The biggest challenge endurance athletes like triathletes, cyclists, and runners face is maximising their energy levels but, oddly, it is also one of the least understood aspects of these sports.
Understanding how to fuel the body is essential for effective training and an increasingly important aspect of competitive strategy.
Today’s top competitors have teams devoted to managing their nutrition and supplements to find the most effective way to fuel the body, whether in training, during the event itself, or in the recovery phase.
Not everyone has the backup of nutritional boffins, but that doesn’t mean the information you need for a nutritional advantage is beyond your grasp – it’s all out there, just not all in the same place.
That’s why Wiggle has put together this extensive guide on how to fuel your body for endurance.
We’ll guide you through the main nutrition and supplements needed to maximise your calories, show you when and what to eat before, during, and after your event, and pass on some of the latest thinking and research in the field.
Together explanations of how the latest gels, bars, and drinks work throughout these phases, this guide should give you the tools to build a winning nutritional strategy and see real-world improvements in your performance.
Understanding, Preparation, and Execution
We've divided up this article into Understanding, Preparation, and Execution. This will hopefully help you navigate each area of this complicated topic and make it easier to understand. The section headed Understanding is aimed at giving you the tools and context to make your own rules. Preparation will talk about the training phase, while Execution will discuss race or event day nutrition and supplements and some of the most popular products used.
In this section we’ll be providing the basis knowledge to help you understand how nutrition and supplements interact with your exertion levels.
Getting to grips with supplements and nutrition for endurance
The problem with understanding how nutrition and supplements work for the endurance cyclist, runner, swimmer, or triathlete is that the rules change depending on your unique physique and how it responds to effort.
The only way around this problem is understanding how nutrition and the body interact. This is a bit more complicated than following someone else’s rules, but ultimately it empowers you to find the right solution for own body and approach to training and racing.
By internalising a few principles, you’ll be able to design your own approach, make decisions on the fly, adjust to change, and create a flexible, versatile strategy that’s bespoke.
Fundamentals of endurance nutrition and supplements
There are a few things to understand before we get into the nitty gritty of endurance nutrition and supplements.
Firstly, that there two types of energy used by the body: fat and carbohydrates.
The key thing to understand is how the body switches between these fuel sources depending on the amount of effort you’re putting in.
This is key to a successful training or event strategy.
At low levels of exertion, your body will use its fat reserves. This is because there’s a lot of it. Even if you’re quite svelte, what fat stores you have will provide a rich and sustainable source of energy.
However, as you increase your exertion level, the body needs something more efficient and quick burning, so it turns to carbohydrates.
After your effort exceeds around 60% of your maximum levels, your body becomes a hybrid engine using equal amounts carbs and fat. Above 60%, carbs take over, giving the body a fuel source it can burn quickly.
At 95% of your max intensity and above, your body is running on carbs alone.
It’s a great system but with one drawback: the light that burns twice as bright burns half as long.
More work, less fat burn?
Here’s an illustration of how the body moves between fat and carbohydrates during exercise depending on your level of exertion. It may seem strange that you burn less fat as you do more exercise, and in truth, it’s a little more complicated.
There is a rate of exertion at which fat burns most efficiently – at around 50-65% of maximum effort, as highlighted in grey in the above table. You don’t burn fat watching Netflix - you have to be exercising at at least 55% of your max intensity or more to get the process firing.
This fat burning region of exertion is often called the “MaxFat” level.
What’s important to understand is that higher levels of effort use more carbs as a percentage of fuel used.
As you increase the level of activity, you burn more fuel. This fuel source begins as mostly fat and eventually becomes mostly carbohydrates as you hit peak exertion levels.
What is Glycogen?
So far we’ve been talking about carbs, but what we’re really talking about is their end product, glucose, the simple sugar from which carbohydrates are made. It’s this sugar your muscles convert into movement (by way of processes too complex to bore you with here…).
The body breaks down ingested carbohydrates into glucose, which is then free to roam the blood stream – this is your blood sugar.
When not in use, the body stores it in the muscles and the liver in a quickly retrievable form - glycogen.
When needed, the body breaks up the stored glycogen chains, turning it back into glucose to keep you moving.
But should you run out of blood glucose and glycogen, you hit ‘the wall’, commonly known as the ‘bonk’.
This is a bad situation to be in. When your glycogen stores and blood sugar run out, the body will break down the next most easily available fuel source - your muscles.
Turning them into fuel to be used for energy, it undoes all your hard work in training and effort it took to build these muscles up.
It’s a situation best avoided.
Once exhausted, glycogen takes 20 hours or more to replace.
Blood glucose can be replaced much faster with a calorie injection from some simple carbohydrates – the simpler the better.
But even then, you can’t absorb calories faster than you use them at high or even moderate intensities.
So no, you can't run forever even if constantly pumping your body full of carbs.
This is where strategy comes in.
The Glucose-glycogen cycle
Carbohydrates in your diet are broken down to create glucose, which is used for easily accessible energy.
When your body senses extra glucose, it converts it to glycogen through a process called glycogenesis for storage. Around 400g of the calorie cache is stored in muscle (worth around 2,000 calories) while 100g (400 calories) is stored in the liver.
As your blood glucose levels begin to run low, your body converts the glycogen back to glucose by a process called glycolysis for use. This switching back and forth is called the glucose cycle.
The importance of water
Your body runs a tight ship when it comes to the concentrations of glucose and water in the blood.
Sports gels are a concentrated form of carbohydrates (which it will turn into glucose) and boost your blood sugar, so your body will take drastic action if the dilution gets too high. To compensate, you need to be drinking lots of water.
You should also aim to replace the water you lose through sweat throughout your race or training ride.
Find out how much you lose over a given distance by weighing yourself at the start and end of a ride, and not drinking during.
Remember, however, that heat, humidity, and intensity will affect the results, so be prepared to add or subtract slightly to compensate for a changes in conditions and intensity.
See the section on Hydration below for more.
The role of electrolytes
The process of turning glucose into movement uses electricity. It’s the electrical impulses moving across the cell membranes in your muscles that cause them to contract. One thing we know about electricity is that it needs to have conductive material to flow - this is where electrolytes come in.
What’s an electrolyte and what does it do?
You may have heard of electrolytes, but not know exactly what they are or what they do.
In short, they’re salts.
There is a variety of electrolytes in the body, each at a range of concentrations: calcium, potassium, chlorine, magnesium, phosphate, and sodium. Sodium outweighs the rest significantly, responsible for around 90% of the total.
They allow the electrical impulses to fire efficiently in the muscle. They are kept in a steady balance by the body to allow normal function, but you can lose many of them through sweat, which is what gives it its salty taste.
If you get very low on these salts it can be a horrible experience - often compared to a feeling like a horrible hangover.
It can be very uncomfortable, so make sure you don’t overlook your electrolyte needs, especially if you sweat a lot.
Losses vs Gains:
The amount of fluids, electrolytes, or carbs you take in can’t outpace how much you’re using when you’re training or racing.
The reference table below shows how much is typically used at around 90% effort, and how much can be effectively replenished in an hour.
Notice there is a deficit between amount used and how much you can be replenished. At some point, you run out no matter how well you refuel.
Type How much you use per hour How much you can absorb per hour
Fluids 1000-3000ml 500-830ml
Sodium 2000mg 500-700mg
Calories 700-900 240-280
The need for strategy:
Because you can’t add more energy than you use when exercising, you need a strategy.
If you’ve followed the article so far, you’ll realise nutrition isn’t just about quantity, it’s about balance.
To get the best results, you need to manage your food, supplements, and exertion levels to hit your natural peak.
This means preserving your glycogen levels, sustaining your blood glucose level, encouraging body fat burning where possible, and balancing hydration with electrolyte concentration.
You’re now thinking it all sounds too complicated, right? Well, we’re about to make it all a lot easier.
The negative split
Just because nutrition is complicated doesn’t mean there aren’t easy solutions.
One such solution is the negative split.
Many modern endurance competitors are increasingly using the counter-intuitive technique of negative splits during races and training.
This is when you begin slowly, gradually increasing your pace throughout the race, and finishing faster than you started.
The technique takes advantage of how the body uses different fuel sources at different levels of exertion and was used by Kenyan marathon champ Eliud Kipchoge when he slashed the previous world record by over a minute in mid-2018.
What’s great about this technique is that it preserves your glycogen, allowing the body to pull on its reserves gradually throughout the race and reducing the risk of a bonk.
In the final stretch, you can surge with abandon without fear of hitting the wall.
How to work out a negative split
To work out a negative split strategy, identify a target finishing time then break this down into achievable splits, tapering the times toward the end and giving yourself extra time at the beginning.
Your starting pace may feel uncomfortably slow, but this is all part of the plan.
Surging is the enemy of glycogen and will undo your carefully attuned strategy, so it’s best avoided until the final stretches.
Should I carb load?
There is little agreement surrounding the idea of ‘carb loading’.
The idea is to deplete and then load the body with carbs in the days before the event while tapering off your training, with the aim of building a bank of glycogen.
There is some agreement, however, on the ‘depletion stage’ of traditional carb loading strategies. This entailed a spartan carb starvation regime for around 24 to 36 hours before diving into a carbohydrate glut for the days leading to your event.
Today, few elite athletes still adopt the strategy.
As for just adding loads of carbs to your diet ahead of the event, there is mixed advice.
Some advocate bowls of brown pasta in the 24 hours beforehand, others recommend sticking to your normal diet.
Our recommendation is to keep a note of what you’re eating before your training sessions and then jot down how you felt throughout your session to see if you spot any patterns. Eat more, eat less, experiment and find out what works for you.
In general, a balanced diet and consistent training will provide more benefits than any carb loading strategy, so make that the priority.
Now you have a strong knowledge of what the main supplements are and how they work with your body, lets look at your preparations for the race or event and how you can use nutrition and supplements to maximise your training.
Nutrition and supplements at the training stage
Just like everything else associated with race day, from technique to breathing, you need to practice your approach to nutrition before the main event.
This will help avert any event-day disasters and train your body to adapt to the nutrition it will get on the day.
There’s also a skill to eating on the go, especially on a bike, so if you’re a triathlete or road cyclist, you should practice the movement of reaching into your jersey pocket, plucking out a gel or energy bar, and consuming them.
If you’re a cyclist taking energy bars in your jersey, open them before you set off. Unwrapping an energy bar one-handed isn’t easy.
Gels, particularly, need some getting used to. Remember, they are basically concentrated sugar, and while they are incredibly effective they’re not always incredibly delicious.
There are a lot of flavour variations and varying concentrations out there, and you may have to kiss a lot of frogs before you find one you love.
But it’s not just your taste buds you have to train. If your body is unfamiliar with receiving a glucose boost, it can shut down the stomach for business, diverting all the blood to the limbs. If this happens, you’ll find it will reject additional fuel, such as a gel.
A bit of practice will mean the body will anticipate the energy top-up and be ready to receive.
Hypotonic, Isotonic, Hypertonic
Gels and sports drinks use water as a carrier for the carbs they provide. Some are highly concentrated, some are diluted and contain a lot of water. Those labelled as 'hypotonic' are highly concentrated, containing higher levels of salt and sugar than is usually present in the body. 'Isotonic' drinks contain a similar concentration as the body, while 'hypertonic' gels or drinks are more highly diluted, containing a lower concentration of salt and sugar than found in the blood stream.
Your preparations are complete - now it's time for action. Here's how to turn your nutrition and supplements into success.
How to train and how to race
Your goals for training and competing are not the same.
Training, is about pushing yourself and expanding your capability. This means safe and controlled over-stressing, pushing your body to expand its limits. Of course, this makes you tire sooner and places a lot of importance on a good recovery regime.
It's important you consolidate this progress, feeding your muscles with protein and ensuring you’re getting enough rest and sleep. Staying healthy and avoiding training sessions should also be high on the list, and supplements can help here too.
Racing or taking part in an event like a sportive or 10k, meanwhile, is different. That’s when you maximise what you’ve got, which for endurance running, riding, or swimming means being as efficient as possible – conserving what you can while achieving the fastest overall speed.
Nutrition and supplements for training
Carbohydrate gels like the SiS GO Isotonic Gel deliver an easily digestible and quick supply of carbohydrate for energy during exercise. A selection box like this is a great way of finding the gel flavours you like, as some are not to everyone's taste. This is a great option for those at the training stage, practising with gels before an event or race.
For recovery after a tough training session, products like the High5 Recovery Bar are convenient, providing 14g of protein and 22g of carbohydrate to help muscles recover their glycogen stores and aid in muscle building.
While improvements in fitness reduce your susceptibility to disease generally, hard training can temporarily weaken your defences. Vitamin supplements help reinstate the balance, helping the body's natural defences. Losing days or longer through illness can be costly to progress, so a little help can go a long way.
The big day - nutrition and supplements for race or event day
Pay close attention to your energy levels, hydration, and electrolytes, and ensure they are tuned to your level of exertion.
Don't wait until you begin to fade before taking on extra energy. It takes a while to hit your bloodstream and if you're starting to bonk before you hit a gel or nutrition bar then it's already too late. In training, you should have developed a good idea of how often and how much works for you, so use it to create a schedule and stick to it if you’re feeling good.
Event duration: 30 minutes – 1 hour
If you've paced yourself correctly and stocked your glycogen stores properly over the past few days, it’s likely you won't need additional energy for an event lasting up to an hour or slightly more. If you’ve missed a good breakfast and plan on pushing hard throughout, then a gel around ten minutes before you set off should kick in around 15-20 minutes later and pull you through.
Make sure you go into the event well hydrated, and if you're intending to push hard for the full distance you'll might need to replace water lost through sweat.
If you’ve packed a lot into the hour, with a lot of surging, hill work, or anaerobic effort, a recovery shake with a high protein component is recommended to aid muscle recovery and development for your next event.
Event duration: 1 – 3 hours and above
As mentioned above, the average person has around 90 minutes worth of glycogen stores to call on at high levels of exertion. Supplementing your energy levels then can give you an important boost. Here are some of the most important nutritional strategies and products used by experienced endurance athletes.
Carbs: Your glycogen stores last around 90 to 120 minutes, depending on your level of fitness. Many endurance athletes take a gel or a simple carb hit (like a nut bar) 10 minutes or so before setting off, then at the hour mark keep blood glucose levels from falling. However, ensure you've tried this in training as sending blood to the stomach early on doesn't work for everyone and needs tested.
Most people can only absorb a maximum of 280 calories per hour – even this takes practice. Calorie quantities of gels vary from brand to brand, so don’t blindly take them. Check the calorie content and don't exceed the 280g figure or you could experience gastrointestinal discomfort.
Aim for one gram of carbohydrate per kilo of body weight, each hour – which makes it easy to calculate: A 60kg individual should take 60 grams of carbohydrate an hour, while an 80kg person would need around 80g per hour.
By event day, you will have practised with a variety of energy gels in terms of taste, consistency and effect. You should also be adept at taking them on the move. This 38g High 5 Energy gel contains 23g of carbohydrate.
Energy bars take longer to digest but provide a more steady release of sugars into the bloodstream. They're also great for those who can't quite stomach the consistency of gels or their sugary taste. These PowerBar Energize Energy Bars contain around 842 calories - around 39g of carbohydrate - enough to help combat falling glucose levels. As they take a little longer to digest, you may need to take them a little earlier than a standard gel.
Added to a water bottle, these energy powders can provide a steady stream of carbs for an energy top-up. Remember to be careful about using these at the same time as energy gels or bars. Combining carb supplements like this can lead to over-doing it and flooding your body and bloodstream with excess sugar. Aim for one gram of carbohydrate per kilo of body weight, each hour.
How much electrolyte you need to replace can be tricky to work out accurately. People sweat at vastly different rates while different conditions will also play a part. Meanwhile, the amount of salts lost per litre of sweat varies too.
Electrolyte tabs generally provide 700mg per tablet because the average person loses anywhere between 700mg and 1000mg of sodium for every litre of sweat. The average person, meanwhile, sweats between 0.8 and 1.4 litres per hour during exercise.
That means, if we assume you’re around the average person, one solution with a 700mg tab per hour is probably about right, unless you’re a heavy sweater. Again, start with this approximate figure and refine it during training. One major difference between electrolytes and carbohydrate energy is that you shouldn't take on extra electrolytes at the beginning of your event. Just aim to replace what you've lost as you go.
It’s important to find the right balance of electrolytes. Low concentrations of salts can make the body think it’s dehydrated and trigger the urge to urinate – leaving you even more dehydrated. Over use will make you excessively thirsty and you could take on too much water.
The High5 Zero tabs above contain Vitamin C and five electrolytes, including sodium, magnesium and potassium.
At the risk of insulting your intelligence, yes, hydration is important. However, it’s more important than you think, especially when using energy gels.
As mentioned, the body works hard to balance its levels of blood sugar and overdoing it can lead to gastro intestinal discomfort.
Without water, energy gels also take longer to digest and enter the blood stream.
Be especially careful if taking gels with an energy drink, which are often also high in sugar. Combining them means it’ll be very difficult to manage and you may overload your body’s ability to absorb it.
A decent water bottle is all you need!
Another option to consider is caffeine. In moderate doses (around 3-6mg per kg) it can provide a short term boost, and is especially useful towards the end of an event.
Along with better focus, studies have shown caffeine dilates the blood vessels and aids circulation. Again, moderation is the key to avoid giving your digestive system too much to do.
Caffeine infused drinks like GU's Energy Gel can provide a stimulating when your energy levels start to lag.
Recovery phase nutrition and supplements
Being sore and exhausted after a race is tough, but it also presents an opportunity. With your body depleted, now is the time to rebuild stronger by giving the body the best building blocks available.
Make sure you replenish your energy and hydration needs and, importantly, provide your body with the essential protein it needs to repair and strengthen those painful muscles.
Depending on the intensity of your ride, run, or tri, you should aim for 1.2 to 1.4g of protein per kg of body weight per day to build muscle.
Protein shakes like Reflex 100% Whey Protein will help you to easily meet your protein requirements, ensuring your muscles have the right building blocks to repair and strengthen.
Recovery drinks like Torq provide a 3:1 blend of carbohydrate and quality whey protein. This ensures your glycogen levels are restored and aids the natural recovery process.