GLOSSARY

Fluid Retention After Exercise is fluid remaining after recovery intake, influenced by meals, sodium and observation duration.

Retention describes how much ingested fluid remains over the observation period, not merely how much was swallowed. Urine, other losses, beverage composition and food affect it. A retention percentage needs a defined denominator and time interval. Greater retention in a short experiment does not automatically mean better health or performance, and may be undesirable in someone with fluid overload.

The beverage hydration index compares cumulative urine after water with cumulative urine after a test drink over the same protocol interval. A higher ratio generally reflects lower urine output than water under those conditions. Resting tests do not rank overall health or competition performance. Interpretation needs the observation time, dose, starting hydration and study population rather than simply choosing the highest number.

The kidneys regulate water and solute excretion to stabilize the internal environment, alongside thirst and vasopressin signaling. They do not create new water. Exercise, illness and some medicines can alter these responses. Fluid swallowed is therefore not identical to fluid retained, and increased urine after substantial drinking can represent normal regulation rather than proof that water cannot hydrate the body.