## 2 Materials and Methods
### Assessments
#### 2.4.4 Punching Peak Force  
Punching peak force was recorded using CAPSTONE software version 1.13.4 (PASCO(r), Roseville, CA, USA) connected to a force plate (Pasco PS-2142, PASCO(r) Scientific, Roseville, CA, USA) operating at a sampling rate of 1000 Hz. The force plate was mounted vertically on a wall at a distance that allowed boxers to execute straight and curved punches with proper technique. The force-time data were captured during the moment of initial contact, and the peak force value within that impact window was used as the primary kinetic variable. A double padding of 21 kg and 30 kg high-density foam was installed with the same dimensions as the force plate (35 \(\times\) 35 cm). The boxers performed a three-punch maximum protocol including straight punches and curved punches with both hands to the vertically mounted force plate, interspersing a five-second rest between each type of punch. Prior to the maximal punching protocol, participants performed a standardized three-minute round of boxing with punching techniques visualizing an imaginary opponent, dynamic activation, and mobility exercises, in addition to a three-minute round of the boxing-specific exercise protocol (BSEP) [28]. The above is based on recommendations on the inclusion of specific activities in the warm-up task to ensure ecological validity [29]. Based on the study by [PERSON] et al. [28], prior to and at each one-minute interval of the warm-up BSEP round, participants performed submaximal efforts of the punch types described above at progressive self-perceived intensities at 50%, 70%, 90%, and 100% of the force plate. In the maximal and submaximal punching efforts, athletes were asked to punch a target (red circle) located in the middle of the protective foam padding, which corresponded to the center of the force plate. Additionally, participants were asked to perform all punches at a self-selected distance to replicate punching technique from training and competition, thereby increasing ecological validity. Finally, boxers were asked to wear their own hand wraps and 16-ounce gloves during each testing session to protect their hands.  
Prior to the intervention period, the reliability of punching peak force assessments was evaluated using a test-retest design. Each participant performed two punching assessment sessions separated by 48 h under identical conditions. The intraclass correlation coefficient (ICC, two-way mixed-effects model, absolute agreement, single measure: ICC(3,1)) was calculated to assess relative reliability for peak force across all punch types (jab, straight, right cross, and left cross). The standard error of measurement (SEM), coefficient of variation (CV), and technical error (TE) were also calculated to determine absolute reliability. The reliability results of the punching peak force assessments showed that no significant differences were found in the test-retest comparison. The peak force of all punches showed excellent reliability during the test-retest (jab punch ICC of 0.91; straight punch ICC of 0.92; right cross punch ICC of 0.95; left cross punch ICC of 0.97). The coefficient of variation (CV) for the peak force of the punches ranged between 5% and 20%. The standard error of the mean was similar for the jab (SEM 11.40), the right cross (SEM 14.49), and the left cross (SEM 11.16), being higher for the straight punch (SEM 18.49). TE for peak force was 44.1 N for the jab, 87.4 N for the straight punch, 57.1 N for the right cross, and 46.6 N for the left cross.  
The first day's assessments began with the measurement of BM, CMJ, and punching peak force. On the second day, back squat 1 RM was assessed, and on the third day, the retest was conducted for the evaluation of the CMJ and the punching peak force. Prior to the start of the intervention, the AEL group performed two familiarization sessions with 48 h of rest between them for the correct execution of the CMJ with AEL.