Carbohydrates and Exercise:
Carbohydrates are your main source of fuel when you exercise – you cannot perform well without them. When carbohydrates are eaten they are broken down into glucose which enters the bloodstream. The pancreas then releases a hormone called insulin, which takes the glucose out of the blood and into the cells where it is used as energy. Any excess glucose is stored in the muscles and liver as glycogen ready to be used when needed. On average, the body has enough glycogen to fuel between 90 – 180 minutes of endurance activity. The higher the intensity, the faster the glycogen stores will be depleted. Low muscle glycogen stores can lead to reduced training intensity and early fatigue.
It is important to keep your glycogen stores stocked up by eating and drinking at the right times, and also by eating the right types of carbohydrates. Refined carbohydrates such as pasta, Jaffa cakes and chocolate have all been heavily processed and are high in sugar but very low in fibre and nutrients such as the B vitamins, zinc, magnesium and chromium. This means they release glucose quickly into the bloodstream, which causes a rapid surge of energy followed by a fast drop as insulin works to bring your sugar levels back down. This can leave you feeling tired and can affect your performance. The only time when it is ok for you to eat refined carbohydrates such as chocolate or cake is straight after exercise when you need to replenish your energy levels and get glucose to your muscles fast. See below for what to eat before, during and after exercise.
To avoid your blood sugar levels fluctuating and to maintain steady energy levels throughout the day and during exercise, focus on eating complex carbohydrates, which are in their ‘whole’ state. These foods include oats, wholemeal pasta, brown rice, brown bread, rye, barley, quinoa, lentils and pulses. These foods also contain the B vitamins, zinc, chromium and magnesium, all needed for balancing blood sugar.
For an athlete, maintaining your blood sugar levels and therefore your insulin supplies is especially important since insulin encourages the production of insulin growth factor (IGF), which is required for muscle growth. Insulin is also needed to take amino acids (the breakdown product of proteins) directly to muscle cells and therefore increase growth rate. Eating little and often can help maintain insulin levels so always aim for regular meals plus healthy snacks in between such as fruit and nuts.
Eating and drinking before, during and after training:
The carbohydrate you eat prior to exercise is more effective at enhancing performance than the carbohydrate you consume during exercise. Take your carbohydrates around three hours before exercise if possible so that they are properly digested before you begin training. You can consume up to 100g of carbohydrates before training either through foods or a carbohydrate replacement drink.
Ensure you have plenty to drink before exercise as well. Around two hours before exercise have about 500-600mls of water. Then about 15 minutes before exercise drink another 500mls.
When training time is under an hour, water is all that is needed but energy drinks may be used. However, when training is for longer than an hour, carbohydrates drinks are required. Your glycogen stores last for around an hour and then may start dipping, your body then begins to take up glucose from the bloodstream but it cannot do this endlessly, hence the need for carbohydrate drinks. It is important to start drinking no less than 30 minutes into the training as it take 30 minutes for the carbohydrates to be absorbed into the blood and to be ready to fuel the body.
After training it is important to replace glycogen stores to maintain energy otherwise you may find the next day’s training hard work. You have a 2-hour window in which to do this, however, it is preferable to do it within the first 30 minutes after training. After training, your first step should be to re-hydrate with sips of cold water. Ensure you drink at least four glasses of water before any food. You can then eat or drink some carbohydrates. At this stage it is OK for you to eat refined carbohydrates or have a recovery drink as you need to get glucose to your muscles fast.
Once you have re-hydrated and taken in some glucose, you can then have a meal which includes complex carbohydrates and protein. Complex carbohydrates are much more effective at replenishing glycogen levels than refined carbohydrates, and help maintain energy levels after exercising. If you have been training in the morning, ensure that you eat regular snacks which include complex carbohydrates throughout the day to maintain glycogen synthesis (e.g. piece of brown toast, pitta bread or oatcakes and hummus, fruit and nuts, home-made flapjack).
You also need protein in the recovery period since if you don’t eat enough protein you will break down muscle as fuel. Therefore include protein in your meal or have a protein shake.
What to drink
Hydration is vital during exercise. The longer and more intensely you exercise the more you need to drink. Dehydration is a major cause of fatigue and poor performance. Thirst is a poor indicator for dehydration as it’s then too late – drink before you feel the thirst.
– Drink 500ml 20 minutes before training.
– Drink 150 – 250 ml during training, every 15/20 minutes
– 1-1.5litres after exercise
Types of drinks:
– Isotonic – these are the best source of glucose. SIS Go or Lucozade Sport are good.
– Hypotonic – these are good for replacing lost fluid and when energy is not required.
– Hypertonic – good for replenishing glycogen stores.
Make your own drinks:
– Isotonic: 200 mls of concentrated orange squash (not diet), 1 litre of tepid water and a pinch of pink Himalayan salt. Mix and chill.
– Hypotonic: 100 mls of concentrated orange squash, 1 litre of tepid water and a pinch of pink Himalayan salt. Mix and chill.
– Hypertonic: 400 mls of concentrated orange squash, 1 litre of tepid water and a pinch of pink Himalayan salt. Mix and chill.
Protein and Exercise
Protein is essential for many body functions including muscle growth, healthy skin and hair, energy production, healthy blood, hormone and enzyme production. If you are an athlete or exercise heavily, you have a much higher requirement for protein than the average person as you use protein for energy and muscle growth, and you also lose protein when you sweat. Protein is also necessary for maintaining steady blood sugar levels as when eaten with carbohydrates (e.g. a jacket potato with tuna) it slows down the release of sugar and so keeps your energy levels maintained for longer. Protein is also important during the recovery period after exercise – if you are lacking in protein, you will break down muscle as fuel, which no athlete wants.
Good sources of protein include chicken, fish, red meat (in moderation), eggs, nuts, seeds, lentils and beans. Ensure you include protein at every meal. If you are training hard it can be difficult to get all the protein you need in one day. This is where protein supplements and drinks may benefit you.
Antioxidants and Exercise
Your body is permanently creating energy from the food you eat to enable you to function. The process of turning fat and sugar stores in your body into energy is called oxidisation. Unfortunately, while oxidisation provides you with energy, it also produces toxic by-products called free radicals. These free radicals can cause damage to cells and increase the risk of injury and infections. Obviously when you exercise your need for energy increases considerably. This means you are producing a lot more free radicals than when you are sedentary. So while exercise is very beneficial it does cause damage to the body! Our bodies also have to fight off free radicals caused by pollution, smoking and smoky atmospheres, and eating fried, barbequed and smoked foods.
Fortunately the body has a defense mechanism and uses molecules called antioxidants to fight the free radicals. Antioxidants include the vitamins A, C and E, as well as zinc and selenium and an amino acid called glutathione. As an athlete it is really important to ensure your diet is high in antioxidants as you will be producing a lot of free radicals. Ensuring plenty of antioxidants will help you maintain a healthy immune system, reduce muscle damage and speed up post exercise recovery. A healthy diet high in fruits, vegetables and good quality protein and complex carbohydrates plus a supplement will provide lots of antioxidants. The best sources of antioxidants are fruit and vegetables, especially the brightly coloured ones such as carrots, sweet potatoes, tomatoes, oranges and strawberries. A healthy diet combined with carefully balanced training and sleep can actually enhance immunity.