Most triathletes, cyclists and runners resort to indoor training every winter, as it's usually the easiest way to keep up your training without getting side-tracked by the elements.
With this in mind, how much and what should you be drinking and eating when training indoors? Should this be different to your usual? The only correct answer is: it depends on a few factors.
It depends on your goal. If you are just riding or running and performance is not important, nutrition is also less important.
BUT...
If you want to race or challenge yourself, nutrition will become crucial.
It also depends on the duration of your workouts. If you are training under 45 minutes, then nutrition has a limited effect. However, if you are doing two hours or more at a more advanced level that it is physically challenging, nutrition will help you to maintain power and speed. Even sessions that last about 1 hour can benefit from regular small sips of a carbohydrate drink. (Read about Fuel-5 here).
In general, liquid formulations can deliver carbohydrate faster but gels are also highly effective, and solid foods, as long as there is not a lot of fibre, fat or protein can work as well.
There is an often debated view that you should drink the same amount as you sweat. In reality, this is not necessary and pretty hard to achieve. This is especially true on the bike, as for many people, sweat rates will be slightly higher, because cooling wind is significantly reduced when compared to riding on the road.
As a result of less cooling wind, body temperature will increase much more rapidly indoors, and sweat rate will be higher. This means fluid requirements will be slightly higher too and it is then worth considering your hydration levels.
The best way to check whether you are drinking enough is to step on the scales before and after a session. If the difference is less than 2-3%, you drank enough. If your weight loss is much greater than this, you should probably be drinking more.
Can indoor training can improve your nutrition?
Training indoors is a great way to improve your nutrition come race day.
1) You can use the indoor sessions to personalise your drinking plan by establishing your sweat rate. We all sweat differently and therefore each drinking plan must be personalised.
Want to test your sweat rate? Find a session that is at least an hour, and at an intensity that is near to race pace. Measure your body weight before and after the session (ideally naked body weight), measure the weight of your bottle(s) before and after using a kitchen scale, and if you also know the exact duration of the session, you can get a pretty good estimate of your sweat rate.
Not all of the weight loss will be sweat (water) and you may also lose some carbohydrate and some fat, but it will be a close enough estimate. If you repeat this measurement several times in different conditions you will get a really good idea of your sweat rate.
If you combine these measurements later with measurements outside, it will become even more predictive.
2) By practicing your race day nutrition plan indoors, when race day comes, you will have it tuned to perfection and can cross off a significant variable that could ruin your chance of a PB.
You must have a plan for your race, a certain amount of carbohydrate drink and a certain number of gels you want to take in. In training you can simply have everything you want to use lined up next to your bike or treadmill and take these products at exactly the right times.
3) Using the same products trains your gut. Let your gastro-intestinal system adapt and practice what you are planning to do in a race day several times in training. If you repeat this several times, you can then try to gradually increase your carbohydrate intake and also fluid intake a little. This is often referred to as training the gut.
Say you have a nutrition plan with 60 grams of carbohydrate per hour, this equates to 2 gels plus half a bottle of sports drink per hour. Try this once a week so you can tolerate this intake level.
If you are struggling, start with around 50 g/h, and building up to 70 g/h, maybe even 80 g/h. If you can tolerate 70 g/h in training, it is likely that you can tolerate 60 g/h later in your races without any problems.
4) If you are going to compete in hot conditions, heat acclimation is essential. If you are not living in a place with similar conditions, you will have to simulate these conditions at home. Simply crank up the heat in your garage, spare room or wherever your pain cave is.
Add a humidifier to simulate the race conditions or if you can't heat up the room and you don’t have a humidifier, add some extra layers of clothing. The most important thing is that you increase your core body temperature significantly. Ten sessions of 1-1.5h should give you most of the adaptations you need to compete in even the most extreme conditions.