Your eXpert Guide to
Energy & Endurance

The importance of carbohydrates to fuel exercise performance has been recognised since 1939¹. Energy drinks were the first sport supplements available to athletes and are still highly used today. Scientific research agrees that energy products have a direct effect on improving endurance performance. Energy drinks are widely available supplements in local shops and gyms.

Energy products supply high amounts of carbohydrates in the form of:

• Energy powder that mix with water to make a sports drink
• Carbohydrate pre-mixed and ready-to-drink
• Energy bars

Energy products contain the right types of carbohydrates in the right quantities. They can be used before, during or after exercise. Some products specialise in one of these areas distinguished by the added ingredients (see table 1). Added ingredients may include electrolytes, protein, vitamins, minerals and stimulants and their use is dependant on when the product is designed to be used.

Table 1: Typical ingredients added to carbohydrate energy drinks and whether they are best before, during or after exercise

Carbohydrate stores in the body are limited. If carbohydrate levels are low, exercise performance will be reduced. If you train for longer than an hour you need to supply your body with carbohydrates. Sports drinks, gels and bars supply your muscles with a ready supply of blood glucose for immediate energy. This will reduce the use of stored energy helping you train longer.

In a study at Loughborough University, runners were given either a sports drink or water during the first 60 minutes of a run then asked to run until they couldn't keep going any longer. Those who consumed the sports drink were able to run almost 12 minutes longer than those who drank only water³.

Energy products will:

Your body's carbohydrate stores are limited so it is important to supply the right fuel before, during and after exercise

• Prolong exercise⁴
• Increased time to exhaustion³
• Replace lost fluids
• Replace reduced energy stores after training⁵
• Maintain high intensity exercise for longer⁴

Energy products will benefit you if you are involved in the following sports.

Continuous endurance sports⁴:

• Running
• Swimming
• Cycling
• Triathlons

Intermittent sports³:

• Football
• Rugby
• Tennis
• Basketball
• Netball

During high intensity, long duration exercise, carbohydrates in the form of glucose fuel your contracting muscles. The glucose is found in the blood and stored in the muscle as glycogen. Fatigue during exercise is a result of reduced or depleted muscle glycogen. During intense training, blood glucose falls. To prevent this, stored carbohydrates are released from your muscles. As carbohydrate stores are limited, reduced stores lead to fatigue.

Energy drinks replenish carbohydrate levels to fuel exercise performance. Energy products increase exercise time, delay fatigue, maintain high intensity exercise and improve recovery. These factors result in higher intensity training and more adaptation that will improve performance.

Energy products can have beneficial effects when used before, during or after exercise.

Before exercise

Topping up carbohydrate stores before training will delay fatigue and make your training feel easier. Eating a carbohydrate based meal 2-4 hours before your training will help you train harder and longer. It is recommended that 2.5g carbohydrate per kg of body weight is consumed in the 3 hours before exercise⁶. Running on an empty stomach would result in being unable to maintain the same exercise intensity and being fatigued earlier.

Energy products help to prolong exercise, increase time to fatigue and replace lost fluids and energy stores during endurance exercise

A carbohydrate snack 30 - 60 minutes before your workout will give you an energy boost. Sports drinks and gels are handy as they are light on the stomach.

During exercise

Long aerobic exercise
Supplying carbohydrates to the body when exercise lasts 60 minutes or more can improve your performance. The carbohydrates will increase time to fatigue⁷ and help you to maintain high intensity exercise for longer⁸. The improvements in performance are due to the carbohydrates consumed during exercise maintaining blood sugar levels and ensuring a constant energy supply to exercising muscles. Carbohydrates also speed up water absorption.

Generally it is recommended that endurance athletes have 30-60g carbohydrates per hour⁹. These carbohydrates should be in the form of glucose, sucrose or maltodextrins. Fructose should be avoided as it has been known to cause stomach upsets.

Aim to consume 500ml - 1 litre per hour of an isotonic sports drink (containing 4-8g carbohydrates per 100 ml)⁹.

Intermittent sports
Sports such as football, rugby and tennis can also benefit from supplying carbohydrates during exercise. In research that simulates the start and stop sprinting nature of these sports carbohydrates are shown to improve performance³.

Exercise in the heat
During exercise in warm conditions or long duration exercise your carbohydrate drink should contain electrolytes. Electrolytes, mainly sodium, are lost during sweating. Electrolytes act to maintain proper functioning of cells, tissues and organs and optimal fluid volumes. When salt is lost during sweating and only water is consumed your blood salt level is diluted. This can cause feelings of confusion, cramps, weakness and, in extreme cases, collapse, seizure and comas¹⁰.

After exercise

Replacing energy stores after an intense workout is crucial if you want to train hard the next day. The faster rates of glycogen storage are in the first hour after exercise¹¹. Therefore it is recommended that carbohydrates are consumed as soon after exercise as practically possible. This starts the recovery process and allows maximum time for energy stores to be rebuilt¹². The addition of protein to carbohydrates has been shown to further increase carbohydrate storage when ingested after exercise¹³.

Guidelines suggest that for faster recovery you should ingest 1g-1.2g carbohydrates per kilogram of your body weight per hour. Carbohydrates consumed for recovery purposes should be moderate to high glycemic index. Also consume carbohydrates such as glucose and sucrose, rather than fructose.

Get into the habit of having a drink or snack containing carbohydrates (such as an energy bar, energy drink or a meal replacement shake or bar) straight after a run.

Table 2: A summary of how much carbohydrate should be consumed and when before, during and after exercise.

Energy products come in 3 main forms:

• Powders
• Ready-to-Drinks
• Gel

All products have the same principle but some are more convenient. There is no difference in the rates of carbohydrate replenishment between solid food and liquid drinks. The difference will be in how each product was designed to help you by providing different concentrations of carbohydrates. Ingredients can be added to suit specific types of training. For example, electrolytes for training in the heat or caffeine for pre workout energy.

Energy Powders

Energy powders mix with water to produce a sweet flavoured drink. They are generally the cheapest way to use energy products.

Energy ready to drinks

During high intensity, long duration exercise, carbohydrates in the form of glucose fuel your contracting muscles

Energy ready to drinks are pre mixed energy drinks. They often have the same formula as the powdered drinks but offer the benefit of convenience. They come in handy throw away bottles which are perfect when you're out and about or on a run and don't want to carry your water bottle on the whole route.

Energy gels

Energy gels provide a highly concentrated source of carbohydrates, such as glucose and maltodextrins. They are ideal for supplying carbohydrates pre exercise and during exercise to delay fatigue. Water needs to be drunk with the gels to ensure proper absorption.

Energy bars

Energy bars provide a convenient energy fix before, during and after exercise. Energy bars are just as effective as liquid carbohydrates for promoting refueling. Make sure you eat the bar with enough water to replace fluids lost in sweat and to aid digestion. Although they can be eaten anytime, it can be difficult to eat bars during exercise so would be recommended either as an energy snack or after exercise.

There are no potential adverse effects of energy products. Some pre-workout formulas contain caffeine so beware of everyday caffeine consumption. Too much may cause nervousness, irritability, sleeplessness and occasionally rapid heartbeat.

How can I avoid 'hitting the wall' during a marathon?

'Hitting the wall' occurs when your muscles run out of glycogen and your blood sugar level plummets. At this stage, you're in real trouble. Your body needs some carbohydrate to burn fat. When there are no carbohydrates your brain and nervous system can't work properly. This makes exercise difficult, if not impossible. You may feel weak, dizzy, nauseous and disorientated. Here's how to avoid hitting the wall.

Consume carbohydrate at regular intervals during your run, aiming to have 30 - 60 g carbohydrate for every hour of exercise. That's equivalent to drinking 500 - 1000 ml of sports drink (containing 60 g carbohydrate/ litre) each hour. Take regular sips and start drinking early as it takes about 30 minutes for the carbohydrate to reach your active muscles. This will help to keep your blood sugar levels steady and fuel your active muscles during that last stage of the race.

How much should I take in before a big race?

Pre-race you should have already made sure your muscles are glycogen loaded through the intake of complex carbohydrates, this is called 'carb loading'. Just prior to the race you should sip on a carbohydrate drink to increase circulating blood glucose levels.

How much rehydration drink should I use throughout my race and workout?

Typically you should be focusing on rehydration and energy replenishment. Following the first hour of a race you should take in 150-300kcal of energy per hour. Fluid intake should be approximately 10 ounces of water every 15 minutes, which should include some form of electrolytes (this will depend on temperature and how heavily you sweat).

Energy drinks in the past have always made me feel sick, is there anything I can do to stop this?

In the past many energy drinks incorporated fructose as a carbohydrate source until we found out it is not easily digestible which can lead to the problems you describe. Most drinks now use a maltodextrin based carbohydrate, which will alleviate your past problems. Other factors include having your carbohydrate drink too concentrated, which slows gastric emptying (the rate the carbohydrate and fluid is absorbed) and this can cause people to feel sick. If this occurs simply add more water.

Is more better when it comes to drinking carbohydrates during exercise?

It is recommended that 30-60g carbohydrates are consumed per hour of exercise. This represents the maximum rate at which carbohydrates are broken down and used as an energy source. Taking more than 60g per hour or concentrations higher than 7-8% during exercise will have no additional benefits and may even hinder performance by causing stomach upset⁸.