Your Biggest Water Reservoir Is Not a Glass

This is a good occasion to address something that is constantly underestimated in the fitness context. Water is not a beverage. Water is infrastructure. And the biggest reservoir for it in your body is not your stomach, but your muscles.

In heat and prolonged movement, the sweat rate can exceed two liters per hour. Over a long afternoon, this adds up to an amount that hardly anyone drinks back.

Additionally, there’s the part that most misinterpret: Alcohol inhibits the antidiuretic hormone vasopressin. This disables the very mechanism with which your kidneys usually retain water. You excrete more than you take in – regardless of how much you drink. This is the real core of what we feel the day after: headaches, concentration lapses, muscles feeling like cotton.

And then there’s the 2 percent threshold. This is surprisingly reached quickly: At 75 kilograms, a deficit of one and a half liters is enough for strength, endurance, and mental clarity to decline.

Your body is made up of about 60 percent water – but it is not evenly distributed. Muscle tissue is about 75 percent water. Fat tissue is only about 10 percent.

Dehydration is thus also a matter of body composition. Not just a matter of discipline when drinking.

By the way, this is one of the reasons why we never treat muscle as an aesthetic issue. Muscle is an organ. It stores water, glycogen, and amino acids, it helps regulate your blood sugar, and it determines how resilient you are against external stresses. Including heat.

When it comes to water storage, there’s a substance that has stubbornly held onto a misunderstanding.

Creatine is osmotically active – it actively pulls water into the muscle cell. In a controlled study, total body water significantly increased through supplementation, without shifting the fluid distribution in the body. The increase thus occurs within the cells, in the range of two to four percent of total body water. This is not ‘being bloated’, but a filled cell.

And now the myth: ‘Creatine dehydrates you and causes cramps.’ A systematic review with meta-analyses examined this – and found none of it. No negative effects on thermoregulation, no greater degree of dehydration, no worse hydration markers, no reduced plasma volume. Cramps did not occur more frequently; in the controlled data, they were rather less frequent.

So, those taking creatine are not worse off on a hot day. Quite the opposite.

We wish you a calm Sunday – with a glass of water within reach.