Fitness

A good condition means that you are good at absorbing and transporting oxygen. The better the body is at absorbing oxygen, the better you can utilize energy from sugar. This is because pyruvate can produce more ATP when there is enough oxygen inside the mitochondria. If there is not enough oxygen in the mitochondria, pyruvate is converted to lactic acid instead. The process of pyruvate being converted without oxygen does not give the body any great energy benefit.

Fitness

The fitness number is a measure of a person’s fitness. The fitness number describes how much oxygen you can absorb per minute compared to how much you weigh.

 

    $$ Fitness = \frac{O_2 (mL)}{Body mass (kg) \cdot minutes} $$

 

 

A man with a fitness score of 42 can absorb 42 mL of oxygen every minute for every kilogram he weighs. If he weighs 85 kg, he absorbs 85 times 42 mL per minute. That is, he absorbs 3570 mL of oxygen per minute.

Changes in connection with cardio training

When you train your fitness, the body becomes better at utilizing energy from sugar. In connection with cardio training, the overall changes in the body are:

  • That the heart becomes stronger and can therefore pump more blood into the body per minute.
  • More small blood vessels develop so that the blood can be transported to the cells more easily.
  • More red blood cells develop, so the blood can contain more oxygen overall.
  • The muscle cells form more mitochondria, so there can be a greater burning of sugar.

Cardio training

You can train your fitness in different ways. However, it is important in all cardio training that you get your heart rate up. The fact that the heart rate increases is due to the body’s need for oxygen becoming greater. The body therefore pumps blood around the body faster to be able to transport more of the required oxygen.

  • Continuous training

During continuous exercise, the body’s heart rate should be the same at all times. The body must work at a constant intensity for long periods of time.

Example: A run of at least 20 minutes, where you run at the same speed for the entire trip, is continuous training.

Explanation: In the example above, you move at the same speed, and thus the same intensity, for longer periods of time. Therefore, the body’s energy metabolism is constant. Since the body’s energy metabolism is constant, the oxygen requirement will be the same throughout the run. Therefore, the heart rate is constant throughout the workout.

  • Interval training

Unlike continuous training, the body does not work under constant intensity during interval training. This means that energy burn varies during training. The heart rate is therefore not constant, as the body’s need for oxygen depends on the energy burn.

When using interval training, it is important that the work intensity is very high during the periods when the heart rate must be particularly high. The body has to work almost to the maximum it can.

Example: A 20-minute run, where you alternate running fast for two minutes and walking for two minutes.

In many sports, interval training is useful. Football is an example of a sport where the body’s work intensity varies. When you play football, there are many changes of pace and pauses in connection with game stops.