Supplement research


Sports Hydrate

What is a Sports Hydrate?

A sports hydrate is a drink that contains primarily carbohydrate, water and sodium. It is used for optimal hydration and as a fuel source during exercise.

Proposed Benefits of a Sports Hydrate

A sports hydrate is designed to provide optimal hydration before, during and after physical exercise. Sports hydrates also provide carbohydrate which is an important fuel for the exercising muscle.

Mechanism of Action of Sports Hydrate

Dehydration during exercise can cause adverse effects on both physical performance and health (1,2). It is estimated that if an athlete becomes dehydrated by as little as 2%, this may negatively affect physical performance by 20%. Therefore the ingestion of fluid during exercise is paramount. Also the factors that effect fluid availability (e.g. gastric emptying and intestinal absorption) are important considerations. It is also important to supply fuel for certain sporting events. The carbohydrate component of the sports drink is thought to maintain blood glucose levels at a time when muscle glycogen is low.

Sports drinks are designed to optimise the gastric emptying (the rate at which fluid is emptied from the stomach) and intestinal absorption of fluid, whilst also providing energy for the exercising muscle. One of the strongest inhibitors of gastric emptying is carbohydrate concentration. However, fluids containing 4-8% carbohydrate (i.e. 4-8g of carbohydrate per 100ml) will have minimal effects on this. Therefore sports hydrates are designed with this physiological factor in mind. Beverages which contain higher amounts of carbohydrate slow gastric emptying of the fluid, as well as slowing intestinal absorption which may result in inadequate hydrate in certain environmental conditions (3,4). A sports hydrate should therefore deliver both fluid and fuel to the athlete in a form that does not compromise hydration.

Salt has been shown to aid the absorption of water into the intestine and to retain fluid. The consumption of a salt containing beverage during exercise will promote fluid retention and help maintain the osmotic drive to drink, thus enduring adequate fluid intake (5).

Adding carbohydrate and sodium to a beverage will enhance intestinal absorption of water when a relatively low osmolality is maintained. Also by adding sodium to a carbohydrate-containing drink designed to maximise absorption, the body's own stores of sodium can be spared. The sodium in a sports drink may partly cover the sweat losses induced by exercise.

Research on Sports Hydrate

The formula that most sports hydrates are based on (i.e. 4-8% carbohydrate, 500-800mg sodium/L), results in optimal gastric emptying and fluid absorption (6).

Several studies have shown performance benefits from fluids containing carbohydrate and electrolytes. The performance benefits are shown during intermittent exercise (7,8) and during prolonged exercise (9,10).

Rating of Efficacy for Sports Hydrate

10/10

 

References

  1. Montain S.J. and Coyle E.F. The influence of graded dehydration on hyperthermia and thermal regulations. J Appl Physiol. 1992:1340-1350, 1992.
  2. Walsh R.M., Noakes T.D., Hawley J.A. and Dennis S.C. Impaired high-intensity cycling performance time at low levels of dehydration. Int J Sports Med. 15:392-398, 1994.
  3. Maughan R.J. Gastric emptying during exercise. Sports Sci Exch. 6:1-6, 1993.
  4. Vist G.E. and Maughan R.J. The effect of osmolality and carbohydrate content on the rate of gastric emptying of liquids in man. J Physiol. 486:523-531, 1995.
  5. Wilk B. and Bar-Or O. Effect of flavour and NaCl on voluntary drinking and hydration in boys exercising in the heat. J Appl Physiol. 80:1112-1117, 1996.
  6. Rehrer N.J., Beckers E.J., Brouns F., ten Hoor F. and Saris W.H.M. Exercise and training effects on gastric emptying of  carbohydrate beverages. Med Sci Sports Exerc. 21:540-549, 1989.
  7. Jackson D.A., Davis J.M., Broadwell M.S., Query J.L. and Lambert C.L. Effects of carbohydrate feedings on fatigue during intermittent high-intensity exercise in males and females. Med Sci Sports Exerc. 27:S223, 1995.
  8. Murray R., Seifert J.G., Eddy D.E., Paul G.L. and Halaby G.A. Carbohydrate feeding and exercise : effect of beverage carbohydrate content. Eur J Appl Physiol. 59:152-158, 1989.
  9. Ball T.C., Headly S.A., Vanderburgh P.M. and Smith J.C. Periodic carbohydrate replacement during 50 min of high-intensity cycling improves subsequent sprint performance. Int J Sport Nutr. 5:151-158, 1995.
  10. Below P.R., Mora-Rodriquez R., Gontalez-Alonso J. and Cyle E.F. Fluid and carbohydrate ingestion independently improve performance during 1 hr of intense exercise. Med Sci Sports Exerc. 27:200-210, 1995.