Sodium Preloading: General Athlete Guidelines
Purpose: Help retain fluid before prolonged exercise, especially in the heat. These are starting points for healthy adults to trial in training—not a requirement before every session.
Short or easy session; cool conditions
Normal meals and drinking to thirst. Usually no special sodium preload needed.
Usual routine
Long or hot session/race
Trial 500 mL (17 oz) fluid containing 750 mg sodium.
Start about 90 minutes before; finish about 45 minutes before.
Heavy sweater facing a long, hot event
Start with the same 500 mL + 750 mg sodium. Heavy sweating alone does not mean you should double the dose.
Same timing; assess comfort and tolerance in training.
Optional evening-before preparation for a long, hot event
500 mL fluid containing 750 mg sodium, as part of usual evening fluid intake. Evening before; only if previously tested and useful.
Very high sweat losses or limited access to drinks during the event
Have a sports dietitian individualize the plan before using larger volumes or stronger concentrations. Test before race day.
The 500 mL/750 mg approach is a practical protocol published by Precision Fuel & Hydration, a commercial electrolyte provider; it is not a universal dose for every athlete. Protocol and timing
Check the units: A drink with 1,500 mg sodium per litre delivers 750 mg in 500 mL. Sodium and salt are different measurements.
Include this in your normal fluid intake. Do not add it on top of large amounts you are already drinking. Smaller athletes may need less.
Keep normal meals and normal salting. Avoid stacking extra salt capsules on top of the preload.
Trial it during training. Reduce or stop if it causes nausea, bloating, or stomach discomfort.
Keep drinking during exercise appropriate to your needs. Preloading does not replace your race hydration plan, guarantee cramp prevention, or protect against overdrinking.
The AIS reserves more concentrated pre-exercise loading strategies for situations such as heat and large sweat losses that cannot practically be replaced. AIS guidance
Medical exception: Athletes with kidney or heart disease, high blood pressure, or prescribed sodium/fluid restrictions should get clinician guidance before sodium loading.