Article

The Facts About Hydration and Exercise

Published on Friday, January 06, 2023
by Alexander Koch

Health & Wellness

Hydration During Exercise: What’s the Best Strategy?

“Moisture is the essence of wetness...”
—Derek Zoolander

Water is essential to life.

The human body is composed of roughly 55–60% water. We constantly lose water through everyday processes, including breathing and sweating, to regulate body temperature.

Exercise increases water loss through both respiration and sweating. The water in our bloodstream, called plasma, is the main compartment from which we lose water during exercise to sweat. If plasma volume drops too much, our ability to regulate body temperature becomes impaired, and the heart must work harder to circulate a more concentrated blood supply.

A Brief History of Expert Recommendations on Fluid Replacement

A proper drinking strategy during exercise might seem like an easy question to answer. Surprisingly, expert recommendations have changed dramatically over the past 50 years.

Old, Old School – Don’t Drink!

Back in the 1960s and 1970s, many sports medicine experts recommended avoiding drinking during exercise. If you’ve seen the film Remember the Titans, it reflects the prevailing mindset of that era. Football players in the movie are instructed not to drink water during practice, which seems shocking today.

At the time, it was commonly believed that drinking water during exercise could cause cramping. Athletic trainers frequently provided salt tablets to athletes to prevent cramps.

Expert opinion began to shift after several high-profile events, including the death of British cyclist Tommy Simpson during the 1967 Tour de France. Simpson collapsed and died during the race, and dehydration was initially considered a contributing factor. Later analysis revealed that amphetamine use also played a role in the fatal event, complicating the interpretation of dehydration’s role in his death.

Middle-Aged School – Drink Ahead of Your Thirst!

By the 1990s, expert recommendations had dramatically shifted. Instead of avoiding fluid intake, athletes were encouraged to drink fluids on a scheduled basis during exercise. The American College of Sports Medicine (ACSM) published guidelines recommending structured drinking schedules to prevent dehydration.

The common phrase during this era was: “By the time you feel thirsty, it’s too late.” While that advice sounded convincing, it raised an important question: too late for what?

In reality, drinking excessively ahead of thirst can create its own health risks. Overconsumption of water during prolonged exercise can lead to exercise-associated hyponatremia, a condition characterized by dangerously low sodium levels in the bloodstream.

When sodium levels fall too low, fluid can shift into cells, potentially causing swelling in the brain, a condition called cerebral edema. Symptoms can include confusion, dizziness, seizures, coma, and in rare cases, death.

Some researchers have even proposed that hyponatremia may have contributed to the death of martial artist Bruce Lee, although this remains a debated hypothesis.

What Is the Best Practice?

More recent perspectives have shifted toward a balanced approach. The American College of Sports Medicine acknowledges that sweat rate varies widely between individuals and environmental conditions. Because of this variability, hydration strategies should be individualized.

One common recommendation is to try to limit fluid losses during exercise to less than about 2% of body mass, as larger losses can impair performance and thermoregulation.

Sports drinks can be helpful during prolonged exercise lasting more than an hour because they contain electrolytes, including sodium, which can help replace what is lost in sweat.

However, many experts now emphasize a simpler strategy: drink according to thirst. Research suggests that thirst is generally an effective guide for maintaining hydration during exercise without increasing the risk of overconsumption.

The reality is that the best hydration strategy for most people is fairly simple: keep fluids available and drink when you feel thirsty.

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