You might be on the wrong track here...
You see, adrenalin's main purpose as a hormone, putting it simply, is to alert the body its time to enter "survival mode". Essentially, it's telling your body that this is a dangerous situation where your life might be at a risk, and so it triggers several processes in your body to ensure you can overcome the apparent threat. To note a few:
- Your pupils dilate so you can get as much light as possible.
- You turn pale as the blood is diverged away from your skin and pumped into your brain, muscles and other critical parts, ensuring you have more energy where you need it and that you'll bleed less temporarily from not severe cuts.
- your muscles become less limited by the brain so that you can defend yourself or run away.
- your immune system is partially suppressed (mainly by a hormone called cortisol) along with your pain response, meaning you won't be slowed down as much by pain or by some inflammation your body may be fighting at the moment.
Sounds awesome right? During a full on adrenaline rush, wounds don't hurt as much, you're usually more concentrated on what's causing the problem and you're tapping into more of your strength than you normally would. It's almost like a superhero mode. Why then isn't it on all the time? Well... You see, fight or flight mode isn't good for you. Actually it's kinda terrible and the only reason it exists is that it can give you a temporary edge at keeping yourself alive. Let's go back at the main "superpowers" the adrenaline rush usually gives you.
you feel less pain. Sounds awesome, right? Wrong. Pain doesn't exist to leave you inconvenienced, it exists to let you know you're hurt or hurting yourself, and a cut hurting when you move your hand is a signal not to move your hand when you can so your body can patch it up more easily. In fact, there are actually rare instances of people that cannot feel pain, which sounds great until you realize they might sustain a life threatening injury and be completely unaware of it until it's too late. There's also the problem that leaving your immune system suppressed in the long run is very bad, leaving you open to infections and diseases, which is why stressed out people (who often release more cortisol into their bloodstream) can be more prone to getting sick.
extra strength. Again, sounds very useful right? Wrong again. You see, you're actually pretty strong, we all are, and developing our muscles enhances this. What's the problem then? You see, our muscles at full power, in general, can exert more force than our bones can handle. Yep, we don't tap into all our strength because if we did we could easily hurt ourselves badly, seen in cases of people having muscle spasms accidentally breaking their own bones as their muscles tensed up involuntarily and without the proper limits. Even when that extreme case doesn't happen, you're still, on average, exerting your muscles way more than normal, that's not going to feel as awesome tomorrow.
greater focus and energy. No, you won't blow up your brain by focusing too much here, but there's still a problem: energy consumption, because that rush of energy doesn't come from thin air. In an adrenaline rush, you break down your body's sugar reserves so you have plenty of energy during said rush, but that's not exactly something you can maintain without burning through a lot of energy.
bonus round: no Mercy. An adrenaline rush is not something meant to be sustained for long periods, it's a short burst of explosive activity meant to boost your chances of survival when facing something you perceive as a threat, and precisely because it's not meant to last, your body does one extra thing I didn't mention: in order to ensure everything it has is being pumped into what will help you survive, it also diverges resources from several processes that will not be crucial to you in the next couple minutes, including "minor" things such as digestion, and cell division. Also also it can result in relaxation of the bladder, which can cause what's stored in it to get...released.
Summing up: an adrenaline rush may sound like a cool thing where you're undoing the limits of your body, but at the end of the day, it's an extremely stressful process where your body leaves itself more vulnerable to injuries, immunosuppressed and cranked up on sugar so that you can live to regret having had to do it another day.
You're absolutely spot on that they'd get hungry, thirsty and have their energy reserves deplete faster. You can also add to that however a high probability of them getting sore muscles, overall tiredness, and also that their healing will not improve during the surge. If anything they'll most likely heal slower (it's time to run from or kill what's trying to kill you remember? If you waste resources trying to patch your wounds now, you'll probably not live long enough for them to fully heal). From a more realistic perspective, your adrenaline manipulation might be mostly useful to let you enter an adrenaline rush at will.
As for explosives related to adrenaline, that's also a hard pass. The adrenaline may leave you in an "explosive" state, but that's about it. There's basically no real world animal abilities related to controlling fire other than putting it on a weapon by covering it in flammable material (also, from your own body's perspective: "why would you do that? I'm weak to that too you know?").
but what would be the right track?
So, now we've gone through the "UM, AACHTUALLY" part, what do we need to get proper adrenaline powers and fire manipulation without straying too far from reality? Let's get into this:
To fully get the best experience possible when intentionally flooding yourself up with adrenaline, you'll probably need them to Have the following:
Fast healing. Not mid-adrenaline fast healing, faster healing in general, realistically this would increase the risk of cancers forming without some measures, but let's not worry about that right now. Point is: an adrenaline rush puts your bones and muscles through a lot of exertion as well as microtears and microfractures, and we need those to heal quickly so we're ready for the next rush. Faster healing and a strong immune system will help you fend off better dastardly diseases and annoying cuts when you're not rushing.
Stronger bones, ligaments, tendons etc. We're boosting up the muscular and skeletal systems. You're mainly limited by how much force your muscles can exert and how much of that force you can handle. You'll still wreck yourself if you somehow use your muscles too much, but you'll last longer.
heat resistance. Here we enter the fire part. Here's a fun fact about cell division and muscle working: those can produce a large amount of heat, which itself can be harmful to you. Crank up your ability to withstand greater temperatures inside and outside yourself so you can still function well even if your temperature goes up too fast. If we were to crank this up to supernatural levels (with your tissues also having to be supernaturally immune to the effects of fire and temperatures that would cause you to literally break down at a molecular level), you could theoretically exert yourself until you're hot enough to inflict burns on others by touching them, or getting too close.
Beetle powers. We're talking bombardier beetles specifically. These little fellas have special glands in their rear which produce 2 different chemicals. When combined, these chemicals mix creating extremely hot vapor, hot enough to burn human skin and capable of irritating the eyes and respiratory systems of predators. Add some of these to your character and they too would be able to produce sprays of Bruning vapor. It's not fire manipulation, but you're still delivering burns in more than one way (also it still technically counts as adrenalin-related, these are defensive structures usually used when the beetle is already in flight or fight mode).
Summing up: can adrenaline manipulation give you fire powers? No, it really can't, and from a realistic perspective, all it does is allow you to enter a physiological state meant only for emergencies whenever you want. HOWEVER, if we stray a little bit from reality (or a lot when it comes to one of the heat-related powers), you could potentially have someone who can benefit from an adrenaline rush better than others, and who might still be able to burn people, and that holds somewhat true even if we don't give your character the power to dive into an active volcano and be totally fine.
