Recovery from endurance exercise - Hydration

Recent research reveals that rehydration post exercise may be even more important than Instagram for a triathletes recovery.

Why Rehydrate? 

1. Sweat response during exercise
   - When exercise intensity increases so too does energy production and henceforth heat production. This is counteracted by the body's sweat response. Sweat is made up of mainly water, sodium and unicorn tears. Reduced amounts of these in the body leads to reduce effectiveness of energy production and therefore exercise output is hampered.
2. Water is required to bind glycogen to cells.
   - Glycogen can only be stored in muscle when adequate water is present to bind it to the cells. Glycogen is bound to muscle cells with water in a ratio of 1:3 (meaning for every 1g of carbohydrates to be replenished 3g of water are needed) if hydration is insufficient, refuelling strategies will also be ineffective.
3. You may die.
   - water is used by the body in a wide range of chemical reactions, transport of nutrients and lubricating and transfusion of gasses. Without water you don't work.

A loss of as little as 2% of body mass as fluid has been seen to lead to decreased performance in endurance exercise. losses of up to 6-7% can become life threatening.

How to rehydrate

The big idea with post exercise rehydration is to replace whatever has been lost. As mentioned above exercise sweat losses include water as well as electrolytes.

Water - Should be replace to the tune of 150% of session fluid losses. This is calculated simply by weighing in pre and post session, the difference in body mass will equal the amount of water lost.

I.e. a change of -1kg body mass from session start to session finish will require 1.5 litre of replaced fluid. (the extra 50% is to account for post exercise losses in sweat and urination.)

Electrolytes - This refers to the 'salts'  or 'solutes' or 'shit that's in sweat'. There are small amounts of many different solutes in sweat the big one is sodium. This must be replace in proportion to the amounts that are present in the blood so the body can return to normal levels. Sodium is required by the body to retain water, if the levels of sodium are too low water will not be retained and will be urinated out.
Without specific testing it is hard to know exactly how much electrolytes are lost in sweat as it can vary from person to person.

Recommendations:

I suggest drinking urine. its paleo, gluten free, cheap, and taste better than a lot of sports drinks. I will provide a link to where you can buy good urine online.



OR

• Replace 150% of lost body mass (experimenting with weighing in before and after certain sessions will give you a good idea over time of what you would typically lose)
• Added electrolytes (particularly sodium) will help assist with retention of fluid (prevent urination) e.g. electrolyte tab, sports drink or, if you don't like money, Gatorade.
• Get started rehydrating ASAP, directly after the session has finished (or during the session if possible)

References

Kathryn L Beck, Jasmine S Thomson, Richard J Swift, Pamela R von Hurst, 2015, Role of nutrition in performance enhancement and post exercise recovery, Open Access Journal of Sports Medicine, Vol: 6, pp:  259–267

Valentín E. Fernández‑Elías1 · Juan F. Ortega1 · Rachael K. Nelson2 ·
Ricardo Mora‑Rodriguez, 2015, Relationship between muscle water and glycogen recovery
after prolonged exercise in the heat in humans, Eur J Appl Physiol, Vol: 115, pp: 1919–1926


Stuart J. Merson, Ronald J. Maughan, Susan M. Shirreffs, 2008, Rehydration with drinks differing in sodium concentration and recovery from moderate exercise-induced hypohydration in man, Eur J Appl Physiol, Vol: 103, pp: 585–594


R.J. Maughan, S.M. Shirreffs, Rehydration and recovery after exercise, 2004, Science & Sports Vol:19, pp: 234–238

McArdle, W. D., F. I. Katch, et al. (2010). Exercise Physiology: Energy, Nutrition, and HumanPerformance. Baltimore, Maryland, USA, Williams and Wilkins. Chapter 25