Carbohydrates And Exercise

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carbs and exercise

No matter you do high-intensity strenuous exercises or low-intensity endurance exercises, carbohydrates play a critical role in sustaining the energetic sustenance of working muscles. We must understand the relationship between carbohydrates and exercise to achieve our goal from our workouts. 

Where are carbohydrates stored in the body?

Two major sites for storage of the carbohydrates in the body are muscle and liver. Carbohydrates are stored in the form of glycogen. Glycogen is many strings of glucose molecules attached. Glucose is what our cells directly use for energy requirements. So when the body needs fuel, it calls for glycogen stores to remove individual glucose molecules from the strings and make them available to the cells.

Why do we need Carbohydrates?

The major task of carbohydrate stores in muscle is to provide glucose to cells for muscle energetics. The liver store maintains the glucose level in the blood. We need to understand that during exercise, muscles extract glucose from the blood. However, if we compare the stores, there is very little glucose in the blood. Normally the total store of carbohydrates (the total of muscle, liver, and plasma) in a body weighing 70 kgs is about 2000 Kcal. This is not a very large amount of energy. There are limited amounts of carbohydrates available during a prolonged period of exercise, these stores will deplete for sure. 

The major source of fuel in our body

If we compare fat stores in our body, for an average built of 70 Kgs, it will be about 110,000 Kcal of energy. That is almost 50 times more than that of carbohydrates. Hence there is no chance of depleting our fat stores during a single bout of exercise. The key to endurance training is to adapt to using fat as the major source of fuel, thereby preserving our precious stores of carbohydrates.

Factors influencing carbohydrates consumption

There are various factors on which our consumption of carbohydrates depends. The most important ones are enumerated below. 

  1. Intensity and duration
  2. Type of activity
  3. Nutritional Status
  4. Training level

Intensity vs fuel source

Many tests conducted to ascertain preferred fuel source at different intensity and duration shows that at the early stages and lower intensity fat is the preferred source of fuel. However, as the intensity/ duration increases body switches over to carbohydrates as the preferred source of fuel. A point during a workout where carbohydrates become more preferred fuel than fats is the crossover point. 

Once we reach the crossover point, we have limited fuel left. Hence if we keep the same intensity the store will deplete to a level where the fuel source will be inadequate. Hence we will have to either slow down our intensity or completely stop. 

How to plan carbohydrates

Now that we are clear about the relationship between carbohydrates and exercise, we can plan our training accordingly. Let us examine a few cases.

Long-distance running – Here You must ensure that fat is used as a preferred source of fuel and we do not increase our pace to the extent that we reach crossover point. Once we reach the crossover point, we will have carbohydrates as the preferred fuel which will exhaust soon. Hence we will have to slow down considerably or stop.

Sprinting – High-intensity short-distance running completely relies on carbohydrates. Hence we must ensure that between two practice sessions, we give enough time to rebuild the reserves in our muscles by moving our reserves from the liver. 

Remember we cannot sustain this high intensity for a longer duration more than about 60 sec or so. Hence if the event is longer than that, but still short like a 1-mile run, we will have to train our muscles to use fat too as a source of fuel.

Weight training – this will require a good source of carbohydrates. However, in case you want to use fats as the preferred source, you must pick light weights and do more repetitions. 

Walk or low-intensity workout – Body use carbohydrates but in a very small quantity. However, since fat stores are huge, there is not much change in the total Kcal reserves. As we increase the duration of the walk and take it over 60 minutes, the body continues to use fat as preferred fuel however now muscles also have reduced carbohydrates. This leads to the body sending a signal to produce more fuel from fats. Thus an overall higher consumption of fats. 

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