GLOSSARY

Fluid Output is fluid leaving the body, with recorded and unrecorded routes specified for meaningful accounting.

Water leaves through urine, skin, breathing and feces, with variable contributions. Sweating can dominate during hot exercise, whereas vomiting or diarrhea adds gastrointestinal fluid and electrolyte losses. Water loss continues at rest. Measuring urine alone therefore does not measure total output. Any balance estimate should acknowledge unmeasured routes rather than presenting an incomplete record as a precise whole-body measurement.

Sweating varies with intensity, heat, humidity, clothing, heat acclimation and individual characteristics. Sweat volume and sodium concentration are different measurements: the heaviest sweater does not necessarily have the most concentrated sweat. Total loss depends on both. Salt marks on clothing provide a clue, not a substitute for valid testing or repeated records from comparable training sessions.

Practical sweat estimation compares pre- and post-session mass using the same scale, dry skin and minimal clothing, while recording drinking and urine. Wet clothing, food and very long sessions introduce error. This estimates whole-body loss. A patch at one skin site does not automatically represent the entire body's sweating or composition without a validated sampling and interpretation method.