We've just had one heatwave; there's another forecast in a few days, and let's be honest, this is shaping up to be a proper scorcher of a summer. So before you head into the gym sweating buckets before you've even stacked the bar, let's talk about what's actually happening to your body in the heat, how hard you should really be training, and whether supplements can help you keep showing up and grafting when the mercury's up.
Sweating loads isn't a bad sign
Let's clear this one up straight away: a soaked t-shirt doesn't mean you're "detoxing" or burning extra fat, and it doesn't mean you're overdoing it either. Sweat is just your body's air conditioning. When your core temperature rises, you sweat; that sweat evaporates, cooling you down. In a hot gym with humidity stacked on top, that evaporation slows right down, which is why you might feel like you're sweating more but cooling down less. That clammy, can't-shake-it feeling is humidity getting in the way of your own cooling system, not a sign something's gone wrong.
So how sweaty is too sweaty?
It's less about the puddle on the floor and more about what comes with it. So you need to be alert to and watch out for:
- Sweat suddenly stopping during intense effort in the heat, this is a red flag, not a good sign. It can mean your body's struggling to keep up.
- Dizziness, headache, or nausea creeping in.
- Heart rate that won't settle even when you back off the pace.
- Confusion, irritability, or just not "being right": often easier for a training partner to spot than yourself.
Any of these, and it's time to stop, get cool, and get fluids in, not push through for one more set; it all about how to train safely in the gym during a heatwave.
How hard should you actually train in a heatwave?
Here's the honest answer: probably not as hard as you would in March. That's not you going soft, that's physiology. Your body's diverting blood flow to your skin to cool you down, which means less is available for your working muscles. Your heart's already working overtime just to keep you regulated, before you've even picked up a weight.
So here are a few sensible shouts for heatwave training:
- Drop the intensity 10–20% on the days it's genuinely roasting, especially for anything long and grindy like circuits, conditioning work, or high-rep sessions.
- Train earlier or later in the day if your gym lets you, when it's not a sauna in there.
- Shorten your rest-to-work ratio expectations; you'll likely need longer between sets to get your heart rate back down.
- Be alert to grip, coordination, and focus. These go first in the heat, well before strength does, and they're often how injuries creep in.
- Don't chase PBs this week. Save the heavy singles for when the gym's not 36 degrees and you're not already two litres down on fluid.
Training through a heatwave isn't about toughing it out for the sake of it, it's about training smart so you're still able to train next week too.
Can supplements actually help?
This is where a bit of know-how goes a long way, because heat changes what your body actually needs from a session. Hydration and electrolytes should be your first port of call. Sweat doesn't just lose you water, it strips out sodium, potassium and magnesium too, the stuff your muscles and nerves actually run on. Plain water alone, especially after a proper heavy sweat, doesn't replace what you've lost and can leave you feeling flat, crampy or headachy even after you've "rehydrated." Our best-selling Protein Dynamix Hydrate Electrolyte & Vitamin drink is built exactly for this, designed to keep everything ticking over when conditions aren't on your side.
Creatine is fine to keep taking, just keep an eye on your water intake. There's an old myth that creatine causes dehydration or cramping in the heat. It doesn't, but creatine does pull a bit of extra water into your muscle cells, so it's worth being deliberate about topping up fluids rather than leaving it to chance on hot days.
Go easy on stimulant-heavy pre-workout. A big hit of caffeine raises your heart rate and core temperature before you've lifted a thing, not ideal when the gym's already doing that job for you. If you're training in serious heat, consider a lower-stim option or simply less of your usual scoop. Browse our Energy Booster range if you want to dial things in rather than guess.
Protein still matters; maybe more than usual. Heat can knock your appetite, which makes it easier to fall short on protein right when your body's working harder to recover. A protein shake or bar is an easy way to hit your numbers without having to face a big meal in the sticky heat.
The bottom line
Sweating like mad in the gym during a heatwave isn't something to fear, it's your body doing its job. The trick is training with a bit of sense (lighter intensity, smarter timing, listening to the warning signs) and supporting your body properly with the right hydration, electrolytes and fuel rather than just grinding through on willpower and tap water.
With more hot spells forecast before summer's out, now's the time to sort your hydration and recovery supplies, not when you're already three sessions deep into a heatwave wondering why you feel rubbish.
Stay hydrated, train smart, and we'll see you in the gym.
