Nutrition for Cyclists

N4C_AmazonFirst of all, an enormous vote of appreciation and thanks to all of the readers of Tuned In To Cycling over the years who have provided helpful comments, support and motivation for me to write a book about cycling nutrition. It’s finally happened. Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride is now available for purchase at Amazon.com.

The book grew out of the nutrition posts here on Tuned In To Cycling and, like those posts, combines suggestions and recommendations for what to eat and drink before, during and after a ride with information about how the body responds to endurance athletics.  To help you decide whether or not you’d like to purchase the book, I’m posting the book’s Introduction here which will give you a good idea about what’s in the book and how it relates to the posts that have appeared on Tuned In To Cycling.

If you decide to buy the book and you think it is useful for other cyclists and worth a 4 or 5 star review, I would greatly appreciate it if you would leave a review on Amazon.  Positive reviews are a huge factor in helping a self-published book find an audience among the millions of ebooks published on Amazon.

Here’s the Introduction to  Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride.

Chapter 1. Introduction

Here’s a quote from former U.S. President John F. Kennedy that many cyclists know well.

Nothing compares to the simple pleasure of a bike ride.

Anyone who has spent any time on a bike knows that it’s true . . . . until it isn’t.
Here’s another saying cyclists know well.

Eat before you’re hungry, drink before you’re thirsty.

Short of a catastrophic accident, nothing can turn a pleasant, joyful or exhilarating bike ride into a nightmare faster than failing to provide your body with the nutritional support it needs to carry out the ride. Nutrition for Cyclists is designed to give riders of all experience levels useful information about meeting the nutritional demands imposed on the body by endurance athletics. Good nutrition can help you get the most out of your ride no matter what kind of ride you like to do.

Finally, one more saying that everybody knows.

Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime.

Nutrition for Cyclists contains recommendations about what to eat and drink before, during and after a ride. That’s the “give-a-man-a-fish” part. However, no book can give you a recipe for what to do in every possible nutrition-related situation that might arise when you’re riding the bike. Even if a book like this were possible, would you want to memorize it so you would be prepared for anything?

Nutrition for Cyclists also contains a good deal of information about how your body works when you’re engaged in athletic activity. That’s the “teach-a-man-to-fish” part. The more you know about how your body processes food and drink, and about what can happen when there is not enough food or drink for your body to process, the better prepared you’ll be to understand what’s happening to you on the bike.

The short-term goal of Nutrition for Cyclists is to get you started with recommendations about eating and drinking before, during and after a ride. The long-term goal is to give you information about nutrition and endurance athletics so that you will be able to make informed decisions about what’s happening to you on the bike and what you can do to make it better.

The information presented in Nutrition for Cyclists is based on research findings reported in peer-reviewed journals in the fields of human physiology, and nutrition and sport science. The internet is awash with assertions, recommendations, and unsubstantiated claims about exercise nutrition. Some of this advice is supported by sound research. Much of it, including a number of widely cited and uncritically accepted ideas, is not. As will be discussed in the next chapter, focusing on information that is well supported by sound research does not mean that everything in Nutrition for Cyclists is “right” or “true”. It means that this information is the best we have given the current state of scientific research on exercise nutrition.

Nutrition for Cyclists grew out of a series of posts on Tuned In To Cycling, a blog I started in the spring of 2008. While Tuned In To Cycling has posts on many cycling-related topics, the posts on nutrition have proven to be the most popular with cyclists from all over the world. Some of the content of this book has been copied verbatim from the posts on Tuned In To Cycling, some of it is a revised or rewritten version of what’s on the blog, and some of it is new. Everything in Nutrition for Cyclists was checked against the current research literature. If a section of the book has been lifted verbatim from the blog, it means that research published between the time the original post was written and the book was published did not demand changes in the information that had appeared in the blog.

For both new readers and followers of Tuned In To Cycling Nutrition for Cyclists provides the convenience of a self-contained source for nutritional information that is organized into sections devoted to what to eat and drink before, during and after a ride. Also, publication as an ebook means Nutrition for Cyclists is conveniently available anywhere you have a Kindle or any other device with a Kindle app.

Carbohydrate Loading

This post is adapted from Nutrition for Cyclists: Eating and Drinking Before, During, and After the Ride, a forthcoming ebook which I will be publishing for Kindle on Amazon.com.

Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride can now be purchased on Amazon.com.  For information about the book and how it relates to what I’ve posted to Tuned In To Cycling, please check out this post.

eating spaghettiWell-organized and popular century rides often offer an all-you-can-eat pasta dinner the night before the ride.  If you go to the dinner, you’re likely to see people putting away enormous plates of pasta and if you ask them why they’re eating so much spaghetti they’ll tell you that they’re carbo loading for the next day’s ride.  What is carbohydrate loading and is eating a lot of spaghetti the night before a big ride the right way to go about it?

The basic idea behind carbohydrate loading is that glycogen stores in the muscles and liver can be increased over the norm by following specific exercise and dietary regimens in the days before a ride.  The increased glycogen stores should then translate into a longer time before fatigue sets in due to glycogen depletion during the ride. There are three recognized carbohydrate loading methods and I will suggest an alternative approach.

The original and most severe method follows a week-long regimen. On the 7th day before the ride, you exercise to exhaustion.  This exercise bout should last a minimum of 90 minutes.  The next 3 days are a carbohydrate depletion phase during which you train lightly while keeping carbohydrate intake at only 10% of your daily caloric intake.  The final 3 days before the big ride are a carbohydrate loading phase.  You continue to train lightly while jacking carbohydrate intake up to 70% of your daily caloric intake.  It’s important not to increase your total caloric intake from the norm over the 6 days of carbohydrate depletion and loading.  During the 3 day depletion phase you replace calories normally consumed in carbohydrates with calories consumed in fats and proteins. During the 3 day loading phase your replace fats and proteins with carbohydrates.

drink-b4-thirsty-mod-4-customThink about this for a minute.  The depletion phase is an extended period of controlled hypoglycemia, essentially a 3 day bonk.  During that time you can be expected to experience all of the negative effects of bonking including weakness and lethargy, anxiety, depression, hostility, feelings of hopelessness and failure, low levels of emotional control, reduced awareness of your surroundings and confused thinking.  In addition, the immune system will be depressed and you will be more susceptible to contracting an illness that may still be present when the ride comes several days later.

A 3 day bonk is hard.  Very hard.  The second method eliminates the bonk by eliminating the depletion phase. On the 7th day before the ride you have a long exercise session but you don’t exercise to exhaustion.  For the next 6 days you engage in progressively lighter exercise sessions each day.  Some people recommend tapering the level of exercise down to a day of rest on the 6th day.  For the first half of this 6 day period you ingest carbohydrates at a normal 55% – 60% of your daily caloric intake.  For the final 3 days you ramp carbohydrate intake up to 70% of your daily caloric intake, again by replacing fats and protein with carbs.

The third method is the easiest of the three. During the week before the big ride you exercise lightly and eat normally.  On the day before the ride you do a very short, 3 minute high intensity workout.  The workout should be made up of a 2.5 minute session at 130% VO2 max which is roughly equivalent to the fastest pace you can maintain over approximately 4 minutes of all-out running or cycling.  Follow this 2.5 minute effort with a 30 second flat-out sprint.  If done properly, this 3 minute workout is going to hurt.  During the following 24 hours ingest 12 grams of carbohydrates per kilogram of lean muscle mass.  Muscle mass can vary greatly depending on age, gender and degree of muscular development.  Based on a very rough average of 35% muscle mass for men and 27% muscle mass for women the carbohydrate intake over the 24 hour period would total approximately 305 grams for a 160 lb. male and 191 grams for a 130 lb. female.

If followed correctly, all three of these methods should produce a markedly enhanced level of glycogen storage on the day of the big ride.  Neither anecdotal reports (which are basically worthless) nor research studies have reached a clear consensus on how much better or worse one method is relative to the others.  The bottom line is that all three methods are effective if followed properly.

baby spaghetti dumpNow, I’ll suggest a fourth method that is usually not discussed in the literature.  Forget about it. Don’t bother with any of this stuff.

Wait . . . what? Consider the kind of riding you do.

If your ride takes less than 90 minutes, carbohydrate loading is a non-issue because proper eating before, during and after your previous ride should have adequately prepared you for the next ride.

If your ride takes longer than 2.5 or 3 hours, you’re going to have to eat during the ride anyway because even perfectly executed carbohydrate loading isn’t going to provide you with sufficient glycogen stores to last for this length of time.  All carbohydrate loading is doing is delaying the time before you have to start eating.

Wiggins eating_croppedIf your ride takes between 1.5 and and 2, maybe 2.5 hours, carbohydrate loading might allow you to get through the ride without ingesting any carbohydrates. But why would you want to do this? If you enjoy rides that last more than 90 minutes you would be much better served by becoming proficient at eating on the bike to fully supply your nutritional needs during the ride. You get better at what you practice and if you find a way to avoid eating on the bike, you’re not going to get better at eating on the bike.

The fundamental goal of cycling nutrition is to provide full nutritional support for your ride.  A competitive race, a long organized or training ride, and a Sunday afternoon toodle around the neighborhood all make different demands on your body but whatever the ride, you will do it better and enjoy it more if you provide the nutritional support the ride needs.  The simplest and most effective way to do this is to develop the habit of ingesting small amounts of carbohydrate regularly during the ride.  The best way to develop the habit is to practice doing it.

If properly carried out, carbohydrate loading can fully support rides lasting 1.5 to 2 hours, maybe a bit more, if you don’t ingest any other carbohydrates during the ride. It’s not much use for rides lasting less than 90 minutes or more than 2, maybe 2.5 hours.  Eating properly during the ride can fully support any kind of ride you want to do. The choice is yours.

“Superstarch” and the Endurance Cyclist

cyclist with appleA comment from a reader led me to take a look at a slick website hawking a product called Generation Ucan that is marketed as delivering several “scientifically validated” benefits to people engaged in athletic activity.  From the serious beginner to the most highly-paid professional, athletes are notorious for their susceptibility to being taken in by products that claim to improve performance.  The Generation Ucan website has several of the characteristics that are often associated with nutrition scams that make fabulous claims while trying to sell untested or poorly tested junk to gullible people so I decided to take a closer look.

What is it?

waxy-maize-starch_2 (2)Generation Ucan is hydrothermally modified waxy maize starch.  The starch is processed under conditions of higher than normal moisture (hydro) and heat (thermal) which changes the chemical properties of the starch molecules.   One effect of this treatment that is of interest to endurance athletes is that the carbohydrates in hydrothermally modified starch have a low glycemic index.  Generation Ucan calls HMS “superstarch” which is such an obvious and ridiculous marketing ploy that I’ll avoid it.  What they’re selling is hydrothermally modified starch or HMS.

sciencequizlogoThe Generation Ucan website is filled with phrases like “lab tested”, “scientifically proven”, “our science”, and “proof/validation”.  First of all, reputable research scientists virtually never talk about “proof” like this.  We talk about the extent to which the experimental evidence supports or fails to support the conclusion.  The marketing-hype alarm goes off big-time when “science” and “proof” occur together in product marketing.

What scientific evidence does Generation Ucan actually provide?

The website has links to a couple of white papers that talk about research that supports their claims for their HMS.  White papers are documents produced by a company with the aim of selling a product.  Generation Ucan’s white papers reference “internal studies” as evidence that HMS is wonderful.  As evidence to support their claims about HMS, these internal studies are worthless.  Not enough information is given to determine whether the research was carried out rigorously and properly.  The internal studies may provide good evidence or they may not.  There’s no way to know one way or the other.  However, if the science was good, you would expect it would have been published in a top-rated peer-reviewed journal.  There is no indication on the website that these internal studies were submitted to a reputable journal or survived a rigorous peer-review process.  Basically, the white papers contain a lot of unsubstantiated claims tricked up to look like science.

The Generation Ucan website also provides a prominent link to an article in Men’s Health Magazine that promotes the product.  Men’s Health Magazine?  Lol, really?

Buried in the science section of the website they have a link to downloads.  Follow that link and what you mainly find are sales kits.  Sales kits in the scientific evidence section?  There are seven of these sales kits.  There are also two links to their own white papers, and one link to an article in the journal Nutrition about HMS.  Nutrition is a peer-reviewed journal and this article is the only reliable scientific evidence that I found on the Generation Ucan website.

cyclist in labThe article in Nutrition is the real deal although it should be noted that Generation Ucan funded the research project that is reported in the article.  What does it report?  Nine male cyclists engaged in a 150 minute cycling session at 70% VO2(max) – that’s fairly intense – followed by a 100% VO2 (max) time-trial to exhaustion.  Before the exercise session and immediately afterwards the cyclists were given either HMS or maltodextrin.  Maltodextrin is a sweetener often used in candy, soda and many other products.  HMS and maltodextrin are both sources of carbohydrates.

Note that they didn’t call their HMS “superstarch” when they submitted the research for peer review.   If they had, they would have been laughed out of the room.

Ucan insulin dataThe study found that the HMS group had a lower initial insulin spike than the maltodextrin group.  They also found that the HMS group showed a higher level of fat breakdown during the recovery period.  There were no reliable performance differences between the HMS and maltodextrin groups during either the 150 minute exercise period or the time-trial to exhaustion that followed.  There was also no reliable difference between the two groups in the level of fat breakdown during exercise.

The authors of the article note that the increase in fat breakdown during the recovery period after exercise was probably due to the HMS that was given after the exercise period.  Their research doesn’t test this hypothesis but it is plausible given what is known about the effects of HMS and the relationship between insulin and fat burning.   Insulin is prominently involved in the regulation of fat oxidation.  Lower levels of insulin correspond to higher rates of fat burning and vice versa. The study in Nutrition provides good evidence that HMS reduces insulin and reduced insulin typically produces higher levels of fat oxidation.

Keep in mind that this study in Nutrition is the only reliable scientific evidence that is given on a website that heavily stresses the scientific basis for their claims about how wonderful their product is for athletes.  While this isn’t much, it’s more than you often get on websites that sell wonder foods for sports nutrition.  There is some real science here.  The study provided good evidence that HMS reduces insulin levels.  This information could be of interest to people who are looking to lose weight because reduced insulin levels correspond to higher levels of fat burning after exercise.  It’s worth repeating that the study showed no differences in performance between those who exercised after ingesting HMS and those who ingested maltodextrin.

What claims does Generation Ucan make about their product based on this scientific evidence?

snake-oil-salesman-bigThey claim that their HMS produces “optimized performance”, “sustained energy”, “enhanced fat burn”, “speedier recovery” and “no gastric distress”.  The claim about enhanced fat burn is supported by the evidence in the Nutrition article.  The scientific evidence they reference on the website has nothing at all to do with sustained energy, speedier recovery or levels of gastric distress.  As far as “lab tested” or “scientifically proven” these claims are completely unsupported by the scientific evidence the Generation Ucan people provide.  They give you no good reason to believe HMS provides any of these benefits.

The claim about optimized performance is outrageous.  I expect many people looking at the Generation Ucan website uncritically will understand this as meaning that performance is better if you use their HMS than if you use other carb sources during exercise.  The article in Nutrition that is offered as the only reliable scientific evidence given on the website flatly contradicts this interpretation.   There was no difference in performance (or fat burning during exercise) between the HMS group and the maltodextrin group in the study.

lawyerI have no doubt that company lawyers can parse the “optimized performance” statement to mean that Generation Ucan’s HMS produces optimized performance in the sense that it matches the “optimal” performance levels expected after ingesting carbs from candy, soda or energy drinks.  When you have to rely on lawyers to weasel out of charges of false advertising, there’s clearly something wrong.  Anyone with a lick of common sense can see that, at best, the “optimized performance” claim is highly misleading.  At worst, it is pure bullshit designed to sucker you into buying their product.

What’s the take-home message about Generation Ucan’s HMS?  The product is likely to lower insulin levels.  This can be useful to people who want to burn fat.  If this is one of your goals, taking Generation Ucan’s HMS immediately after exercise may be useful.  If you are diabetic, don’t go near this product without consulting your doctor.  As far as supporting performance during exercise, their HMS is unlikely to be any better, or any worse, than many other sources of carbohydrates you can eat or drink on the bike.

What’s the take home message about the Generation Ucan company based on how they present themselves on their website?  Either the people who are trying to convince you to buy their HMS have the scientific training to tell the difference between good science and junk science or they don’t.  If they do, then the science heavy promotion on the Generation Ucan website is purposefully designed to mislead you into buying their product based on unsubstantiated claims that they figure you are either too ignorant or too stupid to recognize for what they are.  If they don’t, what are they doing marketing their product with a website that goes heavy on the science?  In either case, why should you believe anything they have to say?

Cycling and Weight Loss Part 1: Riding the Bike to Lose Weight

A champion

A champion

This is the first of a series of posts about riding the bike to lose weight.  Throughout this discussion of losing weight it’s important to keep in mind that eating has many consequences for health, athletic performance and weight gain or loss. We’ll start by focusing purely on weight loss but it is very important to keep in mind that the “best” diet for losing weight is unlikely to be the “best” diet for maintaining your health or a high level of athletic performance.

A lot of people aren’t going to like these posts.  I noted in a recent post that Americans spend about $50,000 on diet industry products and services every 80 seconds, 24/7/365. If you work for 50 years and average $50K a year, Americans spend more on diet stuff in an hour and 10 minutes than you will make in your entire life. 24/7/365.  The people who are spending that money and the people who are raking in the cash from all that stuff are going to be especially unhappy with these posts.  Why?  Because if you’re riding your bike to lose weight, most of that stuff is a waste of time and money.

Many people get into riding the bike as a way to lose weight and others who are interested in the health benefits of riding have weight loss as a secondary goal.  This is a good idea because riding the bike can be a great way to lose weight.

Shoes on scaleThere are a couple of ways to go about this.  One approach is to focus your attention on losing weight.  You buy diet books and scour the internet for info about losing weight.  You pay careful attention to things like how many calories there are per serving size.  You count calories for each meal and snack. You weigh yourself obsessively.  You may fork out money for the advice of a licensed nutritionist.  If you are especially gullible you buy a magic bracelet.

This approach to losing weight is often accompanied by the view that riding the bike is a type of exercise that is going to be used as a weight loss procedure.  Exercise is onerous but you have to do it.  People with this attitude will often want to maximize their weight loss for every minute they have to spend on the bike.  They’ll want to know things like what’s the smallest amount of time they’ll have to spend on the bike to burn X number of calories, what’s the absolute minimum they have to eat on the bike to get through a longer ride and exactly when they should eat in order to survive the ride on this absolute minimum.  They’re always worrying about numbers.  They’re not having much fun.

Happy cyclist_cropHere’s a second approach losing weight on the bike.  Forget about losing weight.  Forget about measuring this and calculating that, about eating so much of this kind of food and so much of that kind of food, about magic bracelets and paying for the advice of licensed nutritionists.   Forget about all of it.  Instead, enjoy riding your bike, ride frequently and consistently, and keep trying to get better at it.  That’s really all you need to do.  You will almost certainly lose weight.

The basic story is very simple.  Your body needs energy to function.  That energy is measured in calories.  The type of calorie that is used when talking about weight loss and nutrition is sometimes called a large calorie or a kilocalorie. One kilocalorie is the amount of energy that is needed to raise the temperature of 1 kilogram of water by 1 degree Celsius.

If you are alive, you are burning calories. Calories are burned when you sleep, when you think, when you go through your normal daily activities and when you ride.  The fuel that provides these calories is glucose.  The glucose is derived either from carbohydrates, proteins or fats that are being broken down in the digestive system from food you have recently eaten or from reserves stored in the body.   If there is not enough glucose in the blood stream to fuel ongoing activity, the system starts breaking down stored reserves to get the glucose it needs.  When stored fat is broken down, people start losing the kind of weight they want to lose.

calorie-balanceLosing or gaining weight depends on the balance between the calories you burn and the calories you ingest during the day.  If the calories you ingest are less than the calories you burn, you will lose weight because the system will turn to its stored energy reserves (which include stored fat) to get the energy it needs.  If the input calories are more than the output calories, you will gain weight because the excess calories will usually be stored as fat.  If input and output are about the same, your weight will be stable.  Thinking only in terms of weight loss (and not health or performance), it doesn’t matter if the calories being burned are coming from carbs, proteins, or fats.  A calorie is a calorie. That’s almost all you really need to know.

Almost but not quite.  There’s one important modifying factor to consider that we’ll look at in more detail in the next two posts in this series.  In order to take this modifying factor into account when you’re riding your bike, you need to try to get better every time you ride.  Every time out try to get a little stronger, go a little faster, ride a little longer.  That’s really all you need to do.

Riding like this will result in weight loss for the simple reason that in most cases when you add the calories you burn during the ride to the calories you burn during the rest of the day the total calories burned is greater than the calories you take in by eating.  If you burn more calories than you take in, you will lose weight.  Simple. And you don’t need to support the diet industry with your hard-earned cash to do it.

People who take the first approach try maximize weight loss by obsessing over how many calories, what kind of calories, when you eat those calories, and all the rest of it.  People who take the second approach try to maximize the enjoyment they get from riding the bike.  They work on spending more time on the bike doing the things they enjoy about riding the bike. When you engage in exercise or athletic activity you’ll burn the calories whether you enjoy what you’re doing or hate it, whether you’re thinking about losing weight or thinking about whatever you think about when you’re having fun.  So, why not give your attention to enjoying yourself and having fun rather than on how much you’ll weigh the next time you get on the scale?

food-nutriiton-bannerWhen you focus on riding the bike because you enjoy it rather than riding the bike as a weight loss procedure all of the questions about calories and weight loss turn into questions about how to be a better rider.  Getting better on the bike usually means increasing your strength and endurance so you can ride harder, longer or faster.  Eating isn’t about minimizing calories anymore, it’s about supporting performance.  As your performance increases and you ride harder, longer or faster, you burn more calories whether you’re trying to lose weight or trying to be a better cyclist.  If you ride hard enough and often enough, you can eat whatever you want because no matter how many calories there are in what you eat, you’ll burn more on the bike and lose weight.

If you don’t really enjoy riding the bike, find another type of exercise that you do enjoy.  If you enjoy something, you’ll want to do it; if you want to do it, you’ll find a way to do it; if you do it, you’ll burn the calories and lose the weight.  Find something energetic that you enjoy, do it frequently and consistently and always try to get better at it and the weight will come off.  It won’t happen overnight, it won’t happen fast, you’ll hit plateaus, but if you keep striving to ride harder, faster, stronger, longer, you will lose weight.

Once you’ve started to lose weight there’s another factor you have to consider which we take a look at in the next post in this series.

Cycling Nutrition: The Value of the Glycemic Index for Cyclists

idiots guide

Information about the glycemic index and many other topics can be found in Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride which can be purchased on Amazon.com.  For information about the book and how it relates to what I’ve posted to Tuned In To Cycling, please check out this post.

The diet industry is big business; in the US it is estimated that people spend in the neighborhood of $35 billion dollars a year on diet-related products.  (To make that number more comprehensible, if you make $50,000 a year Americans spend your yearly salary on diet products approximately every 80 seconds.  24, 7, 365.)  A large part of this industry relies on consumer ignorance and gullibility to enable the promotion and sale of one fad diet idea after another.  One of the ideas heavily promoted in the diet industry is the glycemic index.

Is the glycemic index useful? Yes.  Is it all the diet industry makes it out to be?  Not even close.  For our purposes here, is it useful to cyclists?  I think the best answer here is – marginally.

First of all, what is it?  The glycemic index is an indicator of how long it takes food to be converted to glucose in the blood.  Glucose is the fuel that muscles burn when they are working and on-the-bike cycling nutrition and performance is largely about glucose production and consumption.  Having an idea of how long it will take to get the food you eat while you ride converted into blood glucose has the potential to be very useful.

Will the glycemic index tell you how long it takes for the Powerbar or raisins you ate to be converted to blood glucose in seconds, minutes and hours?  No.  The glycemic index compares the time it takes for a particular food to be converted to glucose in the blood to the time it takes for pure glucose ingested orally to appear as glucose in the blood.  Glucose is arbitrarily assigned a glycemic index value of 100 to serve as a basis for comparison.  Particular foods are then given a glycemic index value, typically less than 100, based on how long they take to be converted to blood glucose in comparison to pure glucose.  A high glycemic index indicates a food is rapidly converted to blood glucose; a low glycemic index value means it takes a relatively longer time for that food to be converted to blood glucose.  The glycemic index doesn’t tell you how long it takes to get blood glucose out of food, it gives you a rough idea which foods are converted to blood glucose more quickly than others.

eating on bikeThis sounds like it should be of great use to the cyclist.  You’re burning glucose constantly on the bike, you need more, you’re eating to get more, the glycemic index will tell you what to eat to get that glucose as quickly as possible.

It’s all good, right? Not really. Why not?

The glycemic index of most food varies with so many factors that the rough idea the glycemic index gives you of which foods are converted into blood glucose faster can be very rough indeed.  Here are some examples.

  1. For many foods, glycemic index varies as a function of how the food was prepared (pasta boiled for 10 minutes has a different glycemic index than pasta boiled for 15 minutes), when it is eaten relative to when it was cooked (potatoes often have a higher glycemic index when eaten after cooking than they do if refrigerated  and then reheated and eaten the next day), how ripe the food is when eaten (generally, the glycemic index of fruit increases as the fruit ripens), or which variant of the food type you are eating (different types of raisins have different glycemic indices).
  2. Glycemic index for a particular food varies depending on what is eaten along with that food.  Fat, protein or fiber eaten along with a particular food usually results in a lower overall glycemic index.  For example, you’ll usually get faster blood glucose from raisins eaten alone than the raisins in a cookie.
  3. Different people will have a different glycemic index for the same food because individuals differ in how efficiently they digest carbohydrates.  In addition, the same person may have a different glycemic index for the same food when that food is eaten at different times of the day.
rough categories

The glycemic index values that are used to define the categories in this image are rough guides.

Considering all of these factors, I think the glycemic index can be modestly useful to the cyclist planning what to eat during a ride.  There are many glycemic index charts for different foods that can be found on the internet.  The specific numbers given in these charts are best thought of as rough estimates.  For the cyclist it’s probably most useful to consider glycemic index in terms of three rough categories: High, medium and low glycemic index foods.  High glycemic index foods will probably provide needed glucose throughout the ride.  On long rides of two hours or more, low glycemic index foods can produce needed glucose later in the ride if the food is eaten early in the ride.  As you get closer to the end of the ride, higher glycemic index foods are more likely to be beneficial while you’re still on the bike.

WARNING:  The nutritional needs of a person engaged in 60 to 90 minutes of moderate to intense exercise or a long ride lasting more than 2 hours are very different from the nutritional needs of that same person going about their daily activities.  High glycemic foods can be very useful while you’re on the bike.  A steady diet of high glycemic foods when you’re not engaged in endurance exercise has been shown to be related to various health problems such as obesity (and all of its related problems), diabetes and, at least in animal studies, a shortened life span.  High glycemic foods eaten while you’re riding will generally help you.  A day-in, day-out diet of high glycemic foods when you’re not exercising will generally hurt you.

Dehydration and Over Hydration (Hyponatremia) for the Cyclist

More information about dehydration and how to avoid it can be found in Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride which can be purchased on Amazon.com.  For information about the book and how it relates to what I’ve posted to Tuned In To Cycling, please check out this post.

There’s a lot of water around us; roughly 70% of the earth’s surface is covered in water. There’s also a lot of water in us; roughly 60% of the human body is water. The balance between the water inside and outside our bodies has to be kept within a fairly narrow range or bad things can happen. Either too much or too little water inside the body can, in extreme cases, be lethal.

When you ride your bike your body loses water in the form of sweat. This is a good thing because the evaporation of sweat from the skin is the main way your body sheds heat while you’re on the bike. Without that cooling the increase in body core temperature from the heat generated by your working muscles would kill you fairly rapidly.

Sweating is good but the fluid loss that comes from sweating is not so good. When you lose water through sweat you become dehydrated. At extreme levels dehydration can lead to heat stroke which can be life threatening. However, even relatively mild levels dehydration can have negative effects on cycling performance.

How dehydration affects your body

For the endurance cyclist the main effect of dehydration is to decrease the volume of blood in the system. This has two major consequences and both of them are bad.

First, a decrease in blood volume reduces the body’s ability to shed heat and thus leads to an increase in core temperature. This works in two ways. The main way the body sheds heat during exercise is through sweating. When blood volume is decreased through dehydration sweating decreases because the water in sweat is derived from blood plasma. You can’t sweat it out if it’s not there in the first place.

In addition to sweating, the body sheds excess heat by radiation and conduction if the air temperature is lower than the body temperature. When body temperature rises the blood vessels near the surface of the skin expand (vasodilation). This brings more of the blood into close contact with the surface of the body so that heat carried by the blood can be lost through conduction and radiation. A decrease in blood volume decreases the amount of blood that can be brought into contact with the body’s surface thereby partially offsetting the benefits of vasodilation.

The second negative effect of the decrease in blood volume caused by dehydration is that the blood becomes thicker or more viscous. The heart has to work harder to pump the thicker fluid through the body. Blood flow becomes more sluggish. During diastole (the resting phase when the heart fills with blood) the heart may not completely fill with blood so that the volume of blood pumped with each heartbeat declines. Blood flow throughout the body declines and blood flow to the working muscles is critical for the cyclist because it brings fuel to the muscle in the form of glucose, and carries away waste materials and heat.

How dehydration affects performance

Dehydration and increase in body temperature are separate factors that have independent effects on athletic performance. They also interact with each other to decrease performance. It’s helpful to keep in mind how both of these factors are affecting performance both individually and in combination.

A loss of as little as 2% body weight (3 lbs. for a 150 lb. person) can negatively affect athletic performance. This negative effect increases as the amount of time spent performing the exercise increases. A study carried out with runners showed that a roughly 2% loss in body weight due to dehydration produced approximately a 3% loss in performance over 1500 meters and a 5% loss in performance over 5K or 10K meters. A loss of 5% body weight through dehydration (7.5 lbs. for a 150 lb. person) has been shown to produce approximately a 30% loss in performance.

VO2 max is a measure of the maximum amount of oxygen a person can use during exercise and is widely used as a general measure of aerobic fitness. Studies carried out in cool laboratory environments have shown a 5% decrease in VO2 max with a 3% decline in body weight through dehydration. The negative effect of dehydration on VO2 max is increased in the warm or hot environments the cyclist usually experiences. Decreases in VO2 max are most probably caused by the decrease in blood volume produced by dehydration that was discussed earlier. Note also that increased body temperature can reduce VO2 max even when individuals are fully hydrated. In other words, dehydration and increased body temperature act alone and in combination to decrease VO2 max.

Whether or not it is accompanied by a decrease in VO2 max, dehydration produces a decline in endurance as measured by the time it takes to reach exhaustion. A loss of 5% body weight through dehydration can decrease endurance even for low intensity exercise (e.g., low intensity walking). The loss in endurance increases markedly as either the intensity of exercise increases or the level of dehydration increases.

Endurance is also affected by core temperature; as core temperature increases, endurance decreases. Because dehydration has a large effect on the body’s ability to shed heat, core temperature rises more quickly and endurance decreases more quickly as dehydration increases. In addition, dehydration produces a lower tolerance for increased core temperatures. Exhaustion occurs at lower core temperatures for dehydrated individuals as opposed to hydrated individuals.

As if all that isn’t enough, there is evidence that suggests that dehydration in combination with increased core temperature my cause glucose to be burned more quickly and less efficiently in working muscles. Glucose is the fuel that powers muscle activity, it’s almost always in short supply for the endurance cyclist, and the evidence suggests it’s used less efficiently when dehydration is accompanied by increased core temperature (which it almost always is). You’re trying hard to keep going and avoid the bonk by paying attention to what you eat while you’re riding, you are always short on fuel, and dehydration is causing you to burn the limited fuel you have available less efficiently. Not good.

Stay hydrated.

Over hydration or hyponatremia

Is it possible to drink too much water? Yes, the condition is called hyponatremia and in rare cases it can be fatal. When the body is over saturated with water the sodium in the body becomes diluted. When this happens individual cells throughout the body swell with the result that a variety of bodily functions may be disrupted.

At present we don’t know as much about athletically induced hyponatremia as we would like. The condition was first described in 1981 and much of the data that exists about hyponatremia is drawn from samples of convenience taken at popular athletic events such as marathons and reports from the military documenting the consequences of water consumption during training. The problem with samples of convenience is that important variables are left uncontrolled that need to be controlled in order to draw sound and justified conclusions from the data.

Hyponatremia is diagnosed based on the level of sodium in the blood and measuring serum sodium level is relatively easy. The problem is that the serum sodium level that is widely accepted as indicating hyponatremia may be accompanied by a variety of symptoms ranging from confusion or seizures, through headaches and stomach distress, to, in many cases, no symptoms at all.

Hyponatremia began to be commonly observed along with the rise of marathon running as a popular hobbyist sport. In order to prevent dehydration and heat stroke race organizers frequently stress the importance of staying hydrated during the run and they provide frequent water stations along the route. In addition, manufacturers of “sport drinks” often market their products at open running events and pay the organizers to make their drink available to runners along the route.

Under these circumstances you might expect relatively inexperienced hobbyist runners to drink too much during their run. There appears to be evidence that this is the case. Hyponatremia has been observed to be much more common among inexperienced runners who train at slower speeds and take more time to complete the marathon.

At present, it is unclear whether women are more susceptible to hyponatremia than men. Some studies suggest they are, other, better controlled studies, suggest there’s no difference. Also, there is no evidence that the sodium content of many “sports drinks” serves to prevent hyponatremia .

How can you tell if you’re drinking too much water when you ride? A rough method is to weigh yourself right before and right after your ride. If you gained weight and drank a lot of fluids during the ride, you were probably over hydrating.

In the absence of medical complications, avoiding hyponatremia is basically a matter of common sense. Anecdotal reports in the medical literature about people who experienced extreme hyponatremia include very slow runners who took very long times to finish marathons and who reported drinking at every water station along the way and a woman who prepared for her marathon by drinking 10 liters of water (!!) the night before. Use your head for something besides a place to keep your helmet while you ride and don’t drink excessive amounts of fluids and you shouldn’t have a problem. Most important, don’t become dehydrated because you’re afraid of hyponatremia.

Cycling in Heat and Humidity

More information about hydration can be found in Nutrition for Cyclists: Eating and Drinking Before, During and After the Ride which can be purchased on Amazon.com.  For information about the book and how it relates to what I’ve posted to Tuned In To Cycling, please check out this post.

It’s hot. It’s humid. Even worse, it’s hot and humid. How do you handle heat and humidity on a ride? You already know the answer. Hydrate. Is there anything else you can do? Yes, but hydration is far and away the most important thing you need to combat heat and humidity. Understanding how heat and humidity affects you when you’re riding (or engaging in any other kind of exercise) can help you counter their ill effects.

How the body keeps cool

“Normal” body temperature is a slippery concept because many factors such as the time of the day, how temperature is measured, your state of athletic training, and where you are in your menstrual cycle if you are a woman (among other things) affects body temperature. For most cycling purposes, exact measures of normal body temperature along with exact measures of safe increases in body temperature aren’t very useful. You’re not going to know what your body temperature is while you’re riding because you’re not going to be taking rectal temperature measurements while you’re on the bike. Also, it doesn’t really matter what constitutes a “safe” increase in body temperature because you are going to be stressing your body’s ability to maintain that safe level when you ride.

The human body is a homeostatic system. This means it adapts to changing environmental circumstances in order to maintain certain physical and physiological parameters within acceptable boundaries. One of the most important of these parameters is core temperature. Combating heat and humidity is mainly about keeping core temperature down.

Our bicycles are extraordinarily efficient machines. Under optimal circumstances approximately 99% of the energy put into the pedals is transferred into forward motion; only 1% is lost. Unfortunately, our bodies are not nearly as efficient. Approximately 75% of the energy generated by physical activity is lost as heat. The heat generated by our muscles raises body temperature when we exercise. The harder you go, the more heat you make and the more stress you place on your body to shed that heat and keep core temp down.

There are two main ways the human body sheds heat. When the temperature of the body is higher than the temperature of the surrounding environment heat is shed through conduction and radiation. Here’s how this works for the cyclist. Your working muscles generate a lot of heat. Much of this heat is transferred to the blood which carries it away from the working muscles. When blood temperature reaches a particular threshold, vasodilation (expansion of the blood vessels at the surface of the body) occurs which brings a larger proportion of the blood into close contact with the surface of the body where it can shed its heat to the surrounding environment. When you stand close to a person who has been exercising hard you can feel the heat coming off their body. That’s heat that has been shed through conduction and radiation.

Conduction and radiation can only reduce body heat if the surrounding environment is at a lower temperature than the body. If air temperature is higher than body temperature, the body takes on heat from the environment. If you are riding on a hot day, conduction and radiation aren’t going to be nearly sufficient to shed the heat you’re generating.

The second way the body sheds heat is through evaporative cooling. When core temp rises to a critical threshold, the sweat glands are triggered and sweat is produced on the surface of the skin. The sweat evaporates and the evaporation cools the body. Under most circumstances, and especially when it is hot outside, evaporative cooling is the main way the cyclist sheds heat.

How increased core temp can hurt you

When you exercise your core temp rises. When core temp rises you sweat. When you sweat you lose fluid. If you lose enough fluid you become dehydrated. Dehydration and overhydration are important issues for the cyclist that are taken up in the post Dehydration and Over Hydration (Hyponatremia) for the Cyclist.

Even low levels of dehydration can affect performance. Loss of 2% body weight through fluid loss has measurable negative effects on athletic performance. Holding fluid loss constant, the negative effects increase the longer you ride or the hotter it is when you ride. As fluid loss increases beyond 2% body weight., the negative effects of dehydration increases rapidly and markedly.  This is the good news.

The bad news is that loss of body fluids can produce severe dehydration and heatstroke. The symptoms include headache, nausea and vomiting, sweating stops or is severely reduced, very rapid breathing and heart rate, confusion, delirium, loss of consciousness, death. Heatstroke is a life threatening medical emergency. In a lifetime of athletic activity that has produced broken bones, snapped tendons, knocked out teeth, severe lacerations and several surgeries, the one time I suffered serious heatstroke (while running in competition) was – easily, hands down, no contest, and by far – the worst physical experience of my athletic life. You don’t want to go there, it’s terrible.

How all of this affects the cyclist

Heat is bad. As the air temperature rises, the difference between body and air temperature decreases which weakens or eliminates conduction and radiation as methods of shedding heat.

Humidity is worse. Evaporative cooling is the primary way humans shed heat and it becomes even more important when exercise is producing a lot of excess heat. Humidity is an index of the amount of water vapor in the air; the higher the humidity, the more the air is saturated with water. The more the air is saturated with water, the less water it can take on which means that sweat is less likely to evaporate. The body continues to produce sweat so that evaporative cooling can bring body temperature down, but the sweat rolls off the skin rather than evaporating and cooling the body.

The air flow produced by moving on the bike can be a help here. When you stand still and sweat the air around you becomes saturated and sweating produces less evaporative cooling. When you’re rolling on the bike, the air around you is constantly being refreshed with air that is less saturated.

Heat combined with humidity is the worst of all. High heat coupled with high humidity sabotages both of the body’s mechanisms for shedding heat. The high air temperature reduces or eliminates conduction and radiation and the high humidity reduces evaporative cooling.

What can you do about it?

First and foremost – HYDRATE. Drinking water won’t cool you directly but it will replace the fluid you’re losing to sweat. This is critical for avoiding dehydration and heatstroke. Don’t screw around with this. Heatstroke can kill you.

How much should you drink? It depends on how much fluid you are losing to sweat and this will vary as a function of many factors such as how hot it is and how hard you’re working. Don’t use feeling thirsty as an indicator of whether or not you need to drink. The body is relatively slow to send thirst and hunger signals. You will usually have lost 1% to 2% of your body weight in fluid loss before you get the thirsty signal. By that time you’re already losing the battle of shedding excess body heat. A common mantra for cyclists is “Drink before you’re thirsty.” It’s great advice. Drink small amounts often rather than large amounts less frequently.

It’s possible to overhydrate which can lead to a condition called hyponatremia where there are abnormally low levels of sodium in the body (the excess water dilutes the sodium). This can also be life threatening although it rarely is. When hydrating your goal is to continually replace the fluid you lose through sweating without going to extremes with either too much water or not enough. For the cyclist riding in heat and humidity it’s better to err on the side of limiting dehydration as opposed to limiting hyponatremia. Don’t prepare for riding by drinking liters of water beforehand and be sensible on the bike. A future post will look at hyponatremia in more detail.

Wear the right clothing. No clothing at all would be optimal but sunburn, chafing from the bicycle seat and indecency laws make that impractical.  If you’re not going to go nude, you want form fitting clothing that wicks moisture. Loose clothing traps air between the cloth and your skin which acts as insulation and reduces evaporative cooling. Wicking material moves the sweat from your skin to the air where it can evaporate and cool you. Cycling clothing has both of these properties so if you wear tight fitting cycling shorts and jerseys, you’re good. If you ride in a loose fitting cotton shirt, you’re asking for trouble when it’s hot and humid.

If you’re not racing, consider ramping down your work level on hot and humid days. If you ride at a slower pace, your leg muscles aren’t working as hard and are producing less excess heat.

If you have enough water, pour it on yourself. Evaporating sweat and water both produce evaporative cooling. Remember, though, that the water will do more to help you when it’s inside your body than when it’s on the outside. Don’t become dehydrated because you poured your water over your head.