Eat to Train, Train to Eat

by Ian McLaren

Eating is a critical part of training, which is good because it’s one of the more fun parts, alongside rest and recovery and buying new stuff (yes I do need new wheels/shoes/watch/swimming things). I could stop there and keep it short this week, but it’s worth covering in a bit more detail and with random metaphors.

Coaches always talk about training zones: aerobic effort, lactic (sometimes called anaerobic) effort, VO2 max, etc. These zones are covering the different ways the body produces energy for the muscles to propel you. Aerobic exercise is where the body combines oxygen with stored fuel to produce energy. This is the sustained energy system that keeps you going through endurance exercise. If you are going to be exercising for more than 3 minutes, you will be using aerobic energy.

But there’s is a limit to how much oxygen you can get into the body, which will restrict how much aerobic energy you can produce. This limit is your VO2 max, which varies from person to person, depending on factors like fitness, age and if you are following the type of training program that got Lance Armstrong banned.

When you start getting close to your aerobic limit, the body will break out the lactic energy system which doesn’t need any oxygen to work. Think of the aerobic energy system like a car engine (apart from Kev and his Leaf). An engine uses petrol which it burns with oxygen to produce energy. It will keep going forever, so long as it has fuel and oxygen, and bits don’t wear out and break. If you want to go faster, you can add nitrous oxide, to make a bigger bang and generate more power. The downside is if you do that too much the engine will blow up.

For the body, aerobic energy lets you go all day and lactic energy is like nitrous; it lets you go really fast for a short time before you blow up. Using the lactic energy system generates lactate and acid in the muscles, which is why you start to feel the burn. If you are only just around your threshold, the body can flush out the muscles as quickly as the lactate and acid is produced. Press on harder and it just builds up until you grind to a halt.

One of the goals of endurance training is to be able to race as close to that limit as possible without going over. Particularly as the lactate and acid gets flushed out into the stomach, which is why if you push really hard, you can have a slightly messier end to a race than planned.

This is a great time to go back to where we started, eating.

To be able to train or race, you need sufficient stored energy reserves for the session. As the body is burning energy all the time, even when you aren’t exercising, you’ll need to plan to eat so you have the energy when you start. Eat too close to a run and it’s going to be so funny it will have you in stitches. Don’t eat and it’s the opposite—you will run out of energy. Generally leaving 2.5 hours between a big meal and running should allow the food to have digested enough that you won’t get to enjoy it again. If it has been too long, snacking on something light and easy to digest, like a banana, honey on wholemeal toast bagel, or a gel 20 mins before the start works. 

The main source of energy for aerobic exercise is going to come from the carbohydrates. The body will also burn stored fat, but it’s harder to break down, and you still need carbs to get the process going. The amount of energy your body can store from carbs will vary from person to person, and the length of time you can exercise for on those reserves also varies.

The more you train the more efficient muscles become, allowing you to go longer and faster on the same reserves. For me that limit is between 2 and 3 hours depending on how hard I’m pushing and my fitness level. If I’m going out for a 5K, I’ll be OK on whatever I’ve eaten. But if I’m going out for over 2 hours, I’ll need to re-fuel or have the joy of running out of energy and bonking.

Re-fueling the body is more like Kev’s electric car than a petrol car; you can’t stick fuel in and burn it immediately. Similarly you can’t wait until you have run out of stored body fuel before eating, unless you want to stop and recharge for 20 mins. Starting to eat early and keeping topped up will hopefully prevent you running out. If you’re pushing hard, close to your aerobic limit, you’ll be getting some lactate and acid being dumped into the stomach. This can make eating and digesting a little challenging, particularly if you aren’t used to it. 

Which is where training to eat comes in. 

If you’re going to be doing a race during which you’ll need to eat, you need to practice eating during training. There are practical skills to learn like being able to open a gel while riding without getting very sticky handlebars. But it’s also to find what gels and energy drinks work for you, and how many you need or can stomach in an hour, compared with what the manufacturers recommend. If you have too much fructose, it’s very easy to experience gastric distress, and spending 15 minutes in a portaloo mid-race can make PBing challenging.

This practice will help you develop your feeding strategy for the race, so you don’t end up with 50 gels taped to your top tube at the start and 45 still there at the end. Planning out what to eat for a race, on race day and even in the days before the race, is a topic in its own right (and means I have something else to write about and won’t run out of topics before lockdown ends).

Eating doesn’t stop once you have finished training and the endorphins are buzzing. Post-exercise is when you need to eat to be prepared for the next session. Replacing the burnt energy stores has been shown to reduce muscle stiffness and soreness, and it also gets protein in to start the process of repairing muscles.

The last research I saw said eating carbs and protein at a ratio of 2:1 post exercise is optimal for restoring energy and starting the muscle repair. The amount you need will depend on how long and hard you were training, along with your body makeup and fitness level. If you are training hard, building strength, or even using muscles you normally ignore because you’re a swimmer, cyclist, or runner who has just taken up triathlon, you will need more protein to support the muscles. If you’re an experienced athlete, it will be different as you are just maintaining what is already there.

So keep training and keep eating. It’s a virtuous-circle: the more you train, the more you can eat. Now after all that typing, it’s time for a recovery trifle.