Fluid levels are vital to help achieve maximum performance, with fluctuating electrolyte levels and dehydration in excess of 2% of body weight shown to consistently impair aerobic exercise performance. “Proper hydration during training or competition will enhance performance, avoid ensuing thermal stress, maintain plasma volume, delay fatigue, and prevent injuries associated with dehydration and sweat loss” (Von Duvillard SP, Nutrition, 2004).
Fluids should be consumed before, during and after training. Prehydration should be commenced 1-2 hours prior to training or competition and should involve around 500ml of fluids. This ensures plasma electrolyte levels are as close to normal when exercise is commenced.
Recent research has also shown that hyperhydration (over drinking, 1.5-2 litres) prior to exercise may delay dehydration and improve performance in endurance athletes. Countering previous older studies that suggested hyperhydration can lead to hyponatremia (an imbalance between the water and sodium (salt) inside and outside of the body’s cells).
The total amount of fluid taken in during and after exercise should equate to the amount of fluid lost during the training session or competition. This can be worked out by measuring your weight prior to the session and at the end of the session, this will vary between individuals as everyone sweats at different rates. Each kilogram lost is equal to a litre of fluid lost. It is important to remember that consistently taking on more fluid than has been lost outside of hyperhydration for training or competition can lead to other problems which will affect overall performance and health.
Sport drinks with carbohydrates and electrolytes can be used in certain circumstances before, during and after training to maintain blood sugar concentration levels, to provide fuel for muscles and reduce the risk of dehydration. They should be used carefully by athletes who have been training intensely for 60 + minutes as these drinks can lead to dental decay.
Some recent studies have shown drinks which contain a 2:1 ratio of glucose to fructose improve carbohydrate delivery and oxidation of exogeneous (from outside the body) carbohyrdates to improve cycling time trial performance by 8%.
Improper hydration not only impairs aerobic performance it can also lead to dehydration and hyponatremia. Dehydration occurs due to a loss of water within the body affecting how the body functions at a cellular level. This results in symptoms such as excessive thirst, dry mouth, weakness, dizziness, sluggishness, confusion.
While hyponatremia occurs when there is an imbalance between the salt (sodium) and water inside and outside of the cells in the body. During vigorous exercise sodium is lost through sweating, this loss of sodium in the body’s fluids outside of the cells results in water being drawn into the cells (osmosis), causing them to swell. It is the swelling of the cells which leads to symptoms similar to dehydration, such as, dizziness, confusion, weakness, headache, nausea, vomiting.
Isotonic Sports Drinks
Isotonic sports drinks, such as Powerade and Gatorade aim to combat hyponatremia by affecting the movement of sodium and water from inside the cell to outside the cell. The basis to isotonic fluids are sodium and water and the concentration is set so that when consumed the sodium and water inside the cells, equal that outside the cells. This prevents any sodium or water moving in or out of the cell, preventing cellular fluid loss and cellular swelling.
Isotonic drinks also contain carbohydrates (around 6-8%) this is to aid in energy production and the sweetness from the carbohydrates entices drinking. Most sports drinks also contain additional electrolytes such as potassium and chloride.
The latest research on recovery following resistance training, low to moderate aerobic and intensive aerobic training shows that milk, preferably chocolate and low fat, aids in increased muscle hypertrophy (growth) and lean muscle mass as it appears that milk affects protein metabolism, increasing muscle protein synthesis. It also rapidly replenishes muscle glycogen stores (energy stored in muscles) faster than traditional carbohydrate drinks (isotonic drinks).
This research suggests that a combination of isotonic drink and milk is required to aid in muscle recovery as well as fluid recovery. Using this preliminary research it would appear that using isotonic drinks and water prior to and during exercise followed by chocolate milk and water post exercise provides for the best rehydration and recovery.
There is also limited research supporting the use of tart cherry juice to aid in recovery following strenuous and endurance exercise. The juice is high in anti-oxidants and therefore reduces the oxidative stress muscles undergo during strenuous exercise, reducing inflammation and lipid (fat) perioxidation. It has also shown to reduce muscle strength loss associated with exercise induced muscle damage. The juice needs to be consumed in the days before exericse and for 48 hours following exercise.
Advanced recovery for the semi-elite and elite athlete
EPOC or exercise post exercise oxygen consumption involves increased oxygen uptake following strenuous or high intensity training (ie. triathlon or marathon training). This increased oxygen aids in recovery helping to return the body to it’s base line, replenishing oxygen stores, resynthesis of ATP and creatine posphate, removal of lactate, and increased circulation and ventilation.
To maximise EPOC the following protocol should be followed:
50 minutes or more at 70% or greater of VO2 Max (Submax)
6 minutes at 105% or more of V02 Max (Supramax)
EPOC will increase with intermittent training (ie. 2 minute rest periods)
Following any high intensity or strenuous training a cool down should involve 9 minutes of low intensity cardio, which returns pH to normal and reduces lactic acid, followed by 10-15 minutes of stretching.
Connolly DA, et.al, Ëfficacy of a tart cherry juice blend in preventing the symptoms of muscle damange”, British Journal of Sports Medicine, 2006, December, Vol 8, pages 409-410
Goulet ED, et.al, “Pre-exercise hyperhydration delays dehydration and improves endurance capacity during 2 h of cycling in a temperate climate”, Journal of Physiological Anthropology, 2008, September, Vol 5, pages 263-271
Howatson G, et.al, “Influence of tart cherry juice on indicies of recovery following marathon running”, Scandinavian Journal of Medicine and Science in Sport, 2009, Oct 21, (e-journal, yet to be printed)
Karp JR, et.al, “Chocolate milk as a post exercise recovery aid”, International Journal of Sports Nutrition and Exercise Metabolism, 2006, February, Vol 1, pages 78-91
Roy BD, “Milk: the new sports drink? A Review”, Journal of the International Society of Sports Nutrition, 2008, October, Vol 2, page 15
Sawka MN, et.al, “American College of Sports Medicine position stand. Exercise and Fluid Replacement, Journal of Medicine and Science in Sport and Exercise, 2007, February, pages 377-90
Thomas K, et.al, “Improved endurance capacity following chocolate milk consumption compared with 2 commercially available sports drinks”, Applied Physiology, Nutrition and Metabolism, 2009, February, Vol 1, pages 78-82
Von Duvillard SP, et. al “Fluids and hydration in prolonged endurance performance”, Nutrition, 2004, July-August, Vol 7-8, pages 651-6
Williams MB, et.al, “Effects of recovery beverages on glycogen restoration and endurance exercise performance”, Journal of Strength and Conditioning Research, February, 2003, Vol 1, pages 12-9