Exercise physiology in triathlon, cycling and running - AthleteSportsWorld | TRIATHLON | SWIM | BIKE | RUN | TRAILRUN |

Exercise physiology in endurance sports

We regularly receive questions about nutrition and sports nutrition.
Questions such as: Which sports nutrition should I take and when? How do I deal with sports nutrition? What should i drink?

Our vision is that to properly understand when you take what you need information about which energy sources your body works on. When do you use which energy source and how long can you maintain this.

Energy systems
Our body derives its energy mainly from four components: phosphate (fuel) carbohydrates (fuel) fats (fuel and building material) and proteins (mainly a building material, but if the carbohydrates are used, as well as fuel).

Depending on the energy demand and availability, the body chooses the right component to 'burn'. Endurance sports mainly use the oxygen energy system (aerobic energy system) and therefore the burning of carbohydrates and fats . In competitive sports, it is often necessary to accelerate or sprint. In this case, the phosphate system is addressed very briefly and then the combustion of only carbohydrates in the low-oxygen energy system (anaerobic energy system). The disadvantage of this is that H + ions are released in this system which cause acidification in the muscles.

In addition to the energy components mentioned above, our body also needs vitamins, minerals and enough water to properly process the nutrients contained in food into energy. The amount of energy that a basic component supplies to our body is different.

For example, 1 gram yields:

  • 1 g carbohydrates 4.1 kcal energy
  • 1 gr fat 9.3 kcal energy
  • 1 gram of protein 4.0 kcal energy

To burn this energy, oxygen is required, with carbohydrates per liter of oxygen providing the most energy (5 kcal. For comparison: fats: 4.7 kcal and proteins 4.5 kcal).

The disadvantage of carbohydrates is that they are only available to a limited extent in our body. We only have carbohydrates in stock for a maximum of 1.5 hours in our body. Depending on the demand for energy and availability, the body chooses to 'burn' fats and / or carbohydrates. Carbohydrates are easily available in the form of stored glycogen and blood glucose and provide a lot of energy. Fats provide significantly less energy and it takes the body more effort to burn it. For the most trained cyclists, the supply of subcutaneous fat tissue is countlessly larger than the supply of carbohydrates.

Example: It has been calculated that with average efficiency and aerodynamics it costs around 21 kcal per minute to cycle 40 km / h. The body can store around 2000 to 3000 kcal of carbohydrates, so in this case it means that there is approximately fuel for just 90 minutes. A 70 kg cyclist with an average posture has stored around 125,000 kcal as fat. That means that the body can theoretically cycle for 110 hours or 4.5 days at this intensity on fat as fuel.

In the formula below you see that more than 4x as much oxygen (O2) is needed for fat burning (23 O2) than for burning carbohydrates (6 O2)

Carbohydrate combustion: glucose + 6 O2 + 36 Pi + 36 ADP -> 6 CO2 + 42 H2O + 36 ATP

Fat burning : C16H32o2 (= fatty acid; palmitate) + 23 O2 + 129 (ADP + Pi) -> 129 ADP + 16 CO2 + 145 H2O

Fact: The fat burning process also releases much more water (H2O) than when burning carbohydrates (145H2O compared to 42H2O). This also explains why you lose much more moisture at low intensity.

Because endurance athletes consume a lot of carbohydrates, they have to eat carbohydrates. The recommended dietary percentages for endurance athletes are: 60% carbohydrates, 15% proteins and 25% fats . Athletes often eat too much fat and too little carbohydrates. A vitamin B, iron and magnesium deficiency can also easily arise because they are involved in the energy supply.

Beware of a protein deficiency, because it comes at the expense of muscle mass. Proteins are the building blocks of the muscles. However, the protein content in the total energy value of the meal should not become too large either. The number of calories you burn per day depends on your activities, weight, age and gender.

TIP: Do you want sound advice about the composition of your meals? Then contact a specialized sports nutrition diet.

The total calorie burn per day consists of the resting metabolic rate (or Basal Metabolic Rate) plus the energy required for all your activities. For an average man / woman this is 2500/2000 kcal per day. Cycling is a typical endurance sport, because over a longer period of time energy must be supplied at a relatively constant level. You hereby particularly charge the aerobic energy system (the combustion where oxygen is needed)

With a low heart rate, the basis for energy supply is the burning of fats. This combustion takes 'more' time and is difficult to get going, but ultimately yields more energy. However, if the sport lasts a little longer or becomes more intensive (sprinting, cycling harder) the body will mainly use carbohydrates. So if you mainly want to train your fat burning, then you will have to cycle long sections at low intensity.

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