## 1 Introduction  
Since it was developed in 1970, the Wingate anaerobic test (WAnT) has become one of the main assessments to evaluate anaerobic power independently of the individual's body weight [1]. During the traditional WAnT, the subject is required to pedal as fast as possible without an effort distribution (i.e., all-out) for 30 s [2]. Although this traditional 30 s WAnT has been proved to be a useful and reliable test [2, 3], it commonly induces several detrimental effects, including nausea, dizziness, headaches, and vomiting [4]. In addition, this test to exhaustion produces excessive neuromuscular fatigue, limiting the assessment of other physical evaluations or high-quality training sessions within the following 48-72 h [5]. These aspects together have led to the development of several proposals based on time reductions, including 6, 10, 15, and 20 s WAnTs [6, 7, 8, 9, 10, 11, 12]. These time-shortened protocols measure the power output produced in the first seconds of the test, such as the peak power output (PPO) or power value generated at specific time points (e.g., at the second 10 or 15), to predict other performance parameters like the mean power (MPO) by means of regression analyses [6; 9; 11]. MPO is considered a variable of interest in many investigations [13; 14], since it could be predictive of the anaerobic capacity (i.e., ability to sustain extremely high power) [1; 2; 15]. Another key variable derived from a WAnT is the fatigue index (FI). Including the FI in a regression model could help to adjust the power estimation, since this parameter relates with how the power declines along the test [2]. However, to date, no previous investigation has included the FI as a covariable to predict the MPO by means of a time-abbreviated WAnT. Most of these time-shortened WAnT versions estimating MPO have shown high relationships with the MPO measured by the traditional 30 s WAnT, however, only two studies have analyzed the accuracy (i.e., magnitude of error) of these regression models by means of a cross-validation analysis [6; 16]. Since one of the main goals of the use of the WAnT is to examine the power changes after short- and long-term training/detraining periods, it is necessary to identify whether the changes observed in power are due to the actual modifications in athletes' anaerobic performance or due to an estimation error of the time-abbreviated test (i.e., sensitivity). Thus, practically interpreting the magnitude of error derived from this cross-validation analysis would be essential to examine the suitability of these shortened proposals for daily use. Nevertheless, in addition to the few studies including a cross-validation analysis, no study to date has interpreted the validity of a time-shortened WAnT considering its sensitivity. On the other hand, all time-shortened WAnT models proposed to date have obtained the main variable (power output) and its derivates (i.e., PPO or MPO) in an indirect way [6; 7; 8; 9; 10; 11; 12]. Thus, the power output has been traditionally calculated by multiplying the revolution per second of the Monark(r) cycle ergometer (velocity) by a fixed resistance, commonly corresponding to 7.5% of the subject's body mass (force) [11]. However, since the load placed in the basket of the cycle ergometer remains constant while the moment of inertia changes during the initial acceleration, the actual resistance to overcome is not constant throughout the entire trial [17; 18]. Therefore, this traditional method does not allow for the registration of instantaneous force that the subject is applying to overcome the resistance. This fact could introduce a source of error in the power measurement, since in some cases the accuracy of this variable (resistance \(\times\) velocity) decreases as a consequence of an overestimation of the resistance parameter [19]. Advances in technology have led to the development of power meters that directly measure the instantaneous force applied to the pedals, plate, or rear-wheel axle [20; 21].