How should I fuel for indoor training? Advice from a nutrition specialist

It’s a grim feeling to be empty on the turbo trainer. You’ve got your efforts planned out or you’re in the opening stages of a Zwift race, and all of a sudden, you can’t push the watts as normal. You don’t know why, you’re fresh, rested, motivated and ready to work out, but your legs just aren’t playing ball. It can be a frustrating feeling, but the root of it can often be found quite simply: you don’t have the energy to perform.

Many of us aren’t used to fuelling for training indoors. Maybe it’s because we’re in the comforts of our own home, not facing the cold, wet or windy weather outside. Maybe we don’t feel like we need it as our sessions are short and intense, or perhaps we’ve simply forgotten. But a lack of nutrients, carbohydrates and calories can be seriously detrimental to performance, whether that’s when riding or racing indoors or doing it outdoors. 

Marc Fell, Science Officer at Science in Sport, has some key tips for how to fuel for long and short indoor training sessions, and explains that what you eat before, during and after each workout is crucial to being able to push the power when it matters. When you’re putting yourself through the pain of getting through a turbo session, it needs to be worth it, and proper fuelling can make all the difference. 

There’s a common belief that riders don’t need fuel for riding indoors, can you explain why that is or isn’t true?

Training indoors isn’t just the sweaty pain cave it once was and with the growing popularity of indoor cycling and the development of smart trainers and many virtual cycling apps, this has now become an important tool in any cyclist's training week. Therefore, if riders are relying more on training indoors and spending long hours on the turbo then their fuelling and hydration becomes very important to help facilitate short-term performance during sessions and promote training adaptations post-session.

What breakfast would be recommended for a long endurance ride indoors?

Your breakfast before a long endurance ride should predominantly consist of high carbohydrate foods such as porridge, muesli, breads, fruits, honey, jams etc. and the required quantity of carbohydrate you should aim for will be dependent on the duration and intensity of the session but also the performance goal of the session whether you are aiming to just spin the legs or looking to really get the best out of the session.

How should this be altered based on the length of the indoor session? (e.g., how much should you eat for a 90 min session vs a four-hour session)

Leading on from the previous question, the amount you should eat will be dependent on the intensity and the duration of the session. For instance, if you are going to be doing an endurance session lasting around 3-4 hours you should aim to consume around 2-3 grams of carbohydrate per kilogram body weight around three hours prior to the session, i.e., a 70kg cyclist would therefore aim for around 140 – 210g carbohydrates which could consist of one large bowl of porridge with banana and honey, two slices of toast with jam and a glass of fruit juice.

However, if a rider is undertaking a shorter duration session of around 60-90 minutes the requirement for carbohydrate will therefore be lower so they may aim to consume around 1g of carbohydrate per kilogram body weight prior to the session. Additionally, if a rider is undertaking a shorter endurance ride of less than 60 minutes they may even wish to restrict carbohydrate before this session as research has been found to suggest that this approach before specific sessions may help to promote endurance training adaptations when it is undertaken during lower intensity endurance rides when the demand for carbohydrate as energy is considerably less compared to higher intensity sessions.Image: SWpix/Alex Whitehead

How long before starting your session should you eat breakfast to ensure it is fully digested ahead of starting an effort?

It is recommended that you consume your main pre-training meal 3-4 hours before a session to ensure it is fully digested. However, if you are limited with time due to training in the morning you may wish to consume a lighter breakfast before the session which will be digested quicker and even consume more the evening before to top up your carbohydrate and energy stores as these stores will still be available for the following morning’s session. 

For a session that is one hour or under, is fuelling during that session still important? What would be recommended for this length of session?

Fuelling during sessions of less than one hour in duration could be less important if you have fuelled appropriately before the session as you should have enough stored carbohydrate to supply energy for that session. However, if it is a short high intensity session with efforts or intervals that will be using a lot of carbohydrates for energy it may become advantageous to fuel a bit between efforts or intervals to help maintain energy levels and intensity. This may be something as simple as sipping on a SiS GO Energy drink between intervals which provides 47g of fast acting carbohydrates per serving that will be rapidly digested and absorbed to provide energy as well as contributing to promoting fluid intake and hydration. 

How many carbohydrates per hour should you consume in a longer indoor session?

During longer indoor sessions it is recommended to fuel with 60-120g of carbohydrates per hour on the bike with the higher end of the range being recommended during sessions lasting longer than three hours. Science in Sport provides a range of scientifically backed, easy to consume and convenient fuelling options to help you meet your intended fuelling targets. For example, using the Science in Sport Beta Fuel range during a longer session can deliver 40g (Beta Fuel Gel), 46g (Beta Fuel Chew) and 80g (Beta Fuel Drink) of dual source carbohydrate in the form of both maltodextrin and fructose allowing you to achieve peak rates of exogenous carbohydrate oxidation of over 1.5 g per minute.  The result is maximal rates of carbohydrate delivery, absorption, and utilisation, with minimal gastrointestinal discomfort. 

So, simply by mixing between the different Science in Sport Beta Fuel options during the session will mean you are consuming the recommended amounts of carbohydrates per hour which will ensure you are maintaining high carbohydrate levels and subsequent energy levels. However, you can also incorporate these products with a range of other SiS products, so you don’t get bored of consuming the same fuelling options. For example, Science in Sport GO Energy Bakes which provide 30g of dual source carbohydrates or Science in Sport GO Isotonic Energy Gels which provide 22g of carbohydrate. You could also opt for more real food fueling solutions like small jam paninis, bananas, homemade rice cakes etc. that will also help to maintain energy levels.

One important factor to note is that it takes time for your gut to be able to get used to digesting and absorbing the high carbohydrate intakes during exercise, so it is best to start with around 60g/h and build up to the higher amounts over time as your gut adapts to prevent any gastrointestinal issues. This approach will also provide a great opportunity to practice taking in nutrition on the bike and ensure you are fully prepared for consuming the high amounts when it comes to racing or sportives. Image: SWpix

Is it important to take on more liquids when riding indoors as you produce more sweat?

One of the major differences between indoor and outdoor cycling is that when indoors you sweat more due to the lack of air and wind resistance alongside being on the pedals all the time during a session, collectively meaning you can become very hot very quickly. This means an appropriate hydration strategy is crucial for maintaining performance when cycling indoors. The aim with your hydration strategy should be to prevent fluid losses of less than 3% body weight which has been found to be when performance begins to hinder when such deficits occur. Therefore, you can easily calculate your individual sweat rate to give you a rough estimate of how much fluid you need to consume during a session. This can be simply calculated by measuring your nude body weight before and after a hard 60-minute session with 1kg being the equivalent of one litre. This means that if you lose 1kg over the 60-minute period you should aim to be consuming 1000ml during those sessions.

However, your sweat rate can change between different sessions and different durations therefore as a rule of thumb you should aim to consume 500 – 1000ml per hour of fluids during a session. To further promote hydration during sessions you may wish to include electrolytes in your fluid solutions as electrolytes are lost in sweat and therefore when you sweat a lot during sessions your body will be losing a lot of electrolytes. Simply adding a SiS HYDRO tablet to your water during sessions can help replace the lost electrolytes in sweat or you may opt for a carbohydrate and electrolyte solution like SiS GO Electrolyte Powder which will help promote both fuelling and hydration. 

How important is post-ride nutrition after an indoor training session? How should this vary based on different session lengths?

Recovery can be just as important as pre-training nutrition and during training nutrition as recovering appropriately will help to maximise the adaptation from the session and will also help to prepare you for your next session. The main aims of recovery nutrition are to replenish muscle and liver glycogen stores by consuming sufficient carbohydrates, repair damaged muscle fibres by consuming sufficient protein and rehydrate lost fluids through adequate fluid intake. However, the extent of recovery may slightly differ depending on how much energy you have used during the session, how much fluid you have lost during the session and the period in which you must recover. This means a simple three step approach to your post-ride nutrition could be:

1. Consume a convenient protein and carbohydrate source within 30 minutes of finishing the session, for example SiS REGO Rapid Recovery shake, to promote muscle glycogen resynthesis and muscle repair.
2. Carbohydrate based meal with protein and vegetables ~1-2 hours after finishing the session. The meal should always consume the same protein quantity of 20-40 g but the carbohydrate content may differ depending on how hard the session was with ~1g of carbohydrate per kilogram body weight after easier sessions and 1.5-2 grams of carbohydrate per kilogram body weight after harder or longer duration sessions.
3. Rehydrate by replacing 150% of fluid lost in the four hours after the session. For example, if you lost 1kg during the session, rehydrate with 1.5l of fluid.
4. If you have a small-time frame before the next session later in the day, ensure you add in more high carbohydrate snacks to continue the replenishment of glycogen.