GLOSSARY

Exercise-Associated Fluid Deficit is a deficit associated with exercise, interpreted with intake, losses and starting hydration before assigning cause.

Body water is not completely fixed: drinking, food, excretion and activity change it. Hypohydration describes a reduced-water state, whereas dehydration can describe the process producing it, although everyday usage overlaps. Athletes benefit from starting suitably hydrated and avoiding substantial deficits or excessive intake. The terminology does not require chasing a single unchanging water value throughout every session.

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.

For example, interpret a training day alongside food water, drinks and losses; a morning-to-evening difference without that context does not establish a definite deficit or excess.

Reduced body water can increase cardiovascular and heat-dissipation demands, especially during prolonged hot exercise. Adequate hydration does not guarantee protection against heat illness; intensity, acclimation and environment still matter. Not every performance decline or temperature rise is caused solely by dehydration. Continuing to drink should never substitute for recognizing excessive strain, reducing exposure and obtaining appropriate assessment when warning signs occur.