Read time: 6 mins
There’s something brilliant about training in the summer. The early morning runs while it’s still cool, the long evenings that make a post-work session actually feel appealing, the sense that moving your body outdoors is exactly what you should be doing.
But here in the UK, we’re also getting more frequent heatwaves – and with the UK Health Security Agency issuing amber heat health alerts already in 2026, it’s worth having an honest conversation about what training in the heat actually does to your body. Not to put you off getting out there, but to help you do it smarter.
Because here’s the thing: Most people know that exercising in hot weather feels harder. Fewer people understand why it leads to a higher rate of injury – and what they can do about it.
Your Body Is Already Working Overtime
When the temperature climbs, your body has to work much harder just to keep itself cool. Blood is redirected towards the skin to help release heat, which means less of it is available to deliver oxygen and nutrients to your working muscles. Your heart rate rises faster than normal. You fatigue more quickly. And you start sweating – which is brilliant for cooling you down, but comes with its own set of consequences if you’re not keeping on top of your fluid intake.
All of this means that the same run, ride, or training session that feels comfortable in October can feel genuinely gruelling in July – even at the same pace. That’s not a fitness problem. That’s your body responding exactly as it should to a much more demanding environment.
The issue is that many of us don’t adjust our training to account for this. We go out at the same pace, for the same distance, with the same recovery plan – and then wonder why we’re picking up niggles, feeling flat, or taking longer to bounce back.
What Dehydration Actually Does to Your Muscles and Tendons
This is the bit that surprises a lot of people. We tend to think of dehydration as something that makes you feel thirsty or gives you a headache. But its effects on your muscles and connective tissues are significant – and directly relevant to injury risk.
Your muscles are made up of around 75% water. When you’re not adequately hydrated, the fluid inside your muscle cells reduces, making them less efficient at contracting. Movement feels harder and slower, and your muscles fatigue more quickly – which means your form starts to break down, and the risk of strains and pulls goes up.
Your tendons and joints are also affected. The fluid that cushions and lubricates your joints – known as synovial fluid – is primarily made of water. When you’re dehydrated, your body produces less of it, which can lead to increased friction, stiffness, and joint discomfort, especially during repetitive movements like running. Tendons, which connect your muscles to your bones, also rely on hydration to stay pliable and strong. Without enough fluid on board, they can become tight and more vulnerable to overuse injuries – things like achilles tendinopathy, plantar fasciitis, and patellar tendinopathy.
Put simply: if you’re not staying on top of your hydration, especially in the summer, you’ll feel it in your sessions, your recovery, and your injury risk. A dehydrated body is a more injury-prone body.
The Recovery Problem Nobody Talks About
It’s not just the training session itself where heat causes problems. Recovery takes a hit too.
Hot nights mean disrupted sleep – and sleep is when the majority of your body’s repair work happens. Muscle tissue is rebuilt, inflammation is managed, and the nervous system resets. When that process is compromised by warm, sticky nights and broken sleep, your body simply doesn’t get the downtime it needs to recover properly between sessions.
Add to that the fact that you’re likely losing more fluid and electrolytes through sweat than you realise – not just during exercise, but throughout the day – and it’s easy to see how a run of hot weather can leave the body in a growth deficit. You’re not recovering as well, you’re going into each session with less in the tank, and the load on your tissues is higher than normal.
This is often how summer injuries happen. Not from one dramatic moment, but from a gradual build-up of fatigue and stress that the body hasn’t had the chance to properly recover from.
The Warning Signs to Watch Out For
Heat doesn’t always announce itself loudly. Some of the signs that your body is struggling in the heat are easy to brush off or mistake for something else. Worth knowing:
- Muscle cramps – often a sign of dehydration and electrolyte imbalance, particularly a loss of sodium, potassium and magnesium through sweat. Don’t just stretch through them and carry on – they’re your body flagging that something needs addressing.
- Feeling unusually flat or heavy-legged – if your effort feels disproportionate to your pace or output, that’s a sign your body is under more stress than usual. Back off.
- Niggles that appear from nowhere – a sudden tightness in the calf, a twinge in the achilles, a knee that wasn’t bothering you last week. Heat and dehydration increase muscle fatigue and reduce the body’s ability to absorb load, which can bring underlying weaknesses to the surface.
- Taking longer to recover – if you’re still sore or tired 48 hours after a session that would normally leave you feeling fine, your body is telling you it’s not coping.
None of these are reasons to panic. But they are reasons to pause, reassess, and adjust.
Practical Tips for Safer Summer Training
You don’t need to stop training in the summer. You just need to train with a bit more awareness. Here’s what makes a real difference:
- Time your sessions wisely.
The hottest part of the day in the UK is typically between 11am and 3pm – avoid training in this window during a heatwave. Early morning or early evening sessions are far kinder to your body. - Hydrate before, during and after.
Don’t wait until you’re thirsty – by then you’re already behind. Sip water consistently throughout the day, and for longer or more intense sessions, consider an electrolyte drink to replace what you’re losing through sweat. - Adjust your pace and expectations.
Running in heat is genuinely harder. Training by effort rather than pace during hot spells is a sensible approach – it stops you pushing harder than your body can handle in the conditions. - Don’t skip the warm-up or cool-down.
In the heat, your tissues are already under more stress. A proper warm-up increases blood flow gradually and prepares your muscles and tendons for the work ahead. A cool-down helps bring your heart rate down safely and reduces post-session stiffness. - Reduce your overall training load.
If you’re in a heavy training block, consider scaling back the volume or intensity during a hot spell. A few easier days now is far better than an injury that costs you weeks. - Prioritise sleep and recovery.
Keep your bedroom as cool as possible, stay on top of fluids in the evening, and give your body every opportunity to do its repair work overnight.
How Soft Tissue Therapy Can Help
This is where professional treatment can make a real difference – particularly during periods of high heat and heavy training load.
Regular Soft Tissue Therapy helps to release muscle tension, reduce inflammation, improve circulation and address the kind of tightness and fatigue that builds up over a sustained training block. If your muscles are carrying more stress than usual due to the heat, a targeted treatment session can help your body recover more effectively and reduce the risk of something tipping over into a proper injury.
Acupuncture is also worth considering if you’re dealing with persistent tightness, joint discomfort, or the kind of low-grade aches that summer training can bring to the surface. It works well alongside a structured rehab or training plan, supporting the body’s natural recovery processes and helping to manage pain and inflammation.
And if something does flare up – or you’ve got a niggle that’s been hanging around longer than it should – getting it properly assessed sooner rather than later is always the right call. Understanding what’s actually going on is the first step to sorting it out properly.
Final Thoughts
Training in the heat puts your body under significantly more stress than you might realise – not just in the moment, but in the hours and days that follow. Dehydration affects your muscles, tendons and joints in ways that directly increase injury risk. Recovery is harder when sleep is disrupted and fluid levels are low. And the warning signs are often subtle until something gives way. The good news is that most of this is manageable with a bit of awareness – adjusting when and how you train, staying on top of hydration, and giving your body the support it needs to keep up with the demands you’re placing on it.
Summer training can be brilliant. It just works best when you’re working with your body, not against it.
Need a Hand Getting Through the Summer Unscathed?
Whether you’re in the middle of a training block, managing a niggle, or just want to make sure you’re recovering properly in the heat – I am here, at SLS Therapy to help.
From Soft Tissue Therapy and Acupuncture to full Injury Assessment and Management, every session starts with understanding what’s going on for you specifically – and building a plan that makes sense for your body and your goals.
