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As the weather heats up dehydration can unexpectedly hit, even on shorter runs. Here's everything you need to know on why hydration is important, the dangers of dehydrations, and a comprehensive guide to sports drinks to keep you running easily and healthily whatever the weather. 


Staying well hydrated is key for keeping your body functioning properly, not to mention keeping you at the top of your running game. 


In summer this is especially important; we lose most of our water through sweat, which takes the heat with it as it evaporates, helping us cool down. 


You are at risk of dehydration in both dry and humid conditions. 


Heavy humidity reduces the ability for our sweat to evaporate, as the air is already saturated with moisture. This leaves you feeling hot, sweaty and needing to slow down. 


If the air is dry, the sweat evaporates more quickly, almost as you're producing it, so you're more likely to become dehydrated and put your heart under strain. This is because dehydration causes a decrease in blood volume, which in turn causes your heart to beat faster to pump blood around your body. 


The heat and the sun also increase your body temperature, which makes running more challenging. 


Even if you're properly hydrated, it's normal for your pace to slow down as your internal temperature rises.  


Although severe dehydration is rare, running in the heat can cause some common symptoms. 


The most common signs of dehydration include fatigue, headaches, dizziness and decreased coordination. After you run, ensure you're drinking enough fluids. 



Loss of electrolytes from sweating can cause muscle spasms and cramping during your run and in the hours after. Although it's not serious, ensure you're staying hydrated and eat food high in potassium like sweet potatoes, avocados and bananas. 


Defined by dehydration, headaches, nausea and a core body temperature of up to 40°C, heat exhaustion is common in runners who haven't yet adapted to the heat. 


Other symptoms may include dizziness and confusion, loss of appetite, excessive sweating, pale and clammy skin, cramps in the arms/legs/stomach, fast breathing/fast pulse and intense thirst. 


If you start experiencing these symptoms, move to a cool place, lie and down and raise your feet slightly. Drink plenty of water (this can include sports and rehydration drinks). Try to cool your skin with wet cloths, fans or cold packs. 


Heatstroke is very dangerous. It occurs when your core body temperature hits over 41°C. Symptoms include disorientation, confusion, poor balance, lack of sweat and clumsiness. If you start noticing any of these symptoms seek immediate medical attention. 


Plain water often passes through the body too quickly, and without the necessary sugars needed to start your recovery process. This is where sports drinks come in. 


Most energy drinks contain a combination of quick and slow releasing sugars to provide both fast acting and sustained energy, as well as high amounts of electrolytes such as sodium, chloride and potassium to help replenish what you lose. 


Choosing the right sports drink to maintain the best hydration and electrolyte levels during a run can be tricky, as it depends on whether your're rehydrating or replenishing your energy before, during or after your run. 


Sports drinks are split into three categories. The one you choose depends on your activity and rehydration needs.



Isotonic sports drinks are most similar to the human body as they have a similar concentration of electrolytes and carbohydrates, so they rehydrate and reenergise quickly. They typically contain 6-8% carbohydrates, which is good for replenishing your energy levels. As a general rule of thumb the higher the carbohydrate content the slower the absorption rate into your body. Isotonic drinks have a medium absorption rate, taken up by the body as quickly as water but with added energy. 


Isotonics are the most common sports drinks on the market; think Lucozade, Gatorade and Powerade.They are ideal for shorter duration and high-intensity exercise where energy levels are more important than rehydration. 


  • Electrolytes: Medium
  • Carbohydrates: 6-8%
  • Ideal use: Re-energise (before and during)


Hypotonic drinks have a lower concentration of carbohydrates than the blood but have the highest levels of electrolytes. This means they tend to be absorbed by the body the fastest so they are ideal for rehydration, but not for replenishing energy levels. Their main aim is to replace the water and electrolytes you lose via your sweat. 


This is ideal if you are running in hot conditions or a challenging race where rehydration is paramount. 


  • Electrolytes: High
  • Carbohydrates: >6%
  • Ideal use: Rehydration (during)


Hypertonic drinks are more concentrated in energy than your blood. They contain the highest amount of calories as they average 8% or higher carbohydrate concentration, making them ideal for refuelling and recovering after exercise. As they have a higher carbohydrate level, they have the lowest absorption rate, so should not be used during runs as you're more likely to become fatigued once the energy wears off. 


Water, isotonic or hypotonic sports drinks don't contain enough sugar or electrolytes your body needs to recover from a strenuous run or workout, and as they are absorbed more quickly they pose a higher risk of oversaturating your body with water. The best recovery drink for a long run is a hypertonic drink with a 4:1 ratio of carbohydrate to protein. 


  • Electrolytes: High
  • Carbohydrates: 8%<
  • Ideal use: Recovery (after)




1. Carry a water bottle or water bladder with you:

Depending on the length of your run you should probably carry some water with you, especially in hotter weather where you are more likely to overheat and get dehydrated. If you are running outside for a long period of time, then a water bladder is ideal and will easily fit into a running backpack. If you're in the gym, a water bottle will be easier as many machines have a water bottle holder (and you probably won't be wearing a backpack on the treadmill). 


2. Don't just drink water: This might sound counterintuitive but you need more than water to stay hydrated. When you sweat you lose electrolytes, as well as energy, which can put stress on your body. There is now a huge range of hydration tabs that can rehydrate you with essential electrolytes. 


3. Know your limits: This might sound like obvious advice but if your body is telling you to slow down or stop then do it. In hotter weather, your body will be put under increased stress from dehydration and increased temperatures, so listening to it when it starts exhibiting symptoms of dehydration is really important. If you start exhibiting symptoms of dehydration be sure to hydrate and keep an eye on your intensity. 


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