With the rise of better indoor bike trainers and the development of software like Zwift and BKool, cyclists regularly train on an indoor bike trainer. Not only in winter, when the weather is bad and it gets dark early, but also when time is limited, and going outside is not an option. Virtual cycling has become the norm, and cyclists need to adjust their nutrition and hydration accordingly.
Indoor training is very different from outdoor training. The biggest difference is that indoors, there is no cooling effect from the wind, and in most cases, the temperature is higher. The training objective of indoor sessions is also often different from that of road training. Online platforms for indoor training are primarily designed for short, intensive sessions or races. Few cyclists will spend hours on an indoor trainer for a long endurance ride. By adapting your nutrition and hydration to the specific demands of indoor training, you can improve your performance and enhance training adaptations.
Fuel for the work required
There is not much difference in what is recommended to eat and drink between an indoor session and an outdoor ride. What you should eat and drink mainly depends on the type of training you plan to do. You need to consume enough energy for the work you are going to perform during the indoor session while also ensuring you do not lose too much fluid.
If you are doing a short session of 30 minutes to an hour, it is not necessary to eat or drink anything. However, if you are training intensively for more than two hours, nutrition will help you maintain your power output. Even during a short one-hour session, drinking small sips of carbohydrates regularly can be beneficial.
Hydration during an indoor cycling session
During exercise, you lose fluid through sweating, and excessive fluid loss can negatively impact performance1. It is therefore important to drink during exercise to prevent excessive dehydration. The amount of fluid lost during exercise varies from person to person and depends on the conditions. While it is generally assumed that you sweat more indoors than outdoors, this is not always the case.
There are no scientific guidelines for the amount of fluid you should drink during an indoor session. By weighing yourself before and after a session, you can easily determine how much fluid you lose per hour. Go to the toilet before training and weigh yourself without clothes; after the session, weigh yourself again. The difference represents the amount of fluid lost, which you should adjust for any fluid intake during the session. Knowing how much fluid you lose under certain conditions allows you to tailor your hydration plan and replenish lost fluid during recovery.
Train your gut during indoor sessions
Digestive issues such as bloating, cramps, diarrhoea, and vomiting are common among endurance athletes2. The absorption of fluids and carbohydrates by the digestive system is crucial for an athlete3. Without a well-functioning gastrointestinal system, the body cannot absorb these nutrients, leading to gastrointestinal discomfort. Training your stomach and intestines during an indoor session can improve nutrient delivery during exercise and reduce or even eliminate gastrointestinal issues4.
Once a week, you could use an indoor session to train your gut. It should be an intense session since you are unlikely to consume large amounts of carbohydrates during a low-intensity endurance ride. You could start with 50g of carbohydrates and a certain amount of fluid, gradually increasing to 60g, 70g, and possibly even 80g of carbohydrates per hour. If you can tolerate larger amounts of carbohydrates in training, it is likely that you will also be able to consume more during real races.
Practise your nutrition plan for races or sportives
To optimise performance and prevent hitting the wall, it is important to plan what you will eat and drink before a race or sportive. While this may seem obvious, many athletes encounter problems when they randomly consume food or drinks during an event. Energy bars or gels may not taste as expected, may be difficult to chew, or could cause digestive discomfort. It is better to encounter these issues during an indoor session rather than in a race. Practising your nutrition plan in training allows you to make small adjustments to improve it.
Fasted training on an indoor trainer
Fasted training is perhaps the most popular way to train with low carbohydrate availability (train-low). Train-low strategies can increase the ‘cellular markers’ needed to improve performance and enhance fat oxidation during submaximal exercise. However, it remains unclear how this translates into actual performance improvements5 6 7. Fasted training also has its drawbacks: only liver glycogen stores are depleted, not muscle glycogen stores; recovery can take longer; and some cyclists may feel lightheaded due to hunger, which could compromise safety. If you choose to train fasted, an indoor session is often the safest option.
1. American College of Sports Medicine, Sawka MN, Burke LM, et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390. doi:10.1249/mss.0b013e31802ca597
2. de Oliveira EP, Burini RC, Jeukendrup A. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med. 2014;44 Suppl 1(Suppl 1):S79-S85. doi:10.1007/s40279-014-0153-2
3. Jeukendrup AE. Nutrition for endurance sports: marathon, triathlon, and road cycling. J Sports Sci. 2011;29 Suppl 1:S91-S99. doi:10.1080/02640414.2011.610348
4. Jeukendrup AE. Training the Gut for Athletes. Sports Med. 2017;47(Suppl 1):101-110. doi:10.1007/s40279-017-0690-6
5. Hulston CJ, Venables MC, Mann CH, et al. Training with low muscle glycogen enhances fat metabolism in well-trained cyclists. Med Sci Sports Exerc. 2010;42(11):2046-2055. doi:10.1249/MSS.0b013e3181dd5070
6. Bartlett JD, Louhelainen J, Iqbal Z, et al. Reduced carbohydrate availability enhances exercise-induced p53 signaling in human skeletal muscle: implications for mitochondrial biogenesis. Am J Physiol Regul Integr Comp Physiol. 2013;304(6):R450-R458. doi:10.1152/ajpregu.00498.2012
7. Philp A, Burke LM, Baar K. Altering endogenous carbohydrate availability to support training adaptations. Nestle Nutr Inst Workshop Ser. 2011;69:19-37. doi:10.1159/000329279
