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How to Avoid Hyper-Hydration

BY Abby Coleman

Drinking the right amount of water can help optimize blood sodium levels, which is a vital component of athletic performance. Sports scientist Abby Coleman explains why — and how to best hydrate before a race.

Nervously drinking too much water before a race or a taxing workout could put you at risk of developing low blood sodium levels — otherwise known as hyponatremia — which can have a negative impact on your performance and health. Here’s how to avoid hyper-hydration so that you can perform your best.

What happens when you drink too much water?

Hyponatremia occurs when sodium and fluid in the body are out of balance. In other words, there’s either too much water or not enough sodium in your blood. Normally your blood sodium levels should be between 135 and 145 milliequivalents per liter (mEq/L). Hyponatremia occurs when your sodium level falls below 135 mEq/L.

In most cases, hyponatremia is a result of hyper-hydration, or water intoxication (i.e., the overconsumption of water). According to Precision Hydration, the initial symptoms associated with drinking too much water can include nausea, lethargy, muscle cramps, weakness, fatigue, and headaches. Whilst few and far between, severe cases of hyponatremia can be fatal.

Why does hyper-hydration matter to athletes?

Athletes, especially those taking part in endurance activities, are at risk of exercise-associated hyponatremia. This usually occurs when an athlete either drinks too much water before an event or sweats out too much sodium.

Many people overdrink periodically throughout the day and the excess fluid is soon urinated out. But to overdrink before your event, particularly one of significant duration, can be harmful to your performance.

There are two common ways you might overdrink before an event.

  1. You might inadvertently overdrink because your daily fluid intake has remained high, even though your training load has decreased in the days leading up to a race.
  2. You might nervously sip too much water in the time between waking up and the start of the race.

Whatever the reason, athletes going too hard with “topping up” their fluid levels and overdrinking before a race can raise their risk of exercise-associated hyponatremia.

In many athletes’ eyes, dehydration remains a more compelling topic, as the effects of dehydration in athletes have been widely publicized for decades. It is true that excessive dehydration has proven to be detrimental to thermoregulation and our performance. But when it comes to pre-hydration, overdoing fluids in an attempt to stave off dehydration is counterproductive.

Blood is a mixture of plasma proteins and other solutes, including electrolytes, which are all monitored and maintained within pretty stringent parameters. Consuming an excess of water dilutes blood sodium levels, which in turn decreases plasma osmolality (which measures the balance of electrolytes and water). Lowered plasma osmolality causes diluted blood and urine, which triggers the body to increase its urine production. 

The problem in this scenario is that you don’t just urinate water — you’re also expelling electrolytes from your system. Electrolytes are key for athletic performance, as they boost hydration, muscle function, and neural activity. Losing electrolytes due to low blood sodium levels, in addition to sweating, causes a heightened risk of hyponatremia.  

What the research says about pre-race overdrinking

Important research on the subject comes from Dr. Stavros Kavouras, a professor of nutrition at Arizona State University and director of the Hydration Science Lab. His 2019 paper on hyponatremia incidence rate at the Spartathlon, a continuous 246 km (153 mi) ultra-distance foot race from Athens to Sparta, provides valuable insight.

Stavros and his research team found that about 9 of the 63 ultra-runners who participated in the study started the race in a mildly hyponatremic state (i.e., blood sodium concentration <135 mEq/L), while 41 of the runners developed either mild or severe hyponatremia after finishing the race.

Here’s what Stavros had to say about the findings:

“I think what probably happens is we’ve done a really great job of advertising the fact that most individuals over-consume sodium in their diet and it’s well-known that a high consumption of sodium in sodium-sensitive individuals is associated with hypertension and cardiovascular disease.

However, if you’re an endurance athlete who trains and competes for hours per day in a hot environment, consuming only a small amount of sodium is not recommended because sweat-driven losses can quite often be many times higher than the recommendation for sedentary individuals.

Severe symptomatic hyponatremia not only decreases performance but is also an extremely dangerous condition. Thankfully most people do not develop the condition severely and most of the time are asymptomatic. But, starting a race with low blood sodium levels is a predisposing factor for severe hyponatremia.”

What should you drink before a race?

Before long, hot, or intense training sessions or races, drinking a strong electrolyte drink can optimize your hydration by acutely increasing fluid retention without consuming excessive fluids. There’s strong evidence that consuming additional sodium with fluids before you start sweating is effective in improving endurance performance, especially in the heat.

At Precision Hydration, we’ve worked with plenty of athletes who would benefit from turning up the salt dial and dialing back on the fluid before long, hot, sweaty races. Doing this effectively requires striking a balance with your intake so that you’re aggressive enough to drive some extra fluid retention in your bloodstream without causing gastrointestinal issues or excessive fluid build-up that makes you feel bloated and sluggish.

If you want to test a protocol and see if it improves your performance before your next race, try preloading ahead of your next long, intense training session or B-race. Here are some good parameters to start with:

  • Mix electrolytes into your usual water intake to ensure you don’t drink too much plain water in the build-up to a race.
  • Drink about 500 mL (16 fl oz) of a strong electrolyte drink the evening before your activity.
  • Drink another 500 mL (16 fl oz) of a strong electrolyte drink about 90 minutes before you start. Finish your drink at least 45 minutes before you start to give your body time to fully absorb what it needs and urinate any excess.

Dr. Stavros also offers insight about how ultra-endurance athletes can go about starting a race well-hydrated:

“In general, an ultra-endurance athlete should realize that sodium (and other electrolytes) is a friend for someone who trains daily for many hours and experiences profuse sweating. Adding extra salt in food and increasing their electrolyte intake during exercise can improve electrolyte balance, health and performance. If they can, it might be a great idea to measure electrolyte sweat content and estimate requirements precisely.

I cannot tell you how many times I have worked with athletes who experience cramps, dizziness, and more serious issues during and after exercise that have been easily fixed by increasing their electrolyte intake.”

These simple actions should help get you to the start line of your next race with your hydration in good order — and hopefully keep you from taking too many breaks!

About Abby Coleman

Abby Coleman is a Sports Scientist who completed her BSc (Hons) degree in Sport and Exercise Science at the University of Bath and has worked at the Porsche Human Performance Centre as an exercise physiologist. She also has qualifications in nutritional training, sports massage and sports leadership.

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