Race Day Nutrition (Part Four) – Marc Laithwaite

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So last week (part three HERE) we discussed carbohydrate absorption and the role of insulin, this week, we are going to look at how to take foods on board whilst competing, to avoid stomach problems and maximise performance.

I’m having issues getting energy, what’s the solution?

Your stomach and gut acts a little like a sieve. If you pour water into it, the water passes straight through without any problems. If you pour a milkshake into the same sieve, it will pass through, but will take a little more time and will slowly drip. If you throw solid food into a sieve, it stays exactly where it is. The only way to pass solid food through a sieve would be to mix it up with water and make a thin enough solution, which could then start to drip through.

The solution which enters your stomach, is therefore very important in terms of performance. During endurance events, we eat and drink to get energy, but if the food sits in your stomach, then you aren’t actually getting any energy into your bloodstream. Not only are you receiving less energy, you are also likely to get some kind of stomach problems.

Isotonic is just the tonic

Isotonic refers to a solution which is a similar concentration to fluids in the body. Solutions of 7% are generally referred to as isotonic, this means that 7g of carbohydrate in 100ml of water is isotonic. You can count grams and millilitres as the same thing, so the calculation is simple, 100ml / 7g = 7%.

Drinks bottles generally come in 2 different sizes, 500ml and 750ml so based on the 100ml / 7g rule, the calculations would be as follows:

500ml water + 35g carbohydrate = Isotonic

750ml water + 52.5g carbohydrate = Isotonic

Some solutions are less concentrated than isotonic fluids. For example, water has no carbohydrate in it and no calories, this is classed as hypotonic (hypo = low / less than). Solutions which are more concentrated than isotonic fluids, are classed as hypertonic (hyper = high / more than). An example of a hypertonic solution would be a smoothie.

That’s fine for drinks but what about solid food?

Many athletes choose to eat solid food during their event. As stated above, anything which is above 7% solution is hypertonic. Therefore, all energy bars and solid food is hypertonic. This means that if you wish to absorb solid food effectively, you must add sufficient water to make a 7% solution. For example, a standard energy bar is approximately 50-60g in total weight. We said earlier that 7g in 100ml of fluid would be a 7% solution, so that means you would have to drink 7-800ml of water with each energy bar to make at isotonic solution (56g is 7% of 800ml). In ultra running events, there’s often solid food such as sandwiches at feed stations, so get into the habit of estimating the portion size, e.g. what does 60g of cheese sandwich look like! Eating sandwiches, pasta and cake can very quickly result in a large mass of food gathering in your stomach. As for gels, they work the same way. A single gel contains 20-30g of carbohydrate (you need to read the packet). A gel with 21g would require 300ml to make a 7% solution.

Why is solution an issue?

Taking energy bars, gels and other solid food provides energy, but you have to take a lot of fluid to create an isotonic solution in your stomach. If you fail to take sufficient fluid you will have a thick ‘hypertonic’ solution in your stomach which may not digest and may well lead to stomach problems.

Don’t forget the 60g per hour rule

As we’ve said in previous blogs, it’s unlikely that you can absorb more than 60g per hour of carbohydrate so eating too much food can have a negative impact upon digestion. Eating too much may lead to food gathering in the stomach and leading to feelings of bloating or sickness. The carbohydrate ‘maltodextrin’ seems particularly prone to doing this and all carbohydrate drinks and gels tend to consist of maltodextrin (pretty much every energy drink on the market is the same, it’s flavoured maltodextrin).

It’s known that when you get an accumulation of carbohydrate in the stomach, due to excess food intake, the body is forced to dilute the solution. The strong solution sitting in the stomach starts to draw water other parts of the the body, into the stomach, to dilute the solution and aid digestion and absorption. This action of drawing fluid into the stomach is termed ‘osmosis’.

It’s important to remember that if you do take too much energy, coupled with a lack of fluid, not only are you likely to get stomach issues, the energy will also fail to reach your blood stream and exercising muscles where it is needed. In simple terms, more food may provide you with less energy.

Practical advice:

  1. You need to stick to the 60g limit for carbohydrate intake
  2. A solution of 7% is not always attainable, aim for 10% as a minimum start point for intake:

60g energy powder + 600ml water per hour
60g energy bar + 600ml water per hour
60g of gels (2-3) + 600ml water per hour

  1. You can mix the above, e.g. 30g carbohydrate powder and 30g gels every hour, plus 600ml of water.
  2. Think about what’s the easiest to calculate and what the easiest to obtain during the event. Knowing how much energy is in drinks which are handed up at aid stations or adding your own powder on the go is not really feasible so gels and bars are often simpler to use and to quantify. In truth, you really have no idea what’s being handed up in the drinks bottles, so water is always the safe option.
  3. Feeding is easier when cycling compared to running, so if you’re doing Ironman triathlon, the bike feeding is critical to set you up for the run. If you’re running an ultra, the slower pace can help, but little and often applies.
  4. Little and frequent works best for digestion. A gel every 20-30 minutes or half a bar every 30 minutes is better than a full bar every hour. You still need to drink the correct amount of water to account for solution.
  5. Drinking water only with bars and gels has the benefits of ‘freshening your mouth’. Energy drinks, gels and bars can leave you with a constant sticky taste.

What about the food content?

There is circumstantial evidence to suggest that eating too much carbohydrate may also impact upon digestion and potential stomach problems. If you are prone to stomach issues, then gels with a higher fat content may well work best. There are some very scientific high fat gels on the market, mainly in the US, but if you Google for peanut butter flavour gels, that’s a simple option and you can easily get those in the UK. If you don’t like peanut butter flavour, there’s not much option!

The final step

Ok, so here’s your homework. Go and purchase gels or bars, which you intend to use for your event and take a look at the wrapper. What’s the total weight in grams of the product and what does the content add up to? Remember, a gel may have added water, so a 40g gel may contain 20g of carbohydrate. Don’t just use the actual product weight, you need to check the weight of the ingredients and use that as your gauge. Work out how many you will need and how often you will eat them. If your event uses specific products e.g. Ironman use Powerbar, it’s a lot easier to use these on the day and save yourself the hassle of carrying a lot of product.

Hydration?

That’s coming next week

About Marc:

Sports Science lecturer for 10 years at St Helens HE College.

2004 established The Endurance Coach LTD sports science and coaching business. Worked with British Cycling as physiology support 2008-2008. Previous Triathlon England Regional Academy Head Coach, North West.

In 2006 established Epic Events Management LTD. Now one of the largest event companies in the NW, organising a range of triathlon, swimming and cycling events. EPIC EVENTS also encompasses Montane Trail 26 and Petzl Night Runner events.

In 2010 established Montane Lakeland 50 & 100 LTD. This has now become the UKs leading ultra distance trail running event.

In 2010 established The Endurance Store triathlon, trail running and open water swimming store. Based in Appley Bridge, Wigan, we are the North West’s community store, organising and supporting local athletes and local events.

Check out the endurance store HERE

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