## 1 Introduction
### Protocol and Information Provided by the WAT
Mean relative power: This value is obtained by dividing average power by the weight of the subject. 5. Fatigue Index: The FI represents the loss of power experienced from the moment maximum power is reached and the end of the test [18] or, in other words, the fatigue rate is the rate of decrease in power during the test, expressed as a percentage of maximum power [2] and is related to the total capacity to produce energy through ATP-PCr and glycolytic metabolism. It is the least reliable and valid of the data provided by the WAT. However, it is very sensitive to training effects and sporting speciality, to the extent that elite track cyclists specialising in endurance disciplines have much lower fatigue rates than elite track cyclists specialising in sprint disciplines [18]. It is obtained as follows: (Equation (1) Formula for obtaining the Fatigue Index)  
\[\text{FI}=(\text{PP}-\text{Minimum power})/\text{PP})\times 100 \tag{1}\]  
Another value to take into account is the time needed to reach PP, as the shorter the time needed to reach this value, the shorter the time required to recruit muscle fibres. A longer time to reach PP will indicate subjects with fewer possibilities to recruit muscle fibres and motor units in a faster and more coordinated manner, demonstrating poor capacity for this type of work. This value is therefore related to the proportion of fast fibres to slow muscle fibres, allowing the percentage of fast fibres to be estimated. Thus, the results are important for talent identification or monitoring of training progress in track sprint cyclists. Another indicator of the type of fibres in the majority of test subjects is the analysis of the decrease in power levels. People with a higher percentage of fast contraction fibres will generate higher output power with a corresponding greater decrease over time [20]. Originally, it was assumed that peak power reflected the alkali anaerobic processes (phosphagen) and average power, the rate of anaerobic glycolysis in the muscle. A study by [PERSON] et al. [21] showed that muscle lactic acid rises to extremely high levels in the first 10 s after starting the test, and therefore it is unlikely that PP reflects only alactic processes. It is safe to assume, however, that PP is a reflection (rather than a direct measurement) of the ability of the muscles of the respective limbs to produce a high mechanical power level in a short time. Different considerations to be taken into account when carrying out the \"original\" test:  
* The test should be carried out while the subject is seated on the bike during the entire test;
* It is of vital importance that the test be carried out to the maximum from the beginning; otherwise, the values recorded will not be reliable;
* Although cyclo-ergometers currently in use are taken into account, there are not too many problems in this respect, and it is important that the sampling frequency recorded to be as high as possible [22]. Taking into account the importance of this test, its great usefulness and the large number of studies that have chosen it, a review of the literature seems necessary to analyse the correct protocol to be applied and the variables that can condition performance on the test. A large amount of literature published on this test suggests that there will be several variables to consider and many factors that must be controlled before carrying out the test in order to obtain reliable and replicable results. The aim of this review is to analyse the variables of the protocol that affect the result in the application of the WAT.