Extended Abstract
1.    Introduction
Rashedi et al. (2015) introduced the bench press as one of the most common exercises for developing the pectoralis major muscle and noted that performance in this movement is often used to represent maximal upper-extremity strength among athletes (1). In powerlifting competitions, a successful lift is recorded when the barbell reaches its highest point at the end of the concentric phase, with the elbows fully extended and the wrists aligned in a straight line, showing minimal positional deviation (3). Post-activation performance enhancement (PAPE) is defined as a physiological phenomenon that occurs following a conditioning contraction stimulus (CC) (7, 8). Ballistic or throwing exercises are characterized by explosively projecting the resistance load into the air (7). According to the criteria set by the World Powerlifting Federation, barbell balance at the end of the concentric phase of the bench press is a critical factor. If the athlete completes the lift with substantial wrist misalignment, the attempt may be rejected by the judges (3). Therefore, identifying new training methods that can improve an athlete’s ability to maintain barbell balance at the end of the concentric phase is of considerable importance. The present study was designed to address the following question: What is the effect of ballistic, heavy-resistance, and dynamic stretching warm-up protocols on barbell balance at the end of the concentric phase of the bench press in male students? 
2.    Methods
Eighteen male students (mean age: 23.8 ± 1.3 years; height: 174.4 ± 3.36 cm; body mass: 74.4 ± 3.8 kg), each with at least one year of training experience, participated in the study. Following the 1RM assessment session, participants were randomly assigned to three groups (A, B, and C) according to the protocol proposed by Amiri Khorasani and Gulik (2015) (17). Testing was conducted on three separate days, with at least 48 hours of recovery from heavy activity between sessions. Each evaluation included a general warm-up followed by one of the specific warm-up protocols: ballistic, heavy-resistance, or dynamic stretching of the primary muscles. After completing the assigned warm-up protocol, participants rested for 8 minutes. Subsequently, eight passive reflective markers were attached to anatomical landmarks (lateral tip of the acromion, lateral epicondyle of the elbow, and styloid process of the ulna). In addition, two markers were placed on the barbell, 0.2 m apart (2). Participants then performed a 1RM bench press within the calibrated volume of the 3D motion analysis system. Elbow joint angles and wrist positions were recorded. Barbell balance assessment was conducted as follows. The maximum elbow extension angle at the end of the concentric phase of the bench press was identified. At this angle, the vertical (Z-axis) position of both wrists was determined. The absolute difference between the vertical coordinates of the right and left wrists was calculated and defined as the barbell balance.
3.    Results
The angular velocity of elbow extension was also affected across the different events. A significant effect was observed at Vmax1, Vmin, and Vmax2 (F = 8.9, p = 0.013, η² = 0.32). Post hoc comparisons revealed that angular velocity was higher following the ballistic warm-up protocol compared with the dynamic stretching protocol at all events (Fig. 1). In addition, after the ballistic warm-up protocol, a significant improvement in barbell balance was observed compared with the other two protocols (F = 20.2, p = 0.001, η² = 0.44). Specifically, participants demonstrated better balance maintenance and the lowest difference in wrist positions following the ballistic protocol. Although the heavy-resistance warm-up protocol produced better barbell balance compared with the dynamic stretching protocol, the difference was not statistically significant (F = 1.21, p = 0.85, η² = 0.11) (Fig. 2). 
 

4.    Discussion
The aim of this study was to compare the effects of different warm-up protocols—ballistic, heavy-resistance, and dynamic stretching—on barbell balance at the end of the concentric phase of the bench press. The main findings were that elbow extension velocity was higher at Vmax1, Vmin, and Vmax2 following the ballistic warm-up compared with the other two protocols. Furthermore, barbell balance at the end of the concentric phase was significantly better after the ballistic protocol than after either heavy-resistance or dynamic stretching. This enhancement in performance is most likely attributed to post-activation performance enhancement (PAPE) (2), which, as suggested by Blazevich and Babault (2019), becomes substantive only after several minutes (21). Several mechanisms may explain the observed improvements in bench press performance following ballistic warm-up. The rapid downward and upward phases of the ballistic bench press may stimulate the stretch-shortening cycle with minimal amortization time between eccentric and concentric actions, thereby maximizing the use of stored elastic energy (22). Additionally, ballistic warm-up may enhance potentiation of contractile elements and increase activation of the pectoral and deltoid muscles, the prime movers in the bench press (4). Another possible mechanism is that during ballistic contractions, the threshold for motor unit recruitment is lower than during slower, ramped contractions (22, 23). These findings provide coaches and athletes, particularly in powerlifting, with a practical and accessible strategy to optimize 1RM bench press performance. Practitioners may consider prescribing ballistic warm-up protocols before maximal bench press attempts. 

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of the Faculty of Sport Sciences and Health, University of Tehran (IR.UT.SPORT.REC.1402.136).
Funding
This research did not receive any financial support from the government, private, or non-profit organizations. 
Authors' contributions
All authors contributed equally to preparing the article.
Conflicts of interest
The authors declare that there are no conflicts of interest associated with this article.