Beat the heat by properly hydrating for summer running with these timely tips and suggestions


Most runners can attest to the challenges summer heat can pose for training and racing. Hot and humid weather, increased sweat loss and the risk of dehydration can significantly impact health and performance. Understanding more about human physiology and hydration can help us better prepare ourselves for effective and safe summer running.


Are our bodies really composed of “mostly water”?  That depends on your age.


You have likely heard that your body is mostly water; “70%” seems to be the most common number bandied about.  In fact, the amount of water in your body depends on your age, and it decreases as you get older.  Babies truly are mostly water, about 78%, but this number dramatically drops by the time we reach adulthood.  Men under the age of 50 are about 60% water, while women in the same age bracket are about 55% water.  After 50, this number drops again, with 50+ adult men being approximately 55% water and 50+ women being approximately 47% water.  


Why is maintaining good hydration levels so critical to health?

increase endurance before running a marathon


Proper hydration aids in a number of essential functions:

  • Helps maximize physical performance
  • Helps your body regulate its temperature
  • Moistens tissues in the eyes, nose and mouth
  • Protects body organs, tissues and the spinal cord
  • Carries nutrients and oxygen to cells
  • Lubricates joints
  • Flushes out waste products, reducing burden on kidneys and liver 
  • Helps brain function and improves mood
  • Increases saliva and improves digestion
  • Helps body absorb nutrients

The role of water and hydration in physical activity, particularly in athletes and in the military, is well-documented in the scientific literature. There is a large individual variability in terms of hydration and sweat loss rates, as it is influenced by genetics, gender, environment, age, medications, BMI, temperature, exercise intensity, fitness level, and hormonal and metabolic imbalances and acclimatisation.  It is not uncommon for athletes to lose 6–10% of body weight in sweat loss.The average person sweats between 798 ml (27 oz—about the size of a large Slurpee) and 1390 ml (47 ounces) during an hour of exercise.  Though dehydration will result if these fluids are not replenished, decrements in physical performance in athletes have been observed in dehydration levels as low as 2%. These milder levels of dehydration in athletes can lead to reduced endurance, increased fatigue, altered thermoregulatory capability, reduced motivation, increased chances of tendinitis and increased perceived effort.

Even more alarming is that exercising in hot conditions with inadequate hydration is related to hyperthermia, reduced stroke volume and cardiac output, decreases in blood pressure, and reduced blood flow to muscle.

What are our summer hydration pro tips?

1. ‍Monitor your urine.

Dark-colored urine is indicative of dehydration. Aim for a light-colored (not clear) urine at regular intervals to gauge your hydration level.  


2. Weigh yourself before and after exercise.

Each pound of weight lost is equivalent to about 473 ml (16 oz) of fluid expended. You want to replenish that amount of liquid plus 125 to 150 percent more to achieve optimal hydration, as you continue to lose fluids after exercise.

To put this into perspective, if you lost one pound of weight after a training run, aim for 1000 ml (24 oz) of water to rehydrate yourself.  Check out our fluid calculator to help gauge your maximum and minimum fluid intake. 


3. Track the salt level in your sweat.

The average athlete loses around 950 mg of sodium per litre through their sweat, a significant amount that can impact hydration levels if the sodium is not replenished. Having said that, some athletes lose well over 2300 mg per litre!  Getting your sweat tested is the most accurate way to monitor sodium, but it is possible to cultivate more awareness around your sodium loss levels and to use this to optimize your hydration strategy.  Here are some signs to watch for that suggest you may have a high salt content in your sweat and may benefit from a higher sodium intake :

  • You notice white, salty stains on your clothing after exercising.
  • Your sweat tastes salty and stings your eyes/cuts/grazes.
  • You feel faint or experience head rushes when standing up quickly after exercising.
  • You experience muscle cramping during or after long periods of sweating.
  • You regularly feel terrible after exercising in the heat.
  • You crave salty foods during and/or after exercising.

If this describes you, then it’s highly likely that you are losing a high quantity of sodium through your sweat.  In this case, you may need to increase your sodium intake by adding more salt to your food and eating saltier food, and/or adding electrolyte supplements or sports energy drinks that contains at least 1000 mg of sodium per litre (see below).  

To customize your electrolyte intake, see our Eload Zone Caps.

4. Consume water and electrolytes.

As previously mentioned, it is important to not only practice good training or race hydration by drinking water (and including ample fruits and vegetables with a higher water content in your diet), but by also increasing sodium levels through electrolyte consumption.  This can help your body retain fluids, stimulate thirst and decrease your sweat rate, which will decrease the amount of water lost.

Eload Hydration Formula replaces the amount of electrolytes an average person loses when sweating (per litre, per hour) in their biological ratios.

  1. Drink water before, during and after exercise.

Avoid the trap of drinking water only when you are thirsty; this is a sure path to dehydration.  Bringham and Women’s Hospital Health Hub recommends the following regime for water consumption:

  • Drink 500 ml (16 oz) of water about two hours before your run. Pair this with a snack or meal.
  • Approximately 15 minutes before a run, drink 180 ml to 250 ml (6-8 oz) of water.
  • Drink water at regular intervals for runs over one hour. If you sweat more profusely, you may need 500 ml (16 oz) every 15 minutes. Consume carbohydrates and electrolytes (in the form of dried fruit or sports gels) along with drinking water. Eload Hydration Formula does this for you.
  • Drink at least 473 ml (16 oz) of water after your run, and combine this with food. If you know your sweat rate, replenish with 590 ml to 1000 ml (20-24 oz) per 0.45 kg (1 pd) lost.


The bottom line

Hydration during training and race days is critical for performance, health and well-being. Consuming ample water, along with electrolytes and carbohydrates, as well as monitoring your urine and sweat for signs of dehydration will help you stay in optimal condition and keep you running!