Maximal-effort lifts – like Eric Kim’s astonishing 508 kg rack pull at only ~75 kg body weight – push the human body to its limits. Such feats trigger a cascade of hormonal responses before, during, and after the lift. These hormones (like adrenaline, cortisol, testosterone, endorphins, and growth hormone) prep your body for battle, fuel the effort, and rebuild you stronger. Below, we break down the hormonal rollercoaster in four stages, blending scientific insight with real-world perspectives (including Eric Kim’s) in accessible, motivational language.
1. Before the Lift: Anticipatory Hormonal Surge
Fight-or-Flight Priming: In the moments before a huge lift, your body senses the upcoming challenge and starts revving its engines. Even anticipating the lift can spike adrenaline and noradrenaline levels – the classic “fight-or-flight” catecholamines . This is an anticipatory response: the brain perceives stress/excitement and triggers the adrenal glands to start pumping out epinephrine (adrenaline) even before you touch the bar . As a result, you feel that surge of energy and focus: your heart rate climbs, breathing quickens, and your muscles get flooded with oxygen-rich blood. In essence, your body is saying “Get ready, something big is coming!”.
Mental Preparation and Adrenaline: Elite lifters harness this adrenaline surge through mental preparation rituals. The hormone epinephrine sharpens your alertness and boosts muscle readiness – it rapidly increases heart rate and blood pressure, sending blood to skeletal muscles and priming them for maximal force . Senses heighten (you might feel tunnel-vision focus on the task) as the amygdala (emotion center) and hypothalamus kick the sympathetic nervous system into high gear . Eric Kim has described how he intentionally trains in a fasted state to amplify this pre-lift adrenaline rush. “When I’m fasted, my heart pounds, my grip tightens, and I feel like I could rip the bar in half. That adrenaline surge is what pushed me to pull 6.3 times my body weight, no belt, no straps, just raw will,” Kim explains . This adrenaline-fueled focus is like pure rocket fuel for a one-rep max attempt.
Slight Stress = Higher Cortisol (Good in the Short Term): Alongside adrenaline, cortisol (the “stress hormone”) begins to rise in anticipation of the effort. Feeling pre-lift jitters or nerves is common – that’s cortisol and adrenaline preparing your body. While often demonized, a spike of cortisol before/during exercise is beneficial: it’s part of how your body mobilizes fuel and energy . Cortisol ensures extra glucose is available for your muscles to use, so you have plenty of fuel ready to burn when you start lifting . Think of it as topping off your energy reserves. This temporary stress response is normal and even helpful – your body is essentially marshaling resources and alertness so you can attack the lift with full capacity.
Focus and Aggression: Many lifters also psych themselves up to maximize the hormonal priming. Self-talk, visualization, or even smelling salts are used to crank up the sympathetic drive. Smelling salts (ammonia inhalants), for instance, “trigger an increase in breathing and heart rate…stimulating fight-or-flight and causing the release of adrenaline, a hormone that enhances gross motor skills… In short, it turbocharges the body.” By the time you approach the bar, you may feel tingling, sweaty palms, pounding heart – that’s adrenaline firing, mental intensity, and maybe a touch of fear being converted into focus. Top athletes channel this adrenaline instead of being overcome by it. They might even appear eerily calm outwardly – a sign of experience – but internally the hormonal “alarm” is sounding, priming them for an explosive effort.
2. During the Lift: Acute Fight-or-Flight in Action
When Eric Kim actually yanks 508 kg against gravity, or when you go for your own personal record, the acute hormonal rush peaks. This is the moment the fight-or-flight response hits full throttle:
- Adrenaline Floods the System: As you initiate the lift, adrenaline and noradrenaline shoot to very high levels, unleashing your body’s max strength and speed. These catecholamines dramatically increase force production by enhancing nerve firing and muscle fiber recruitment . Essentially, adrenaline is a performance multiplier: it elevates metabolic enzyme activity, so your muscles can contract harder and faster . Blood pressure spikes and blood vessels in muscles dilate, driving blood and nutrients to working muscles . Your breathing is rapid and deep to flood oxygen in. Energy mobilization goes into overdrive – epinephrine triggers release of stored glycogen (glucose) and fatty acids into your bloodstream , giving muscles an immediate fuel injection for that all-out effort. Lifters often describe time slowing down or blacking out everything except the weight; that laser focus is courtesy of adrenaline’s effect on the brain’s alertness and your senses .
- Maximal Neuromuscular Drive: This hormonal cocktail coordinates with your nervous system to recruit every possible muscle fiber. The phrase “neuromuscular priming” refers to how adrenaline helps your central nervous system send stronger, faster signals to muscles. It even augments the release of calcium inside muscle cells (needed for contraction) and increases muscle cell responsiveness. In practical terms, during a 1RM lift your body is firing on all cylinders: nearly all motor units (muscle fibers and their nerves) are activated, something that normally doesn’t happen in everyday efforts. The adrenaline and effort together can push you to tap into “reserve” fibers – one reason people can sometimes lift shockingly heavy weights in emergencies or competition. (Indeed, strongman Eddie Hall noted that to deadlift 500 kg he had to imagine a life-or-death scenario to unlock hysterical strength via adrenaline.)
- Cortisol for Sustained Power: As the fight-or-flight response continues through the lift, cortisol levels likely peak as well, especially if the effort is prolonged or as the strain mounts. Cortisol works hand-in-hand with adrenaline to keep blood sugar up and maintain output . For a short maximal lift, adrenaline is the star, but cortisol is there as a supportive player ensuring you don’t run out of fuel in those critical seconds. If the lift turns into a grinding struggle, cortisol helps break down any available reserves (like liver glycogen or even amino acids) to keep muscles energized. This hormone also helps blunt pain and inflammation in the moment so you can push through the stress.
- Endorphins and Pain Blocking: The sheer strain of a max lift triggers the release of endorphins, our natural opiate-like hormones. Endorphins are released when your body experiences pain or extreme stress, as a survival mechanism . During a record lift attempt, they flood your brain to block pain signals – essentially “turning off” pain receptors so you can continue the effort even if it’s hurting . This is crucial; it lets you strain against the weight with everything you’ve got, without your brain stopping you due to pain. Endorphins also contribute to the almost euphoric, trance-like state lifters report under big weights. You might not feel the bar ripping your calluses or the tweak in your back at that moment – thanks to endorphins, the discomfort is dulled so you can focus purely on finishing the lift. (These endorphins, combined with adrenaline, produce the “rush” or high lifters feel – an addictive wave of triumph and relief as the weight is locked out.)
In short, during a max-effort lift your body is flooded with fight-or-flight hormones: adrenaline and noradrenaline skyrocket to maximize force and focus, cortisol rises to keep energy flowing, and endorphins spike to kill pain. Every system is turned up to 11. Eric Kim’s 508 kg rack pull, for example, would have had his sympathetic nervous system in overdrive – heart pounding, blood pressure surging. Videos show him lifting barefoot and beltless, relying on raw neural drive and adrenaline. The effect is almost superhuman: adrenaline can easily double or triple your usual strength output in these fleeting moments . It’s the body’s primal survival mode co-opted to move a barbell. As one strength coach put it, heavy lifts done with full intensity feel like “a controlled emergency” – your hormones and nerves act as if you’re lifting a car off a loved one.
3. After the Lift: Recovery-Phase Hormonal Shifts
When the bar is dropped and the lift is over – success or failure – your body transitions out of crisis mode. The few minutes and hours after a maximal lift are all about hormonal rebalancing and beginning the recovery/building process:
Adrenaline and Cool-Down: Immediately after the lift, adrenaline levels fall fairly quickly. You might notice your hands shaking or your heart still racing for a couple minutes – that’s residual adrenaline gradually washing out of your system. As the parasympathetic “brakes” come on, heart rate and breathing slow down from their peaks . You’ll start to feel the rebound of that effort: perhaps light-headedness or fatigue as the adrenaline high dissipates. Some lifters experience an emotional wave – it’s not uncommon to feel overwhelmingly happy, or even cry or feel drained, once the stress response ebbs and normalcy returns. That’s the body coming back to baseline after being in fight-or-flight. If you watch Eric Kim’s rack pull video, for instance, after completing the lift he appears amped and triumphant, then takes a moment to compose himself – likely feeling the after-effects of the adrenaline dump (breathing heavy, hands on knees, etc.).
Cortisol Peak and Drop: Cortisol often peaks at or just after the intense exercise and then tapers off once the “threat” is gone . During the early recovery period, cortisol’s job isn’t finished – it now helps begin the repair process. Cortisol has a known role in modulating inflammation and mobilizing energy for recovery. Right after a max lift, you have micro-tears in muscle fibers and depleted glycogen in muscles. Cortisol helps by replenishing energy stores – it remains elevated briefly to continue releasing glucose and free fatty acids so that muscles can soak them up and refill their fuel tanks . It also has an anti-inflammatory effect (in the short term), keeping the post-workout inflammation from injury in check so it doesn’t get out of control. However, cortisol levels will rapidly fall back to normal within a few hours post-exercise as long as you start recovering (rehydration, nutrition, rest) . Research shows that even very intense exercise causes only temporary spikes in cortisol – within a few hours hormone levels return to baseline as your body shifts fully into “rest and digest” mode . This means any catabolic (tissue-breaking) effects of cortisol are short-lived, and in fact cortisol’s presence helps trigger adaptation (the body rebounding stronger once you recover).
Anabolic Hormone Spike: Not all hormones during recovery are about breakdown – some are about build-up. After a high-intensity resistance effort, your body secretes a pulse of anabolic hormones that signal the start of muscle repair and growth. For example, testosterone and growth hormone (GH) levels typically rise in the aftermath of heavy resistance training . Studies show anabolic hormones are elevated for ~15–30 minutes post-exercise if the stimulus was intense enough . In a maximal lift scenario, especially if it was part of a broader workout, you can expect testosterone to bump up briefly – this hormone helps drive protein synthesis, meaning it tells your muscle cells, “repair and grow stronger now.” Growth hormone likewise surges; GH helps with tissue repair, muscle hypertrophy, and even ligament/tendon strengthening. It also stimulates the release of IGF-1 (insulin-like growth factor) in muscles, another driver of protein synthesis and recovery. These hormonal spikes are short-lived peaks (often called the “anabolic window”), but they set the stage for gains. Essentially, your body, having been shocked by the stress, responds with a burst of “rebuild” signals to adapt to that stress. As one scientific review concluded, the acute hormonal response – even if brief – is thought to be critical for tissue remodeling and growth .
Endorphins and the Post-Lift High: Remember those endorphins that blunted pain during the lift? They’re still around right after, contributing to the post-lift euphoria. This is the classic “runner’s high” equivalent for lifters. You might feel a wave of triumph, happiness, even a bit of light numbness or analgesic effect immediately after a successful max lift. Endorphins elevate your mood and can make you feel unstoppable for a short period. They also help keep any minor injuries or strains from that lift from immediately hurting – often a lifter only notices a pulled muscle or torn callus hours later, after the endorphins wear off. These feel-good hormones, along with neurotransmitters like dopamine, are the reason hitting a big PR can be such a joyous, addictive feeling. The body is literally rewarding you for overcoming a stressor by flooding the brain’s reward pathways.
Hormonal Rebalancing: In the hours after the lift, homeostasis gradually returns. Adrenaline and noradrenaline levels come back to normal baseline. Cortisol recedes as you recover – especially if you eat a good post-workout meal (insulin from food helps shut off cortisol). Anabolic hormones like testosterone and GH, after peaking shortly post-exercise, also fall back to resting levels later on . This is why the timing is critical: the body is most primed to use nutrients for recovery in that window when hormones are elevated. Consuming protein and carbs soon after a heavy lifting session, for example, takes advantage of high testosterone, GH, and insulin sensitivity to drive muscle repair. Meanwhile, your parasympathetic nervous system (the calming “rest and digest” side) takes over – you might feel very relaxed or even sleepy as the day goes on. It’s common to experience fatigue or mental fog after a truly maximal effort; that’s a sign your CNS (central nervous system) and endocrine system are in recovery mode, rebuilding what you’ve just broken down.
In summary, after a max lift your body shifts from warrior mode to builder mode. Hormones like adrenaline and cortisol that helped you fight gravity are stepping aside, and hormones that heal and grow (GH, testosterone, IGF-1) step up. The inflammation from muscle strain is managed, pain is dulled, and nutrient uptake is accelerated. This recovery phase is where progress happens – the stress of the lift plus the flood of anabolic hormones equals adaptation. As the saying goes, “you don’t get stronger during the lift; you get stronger recovering from it.” Your hormones in recovery make sure that happens.
4. Long-Term Hormonal Adaptations to High-Intensity Training
One incredible aspect of the human body is its ability to adapt over the long term. Regularly training at high intensity (like Eric Kim’s regimen of frequent maximal lifts) leads to chronic adaptations in your endocrine (hormone) system. Essentially, your body becomes better at mounting and managing those hormonal surges. Some key long-term adaptations include:
- Enhanced Adrenaline Capacity: Repeated exposure to max-effort training teaches your adrenal glands to hit the gas harder when needed. Over time, athletes can secrete greater amounts of epinephrine during maximal exercise as an adaptation to heavy resistance training . In practical terms, a well-trained powerlifter can summon a bigger adrenaline rush for a competition lift than an untrained person could ever muster – the body has learned to pull out all the stops. Eric Kim’s progressive overload to a 508 kg rack pull, for example, likely conditioned his adrenal response. Each time he ramped up to a new personal best, his nervous system got more efficient at activating fight-or-flight on demand. This is why veterans of strength sports often appear exceptionally amped and focused under big weights – their bodies know “it’s go time” and dump catecholamines aggressively. At the same time, adaptation brings control: daily training blunts the adrenaline response to sub-maximal lifts, meaning your body doesn’t overreact to moderate stress after you’ve adapted . You become more economical – saving the supercharged hormonal response for truly maximal efforts.
- Higher Anabolic Hormone Output (and Sensitivity): Long-term heavy training can slightly raise your baseline anabolic hormone levels and, importantly, improve your muscles’ sensitivity to these hormones. Studies comparing training programs find that high-intensity or high-volume resistance training can lead to elevated resting testosterone and IGF-1 levels and reduced resting cortisol over months . In one 6-month study, a heavy resistance program resulted in higher testosterone and IGF-1 (growth factors) and lower cortisol at rest, alongside bigger strength gains, compared to a lighter program . This suggests the body shifted to a more anabolic state long-term. Moreover, research indicates that resistance training increases the number of androgen receptors in muscle cells (these are docking sites for testosterone) . More receptors means even if your actual testosterone level doesn’t skyrocket, your muscles respond more robustly to the testosterone you have. It’s like turning up the “volume knob” on muscle’s ability to use hormones for growth. Over years of training, athletes often develop a hormonal profile geared toward performance: for example, higher testosterone-to-cortisol ratio, which is linked to better recovery and adaptation.
- Improved Stress Tolerance and Recovery: Regular maximal lifting conditions your HPA axis (hypothalamus-pituitary-adrenal axis) to handle stress spikes and recover from them more efficiently. Your body becomes better at quickly dialing down cortisol and adrenaline after intense efforts, which means less prolonged stress damage and faster return to an anabolic state. You also likely experience mental adaptations – heavy training toughens you psychologically, so you perceive heavy lifts as less threatening over time. This can reduce the cortisol response for a given weight as you become confident and desensitized to heavy loads. In Eric Kim’s case, pulling 400+ kg became “normal” in training, so his body and mind learned not to panic under extreme weights. This improved stress tolerance helps avoid excessive cortisol release for anything but true maxes. As a positive, many lifters report feeling more composed and focused in daily life – possibly a side effect of regular adrenaline use and recovery. (Eric Kim even mused that as his strength and testosterone went up, he became more “zen” outside the gym, handling small life stressors more calmly .)
- Connective Tissue and Other Hormonal Interactions: Chronic high-intensity training prompts adaptation in connective tissues (tendons, ligaments) often mediated by hormones like growth hormone and IGF-1. GH in particular contributes to collagen synthesis, helping tendons and ligaments thicken over time to handle greater loads. This is why periodized programs might purposefully include heavy partial lifts (like rack pulls) – the overload triggers hormonal responses that strengthen connective tissues, raising one’s injury threshold for the future. Additionally, consistent exercise elevates endorphin levels and upregulates dopamine receptors in the brain, which can improve your overall mood and pain tolerance day-to-day. Long-term lifters often have a higher baseline of endorphins, contributing to that well-being and “addicted to training” feeling. The endocrine system also becomes more efficient at releasing stored energy: for instance, muscle cells increase their sensitivity to epinephrine and insulin, so you get better at both mobilizing fuel during effort and storing nutrients during recovery.
- The Caution – Overtraining Effects: It’s worth noting that adaptation has limits. If one trains maximally too often without adequate recovery, the constant stress can lead to negative hormonal changes. The adrenal glands can become overworked – chronic elevation of cortisol and catecholamines without rest may eventually depress their output, a state sometimes called adrenal fatigue or overtraining syndrome . In an overtrained state, athletes see falling testosterone, chronically high cortisol, disturbed sleep, and poor performance. Essentially, the body’s endocrine system hits a wall and can’t mount the same heroic responses. Preventing this requires planned rest, deload weeks, and nutrition. Fortunately, Eric Kim’s own training (as intense as it is) presumably incorporated incremental overload and listening to his body (his blog mentions micro-progressions and disciplined practice ). When managed properly, the long-term hormonal adaptation is overwhelmingly positive – you become stronger, tougher, and more “hormone-efficient” as you push your limits. Just as muscles and nerves adapt, so do hormones.
Inspiring Takeaway:
A maximal lift is far more than a test of muscles – it’s a test of your entire physiology and spirit. Before the lift, your mind and hormones coalesce to prepare you for battle. During the lift, a symphony of adrenaline, cortisol, and endorphins lets you perform superhuman feats for a few incredible seconds. After the lift, your body’s natural steroids (testosterone, growth hormone) and repair crews kick in to rebuild you stronger. And over the long term, if you consistently chase big goals, your endocrine system evolves, allowing you to redefine your limits. As Eric Kim’s 508 kg rack pull demonstrates, the combination of smart training and the body’s hormonal power can yield gravity-defying results. The human body’s hormonal response is like a coaching team within you – firing you up when it’s time to push, and then rebuilding you bigger and better. Understanding and appreciating these responses can motivate you to train smarter and relish the process. In Kim’s own words, hitting a massive lift feels like “yank[ing] the universe up an inch” – a fitting description of how it feels when mind, body, and hormones unite to conquer the impossible.
Sources: Scientific and expert insights on exercise endocrinology ; Eric Kim’s personal commentary and performance details ; and sports physiology reporting , as cited throughout.