Isotonic drinks are popular during intensive exercise and sport because they include a balance of electrolytes and carbohydrates to replace salts, minerals and glucose.
Endurance is “the act, quality or power of withstanding hardship or stress”. Due to significant differences in fitness levels and other variables amongst athletes, an “endurance” event means different things to different people. The Aussie Gelatin Company refers to, “endurance activities” as exercise or an event that exceeds 60-90 minutes. This is commonly the time that an individual requires supplementing nutrition to continue to function optimally. To overcome dehydration, heat stress and muscle cramps we encourage athletes to take a scientific formulated electrolyte and carbohydrate drink.
Endurance activities place increased nutritional and hydration demands on your body. There are higher requirements for water, carbohydrate and protein, minerals and electrolytes, throughout training and during the day to reduce fatigue.
Hot days, dehydration, sweating and a depletion of muscle glycogen are major contributors to reduced performance during prolonged exercise.1
Hydration during exercise is important to avoid heat stress, impaired cognitive function, fatigue and lower performance. Water is often used during activities lasting <70 minutes. Outside of this, carbohydrate and electrolyte replacement has been shown to assist in maintaining performance and speeding recovery (i.e. supporting rapid refuelling of muscle glycogen and reducing muscle cramps etc).
Carbohydrate is the main fuel source for exercise, especially during prolonged and high-intensity exercise. The body stores carbohydrate as glycogen in the muscles and liver, however, its’ storage capacity is limited. When carbohydrate stores are inadequate to meet the fuel needs of a workout this results in fatigue, impaired performance, reduced concentration and even reduced immune function.2
During lengthy exercise, ingesting carbohydrate can prevent blood glucose concentration to drop and may help to maintain high rates of carbohydrate oxidation which is needed to maintain high-intensity exercise. Many athletes have difficulty with consuming food before or during exercise and therefore a formulated drink that will provide carbohydrate is beneficial. Isomaltulose (palatinose) Palatinose is a slow-release carbohydrate that is excellent for prolonging energy levels as it is a carbohydrate that is slowly broken down to glucose for absorption.
Recent findings show that taking a protein and carbohydrate combination during training can enhance recovery, with subjects demonstrating a worthwhile improvement in a subsequent cycling time-trial performance.3
During prolonged exercise, the body gets 5-15% of its energy from amino acids. If no amino acids are supplied, the body will scavenge amino acids from muscle tissue. It is, therefore, worthwhile to supplement with protein with readily available amino acids.
A protein that is easily digested and assimilated is ideal for consumption during exercise as it reduces the risk of stomach upset and ensures optimal uptake of beneficial amino acids. Collagen peptides are rapidly absorbed for faster delivery of amino acids to muscles which protects the muscles during exercise and reduces muscle damage.
Electrolytes replace salt due to losses through sweat. Sweat is comprised of many minerals or electrolytes including sodium plus potassium, magnesium, chloride and calcium. Each of these minerals have vital biochemical and physiological roles in the body and therefore need replenishment during training.
Magnesium, sodium and potassium are electrolytes that provide nutritional support for healthy cardiovascular function and nerve conduction. The electrolytes sodium, chloride and potassium contribute to systemic hydration via their essential role in the maintenance of healthy cellular water distribution and acid-base balance in the body. Additional to this sodium assists fluid retention prior to and during a sporting event, which reduces the need for frequent urination.4
To help develop a fluid intake plan, both during and after exercise, athletes need to know about the magnitude of their sweat losses.
Magnesium is a mineral that experiences significant losses during prolonged exercise and such depletion may be aggravated by mental stress during competition.5
Magnesium is involved in numerous processes that affect muscle function including oxygen uptake, energy production and overall electrolyte balance, further supporting the need for replenishment.
There is evidence that a mild depletion of magnesium impairs physical performance, recovery and can even amplify the negative consequences of strenuous exercise (e.g. oxidative stress).5
Magnesium is an electrolyte which is intrinsically involved in the healthy conduction of nerves, muscle contractions and the normal rhythm of the heart. It supports healthy cellular energy production, storage and utilisation, assists in the metabolism of carbohydrates, plus may increase oxygen uptake capacity and reduce blood lactate levels. It also maintains proper muscle function, all attributes that contribute to magnesium’s ability to help maintain peak performance.
When it comes to recovery, magnesium’s role in muscle relaxation makes it useful for the prevention and relief of muscular cramps and spasms and is beneficial during times of stress.
The osmolarity of sports drinks
When aiming to maximise the effectiveness of fluid and nutrient consumption, it is important to consider the osmolarity of the solution being ingested.
Put simply, the osmolarity of a solution refers to its concentration. An isotonic solution has an osmolarity that is equal to that of the blood. In contrast, a hypertonic solution is more concentrated than the blood, and hence hypotonic refers to a solution with a lesser concentration than blood.
The significance of this in sports hydration relies on an understanding of osmosis. The fluid will move from a less concentrated environment to a more concentrated solution through a semi-permeable membrane (i.e. the gut wall). This means the fluid from an isotonic solution will move at ease from the gut into the blood, providing rapid hydration when compared to a hypertonic solution. Hypertonic solutions such as fruit juice and soft drink tend to stay within the digestive tract longer, delaying gastric emptying and increasing the risk of stomach upset. Isotonic solutions have been found to be an effective means of hydration during training.
A solution providing 4% carbohydrate (in an isotonic dose) is an ideal means of providing a rapid delivery of fluid and fuel to maximise gastric tolerance (i.e. avoid stomach upset). To make a solution more hypotonic, simply add water.
- Ishijima T, Hashimoto H, Satou K, et al. The different effects of fluid with and without carbohydrate ingestion on subjective responses of untrained men during prolonged exercise in a hot environment. J Nutr Sci Vitaminol (Tokyo) 2009;55(6):506-510.
- Carbohydrate – the facts. AIS, Australian Sports Commission 2014. Viewed 26 May 2014, http://www.ausport.gov.au/ais/nutrition/factsheets/basics/carbohydrate__how_much
- Hall AH, Leveritt MD, Ahuja KD, et al. Coingestion of carbohydrate and protein during training reduces training stress and enhances subsequent exercise performance. Appl Physiol Nutr Metab 2013;38(6):597-604.
- Burke L, Deakin V. Clinical sports nutrition. 4th edition. McGraw-Hill, 2010.
- Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnes Res 2006;19(3):180-189.