Dehydration can impact runners in hot and cold conditions – so here’s how to keep your hydration levels intact.
By Rachel Boswell and Katie Inglis
Often, people – especially runners – associate dehydration with hot and humid conditions and assume that it only occurs in the warmer months of the year. However, while your risk of dehydration is indeed heightened when the temperature and humidity rises, it’s important to drink enough fluid throughout the year to safeguard your hydration levels. Even in colder conditions, when you may not feel the need to take those extra sips, hydration is still vital if you want to maintain your running performance and protect your overall health and wellbeing.
Here are some expert-backed tips on how to hydrate effectively as a runner, along with the symptoms of dehydration to look out for when you’re training and racing.
Why is it important to drink water?
Water makes up approximately 60% of the human body and is, as such, critical in regulating everyday biological functions. Among other things, water helps to deliver vital nutrients and oxygen to cells, remove waste from the body, hydrate and protect tissues and organs and maintain a healthy core body temperature. It’s safe to safe that H2O deserves our respect – so we shouldn’t skimp on water consumption.
How much should we drink?
According to the Eatwell Guide from the NHS, we should all aim to drink six to eight glasses or cups of fluid each day. This fluid can include water, of course, as well as low fat milk, sugar-free drinks and tea and coffee.
It’s important to note that this is just a rough guide, as fluid requirements vary from person to person and depend on personal factors such as your age, sex, activity level and overall health, as well as external factors such as the weather and altitude.
Running and hydration
Although you may not realise it, we lose water through various bodily functions including digestion, breathing and day-to-day sweating – so hydration is important before we even factor in activities such as running.
When we run, we sweat and breathe much more than we do in a resting state, which causes us to lose water more rapidly than usual. The same is true in hot weather, but to a greater extreme – running when it’s warm means that we lose even more water, putting ourselves at a greater risk of dehydration if we don’t take on enough fluids.
‘As we run, our core body temperature rises, resulting in a greater thermoregulatory demand,’ says Francesca Bagshaw, a Performance Physiologist at the Manchester Institute of Health and Performance (MIHP). ‘You sweat more and blood flow to the skin increases to help cool the body and decrease your core body temperature, resulting in increased fluid and electrolyte loss. The risk of dehydration and heat-related illness increases as the temperature increases.’
It can be harder to hydrate during the cooler months of winter, because we generally feel less thirsty and less inclined to take on water. Plus, when we run in the cold, the water that we lose through our skin as sweat turns to water vapour more quickly, which makes the water loss less obvious. Wearing more layers to compensate for cold conditions can also increase our risk of dehydration.
What are the symptoms of dehydration?
In short, dehydration occurs when your body doesn’t have enough fluid to function properly – and this can be hugely damaging for your health if left unmanaged. ‘Dehydration can cause overheating and place strain on the kidneys, with earlier stages leading to heat exhaustion,’ says Dr Leon Creaney, a Consultant in Sport and Exercise Medicine at MIHP. It can also reduce your strength and stamina, accelerate exhaustion and cause other problems, such as:
- A dry mouth
- Dark yellow urine
- Constipation
- Muscle cramps
- Headaches
- Dizziness and feeling faint
- Difficulty concentrating
Symptoms of chronic dehydration also include:
- Low blood pressure
- Rapid heart rate
- Rapid breathing
- Sunken eyes
- Dry skin
It’s not surprising that dehydration negatively affects your running performance and can hamper your recovery. When your fluid levels are too low, your mental functions are compromised and your heart must work harder to cope with physical activity. Note the colour of your urine to help you check whether you’re becoming dehydrated – ideally, you want to see a pale straw colour rather than a dark yellow.
How to stay hydrated as a runner
You should aim to drink around 530ml of water at least 30 minutes before and after your run to help prevent dehydration. Recommendations on how much additional water you should consume per hour during a run – especially if you’re out on your feet for a long time – can vary from 300-800ml. When judging how much to drink, it’s important to consider things like the temperature and humidity, how much you tend to sweat and your level of thirst.
If you’re running a longer distance like a marathon, you need to be even more careful with your hydration and consume electrolytes to ensure that you’re replacing both the water and salts lost through sweat. ‘Hydration strategies are vital to marathon running and should be part of your training to help you avoid the risk of dehydration and heat-related illness,’ notes Bagshaw. ‘Practicing your hydration strategy will also help you to avoid gastrointestinal issues and hyponatremia.
‘During a marathon, ensure that you are drinking to thirst with sufficient fluids and electrolytes,’ adds Bagshaw. ‘Intake with carbohydrates can aid your fluid and electrolyte balance, too. I’d also suggest getting a head start, ensuring sufficient hydration in the days leading up to the marathon.’
Still, mild dehydration is not necessarily an issue during a marathon. ‘While common advice is to drink plenty of fluids to avoid dehydration, in a marathon, mild dehydration (-2%) is not harmful and many elite marathon runners finish the race 2-3% dehydrated,’ explains Dr Creaney, who, like Bagshaw, says that you’ll know much to drink during a marathon through practice.
How to make good hydration a habit
Here are some top tips to help you stay hydrated, no matter what the temperature or time of year…
- When you first wake up in the morning, drink a glass of water. Then, drink another glass of water 30 minutes before each meal for the rest of the day. Our bodies can confuse thirst for hunger, so this habit increases water intake while helping to prevent overeating.
- Carry water with you everywhere you go, preferably in a reusable water bottle, so that it’s always there beside you. If you find the taste of water a barrier to regular hydration, try jazzing up the flavour with a fresh wedge of lemon or some unsweetened squash.
- If you find yourself forgetting to drink water, set reminders on your phone or download an app that prompts you to hydrate.
- When it’s cold, you may find it difficult to drink cold water. So, to stay hydrated, drink warms fluids such as hot herbal teas instead. Try to avoid drinking too many caffeinated beverages, though, as caffeine is a natural diuretic which can flush water and electrolytes from your body.
- Some foods are good for hydration, too. Soup is a great option – especially in winter – and fresh fruit and vegetables like cucumber, celery and watermelon all do the trick as well.
