Hydration & Electrolyte Dosing Protocols

Hydration follows a hormetic dose-response curve: both dehydration and overhydration (hyponatremia) impair performance, per Andy Galpin — Training & Metabolism System. A 2% body-weight loss from dehydration is claimed sufficient to measurably impair accuracy/performance; 3-5% loss significantly thickens blood and impairs circulation. Hyponatremia is framed as a dilution problem from excess pure-water intake diluting sodium concentration, not a sodium-loss problem, and can be fatal.

Diagnostic tools: the WUT system (Weight, Urine color, Thirst — credited to researcher Bob Kaplan) as a simple daily gauge without lab osmolality testing; overnight body-weight "float" (normal ~1-2 lb for a 170+ lb person); pre/post-exercise dry body-weight delta to calculate true sweat loss; blood markers (hemoglobin ≥15 g/dL or hematocrit >50% flag acute dehydration); sweat-rate patches ($10-$200, 5-20% error) to bucket into high/medium/low sweater; urine color and salt residue on worn clothing ("salty sweater" sign); nocturia pattern (large clear voids = overhydration, small frequent voids = possible sleep disorder/vasopressin dysregulation).

Dosing formulas:

Galpin Equation (intra-workout): body weight (lb) ÷ 30 = ounces to drink every 15-20 min (~2 ml/kg every 15-20 min).
Pre-exercise: ~0.5 oz/lb body weight generally; 400-500 ml one hour before; 150-300 ml 15-20 min before.
Post-exercise: replace 125% (up to 150% in some studies) of net fluid lost.
Five-step daily protocol: morning water bolus → whole-food water intake → pre-hydration before heat/long sessions → Galpin Equation during exercise → 125% repletion post-workout.
Nocturnal: sip rather than chug, stop bulk fluid ~3 hours before bed (fast ingestion expands blood volume, speeding excretion and nighttime waking).

Electrolytes: intra-workout fluid should be isoosmotic to sweat (~200-400 mg sodium, ~2:1 sodium:potassium) rather than plain water, to preserve the concentration gradients that drive muscle contraction. Sodium needs are commonly underestimated; salt appetite is treated as a legitimate hardwired physiological signal, satisfiable by direct salting of food/water rather than a dedicated pill. Carbohydrate co-ingestion (60-100 g/hr, ~20 g doses every 15-20 min, 5-9% glucose concentration, 2-3:1 glucose:fructose ratio) enhances both fluid uptake and endurance performance via separate intestinal transporters — rehearse exact race-day amounts in training (gut-training) since the gut shouldn't see anything new on race day.