1. Principle of load and recovery

A training stimulus initially leads to fatigue and damage to cells and muscles. After a recovery period, these phenomena are over and the cells have even become stronger. In this respect, the muscle soreness we feel after a hard workout is a good sign (pain is nice!). The cycle of load and recovery MUST be optimally timed: the next training stimulus must connect to the recovery of the previous stimulus, so that a positive spiral is achieved (supercompensation). In practice, this leads to a setup in which 'hard' and 'light' training always alternate. 

2. Principle of sufficient variation and intensity 

It is essential to perform part of the training at a sufficiently high intensity so that all energy systems are developed. It is therefore necessary to train a lot of size as well as to achieve a high intensity. To make progress, intensive training at a high level is by far the most effective. Finally, bear in mind that effective training stimuli always fall outside the 'comfort zone', so it is necessary to refrain from time to time, also in training ('no pain, no gain') 

3. Principle of gradual and consistent build-up 

In practice, it is important to increase the training load slowly and to a limited extent (maximum 5-10 percent per month). The following applies here: listen to your body! It is wise to maintain a certain training stimulus for about six weeks: during this period the body will have adapted and the training effect will have been achieved. 

4. Diminishing Returns Principle 

As we train more, the effect becomes smaller and smaller. World champions have to train very hard, both in size and intensity, to achieve a final improvement of a few seconds in the 10 km. The good news is that even after years of consistent training, progress is still possible, often the best results are achieved after 5-10 years of training. 

5. Principle of specificity 

In a long-distance runner, the leg muscles are trained and the arm and chest muscles are not trained or to a very limited extent. It is therefore best for a runner to almost always do walking training. Strength training in a gym has less value for a runner unless it is specifically aimed at core stability, for example. It is of course always good not to develop the body too one-sidedly. 

6. Principle of periodization 

The New Zealander Arthur Lydiard developed a cyclic program

 through the year, consisting of:

Basic period, of building up condition, in which the emphasis is mainly on size.
Quality period, during which the magnitude remains the same and the intensity is increased. 
Tightening period, during which the magnitude becomes less and the intensity very high. 
Competition period, in which the training is greatly reduced and only the speed is maintained.
Rest period, during which the body can recover after which the next cycle begins. 

7. Principles of Reversibility 

The bad news here is that the effect of years of serious training can be lost from illness in a relatively short time ('use it or lose it'). A period of a month of doing nothing already leads to a considerable deterioration of the condition (around 10%). The good news is that training also has a lot of effect quickly. Here too, a considerable improvement is possible in a month. 

8. Principle of individuality and flexibility 

This is related to genetic and other differences and the trick is to discover which approach works best for you. Adjust the training based on the experiences. Do this carefully to avoid overtraining and injuries! In general it is wise to use your natural strengths ('go with your strengths') 

9. Principle of maintenance 

It is important to keep up the speed. The size can be reduced if desired without major consequences. You can use this by greatly reducing the size in a match period, so that you are always fresh for the matches.