1. Sports drinks aim to replace electrolytes and water lost during exercise to maintain performance levels and hydration. They contain carbohydrates, sodium, and potassium which are depleted through sweat and need replacing. 2. During exercise, sports drinks help prevent dehydration and fuel working muscles by replenishing lost carbohydrates and electrolytes. After exercise, sports drinks aid rehydration and help restore glycogen stores. 3. Proper hydration before, during, and after exercise is important for performance and health. Sports drinks can effectively hydrate and provide nutrients to support exercise when consumed in appropriate amounts tailored to individual needs.

1. Ergogenic aids
Sports drinks as a means of
hydration.
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2. Introduction
The purpose of this study is to examine hydration methods and their effect on performance.
The theory behind nutritional aids is to supply more than the body naturally produces, for
example, Creatine. With more total muscle creatine readily available, the greater the net ATP
produced in the muscle during contraction and also the rate of PCr resynthesis during recovery
increases. (Balsom, Ekblom, Soderlund, Sjodin & Hultman, 1993; Balsom, Soderlund, Sjodin &
Ekblom, 1995; Birch, Noble & Greenhaff, 1994)
Many sports drinks claim to hydrate better than water and it is this that is interesting.
Water is one of life’s most essential nutrients. Being the most abundant component in the body at
60%, it helps to regulate temperature, lubricate joints, transport nutrients and pass waste. Water
is stored both intracellular (blood plasma) and extra cellular (GI tract) and transports electrolytes
(Na, K) and small ions to help regulate fluid balance and the distribution of water inside and
outside the cells. It is fluid balance in particular to exercise that is the limiting factor in terms of
performance. It is the concept of human homeostasis where the amount of fluid lost is equal to
the amount of fluid taken in. If not, this is by definition, dehydration. Fluid balance has many
limiting factors itself, conditions of subject, the amount of physical activity and the environmental
factors.
Mechanisms
The theory behind sports drinks, are that they aim to replace/maintain the electrolytes and water
lost during exercise. Which in turn increases performance or allows the athlete to maintain the
current level of intensity (Rivera-brown, Gutierez, Gutierrez, Frontera & Bar-Or, 1999). This study
also shows the total volume of flavoured water ingested, with 6% Carbohydrate and 18mmol/l
Na+, was higher than that of plain water. Suggesting that sports drinks seem to be more
palatable than water and therefore aid hydration status better.
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3. Many sports drinks contain different ions and claim to have different properties than others, but
realistically they all do the same thing. It has been found (table 1), that the basis of all sports
drinks are carbohydrates from simple to complex. They are essential for energy and for
maintaining and restoring blood glucose after exercise. The more carbohydrates a sports drink
can offer the more potential there is for them to reach the muscles for fuel as each has a different
absorption site and rate. Studies have shown that the inclusion of carbohydrates can increase the
work output and prolong exercise duration, (Tsintzas, Williams, Campbell & Gaitanos, 1993;
Coyle, Hagberg, Hurley, Martin, Ehami & Holloszy, 1983)
Different activities have different rates of carbohydrate utilization. For example a high intensity
cycling event showed that the rate of muscle glycogen use was unaffected by the ingestion of a
carbohydrate solution, (Coyle, Coggan, Hemmert & Ivy, 1986), whereas when a carbohydrate
solution was ingested during a long distance running event the rate of muscle glycogen use
decreased (Tsintzas, Williams, Boobis & Greenhaff, 1995). Also activities with high intensity,
short bouts, showed no depletion but increased performance (Below, Mora-Rodriquez, Gonzalez-
Alonso & Coyle, 1995). The type of carbohydrate and concentration is important, however studies
have shown no major difference between their effects (Coyle et al., 1986) however fructose has
been found to cause some intestinal distress (Murray, Paul, Seifert, Eddy & Halaby, 1989). Sports
drinks containing sodium are better for re-hydration, as sodium helps maintain fluid balance and
promotes the uptake of water into the intestines, (American College of Sports Medicine, (2005).
Selecting and effectively using sports drinks, carbohydrate gels and energy bars. Retrieved
August 3rd, 2011, from http://acsm.org/AM/Template.cfm?
Section=Brochures2&Template=/CM/ContentDisplay.cfm&ContentID=12036). It also decreases
dehydration factors such as urine production through a negative feedback loop. When high levels
of Na+ are detected in the blood stream, the brain releases an anti-diuretic hormone to the
kidneys to reduce the production of urine. This process also retains the volume of water in the
body by using it to dilute the high Na+ concentration. (Control of urine volume. Retrieved August
12th ,2011, from http://www.nsbri.org/humanphysspace/focus4/ep-urinecontrol.html)
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4. Table 1
Different sports drinks readily available and contents.
Lucozade Sport - LITE Carbohydrate – 2g (of which sugars – 1g)
Nlacln – 0.61mg
Vitamin B6 – 0.07mg
Vitamin B12 – 0.03µg
Pantothenic Acid – 0.21mg
Calcium – 37mg
Powerade Xion4 Sodium – 0.05g
Carbohydrates – 3.9g (of which sugars – 3.9g)
Potassium – 12.5mg
Calcium – 1.3mg
Magnesium – 0.6mg
Gatorade Perform Series 02 Low Calorie Sodium – 110mg
Potassium – 30mg
Carbohydrates – 5g (of which sugars - 5g)
Gatorade Perform PRO Series 2 Sodium – 200mg
Potassium – 90mg
Carbohydrates – 14g (of which sugars – 14g)
Calcium – 6mg
Magnesium – 3mg
Gatorade Perform Natural Series 2 Sodium – 110mg
Potassium – 30mg
Carbohydrates – 5g (of which sugars – 5g,
Sugar alcohol – 4g)
Loss of these ions and minerals speeds up the onset of fatigue, which decreases performance.
(Montain & Coyle, 1992; Coyle et al., 1983; Coggan & Coyle, 1989.)
Sports drinks are used before, during and after exercise. These days most companies have
multiple drinks for each, some, e.g. Gatorade, have an entire series. These are founded on the
basis that elite athletes are more susceptible to a greater loss of electrolytes and carbohydrates
through higher intensity and extended duration.
The aim of consuming sports drinks is to prevent dehydration/re-hydrate (defined as >2% loss in
body weight) (Hargreaves, 1996; Burke, 1996). And by keep the body functioning efficiently
during and after exercise. They also aim to replace fluid lost. They speed up the rate at which
ingested fluid leaves the stomach and is absorbed, and also they increase the amount of total
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5. fluid absorbed.
Review
- Pre Exercise
Athletes should begin exercise in a well-hydrated state. Avoiding diuretic drinks such as tea,
coffee and alcohol, is important as these stimulate greater/more-often urinary responses.
Recommendations are that they consume approx 5-7ml/kg BW roughly four hours before
exercise and this should be paired with a meal.
Studies have shown that, athletes that are in a better state of hydration, before exercise occurs,
perform better than dehydrated athletes.
Burge, Carey and Payne (1993) tested 8 international male rowers in a state of dehydration (pre
exercise) and re-hydration (during) and found that Rowing trial time increased significantly from
7.02 +/-0.17 min for the dehydration to 7.38 +/- 0.21 min for the re-hydration (P < 0.05).
Other studies also showed similar results, (Armstrong, Costill and Fink, 2003; Below et al., 1995;
Judelson et al., 2007; Pitts, Johnson and Consolazio, 1944). Athletes that super hydrate can
increase their blood plasma volume; decrease core body temperature and heart rate, which
increase performance. (Kristal-Boneh, Glusman, Shitrit, Chaemovitz & Cassuto, 1995)
- Performance
During exercise a high rate of metabolic heat production occurs and body temperature rises. As a
result the body begins to sweat to promote evaporative heat loss. The ingestion of fluids is vital to
replace fluid balance although the rate at which this is ingested does not match the rate of
perspiration and there is usually some fluid deficit as a result of exercise; also maintenance of
good fluid intake is important to avoid heat exhaustion. (Lyle et al., 1994). The best method to aid
heat exhaustion to is drink plenty of fluids, (Lyle et al., 1994; Walsh, Noakes Hawley & Dennis,
1994) It is difficult to avoid, as thirst is not a good indicator of the body’s requirement for fluid
(Hubbard, et al., 1984; Engell, et al., 1987). If an athlete does not consume enough fluid
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6. correlated to rate at which perspiration occurs, there is a risk of dehydration and in severe cases
serious health effects. Athletes are advised to consume enough fluid to avoid substantial fluid
loss; this in turn maintains plasma volume, electrolytes, prevents abnormal increases in heart rate
and core body temperature and most importantly provides fuel. There is no single volume as it
depends on many factors, such as exercise intensity and environmental factors, but athletes
should consume based on sweat loss and start early and consume frequently. In relation to
sports drinks, consuming too much to fast can cause GI distress, alternatively, too little can have
no affect. Recommendations for carbohydrate intake are, 1g per min in a solution containing
between 6-8% carbohydrate at a volume intake of 0.6-1.2l/h (Coggan & Coyle, 1987)
- Recovery
It is vital to replace lost electrolytes, water and glycogen stores after exercise, although many
athletes never replace or consume fluids at a rate of more than 70% of perspiration, most are
lower (Borad, Burke, Gox, Heeley & Riley, 1996). Sports drinks contain the salts that the body
uses during exercise for performance. The depletion of these causes dehydration. Most athletes
prefer sports drinks, as they are more palatable than water. Generally water, seemingly tasteless,
losses its appeal after a while and quenches thirst. Sports drinks do not tend to quench thirst and
combined with flavours are more appealing, causing athletes to consume more. Evidence has
shown sports drinks to be more beneficial than plain water (Gonzalez-Alonso, Heaps & Coyle,
1992). It must be considered that if another bout of exercise is scheduled the same day or shortly
after the first, it is of higher importance to correctly replace fluids
Table 2
Sweat rates in different athletes competing in different sports
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7. Sport Environment (°C) Sweat Loss (ml/h)
Marathon 6-24 540-1520
Football 10
25
1000
1200
Basketball (m)
(f)
20-25
20-25
1600
900
Rowing 10
30
1165
1980
(Maughan & Shirreffs, 2004)
Table 2 shows textbook data for sweat loss across different sports, although this data is often not
useful as the individual fitness levels, training intensities etc for the athletes are unknown. But as
a mean it shows a large fluid loss in just one hour. This data also does not factor in water loss
from other causes such as respiration and urination.
As a gold standard, it is recommended that athletes replace 150% of fluid lost during exercise.
This can be calculated by the difference in body weight post exercise.
Discomforts
Sports drinks high in CHO and high intensity exercise can cause a decrease in the rate of gastric
emptying, which can cause discomfort to an athlete, as a large amount of fluid sits in the
stomach. (Vist and Maughan, 1995)
Although not sports related, the high sugar content of sports drinks has been known to cause
dental problems. Milosevic, A. (1997), found that all sports drinks available had erosive potential
but not that where directly detrimental to oral hygiene if consumed correctly.
- Hypohydration
When the body looses too much fluid (>2% of BW) through urination, sweating etc, there can be
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8. physiological consequences, which can cause discomfort to an athlete. Hypohydration can cause
an intolerance to heat due to greater heat storage, as the body can not cool down with sweat
(Pitts et al., 1994).
If fluid loss becomes greater than 5%, there are more severe effects including, Increased heart
rate, further increase in core body temperature and nausea.
In cases of fluid loss greater than 10%, medical help should be sought immediately, as this level
is often fatal. Effects include, Vomiting, breathing difficultly, seizures and unconsciousness.
(Signs and symptoms of dehydration, Retrieved March 10, 2011, from
www.sympotomsofdehydration.com)
Effectiveness
- Carbohydrates
Carbohydrates need replacing to restore blood glucose concentration and maintain carbohydrate
oxidation in the later stages of prolonged exercise.
Maltodextrin, a complex carbohydrate, has become vastly popular in sports drinks recently.
Studies have shown that it has no advantage compared to glucose or sucrose but its preferred by
athletes and sports scientists as it is more palatable in concentrations containing >10%
carbohydrate. (Brook, Davies and Green ,1975; Massicotte, Peronnet, Brisson, Bakkouch and
Hillaire-Marcel, 1989; Murray, Paul, Siefert, Eddy and Halaby, 1989; Owen, Kregel, Wall and
Gisolfi, 1986.)
Gonzalez-Alonso, Heaps and Coyle (1992) found that dilute CHO solution was more effective for
post exercise re-hydration than water.
If exercising in a hot environment it is wise to avoid high CHO concentrated drinks as they
decrease the rate of gastric emptying. Exercise of moderate to high intensity requires an increase
in the need to replace CHO. Although there are exceptions, for example, a marathon runner may
run most of their race, metabolising fats and not there CHO stores, whereas a football player,
sometimes performing at high intensities, over 90 minutes plus extra time, will use up more CHO
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9. stores. During moderate to high intensity exercise it is important to balance which need is greater,
fluid replacement or CHO replacement.
- Electrolytes
During intense, prolonged exercise, large amounts of salt can be lost through sweat, (Costill,
1977) and these amounts differ greatly between individuals.
Though salt loss does not effect performance directly, it has been found that sodium chloride
replacement during exercise can increase voluntary fluid intake, protect plasma volume (Below et
al., 1995) and decrease urine production (Vrijens & Rehrer, 1999), all dehydration factors.
A study by Costill and Sparks (1973) highlighted that the ingestion of a glucose solution after
severe dehydration resulted in a greater restoration of blood plasma volume, in comparison to
water.
Practical Recommendations
There are no specific supplementation recommendations for hydration as everyone differs
greatly. The basic guidelines have been outlined. It is the responsibility of the athlete and/or
coach to tailor these to the athletes’ specific sport and daily exercise regime. It is also important
that it is tailored to individual sweat rates and the climate.
The importance of hydration increases as the intensity of exercise increases. During training
periods there will be less re-hydrating occurring than in competition, that is, assuming that training
in less intense.
Conclusions and Further Directions
In conclusion it has been found that sports drinks play a vital role in hydration and re-hydration of
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10. an individual. These drinks contain water, Carbohydrates and Electrolytes that desperately need
replacing after exercise to ensure the human body remains in a state of hydration. The failure to
do this can result, in extreme cases, death.
It has been found that depleted electrolytes have no detrimental effect on performance but an
increase can aid voluntary fluid intake and the replacement of Carbohydrates lost are vital for
blood glucose concentration. Sodium supplimentation offsets urine production and sports drinks
containing multiple simple and complex carbohydrates have the ability to re-hydrate better than
plain water.
Every study stressed the need that recommended dosages/intakes should be made specific to
the athlete/event/environment.
The original focus of this review was to compare sports drinks with water in an attempt to support
or disprove what many sports drinks companies are stating these days; Hydrates better than
water.
A lack of research specific to this caused the review to focus on the effectiveness of sports drinks
alone. Further research needs to be aimed at these allegations made by these companies, not
only for science, but also for athletes.
It has to be noted that there are thousands of athletes competing all over the world that are not at
professional level and cannot afford nutritionists.
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