Sodium is the dominant electrolyte lost in sweat—up to 1,000 mg per liter—and is critical for fluid retention and preventing exercise-associated hyponatremia. Potassium losses are minimal (typically under 200 mg/L sweat) and are rarely a limiting factor during or immediately after training.
The best sports drinks for ultramarathons prioritize high sodium (300-500mg per serving), easily digestible carbohydrates, and flavor variety to combat palate fatigue during 6-24+ hour efforts. Top picks include Tailwind Endurance Fuel, Skratch Labs Hydration Mix, LMNT Recharge, Fast Pickle, and Maurten Drink Mix 320 for their proven track records in multi-hour endurance events.
Sweat rate is the volume of fluid you lose per hour during exercise. To calculate it for running: weigh yourself naked before and after a timed run, subtract any fluid consumed, and convert the weight loss to milliliters (1 lb = 454 ml). This number—typically 400–2,000 ml/hour—tells you exactly how much to drink during training and races.
Zero-calorie electrolytes do not break a fast, but most sports drinks do. Here is how fasted athletes should handle sodium, which products stay fast-legal, and when to stop fasting and start fueling.
Swimmers training in chlorinated pools face unique hydration challenges: chlorine accelerates oxidative stress, and pool sessions mask sweat loss. The best sports drinks for swimmers contain sodium (300-500 mg per serving), antioxidants like vitamin C, and minimal sugar to support hydration without GI distress during high-volume training.
A new Sports Medicine paper says most athletes habitually under-drink — and admits nobody knows what decades of it does. Here is what the evidence actually supports, and what it does not.
Cool air blunts thirst, triggers cold-induced diuresis, and hides your sweat losses. Here’s how to adjust fluid and sodium for fall training and race season.
HIIT training creates rapid electrolyte depletion through short, intense bursts that spike sweat sodium loss. The best hydration strategy combines pre-loading sodium 60–90 minutes before training, sipping electrolyte drinks during intervals, and aggressive post-workout replenishment with 500–700 mg sodium per 16 oz of fluid.
The optimal electrolyte timing depends on workout duration and intensity: pre-load 60–90 minutes before sessions over 90 minutes, sip every 15–20 minutes during high-sweat efforts, and prioritize post-workout replenishment within 30 minutes for rapid recovery.
Taper week hydration is about topping off, not loading up. A day-by-day fluid, sodium, and carb-loading plan for the seven days before your marathon.