The role of the pre-exercise meal includes:
Making sure you feel great and you are excited to exercise
Topping up muscle and liver glycogen stores
Ensuring you are well hydrated
Avoid stomach/gastro issues
The science guidelines are:
Take it 2-4 hrs pre - exercise (I reckon an hour prior is fine, but trial this for yourself)
It should be high in carbs, low in fat, and low-moderate in protein
Just sip on water "as thirst dictates" in the build up
Avoid gels/sugary drinks in the last 30 min prior to exercise
Liquid foods can be better tolerated for the nervous
The most important thing is to choose a pre-exercise meal that you know you will tolerate and makes you feel good. To ensure this is the case you should practise your pre-race meal a lot during training to get comfortable with it and ensure that it works for you. The pre-race meal that is best for you might be completely different for someone else, and that is fine.
Don't do all sorts of different things during training and then become all serious on race day and have 6 weetbix with low fat milk, greek yoghurt, and chia seeds. If you haven't practised it during training, the meal with the best intentions can still double you over with the stitch.
During training for my personal major events I will try to have the meal that I plan on having on race day as much as possible before my weekend long runs. I will also try to practise having it at the time that I will on race day at least a few times. For example, if my race is at 9am, then I will practise having it at 7am, and go running at 9am as much as possible. Before my biggest events I have been known to try and do this in the week leading up to the race to try and get my body into the routine.
What you do on race day will be based on what has worked in training, so I can't emphasise how much you should practise this.
Example pre-exercise meal
4 weetbix with milk, chopped banana, and a piece of toast and peanut butter (approx 90g of carbs).
Two eggs on two toast, with 1/2 a can of baked beans (60g of carbs)
If time is short the following (easily digestible) snacks taken 30-60min prior to a training session can put a pep in your step:
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