Race Day Nutrition (Part Three) – Marc Laithwaite

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Last week we showed you how to calculate the amount of carbohydrate used during cycling and running, in order for you to produce a structured plan for race nutrition. This week, we begin the process of looking at what and when to eat on race day and the first step, is to explain the basic physiology.

Missed part one (here) and part two (here)

Carbohydrates

Carbohydrates or ‘sugars’ are a prime source of fuel when exercising and unfortunately, as explain in previous blog posts, they are relatively limited. The term for stored carbohydrate is ‘glycogen’ and we store glycogen in the muscles (to use for movement) and in the liver (to supply sugar to the brain and maintain blood sugar levels)

There are different types of carbohydrates, but ultimately, they are all broken down to glucose as this is what we use as our prime fuel. When you eat or drink carbohydrate, it first goes into your stomach. We can’t absorb carbohydrates through the stomach wall, so they progress from there into the intestines and are absorbed through the intestine wall

The rate of absorption

The carbohydrates you eat are broken into glucose and pass through the intestine wall into the blood stream. Remember that in recent blogs, we’ve stated that the limit for this seems to be around 60g per hour of glucose. Depending upon the type of carbohydrate and how it is consumed (drink or solid food), the time taken for the carbohydrate to be broken down and absorbed will vary.

Many of you will have heard of the ‘Glycemic Index’. This scale was designed with diabetics in mind and it dictates how quickly foods are broken down and absorbed through the intestine wall. To measure the GI of a food is relatively simple (but complex at the same time). The process is to give someone a specific food, then take blood samples at regular intervals for the next hour to see how rapidly the blood sugar (glucose) levels rise.

The ‘GI’ scale runs from 1-100. Foods with a low score will take longer to reach the blood and give a more consistent supply (slow drip feed). Foods which enters the blood stream quickly, will give a more immediate spike in the blood sugar levels. Pure glucose has a score of 100 as that will lead to a rise in blood glucose more quickly than anything else.

The role of insulin

The reason why the GI scale is so important for diabetics, is the ‘insulin response’. A rise in blood glucose will lead to a rise in blood insulin, which is the hormone responsible for removing glucose from the blood and pushing it into the liver and the muscles.

Your daily diet should be made up of foods low on the GI scale. It you eat foods which are high on the GI scale throughout the day, this results in repeated sugar spikes and subsequent insulin spikes. Over time, your insulin will become less effective (overuse can lead to it becoming less sensitive to glucose). The reduced sensitivity can eventually lead to type 2 diabetes (insulin doesn’t work correctly). You may think, as an athlete, you are not susceptible to type 2 diabetes, but you’d be wrong. It is critical for you that your insulin works correctly, so you should be doing everything in your powers to ensure it does.

The secondary issue relating to insulin, is the impact upon fat metabolism. It reduces the amount of circulating fat by encouraging storage in fat tissue. In terms of your daily diet and metabolism, this has significant consequences upon weight loss and fat use. Constant spikes in blood glucose and insulin will reduce the amount of fat you metabolise throughout the day.

Are we discussing daily diet in this blog or race day nutrition?

Okay, I am going off track a bit, but I think it’s important to understand the foundations. As an athlete, you need a constant and balanced supply of energy to complete your training sessions and to recover quickly. Therefore, you should be eating to encourage a more stable metabolism and that is derived from low to moderate GI foods, NOT high GI foods.

So how does this work during racing?

  1. If you are racing an endurance event, you really need to ensure that you have a steady supply of glucose, without disrupting fat metabolism. A large spike in glucose and insulin, could inhibit fat metabolism, which means you’ll be forced to use more glycogen and run out more quickly.
  1. There are times when you may well need a rapid rise in blood glucose. If you have an extreme low point in the race and find yourself sitting on the road side, you may need an ‘instant hit’. Under such circumstances, you need the quickest glucose spike possible to get you back on your feet. At times like this, who cares about insulin!!

Here’s the thing, if you do scenario number 1 correctly, then you shouldn’t experience scenario number 2. The other issue is that products that are sold to deal with scenario number 2 (high energy, quick acting gels) are being used for scenario number 1. If you are half way through a 12 hour event and your energy levels are feeling relatively good, should you take a product which gives you an instant spike in glucose and insulin? Remember, we are aiming for a ‘constant’ and ‘balanced’ blood glucose level, we are trying to avoid blood glucose ‘fluctuations’.

So this blog is not what I intended when I started typing and none of the original planned information has made the page. Needless to say, this 4 part ‘race nutrition’ series is not going to be 4 parts.

A critical point to take away is that over the years of giving advice, we’ve found that the daily diet can have a huge impact upon training and racing performance. In particular, cutting out high GI foods can lead to a dramatic change in metabolism and enhance your fat utilisation.

Your homework for this blog is to take a look at the glycemic index. You’ll find this very interesting and you’ll probably find that many of the foods you presumed to be ‘sugar spiking’ are not and vice versa.

What if I said that Coke had a score of 60, whilst mashed potato AND jacket spuds had a score of 90 (that means mashed potato and jacket spuds can give more of a sugar spike than Coke!!)

You’ll notice that there is also something called ‘glycemic load’. This takes the volume of food into account e.g. you can’t compare a full jacket spud with a teaspoon of glucose as the volume is very different. Don’t worry about that for now, it’ll over-complicate the matter!

Take a look for yourself, and see what’s low and high. There’s loads of them on the internet, Google glycemic index table. Next week we’ll look at the foods you eat during the event. How can you manipulate the use of drinks, bars and gels to maintain a steady blood glucose supply and avoid the fluctuations that we have discussed above. See… I told you there was a point to this blog.

Until then, stay healthy.

– Marc Laithwaite

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

Race Day Nutrition (Part Two) – Marc Laithwaite

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So last week (Part One Here)we finished by talking about how many calories you use during an event and how to make a quick calculation of fat and carbohydrate contributions. To recap, we said:

80/20: If you are struggling to ride 50 miles / run 15 miles even when fuelling yourself throughout, then apply the 80/20 rule. That means 80% of your fuel is carbohydrate and 20% is fat.

65/35: If you can ride 50 miles / run 15 miles comfortably using fuel, then apply the 65/35 rule. That means 65% of your fuel is carbohydrate and 20% is fat.

50/50: If you can ride 50 miles / run 15 miles comfortably without using any fuel whatsoever, then apply the 50/50 rule. That means 50% of your fuel is carbohydrate and 50% is fat.

Let’s give ourselves a simple scenario. Tom is 43, weighs 82 kg and is racing Ironman triathlon, he falls into the 65/35 category and his main objective is to complete the event without major disaster and to run as much of the marathon as possible. When Tom is riding at his Ironman pace, he is using 820 Kcal per hour, so the calculation works like this:

Fat contribution:  820 Kcal x 35% = 287 Kcal

Carbohydrate contribution: 820 Kcal x 65% = 533 Kcal

Step 1: Discard the Fat

The calories which come from fat do not need to be replaced, even the leanest athlete has ample fat stores for the longest endurance events. Step 1 is therefore to discard the Kcal from fat and focus on the carbohydrate contribution. Carbohydrates is the fuel which must be replaced!

Step 2: Focus on the carbohydrate

For Tom, our calculated figure is 533 Kcal of carbohydrate per hour, so this is our target to replace during the ride. It’s often easier to work in grams as most foods are also measured in grams. Each gram of carbohydrate contains 4 Kcal, so we calculate grams of carbohydrate as follows:

533 Kcal per hour / 4 = 133 grams per hour

Step 3: Apply the maximal intake rule

You may remember from the last couple of weeks, we discussed that the maximum amount of carbohydrate you can take during exercise is 60g per hour. Tom is using 133 grams per hour (just to clarify, that’s not excessive and is realistic). If the maximum Tom can take is 60g per hour, that means there’s 73 grams (133-60) that he’s losing and can’t be replaced every hour.

Step 4: Work out the race total

Tom’s bike time is estimated to be 6.5 hours. If he’s losing 73 grams of carbohydrate per hour which can’t be replaced, what does that add up to over the total bike ride? Well, the calculation is simple: 6.5 x 73 = 474.5 grams. That means that Tom will lose 474.5 grams of carbohydrate, which he can’t replace, by the end of the 6.5 hour bike ride.

Step 5: Work out your time to collapse

The big figure missing here is the actual amount you have got stored in your body, is losing 474.5 grams a big problem? The average human stores 400 grams of carbohydrate stored in the muscles,  and 100g is stored in the liver. There’s also approx 25g circulating in your blood at any given time. For the astute amongst you, the problem has already struck you squarely between the eyes. Tom, sadly, will not be running the majority of the Ironman marathon.

Does this happen in the real world?

Definitely, take a look at the photo below. This is some data for an Ironman athlete taken this week, male veteran, approx 68 kg with a long history of endurance competition. There’s 12 minutes of data on the screen, the first column shows the power output (watts) and the third column shows time in minutes. Prior to this the rider warmed up for 10 minutes at 100-120 watts. Now look at columns 11, 13 and 14 on the far right hand side, they show Kcal per hour, fat% and carbohydrate%. Consider that 120/150/170 watts is not high intensity, despite that and the previous warm up, you can see that the carbohydrate use is very high. Take into account that our athlete is only 68 kg and that Kcal per hour will be greater in larger athletes.

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Would these fugures be similar for running?

Yes, pretty much. The Kcal usage is slightly higher when running at a similar intensity, but the fat usage tends to be a little higher also. I’d suggest that the fat usage is slightly higher as running requires less ‘fast twitch’ fibre contribution, cycling requires a cretain amount of ‘stregth’. Running intensity also tends to be a bit more consistent. Cycling can be hard on the uphill and then rest and freewheel on the downhill, but running is less so.

Should Tom withdraw his entry right now?

Hang on… we know that people can ride the full Ironman bike and then run the marathon. We also know that people run 100 miles, so there’s got to be a catch, these calculations can’t be correct. Will Tom be completely depleted of all carbohydrate even when taking in the recommended 60g every hour?

No, indeed he won’t and the calculations are not so clear cut as above. Your body is pretty clever so it will make some changes along the way to help you out. Throughout the event, your metabolism will switch, so it’s reasonable to suggest that by the time the bike has ended, 50-60% of Tom’s energy will come from fat, rather than the 35% contribution at the start point. That means he’ll only be using half the amount of carbohydrate every hour, compared to when he started.

That’s good right?

In some ways yes it is, it’s saving your carbohydrate stores by halving the amount used every hour. But you need to consider why this change occurs. Your body switches to use a larger amount of fat because it’s ‘RUNNING OUT OF CARBOHYDRATE’ so whilst every cloud does have a silver lining, let’s not look too positively on this change.

As most people struggle to metabolise fat, having to rely upon it will lead to a drop in pace and performance. If we continue our theme of ‘clouds and silver linings’, at least the slower pace means you will be using less Kcal per hour (slower pace = less energy required) so that also helps to reduce the amount of carbohydrate required.

Is anyone else getting concerned here or is it just me?

It’s ok, there is an answer. The 2 key areas for improvement are economy (Kcal per hour) and substrate ulilisation (fat or carbohydrate). If you are aerobically fit, you will be more economical than most people. In fact, for endurance performance, economy is perhaps the most important thing. We can define economy very simply as ‘how much energy do you need to ride or run at any given speed?’

If you take your unfit pub mates for a run, you may well trot along at 8 minutes per mile and hold a comfortable conversation. Your mate on the other hand, may be breathing like a bulldog in a hot car, blowing out of most parts of his body. He will be using far more energy, require far more oxygen and use far more calories. People are like cars, some can go a long way using only a small amount of fuel and some require a regular filling due to their poor economy.

The second thing to consider is substrate utilisation. This simply refers to the relative contributions of fat and carbohydrate towards your total energy need. We’ve discussed this above and in pretty much every blog in the last 6 weeks, so hopefully you’re already familiar with this concept. If more of your energy comes from fat, you’re less likely to run out of carbohydrate. The best athletes in the world require a small amount of energy (Kcal) to ride or run at race speed. If a large chunk of that energy requirement comes from fat, their total carbohydrate use is very small indeed.

The new Tom… we can rebuild him

By making changes to Tom’s training and diet, the new version arrives for the Ironman triathlon using only 700Kcal per hour and 55% is being provided by fat. A quick maths calculation reveals the following:

1. He’s using 315 Kcal of carbohydrate per hour on the bike, compared to the previous figure of 533

2. With his intake of 60 grams per hour (240 Kcal), he now only has a deficit of 75 Kcal per hour compared previously with 292 Kcal (73 grams)

3. As a consequence, Tom runs the whole marathon and Tom becomes a LEGEND…..

Do you want to become a legend? If so, do the calculations and work it out for yourself, then let’s go forwards from here.

– Marc Laithwaite

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

Race Day Nutrition (Part One) – Marc Laithwaite

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In recent articles, we’ve discussed the 2 main fuel sources for endurance exercise (fat and carbohydrate) and how you should optimise your body to burn fat, thereby allowing you to save precious carbohydrate stores. When it comes to race day then the game and the rules change completely. As a recap, when training you should:

1. Ride or run at the correct intensity or follow a specific protocol such as Maffetone
2. Avoid fluctuations in intensity, remember that average heart rate or power output are NOT the critical figures, it’s TIME IN ZONE that counts
3. Eat foods which are balanced with low GI carbohydrates and fats to encourage fat usage and avoid sugar spikes
4. Avoid gels and sugar products based on point 3 above

If you follow the above guidance, over a 12-16 week training period, you can teach your body to utilise a greater amount of fat as fuel and also to use less calories overall, making you more economical. The important thing to remember is that ‘training’ and ‘racing’ are 2 separate things and your fuelling approach should reflect this.

What happens during the race?

Okay, let’s presume that you have trained correctly and maximised your fat burning potential and fuel economy. You reach the first event of the year and when riding or running at race pace you are using 700kcal per hour, 50% of which comes from carbohydrate and 50% of which comes from fat. You only need to worry about the carbohydrate loss as that’s the one which is critical, so let’s focus on the 350kcal of carbohydrate which equates to 88 grams of carbohydrate (4 kcal per gram).

The limitation of carbohydrate intake

Here’s the big problem, you can only absorb approximately 60g of carbohydrate per hour. Imagine that there are small boats, which ‘ferry’ carbohydrate across the intestine wall into your blood stream. Unfortunately you only have so many ‘ferry boats’ so no matter how much carbohydrate you throw in there, the amount which can be ferried is limited to a pretty standard 60g. For our example above, that means that you’re going to fall short. You’re using 88 grams per hour and you can only replace 60 grams per hour. That’s a 28 gram / 112 kcal per hour deficit.

So I can’t just eat more?

Unfortunately not. If you eat more, it’s unlikely to be digested and will simply sit in your stomach or intestines without providing energy. There are a lot of people who suffer from gastric problems during long distance events and this is generally caused by eating too much food which they are unable to digest. It’s really important that you understand, eating more food doesn’t mean you’ll have more energy and it may well mean that you’ll face stomach upsets. I stress this point knowing how obsessed Ironman athletes in particular become with regards to feeding on the bike.

A deficit of 112 Kcal per hour doesn’t sound too bad

No, it doesn’t. But that is based on the presumption that you are only using 700kcal per hour, bigger people and less efficient people may be using more. It’s also based on the assumption that 50% is coming from fat and that may not be the case at all, in fact, as much as 80-100% may be coming from carbohydrate. What makes this worse is that bigger people can’t necessarily take on board more fuel, the 60g limit still pretty much applies. It’s a gut issue, it’s not about how big your muscles are and how much you can store in there.

So the 3 things you might want to know are:

1. How many calories do I burn per hour?
2. How many of them come from fat and carbohydrate?
3. How much should I be taking in as a consequence?

As a start point, you can probably work out your calorie usage by using a heart rate monitor or power meter. Run or ride at race pace and it’ll do the calculation for you, although the power meter is a lot more accurate than the heart rate monitor, it’s still a start point. Warm up, then do an hour at your ‘race pace’ and work out the figures. It’s amazing how many people who consider their training and racing to be ‘serious’, still have no clue how many kcal they use when racing. How can you have any grasp of nutrition requirements without knowing this figure? Once you’ve calculated that figure, apply the following rule:

80/20: If you are struggling to ride 50 miles / run 15 miles even when fuelling yourself throughout, then apply the 80/20 rule. That means 80% of your fuel is carbohydrate and 20% is fat.

65/35: If you can ride 50 miles / run 15 miles comfortably using fuel, then apply the 65/35 rule. That means 65% of your fuel is carbohydrate and 20% is fat.

50/50: If you can ride 50 miles / run 15 miles comfortably without using any fuel whatsoever, then apply the 50/50 rule. That means 50% of your fuel is carbohydrate and 50% is fat.

Are those figures accurate?

Absolutely not, I just made them up. They are by no means 100% accurate but they will give you a good start point and will allow you to calculate an approximate figure. The running figures are less ‘straight forwards’ than the cycling, as the impact of running can really fatigue your legs, so you may find 15 miles difficult, even if your fat burning and fuel economy is good. for cycling, the impact is low, so it’s more likely governed by metabolism and fuel.

Ok, so what’s the next step?

Here’s what we’re going to do. Prior to next week you are going to do a 1 hour ride or run at your ‘race pace’ and then using your cycle power meter, GPS or heart rate monitor, calculate how many calories per hour you are using when exercising at that intensity. I feel this is a pretty important thing for you to understand if you are to race successfully. It’s easy with a power meter for cycling, it does the maths for you. Most heart rate monitors will use your age and weight to work out kcal per hour. There are some tools on the internet such as: http://www.braydenwm.com/calburn.htm which can help to give you a basic idea.

Go forwards my endurance friends and do the maths, next week, we will be looking at planning your intake.

Until then, stay healthy.

– Marc Laithwaite

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