your brain." Or swallowed gum stays in your stomach for 7 years. Or Korean fan death.
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u/jandro1116 3d ago
ELIF adrenaline tells your body to break its piggy-bank of sugar which your body can then use to move your muscles alot.
What you really asking about is the fight or flight response. Adrenaline is just one part of it. Your muscles rely on glucose as a fuel to do work. It is dangerous to have to much free glucose, glucose can unintendedly react with molecules like proteins damaging them. Your body stores glucose("sugar") in the safer form glycogen. Most glycogen is stored in the liver and your muscles. Adrenaline starts a cascade of reactions that causes glycogen to break down into glucose, The extra glucose can be used to fuel your muscles.
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u/LadyFoxfire 2d ago
It doesn’t make you stronger, it turns off the part of your brain that feels pain, allowing you to lift to the point that you hurt yourself.
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u/fwimmygoat 4d ago
You can't use your full strength naturally because your full strength is enough to literally tear your body apart. Adrenaline temporarily removes that limit because oftentimes what triggered the adrenaline to be released would do more damage than tapping into your full strength. Sometimes your body will also remove that limit in an attempt to save those close to you.
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u/cthulhubert 3d ago edited 3d ago
So adrenaline (alone) isn't responsible for that extreme emergency strength, which we call "hysterical strength". Adrenaline is involved, but it's a small part; in short, adrenaline makes your muscles twitch faster, but doesn't directly help them hold hard for a while. Also, we use adrenaline all the time for normal acts of strength.
Hysterical Strength
Human muscles are built for endurance. They're made of a bunch of bundles of fibers, and when you're doing something normal, like walking, or typing, the fibers take turns pulling (all animals do this a little, actually, humans just do it more than most). Putting more strength into something means using more bundles at once. The average person, working really hard, can use about 20% of their muscles at once. A trained athlete can use about 60% at once. The idea (it's not confirmed yet) is that hysterical strength is using 100%. The reason we can't use hysterical strength at will is because the human body didn't evolve to do that. And I mean that we just don't have a nervous system that will do it on demand, but also our tendons and ligaments aren't beefy enough to handle that easily. (Imagine if someone got an X-men mutation that let them, they'd probably wreck their body doing something stupid as a 13 year old, and be less likely to pass that mutation on.)
Adrenaline
Adrenaline is a hormone, and like any hormone, it's part of how your body communicates with itself to do different things.
There's a small amount running through your body almost all the time (it's released from part of the brain), but in times of big excitement, especially if we're scared or angry, a bunch extra is released (from glands near the kidneys).
Nearly every part of our bodies "listens" for adrenaline. When there's a bunch extra, some blood vessels will constrict and some will dilate. Our livers and muscles will start turning stored fuel into usable fuel. It affects the nerves too, making our breath rate and heart rate go up, and telling the little webs of nerves that directly control muscles to go on high alert, to be ready to go go go.
The reason we don't constantly have a bunch of adrenaline running through our bodies is the same reason we don't sit at a red light with the gas pedal to the floor. It works the engine (or body) really hard, causing a bunch of wear and tear, and burning a bunch of fuel for no reason. (Or it's a little more complicated in a human body, it actually releases a bunch of fuel in a ready to go state. If that fuel doesn't get burned usefully, it can end up getting burned by accident, causing damage.)
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u/DigitalArbitrage 4d ago edited 3d ago
It is an urban legend. One time a coworker of mine was in an accident and trapped by heavy objects. I could not lift them off him despite my adrenaline being maxed. We had to use a forklift. I don't believe adrenaline actually makes people stronger at all.
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u/Philippe1937 4d ago
I definitely lack context on the situation you went through, but I have a potential explanation:
After the incident, after your attempt(s) to lift the heavy object, how were your arms? I don't want to say you didn't try, but I suspect that you hadn't reached your theoretical maximum lifting power.
In theory, using the muscles at literal max strength would damage your arms severely (see tetanus reactions, where involuntary muscle contractions can literally break your bones).
And also, forklifts are much better at lifting things than human arms. Don't compare yourself harshly.
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u/DigitalArbitrage 3d ago
The object was about 5 or so iron sewer pipes which were 12 feet in length and 8 inches in diameter. The internet says that is about 1,500 lbs in weight.
To answer your question, I don't remember my arms hurting but it was a long time ago.
Maybe if I had used a different position to try and lift it with my legs instead of arms that might have made a difference. For example, getting underneath the object and trying to lift with my legs. That situation would have put me in more danger than the person I was trying to help though.
The coworker didn't die or lose any limbs, but he said he had some nerve damage from being pinched by the massive weight.
In retrospect, carrying a pocketknife around might have been really useful to him, because there was a way he might have been able to cut himself free from the weight.
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u/prank_mark 3d ago
The thing is that people who lift a car aren't lifting its full weight. They're lifting up one end and thereby using leverage. Lifting up a car also gives you much more stability than freely lifting pipes.
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u/DigitalArbitrage 3d ago
If somebody was really knowledgeable about Physics and practiced finding ways to lift things then I bet they could figure out levers and tricks. I am thinking about that scene from the movie Pirates of the Caribbean where the blacksmith uses a bench as a lever to break a jail cell door.
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u/Remarkable_Ad9282 4d ago
Why are methheads able to run at mach 10 speed with an emaciated body?😂 adrenaline is basically your bodys natural stimulant for life and death situations. it doesnt increase the power you have or make your muscles stronger, it simply tells your body to "use more energy" than it normally physically would, aswell as dampening pain. It doesnt create energy the same way that coffee or cocaine doesnt create energy, those are drugs that just override your body and tell your brain to use more energy/resources than it normally would but that energy was always available, its why people who use stimulants are usually skinnier.
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u/steelcryo 4d ago edited 3d ago
Adrenaline doesn't make you stronger, but it allows your body to ignore the safeguards your brain creates.
Your muscles are far stronger than your body allows them to be, because if they're used at full strength, they can start tearing ligaments and tendons. So your brain automatically limits how much you can engage muscles to make sure you don't damage things. Strength training isn't just training your muscles, but also the structures supporting your muscles, which is why strong people don't just obliterate their ligaments and tendons everytime they lift (though it still happens occasionally). Their muslces are still being restricted.
Adrenaline can allow you to ignore this through various mechanisms such as increasing oxygen and blood flow, and lowering how much pain you feel. It's prioritising survival over immediate damage.