Race Day Nutrition (Part Seven) – Marc Laithwaite


Last week we introduced specific products used during endurance events and how they can fulfil your requirements in terms of nutrition intake.

There are 3 common sports products used during endurance racing:

  1. Drinks powders
  2. Gels
  3. Bars

This week, we’ll check out bars and gels.

What’s in them?

Unsurprisingly, gels tend to contain maltodextrin and glucose, similar to the drinks. In fact, gels are simply condensed energy drinks. They were originally designed to be carried on events where you could access only water, as a source of energy. The thickness of the gel will dictate how much energy they contain. Some gels are very thick and sticky and these contain more energy than the ones which are a thinner, more watery solution. This is based upon the simple principles we discussed a couple of weeks ago, relating to hypo, iso and hypertonic solutions.

As an example, a 41g power gel original contains approximately 27g of carbohydrate. Remember the 60g rule? That means 2 of these gels per hour would be pretty close to target intake. The remaining 14g of the gel is fluid (41g – 27g = 14g) so we can calculate the gel thickness as follows:

Total weight = 41g
Carbohydrate content = 27g
27/41 = 0.66, Therefore this gel is a 66% solution (27 is 66% of 41)

The purpose of that calculation is simply to highlight that gels are extremely ‘hypertonic’, remember that isotonic is a 7% solution. Being hypertonic is not a problem, the more hypertonic the more energy it provides, but it does mean that you need to take fluid with them.

In past blogs we stated that you should aim for no more than 10% solutions, so that means 270ml of water drank with 27g of carbohydrate will be correct, 270 / 27 = 10. It’s important to do the calculation based on the 27g of carbohydrate in the gel, not the 41g total weight of the gel. Technically if you drink 270ml the solution will actually be less that 10% as there’s already 14g of fluid in the gel as stated above. As a practical guide think about a 500ml drinks bottle generally used for cycling, it’s half of one of those with every power gel.

What about Isogels

There are ISOGELS on the market, SIS and High5 make popular versions. By adding more fluid to the gel and reducing the carbohydrate content they can reduce the thickness of the gel solution.

The first thing of note is that they contain less carbohydrate, so you’d need to take more of them every hour. They contain in the region of 22-24g of carbohydrate per gel, so that means you’d be taking almost 3 per hour to get your energy, rather than 2 power gels. That’s a lot of gels to carry if you’re racing long distances.

But ISOGELS are isotonic, so you don’t need water, right?

HIGH5 Isogel
Total weight = 66g
Carbohydrate content = 24g
24/66 = 0.36, Therefore this gel is a 36% solution (24 is 36% of 66)

SIS GO Isogel
Total weight = 66g
Carbohydrate content = 22g
22/66 = 0.33, Therefore this gel is a 33% solution (22 is 33% of 66)

So we said above and in previous blogs that isotonic solutions are 7%. The solutions for the ISOGELS above are 33% and 36%, this is not isotonic, it’s hypertonic. I may be missing something here, so I did phone High5 and ask. They couldn’t answer the question but stated that ‘they were more isotonic than other gels’. I’m not sure that is technically true, as none of them are anywhere near 7%. That’s a bit like me saying I’m tall and when questioned about by lack of height, I reply by stating ‘I’m more tall than Ste Hilton’. Whilst that may be true, it doesn’t make me tall…

Key points:

1. You DO need to drink water with ISO gels
2. If you don’t know Ste, that joke is completely lost

If there’s 24g of carbohydrate in a 66g gel, then you need to take 240ml of water for a 10% solution (240ml / 24g = 10%). However, there is already 42g of fluid in there (66g gel – 24g carbohydrate = 42g fluid). Based on this, 200ml would be sufficient, that’s still more than a third of a 500ml drinks bottle.

What about energy bars?

Bars are an alternative source of carbohydrate. They generally contains things like oats, rice, wheat etc with added sugar syrups such as glucose or fructose. In terms of ‘solutions’ a gel is solid food, so it needs mixing with a significant amount of water to digest and absorb effectively.

As an example, a powerbar energize bar (others are available!!) weighs in as follows:

Bar weight = 55g
Carbohydrate = 39g
Fat = 2g
Protein = 6g

In terms of carbohydrate content, you’d need 1.5 bars per hour to get your 60g intake. If you add up the content weight 39g + 2g + 6g = 47g. We stated that the bar weighed 55g, so there is some fluid in there also plus some other little bits to make the weight up to 55g. If you drank a full 500ml bottle of water with every bar, that would give you just less than 9% solution which is ideal (47/500 = 0.9). That means a full 750ml bottle and 1.5 powerbars per hour would be pretty much on target (remember all bars are different, these calculations are for powerbar energize).

Salt intake

We discussed sweating and hydration last week, which included salt intake. As a recap, salt and sodium are 2 different things. Salt is 40% sodium and 60% chloride. You need to know this as some products give ‘salt’ content and others give ‘sodium’ content. Remember also from last week we said that you are likely to sweat up to 1g of sodium per hour (1000mg). There’s multiple thoughts on salt replacement, regarding how much and whether you need it. I’m not going to go into depth on the matter because this is meant to be a simple and easy to read blog. If it’s warm and you sweat a fair bit, aim for 500-1000mg SODIUM per hour. If you take a bit too much, you’ll just sweat it out anyhow so don’t overly panic.

Let’s presume that you are aiming to take all of your energy by using sports gels or bars. So remember, our targets are 60g of carbohydrate per hour and 500-1000mg of sodium per hour, presuming its warm and you sweat. Here are some options:

SIS GO Isotonic Gel

Includes 22 grams of carbohydrate
Sodium = negligible

High5 Isogel

Includes 24 grams of carbohydrate
Sodium = negligible


Includes 27g of carbohydrate
Sodium = 205mg
2-3 Powergels per hour would give you 410-615mg of sodium, we stated that 500mg was a starting target.

Powerbar Energize

Includes 39g of carbohydrate
Sodium = 192mg
1.5 Powerbar Energize per hour as suggested above, would give you 288mg of sodium, half of that provided by intake of 2-3 Powerbar gels per hour. They really don’t make this easy!!

Some key points:

  1. The amount of carbohydrate in gels and bars varies widely
  2. You need to drink water with all gels and bars for correct absorption
  3. Isotonic gels don’t exist (unless I’ve missed something)
  4. Sodium content varies widely in bars and gels and is often not included

I hope that basic overview helps you to practically apply what you’ve learned over recent weeks, feel free to call into the store and we can talk you through it before your big day.

– Marc

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

Endurance Store Logo

3 thoughts on “Race Day Nutrition (Part Seven) – Marc Laithwaite

  1. Been totally entranced by this series of articles – huge thanks. I just wish my head could get around the maths so I could work out what I need for my Ironman adventure in four weeks’ time to optimize my chance of finishing. I’ll try again BUT …… I really do feel an ‘APP’ coming on (business idea??) I’ll be first to buy it!

  2. Pingback: FOUR WEEKS TO IRONMAN … | Put the Kettle On

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.