## 4 Discussion  
This study was designed to examine the acute effect of four different VBT protocols (VBT\({}_{60\text{-}10}\) + RTT, VBT\({}_{60\text{-}30}\) + RTT, VBT\({}_{80\text{-}10}\) + RTT, and VBT\({}_{80\text{-}30}\) + RTT) on the MAS estimated from an RTT in recreationally trained men and women. Results revealed that, when compared to the control condition (RTT alone), the MAS was acutely compromised after the four different VBT protocols. Regardless of sex, the VBT\({}_{60\text{-}30}\) + RTT impaired the MAS to a greater extent than the VBT\({}_{60\text{-}10}\) + RTT, VBT\({}_{80\text{-}10}\) + RTT, and VBT\({}_{80\text{-}30}\) + RTT protocols. These results suggest that, regardless of sex, running performance (MAS) is impaired when preceded by VBT, especially if the training sets are performed with a low relative load (60% 1 RM) and a high velocity loss threshold (30%). The main strength of this study has been the implementation of the VBT methodology during resistance training sessions. First, the subjects received velocity performance feedback immediately after each repetition. This is of paramount importance, since the provision of velocity performance feedback has been proposed as an effective strategy to increase the quality (i.e., movement velocity) of the strength-oriented resistance training sessions [25]. Second, the individualized load-velocity relationships were used to match the intensity of load to individuals' daily readiness to train. In line with previous research [15], the fastest velocity significantly differed between relative loads, but not for the same relative load. Note that, while the accuracy of traditional methods may be affected by normal daily fluctuations in strength levels [26], the individualized load-velocity profiles provided high stability to prescribe resistance training intensity [27]. Third, velocity loss thresholds have been proposed as a more objective and homogeneous alternative to control proximity to failure during non-failure resistance training sets (e.g., subjects can complete \(\sim\)60% of the maximum possible number of repetitions when reaching 30% velocity loss during the back-squat sets performed against 60% 1 RM) [28]. Of note, while the target velocity loss is commonly determined from the fastest velocity achieved in each training set [13; 14], the fastest repetition from the first set was used in the present study to guide set termination. Like [PERSON] et al. [15], we have observed that the fastest velocity was higher for the first set than the third set. Therefore, if the fastest velocity of each set had been taken as the criterion, the subjects would have been closer and closer to muscular failure in the successive sets. Practitioners must keep this methodological aspect in mind when comparing different VBT studies. The RT-SEP phenomenon suggests that neural and metabolic fatigue derived from previous resistance training sessions may compromise the quality of subsequent endurance training sessions and, consequently, induce sub-optimal endurance adaptations [8]. In line with previous research [10; 29; 30], our results provide further evidence that running performance (i.e., MAS) is compromised when preceded by a resistance training bout. This phenomenon may be related to various mechanisms, including (but not limited to) (i) impaired neural recruitment patterns, (ii) attenuated movement efficiency, (iii) increased muscle damage and soreness, and (iv) reduced muscle glycogen [8; 9]. However, RT-SEP is a complex phenomenon conditioned by multiple training variables, including resistance training intensity and volume as acute interference modulators [9]. Indeed, supporting our hypothesis, the MAS was compromised to a greater extent when a low relative load (60% 1 RM) along with a high velocity loss threshold (30%) was used in the set. This finding partially concurs with the results of [PERSON] et al.