THE SCIENCE OF SPORTS DRINKSWater, sugar and electrolytes

Copyright © TheHealthSciencesAcademy.org

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Introduction

Here is what you will learn in this unit: Types of sports drinks When is a sports drink better than water? How to create your own sports drink Why cyclists benefit from sports drinks How to answer common client questions, including:

Why do sports drinks have electrolytes? Why do sports drinks have sugar? What’s best: still or carbonated? Should I take salt tablets in hot weather? Can fruit juice improve performance? Can lite waters improve performance? Are low-calorie drinks good enough for exercise? Do caffeinated drinks improve performance? Should I avoid decaf drinks for rehydration?

Includes the following downloadable material for immediate use with your client: Easy Sports Drinks Recipes Caffeine Content in Drinks and Food

2

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

The two types of sports drinks3

Sports drinks can be divided into two main categories: fluid replacement drinks and carbohydrate (energy) drinks. Fluid replacement drinks are dilute solutions of electrolytes and sugars

(carbohydrate). The sugars most commonly added are glucose, sucrose, fructose and glucose

polymers (maltodextrins). The main aim of these drinks is to replace fluid faster than plain water,

although the extra sugars will also help maintain blood sugar levels and spare glycogen.

These drinks may be either hypotonic or isotonic. Carbohydrate (energy) drinks provide more carbohydrate per 100 ml than

fluid replacement drinks. The carbohydrate is mainly in the form of glucose polymers (maltodextrins). The main aim is to provide larger amounts of carbohydrate but at an equal

or lower osmolality than the same concentration of glucose. They will, of course, provide fluid as well. Ready-to-drink brands are

generally isotonic. Powders that you make up into a drink may be made hypotonic or isotonic.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

What’s a hypotonic drink?4

A hypotonic drink – often marketed as ‘lite’ or as ‘sports water’ – has a relatively low osmolality, which means it contains fewer particles of carbohydrate and electrolytes per 100 ml than the body’s own fluids.

Typically, a hypotonic drink contains less than 4 g carbohydrate/ 100 ml.

Benefits: As it is more dilute, it is absorbed faster than plain water.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

What’s an isotonic drink?5

An isotonic drink – a typical ‘sports drink’ – has the same osmolality as the body’s fluids, which means it contains about the same number of particles of carbohydrate and electrolytes per 100 ml.

Most commercial isotonic drinks contain between 4 and 8 g carbohydrate/ 100 ml.

Benefits: It is absorbed as fast as (or faster) than plain water. Isotonic drinks provide the ideal compromise between rehydration and refuelling.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

What’s a hypertonic drink?6

A hypertonic drink – such as cola and other ready-to-drink soft drinks – has a higher osmolality than body fluids, as it contains more particles (carbohydrate and electrolytes) per 100 ml than the body’s fluids, i.e. it is more concentrated.

A hypertonic drink usually contains more than 8 g carbohydrate/ 100 ml.

The downside: Hypertonic drinks are absorbed more slowly than plain water.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

When is a sports drink better than water?7

Opting for a sports drink would benefit performance during any moderate or high intensity event lasting longer than about one hour. Numerous studies have shown that sports drinks containing about 40-80 g carbohydrate/ litre promote both hydration and normal blood sugar levels, and enhance performance during intense and/or prolonged exercise.

When exercising longer than 2 hours or sweating very heavily, your client should opt for a sports drink that also contains sodium. Researchers at the Medical School at the University of Aberdeen found that sports drinks containing glucose and sodium can delay fatigue.

In a study carried out by researchers at Loughborough University, those who took the 5.5% sports drink produced running times on average 3.9 minutes faster compared with water, and 2.4 minutes faster compared with the 6.9% drink!

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

How cyclists benefit from sports drinks8

In a study, cyclists given a dilute sports drink (2% carbohydrate) were able to keep going considerably longer (118 mins) than those drinking plain water (71 mins) or even a higher strength (15% carbohydrate ) sports drink (84 mins). The success of the more dilute drink may be due to the larger volume drunk.

At Texas University, 8 cyclists performed a time trial lasting approximately 10 minutes after completing 50 minutes of high-intensity cycling at 85% VO2max. Those who drank a sports drink (6 g carbohydrate/ 100 ml) during the 50 minute cycle reduced the time taken to cycle the final trial by 6% compared with those who drank water.

In a study at the University of South Carolina, cyclists who consumed a sports drink containing 6 g carbohydrate and 100 ml knocked 3 minutes off their time during a time trial, compared with those who drank plain water.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Test your knowledge!9

List 2 instances where sports drinks are better than water:1.2.

Explain why cyclists benefit from sports drinks:

What are the differences between fluid-replacement drinks and energy drinks?

What’s an isotonic drink? What are its benefits?

In the next pages, we show you how to answer some questions that your client may ask you

Answering common client questions

©Shutterstock

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Why do sports drinks have electrolytes?11

Electrolytes in sports drinks do not have a direct effect on performance.

Sodium is the only electrolyte that has a potential benefit but only after, notduring, exercise: it increases the urge to drink, improves palatability and promotes fluid retention.

The increase in sodium concentration and decrease in blood volume that accompany exercise increase your natural thirst sensation, making you want to drink.

If you drink plain water, it effectively dilutes the sodium, thus reducing your urge to drink before you are fully hydrated. Therefore, including a small amount of sodium (0.23-0.69 g/ l) in a sports drink will encourage you to drink more fluid!

Adding sodium to a sports drink does not enhance fluid absorption. Glucose is more important than sodium for promoting fluid absorption.

Other electrolytes, such as magnesium, potassium and calcium, may be included in sports drinks, but there is no proven benefit to performance.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Why do sports drinks have sugars?12

Carbohydrate in sports drinks serves two purposes: speeding up water absorption and providing an additional source of energy,

Relatively dilute solutions of sugar (hypotonic or isotonic) stimulate water absorption from the small intestine into the bloodstream.

A sugar concentration usually in the range 5 to 8 g/ 100 ml is used in isotonic sports drinks to accelerate water absorption. More concentrated drinks (hypertonic), above 8%, tend to slow down the stomach emptying and therefore reduce the speed of fluid replacement.

Studies have shown that consuming extra carbohydrate during exercise can improve performance because it helps maintain blood glucose levels.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Still, or carbonated sports drinks?13

Experiments at East Carolina University and Ball State University found that carbonated and still sports drinks produced equal hydration in the body.

However, the carbonated drinks tended to produce a higher incidence of mild heartburn and stomach discomfort.

In practice, many athletes find that carbonated drinks make them feel full and ‘gassy’, which may well limit the amount they drink.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Can I create my own sports drink?14

Definitely! Commercial sports drinks work out to be very expensive if you are drinking at least 1 litre per day to replace fluid losses during exercise.

If you need to drink less than 1 litre, you probably don’t need a sports drink anyway.

The table in the next page includes some recipes for making your own sports drink!

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Easy sports drinks recipes!15

Hypotonic Isotonic

20-40g sucrose1 litre warm water1 to 1.5g (1/4 tsp) salt (optional)Sugar-free/low-calorie squash for flavouring (optional)

40-80g sucrose1 litre warm water1 to 1.5g (1/4 tsp) salt (optional)Sugar-free/low-calorie squash for flavouring (optional)

100ml fruit squash900ml water1 to 1.5g (1/4 tsp) salt (optional)

200ml fruit squash800ml water1 to 1.5g (1/4 tsp) salt (optional)

250ml fruit juice750ml water1 to 1.5g (1/4 tsp) salt (optional)

500ml fruit juice500ml water1 to 1.5g (1/4 tsp) salt (optional)

DIY sports drinks. Chill after preparing!

Sour

ce: T

he H

ealth

Sci

ence

s A

cade

my

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Should I take salt tablets in hot weather? 16

No, salt tablets are not a good idea, even if you are sweating heavily in hot weather.

They produce a very concentrated sodium solution in your stomach (strongly hypertonic), which delays stomach emptying and rehydration as extra fluid must first be absorbed from your body into your stomach to dilute the sodium.

The best way to replace fluid and electrolyte losses is by drinking a dilute sodium/ carbohydrate drink (either hypotonic or isotonic) with a sodium concentration of 40-110 mg/ 100 ml.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Can fruit juice improve performance?17

Ordinary soft drinks (typically between 9 and 20 g carbohydrate/ 100 ml) and fruit juices (typically between 11 and 13 g carbohydrate /100 ml) are hypertonic; in other words, they are more concentrated than body fluids, so are not ideal as fluid replacers during exercise.

They empty more slowly from the stomach than plain water because they must first be diluted with water from the body, thus causing a temporary net reduction in body fluid.

If you dilute one part fruit juice with one part water, you will get an isotonic drink, ideal for rehydrating and refuelling during or after exercise (see recipes).

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Can “lite”, “fitness” or “sports waters” improve performance?

18

These types of drinks are hypotonic, containing around 2% sugar along with artificial sweeteners, flavourings, sodium, and various vitamins and minerals.

Their high sodium content means they may promote fluid retention and stimulate thirst more than plain water, and the flavours make the drinks palatable – but they don’t deliver much carbohydrate energy (around 10 calories per 100 ml).

They would therefore not be advantageous for intense workouts lasting longer than 1 hour and, even for shorter workouts, offer few advantages over plain water, apart from improving palatability and encouraging you to drink more.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Are low-calorie drinks good enough for exercise?19

‘Diet’ or low-calorie drinks contain artificial sweeteners in place of sugars and have a very low sodium concentration.

They are, therefore, useless as fuel replacers during exercise, although they will help replace fluid at approximately the same speed as plain water.

Artificial sweeteners have no known advantage or disadvantage on performance.

Choose these types of drink only if you dislike the taste of water, and under the same circumstances that you would normally choose water, i.e. for low- to moderate -intensity exercise lasting less than 1 hour.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Can caffeinated drinks improve performance?20

A number of energy drinks containing caffeine claim to improve some aspect of performance, such as alertness, endurance or concentration during exercise.

The exact mechanism is not clear, but it is thought that caffeine at doses of 1-3 mg/ kg reduces the perception of fatigue and allows you to continue exercising at a higher intensity for a longer period.

For a 70kg person, this would be 210 mg, equivalent to about 2 cups of coffee or 2 cans of caffeinated energy drink.

Performance benefits occur soon after consumption so caffeine may be consumed just before exercise, spread throughout exercise, or late in exercise as fatigue is beginning to occur.

As individual responses vary, you should experiment during training to find the dose and protocol that suits you.

A study at the University of Saskatchewan tested the effects of Red Bull energy drink on weight training performance. They found that consuming Red Bull (in amounts equivalent to 2 mg caffeine per kg body weight; each can contains 80 mg caffeine) one hour before exercise significantly increased bench press muscle endurance.

Use the table in the next page as a reference guidance for the caffeine content in various foods and drinks.

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Caffeine content in drinks and food21

Drink or food Mg of caffeine per cup

Ground coffee 80 to 90

Instant coffee 60

Espresso 45 to 100

Cafeterie/filter 60 to 120

Decaffeinated coffee 3

Black tea 40

Green tea 40

Energy/sports drinks Up to 100 (per can)

Can of cola 40

Energy gel (1 sachet) 25 to 40

Dark chocolate (54g bar) 40

Milk chocolate (54g bar) 12

Sour

ce: T

he H

ealth

Sci

ence

s A

cade

my

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Should I avoid decaf drinks for rehydration?22

It is a myth that you should completely avoid rehydrating with caffeinated drinks such as tea, coffee or cola.

Researchers at the University of Maastricht found that cyclists were able to rehydrate after a long cycle equally well with water or a caffeine-containing cola drink. Urine output was the same after both drinks.

However, large doses of caffeine – over 600 mg, enough to cause a marked ergogenic effect – may result in a larger fluid loss.

A study at the University of Connecticut, US, found that both caffeine-containing cola and caffeine-free cola maintained hydration in athletes (drank during the non-exercise hours) over three successive days of training.

The athletes drank water during training sessions but rehydrated with either caffeinated or caffeine-free drinks.

A further study by the same researchers confirmed that moderate caffeine intakes (up to 452 mg caffeine / kg body weight/ day) did not increase urine output compared with a placebo and concluded that caffeine does not cause a fluid-electrolyte imbalance in the body (Armstrong et al., 2007).

Cop

yrig

ht ©

The

Hea

lthSc

ienc

esA

cade

my.

org

Test your knowledge!23

What’s the downside of carbonated sports drinks?

Explain why salt tablets are not a good idea:

Explain how caffeinated drinks improve performance:

Write down your favourite recipe for an isotonic drink:

Write down your favourite recipe for a hypotonic drink:

No Content Sharing. You must NOT share this or any other of our proprietary content, downloads, or materials with anyone. These are ONLY for students of this coursewith The Health Sciences Academy. If you violate or display any likelihood of violating any of our intellectual property rights, we will take immediate legal action.

Prohibition to Copy, Re-write or Reproduce Our Content, Methodologies and Trade Secrets. You must NOT copy, blog, re-sell, re-write, adapt, distribute, and/orreproduce our materials, our forms, our confidential and proprietary methodologies, our trade secrets, our work, our research, our content, our ideas, our healthquestionnaires, and/or our plans. This constitutes plagiarism and is an egregious violation of our intellectual property and trademarks. If you violate or display anylikelihood of violating any of our proprietary intellectual rights, we will take legal action to prohibit such violations and seek compensation for damages.

Copyright © TheHealthSciencesAcademy.org