## 2 Materials and Methods
### Intervention  
The interventions took place in a room adjacent to the measurement site, which was set up and equipped for supervised exercise training for all participants. For both groups, the participants were placed in the supine position, with the knee resting on a wedge with 25\({}^{\circ}\) of flexion. The exercise consisted of performing active knee extension simultaneously with the muscle contraction induced by the passage of the electric co-current.  
Group 1 (\(n=10\)) received an intervention consisting of NMES (symmetric biphasic pulse, bipolar mode, 50 Hz frequency, 350 \(\upmu\)s pulse duration, 1:1 ratio) (S82\({}^{\text{\textcircled{b}}}\); Enraf-Nonius BV, Rotterdam, The Netherlands). A duty cycle of 50% was used according to previous studies [33]. Self-adhesive electrodes (8 \(\times\) 5 cm\({}^{2}\) Pals Platinum(r), Axelgaard Manufacturing Co. Ltd., Fallbrook, CA, USA) were placed on the quadriceps muscle. The positive electrodes were placed distally on the rectus femoris and vastus lateralis, and the negative electrodes were placed proximally on the rectus femoris and vastus medialis. The overcurrent program consisted of 8 s (s) of work (ON-phase) and 8 s of rest (OFF-phase). The ON-phase overcurrent program was designed with a rise time of 2 s, a maintenance time of 4 s, and a fall time of 2 s. The intensity of the electric current was increased to the maximum perceived tolerance, achieving a clear contraction without inducing fatigue. The instructions were: \"When you begin to feel the electric current with a perception of muscle contraction, it is time to start the exercise. You must maintain the position during the 4 s that the current pulse lasts.\" Following the protocol established in previous studies [15; 16], work was performed at 20% of MVCC in four sets of 30-15-15 repetitions, with 30 s of rest between them (Table 1). The load was applied by strap weights.  
Group 2 (\(n=10\)) received the same intervention, combined simultaneously with the BFR therapy protocol [34]. A PTS ii portable tourniquet system (Delphi Medical, Vancouver, BC, Canada), along with an Easy-Fit tourniquet cuff of a specific size corresponding to the patient's thigh, was used. The total limb occlusion pressure (LOP) was achieved using the Delphi PTS system [35]. As is recommended to achieve muscle benefits, LOP was inflated to 80% of the maximum tolerated pressure (50-300 mmHg) [36]. The cuff width was selected based on limb size and was personalized for each player [36] (Figure 2). This individualized approach avoided excessive pressure in participants with lower LOP. Moreover, this system allowed for the precise control of cuff pressure throughout the training, even when natural changes in muscle volume occurred.  
The duration of the exercise was 8 s, with a rest period of 8 s after each repetition. The exercise program consisted of one session lasting 10 min. The interventions were conducted by a physiotherapist with 15 years of experience in exercise therapy and NMES.  
\begin{table}
\begin{tabular}{c c} Load & 20\% of MVCC \\ Volume & 75 repetitions in 4 sets: 30-15-15-15. \\ Rest periods & 30 s between sets, without stopping the application of techniques. \\ \end{tabular}
\end{table}
Table 1: Dosage guidelines for both interventions according to the CERT statement.  
Figure 2: (**a**) Detail of the BFR PTS ii system; (**b**) detail of the occlusion cuff.  
To minimize the risk of bias among participants, the two groups were assessed in separate rooms. None of the study participants had received any theoretical or practical training on the applied procedure prior to the intervention.  
The intervention followed the recommendations highlighted by the scientific evidence regarding the use of BFR [1]. Furthermore, the interventions were conducted according to the recommendations of the Consensus on Exercise Reporting Template (CERT) [37] and the Template for Intervention Description and Replication (TIDieR) checklist [38] (Figure 3). No adverse effects were recorded in any of the intervention groups.