CARBOHYDRATES: ESSENTIAL FOR ATHLETIC SUCCESS!

 BEFORE READING UP ON CARBS, take a few minutes to read two of the Special Topic Page articles that appear to the right of this post. The top one on Sports Injuries and the third one down on Dangers of energy drinks. These are both recent and HIGHLY appropriate to young athletes, their parents and coaches. Enjoy.


Carbohydrates, together with protein and fat, are classified as MACRONUTRIENTS because these three nutrients are the only nutrients that supply the bodily systems with energy.  Of these three, carbohydrates are the preferred energy source by the body. 

There are two types of carbohydrates:  simple and complex. Simple carbs are sugars that contain only ONE six-carbon molecule while complex carbs are made up of two or more of these six-carbon molecules that are joined together in chainlike fashion. The more complex the chain, the longer it takes the body to break down the chain into simple sugar molecules for energy purposes in all the bodily systems.

So, we can think of simple carbs being absorbed into the blood stream at a rapid rate, and therefore being a quicker source for muscular energy, while complex carbs take longer to digest and absorb but supply a longer, steadier energy supply to the body. 

Examples of simple carbs would be common table sugar (sucrose), fructose (found in fruits and vegetables along with complex cabs and fiber) and various forms of sugars that can be derived from foods like dairy products. Glucose, a simple sugar is commonly known as blood sugar because all carbs, both simple and complex are broken down during digestion into glucose. Glucose, or blood sugar, is stored in muscles (glycogen) and the liver (glucagon) with both being the stored form of glucose that is preferred by the muscles and liver respectively.

Both glycogen and glucagon can be converted into glucose for transfer to other body parts when needed. BOTH the muscular system and liver have a limit to how much glycogen or glucagon can be stored. Thus, young athletes who are training regularly need higher carbohydrate intakes than less active teens.

Carbs are the key energy source during exercise. There are MANY factors that influence the amount of carbs used by individual athletes such as:  the Individual’s metabolism, diet, body type AND the exercise intensity, duration and type of activity.

Along with hydration, carb availability is a primary influence on both muscular fatigue AND central fatigue. Proper timing of carb intake before, during and after exercise can greatly sustain or improve performance AND recovery.

                                 GENERAL DIETARY RECOMMENDATIONS FOR ATHLETES

Most sports nutritionists recommend that 6 to 10 grams of carbs for every kilogram (2.2 pounds) of body weight per day. This is read as 6-10 gms/KG/day. This range takes into consideration variations in body size and is influenced mostly by specific needs of various activities such as endurance and power-speed activities. These needs will be discussed later in this post under Performance Needs.

                                    PRE-EXERCISE CARB RECOMMENDATIONS

Carbs should be ingested 3-4 hours prior to exercise with amounts between 1 to 2 grams/Kg body weight. This should be enough to raise glycogen stores at the onset of exercise with potential to improve performance in individuals who have not fully restored the muscular supply of glycogen from training on days prior to competition OR competition that is scheduled very early in the morning and the athlete’s last meal was dinner the night before.

Choice of carbs should come from foods that the athlete knows they have tolerated well through prior experimentation and those that contain a minimum amount of fiber. These meals before competition should be lower in fat so as to promote an optimal rate of stomach emptying and contain enough fluids to maximize hydration state.

                                     CARB RECOMMENDATION DURING EXERCISE

Endurance sports, such as distance running, cycling, swimming and triathlon require frequent intervals of carb intake. Athletes should plan to ingest somewhere between 30 and 60 grams of carbs per hour for exercise or competitions lasting more than one hour. This is most easily done ingesting drinks that contain 5-8% carbs in doses between 600 and 1200 mL per hour. These amounts are determined by the intensity/speed/type of exercise being performed AND are based on the athlete HAVING EATEN A PROPER PRE-EXERCISE MEAL.

                                     CARB RECOMMENDATION POST-EXERCISE

 The standard recommendation for post-training or post-competition intake of carbs is 1.5 grams/KG body wt. and then 1.2 grams/Kg /at 30 minute intervals for anywhere from 1-4 hours. Of course this depends on the duration of exercise, intensity and level of glycogen depletion.  Waiting for an hour or more greatly reduces the rate of glycogen recovery. Usually, when carb replacement follows the guidelines above, the athlete can fully replace all the glycogen stores of the body within 24 hours.

                                    GLYCEMIC INDEX vs. GLYCEMIC LOAD FOOD GUIDE PYRAMID

Most people are familiar with the Glycemic Index (GI) which have been used in nutritional articles and studies as a way to classify carbs based on their effect on blood glucose levels. Before the GI, carbs were categorized according to chemical structure (and still are). This chemical structure separates carbs into three categories; sugars, starches or fibers. The GI has been more relevant when used to classify carbs for disease prevention and treatment purposes.

To further complicate the classifying of carbs, the Food Industry has used terms such as “bad carbs”, “impact carbs” or “sugars” to refer to carb sources that provide mostly simple sugars. Basically, the foods that are primarily termed sugars or impact carbs,  are simple sugars. These simple sugars are listed high up on the GI because they have a large IMPACT on blood sugar levels by causing high amounts of insulin to be released. This release of large amounts of insulin, as a response to the rapid increases in blood sugar levels from ingestion of simple sugars, can lead to hypoglycemia, or drastic lowering of blood sugar to below normal levels.

Conversely, complex carbs (also termed starches) are referred to as “good carbs” because they are likely to contain significant amounts of other nutrients, like dietary fiber, making them more “nutrient dense” than the simple sugars.

Since digestion and absorption of complex carbs are much slower, they are trigger a more stable and sustained release of blood sugar and insulin responses.  Foods that are HIGH in simple sugars are ranked high on the GI scale with foods high in complex carbs ranked low on the GI scale. 

Instead of classifying foods that are either high or low on the GI, it is MORE helpful for athletes to classify carbs according to  food categories that reflect their level of processing. For instance, “refined” foods are those that are highly processed while “unrefined” foods are those that are either NOT processed (natural, whole food sources), or minimally processed.

Refining is a process that done to either simple OR complex carbs. Refining refers to the removal of fiber, nutrients, water and other elements of the food from it’s “NATURAL STATE”.  This refinement of foods results in raising the concentration of sugars in the food which greatly raises its ranking on the Glycemic Index (GI).

Unrefined carb foods are usually healthy, unprocessed foods such as fruits, vegetables and whole grains, which are lower in status on the GI and, therefore, cause lower and more sustained blood sugar levels.

The GI is therefore, a RANKING of foods based on their blood glucose/sugar response compared to a reference food, such as glucose, white grape juice or white bread (which represent a value of 100). In more simple terms, GI values reflect the RATE of digestion and absorption of a carb food.

Since processing greatly affects the absorption rate of carb foods (amount of processing or cooking, amounts of either fructose or lactose (fruit and milk sugars), the ratio of enzymes (specifically amylopectin and amylase) that digest starches and starch-to-protein or starch-fat-ratio of carb foods.

The Glycemic Load method of assessing the glucose(blood sugar) raising potential of foods takes into consideration BOTH the QUALITY (refined or unrefined) and QUANTITY of carbs in a given food source.

So, literature concerning DIETARY INTAKE OF CARBS may refer to either the Glycemic Index (GI ) or Glycemic Load (GL) for use in determining the effects of various carb food sources on blood sugar and insulin levels.

Here are some examples of REFINED vs. UNREFINED FOODS:

REFINED FOODS: cakes, cookies, potato chips, candy bars, jams/jellies, fruit drinks, sodas and salad dressings.

UNREFINED FOODS: brown rice, oat bran, whole oats, whole grain pasta, whole grain bread, fresh fruits and vegetables.

THE GLYCEMIC LOAD PYRAMID classifies carb foods into three levels. Low = values of 0-10, Medium = values of 11-19 and High = 20+ values.

Examples of foods from each value level appear below:

Low Glycemic Load Foods= 10 or <: high fiber fruits and vegetables (not including potatoes), bran cereals (1oz), legumes such as kidney , pinto or black beans.

Medium Glycemic Load Foods =11-19: brown rice, Oatmeal, whole grain breads, whole grain pasta, 100% fruit juice w/NO added sugar

High Glycemic Load Foods = 20+: baked potato, refined cereals, candy (jelly beans, etc.), candy bars (snickers, etc.), fruit juice drinks (w/sugars), white rice (basmati), refined white flour products, bagels, white/refined pastas.

As with the Glycemic Index, a mix of food types from the Low and Medium Glycemic Load Foods should be chosen for meals throughout the day with foods from the High Glycemic Load Food group appropriate for post-exercise/competition recovery purposes as these are the “fast acting” sugars that quickly raise blood sugar levels.

It is important to remember that during a 1-2 hour window post exercise the muscles INCREASE their normal rates of glucose uptake in order to restore glycogen levels that were depleted partially or fully from extended exercise bouts, long and/or intense training or competition.

                     DAILY REQUIREMENTS OF CARBS BASED ON SPECIFIC PERFORMANCE NEEDS

The recommendation for daily carb intakes for athletes of 6-10 grams / KG of body weight/ day can be further narrowed to meet individual requirements based on specific performance needs.

Here are a few examples of how much glycogen is used in various sport activities.

Let’s take training and competitive movement examples that are more representative of Power-Speed Sport athletes for the first example. A 6 second maximal sprint can reduce muscle glycogen levels in the prime-mover muscles by as much as 14% of it’s glycogen total. A 30 second sprint reduces muscle glycogen by 27%.

Each additional sprint will reduce glycogen even further, although the amount used for fuel for each successive sprint GOES DOWN for EACH SUCCESSIVE SPRINT. (this is because muscles can resynthesize a certain percentage of energy sources , ATP specifically, DURING RECOVERY intervals between sprints, lifts, etc.)

Strength training utilizes large amounts of specific muscle glycogen similar to the sprints above.  A single set of 10 reps (using 10-rep Max weight) of curls will reduce the biceps total glycogen stores by 13%. Again, like the sprints above, each successive set will require less glycogen than the first set. Thus, 3 sets of 10 reps w/ 2-3 min. rest, will reduce your biceps’ total glycogen levels by 25%.

Endurance Sports/ Activities use less glycogen at lower rates than high intensity (Power-Speed) activities, however the DURATION and TOTAL WORK of endurance activities is usually much HIGHER. Depending on the duration of the activity, like a Cross Country Race of 3 miles (at very high race intensity) OR a 5-7 mile training run (at a lower intensity level).

There have been no studies showing high carb diets (>60% of daily calories) are any better than medium carb diets (40-42% of daily calories) FOR MAINTAINING PERFORMANCE in strength and power activities.

 There are some results that show high carb diets will better maintain HIGH-INTENSITY EXERCISE ENDURANCE (ability to keep up a high-power output) for athletes, like wrestlers, weightlifters, etc. who have to keep to strict diets in order to maintain their body weight to stay under their weight-class limit.

What researchers have shown is that low carb diets WILL NEGATIVELY AFFECT high-intensity exercise.

For speed-power athletes who also require longer workout durations, such as an hour or more of high volume lifting at intensity levels of 80% or greater of 1RM, will be able to maintain intensity IF THEY CONSUME A CARB DRINK BEFORE AND DURING EXERCISE. This is only the case IF athletes are training with a very high volume and training sessions lasting over an hour.

It has been documented that AFTER strength training sessions, regardless of volume and time duration, intake of carbs will greatly aid in increasing blood insulin levels. This increase in insulin stimulates your muscles to absorb amino acids and glucose from the blood (and also limit amino acid release from muscles) which will help muscles recover and grow and repair muscle tissue. As mentioned above under CARB RECOMMENDATION POST-EXERCISE, carbs ingested after training also enhance the rate of glycogen replacement in the muscles.

Another benefit to maintaining proper amounts of carbohydrate in the daily diet concerns its effect on the immune system. All types of stress CAN have the DETRIMENTAL EFFECT of suppressing the immune system. Exercise, being a physical stress, can add to this negative impact on the immune system.  The positive news is that as athletes improve their fitness levels, this greater conditioning STRENGTHENS the immune system. HOWEVER, high-intensity exercise AND particularly ENDURANCE exercise (this is why many marathoners and 5-10k runners get sick easier after races), suppress the immune system regardless of levels of fitness.

Carbohydrate drink intakes of 1 gram/Kg body weight taken 10 minutes before and 10 minutes after exercise or training sessions can positively interfere with this response by significantly reducing the degree to which your immune system will be suppressed after hard training (running, sprinting, lifting) or racing.

For further info on carbs you may refer to the IAAF Nutrition for Athletes website > https://docs.google.com/file/d/0Bzux-9tuGfqGdU9KMndBQnVIWUk/edit

PART 3 OF DIET/NUTRITION will focus on the third MACRONUTRIENT (Protein, Carbohydrate and Fat are the only nutrients that provide ENERGY) of FAT and it’s importance to the success of the athlete’s diet.