The science of rehydration is about as landmined as any dietary recommendation. But sometimes the Cave Painters of the Left Coast must brave dangers of miss steps in interest of reaching the tenuous safety of partial working conclusions. As always, we believe there are no absolutes; instead a strong focus of heuristics leading to knowledgeable high grounds where the course for our paths are in line with our individual differences. The goal is self optimization.
Rehydration is highly variable to the individual. Hard Stop. The below will provide a few tie down facts by which one can investigate and experiment on ones own rehydration protocol.
- Sweating is a function of core temperature. Sweating decreases blood plasma & sodium (sweat is filtered blood!). This decrease blood volume and electrolytes puts excess strain on heart, increases heart rate & perception of effort.
- The fitter you are, the more you will sweat (also highly variable).
- 3% of body weight loss to sweating can affect performance.
- Consumption of chemical tracers exude out the body within 15 minutes of consumption; sweat out what you consumer rapidly!
- Pre-Hydrating with too much water can cause a condition of hyponatremia prior to event (this is surprisingly common in endurance event racers and can result in accelerated dehydration).
- Fluid retention is directly related to sodium levels.
- Caffeine: For people habituated to caffeine, the diuresis is negligible.
- What is a electrolyte? Charged elements in the intra and extra cellular spaces. Function: cell communication.
- Intracellular: Potassium
- Extracellular: Sodium
- Gradient between both important
- Calcium & Magnesium involved in muscle contraction
- Sodium is the most lost electrolyte from sweating. RDA’s of sodium usually low due to being based off a population average that is relatively inactive.
- May need to exceed RDAs by 3-4X (highly individual)
- Cramps: Dual cause Model
- Neuromuscular theory: Muscle overload and neuromuscular fatigue are root. Fatigue causes the imbalance between excitatory impulses from muscle spindles & inhibitory impulses from Golgi tendon apparatus (muscle spindles & GTA are safety mechanoreceptors in muscle) resulting in localized misfiring
- Dehydration / electrolyte theory: due to reduction of total sodium stores there is a contraction in the intersitial fluid compartment around muscles causing a misfiring of nerve impulses leading to cramp.
- Both are theory; common denominator is misfiring of nerve.
Basics of Rehydration
Understanding that rehydration solution must have a concentration lower than the concentration of the body. Water and solution flows from low concentration to higher concentration (osmosis) and consuming a beverage of this gradient will aid in rapid rehydration; lessening the issues of gastric distress and overall inadequate rehydration. A fast and easy rule is to consume a rehydration beverage that has the least amount of ingredients (colors & artificials). Pre-hydration can also help as the body does indeed have the capability of storing sodium and other electrolytes prior to activity (similar to glycogen loading strategy prior to endurance events)
- Mayo Clinic Guidelines, RDAs for men index 15.5 cups (3.7L) per day, and 11.5 cups (2.7L) per day for women. Using the common approximate measure of 8-glasses of water a day appears accurate.
- Gatorade and most popular sport beverages are at a concentration of 6%. Look for beverages below for optimum absorption. Osmolarity important In ensuring water and electrolytes are brought into the body via the small intestine (water & solutes flow from low concentration to high gradients). Beverages higher in concentration, can impede hydration and pull water from the body resulting in gastric distress.
- Glucose & fructose receptors in the gut are most prolific; ingesting a hydration beverage with these lead in nutrients open the channels for increased water absorption by 200X.
- Loss of 3% or greater leads to decrease in performance: I.E. 150lb -> 4-5lb of water loss. Weigh in before and after to give rough estimate of fluid loss during activity.
- Replace with 16-24oz of water per lb of fluid loss.
- Pre-Hydration: for training 1x per day, consume 16-24oz 60-90 min prior to workout. Recommended to stack with electrolytes as they can be stored. Increased electrolyte & water
- Add electrolytes if more than 3% of body weight is lost.
- Electrolyte types & RDA (can safely assume these amounts should be increased for active athlete as RDAs are based off general population whom are relatively inactive)
- RDA Sodium: 2,300 mg; salt, cheese, soups.
- RDA Magnesium: 400 mg; leafy greens, nuts, seeds, whole grains, fish, poultry & beef.
- RDA Potassium: 3,400 mg; potatoes, poultry, yogurt, nuts.
- RDA Calcium: 1000 mg; fruits, leafy greens, nuts and starchy vegetables.
