When to use this
The early-season or pre-heat week when hydration needs to move from a team guess to an individual number.
- An athlete keeps cramping or fading in the last third of long sessions.
- One team drinking rule is clearly leaving the heavy sweaters behind.
- Hot weather is coming and last season's plan was never actually tested.
Advanced lab
The formula and a worked example
The sheet describes the test. The exact formula, a full worked example, and the replacement targets are here so the result becomes a per-hour drinking number.
Sweat rate is a planning number, not a command — forcing full replacement mid-race invites sloshing and nausea, and in long hot efforts overdrinking plain water carries hyponatremia risk. These protocols are adult-derived, so keep youth targets conservative and send unusual results to a sports dietitian for an individual plan.
Evidence sources
These references support the handout’s general education. Individual medical, supplement, laboratory, or injury questions should be handled by the appropriate qualified clinician.
- Casa DJ, Stearns RL, Lopez RM, et al. National Athletic Trainers' Association position statement: Fluid replacement for athletes. J Athl Train. 2000.
Where to go next
