Hyperhydration: smart strategy or too much of a good thing?
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What is pre-exercise hyperhydration and why does it matter for endurance athletes?
Welcome back to Unlocking Performance, the ministry podcast. Hello, I'm Robert Gorgosch, nutritionist and performance coach. Here in our short format series, we're going to explore nutrition topics in brief episodes before diving into our in-depth long form discussions with different experts. Maintaining hydration is one of the key challenges for endurance athletes, particularly during prolonged exercise in hot and humid environments. where sweat losses can exceed 2 to 3 liters per hour. Even moderate dehydration exceeding 2% of body mass increases cardiovascular strain, elevates core temperature, and can impair endurance performance. Consequently, sports nutrition research has focused not only on replacing fluid losses during exercise,
but also on strategies that allow athletes to begin exercise with greater body water stores. One such approach is pre-exercise hyperhydration. Alan McCubbin shared some very interesting views on this topic in one of his recent reviews that I would like to sum up in the following words. Simply drinking a lot of plain water before exercise doesn't actually help your body hold on to more fluid.
Why does drinking a lot of plain water before exercise fail to increase retained body water?
When you drink a large amount of water quickly, it dilutes your blood and your body senses this and turns off the hormone that normally tells your kidneys to conserve water. As a result, your kidneys just flush the extra water out as urine, so most of what you drank ends up in the toilet before you even start exercising, instead of staying in your body where it's needed. Adding sodium can change this completely. Sodium helps keep your blood at the right concentration, which keeps that water-conserving hormone active and tells your kidneys to hold onto fluid instead of getting rid of it. This means your body actually retains much more of the water you drink. That's why current hydration guidelines recommend drinking about 5 to 10 milliliters per kilogram of body weight, roughly between 100 and 200 milliliters per 20 kilogram of body weight, two to four hours before exercise.
Ideally with some added sodium if you want to maximize how much fluid your body holds onto.
How does adding sodium change fluid retention and what sodium levels are effective?
Research suggests that beverages containing more than 100 mg of sodium per 100 ml improve fluid retention compared with plain water. Such sodium concentrations resemble oral rehydration solutions rather than conventional sports drinks you would normally use during exercise, which generally contain considerably lower sodium levels. Pre-exercise hyperhydration extends this concept further by intentionally increasing total body water above normal hydration levels before exercise. This strategy is particularly useful when athletes anticipate large sweat losses, but are unlikely to replace fluids adequately during endurance exercise, especially long distance races. The objective is not to reduce sweating,
but to create a larger internal fluid reserve that delays the development of dehydration and its associated physiological consequences.
What are common hyperhydration protocols and how much fluid should athletes consume?
Two osmotic agents or hydration helpers are commonly used. Sodium, which primarily expands the extracellular fluid compartment, by increasing plasma osmolality, and glycerol, which distributes throughout both intracellular and extracellular compartments, retaining water more evenly throughout the body. Most pre-exercise research has used relatively aggressive hyperhydration protocols consisting of approximately 20 to 25 milliliters per kilogram body mass of fluid consumed during the one to four hours before exercise. To retain this fluid effectively, most successful studies have used sodium concentrations of approximately 275 to 300 milligrams per 100 milliliter of water. To put this in perspective, five gram or around one teaspoon of table salt contains around 1,900 milligrams of sodium.
Five bicarb capsules contain around 1,400 milligrams of sodium.
What physiological and performance benefits — and limits — does hyperhydration provide?
For athletes who struggle to tolerate large fluid volumes, a more moderate strategy of 10 to 20 milliliters per kilogram may still increase body water, provided the sodium concentration remains sufficiently high.
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Chapters
6 chapters
1
What is pre-exercise hyperhydration and why does it matter for endurance athletes?
0:03–1:33
2
Why does drinking a lot of plain water before exercise fail to increase retained body water?
1:33–2:42
3
How does adding sodium change fluid retention and what sodium levels are effective?
2:42–3:49
4
What are common hyperhydration protocols and how much fluid should athletes consume?
3:49–5:01
5
What physiological and performance benefits — and limits — does hyperhydration provide?
5:01–6:59
6
When should athletes use sodium hyperhydration and how can they reduce GI side effects?
6:59–9:19