The Influence of Swing Machines on Batted Ball Exit Velocity in MLB

ABSTRACT

In baseball, a key component of successful hitting is generating high batted-ball exit velocity, which is associated with improved offensive outcomes such as increased batting average, slugging percentage, and extra-base hit production due to reduced defender reaction time and greater ball travel distance. While bat speed, height, and weight are known contributors to exit velocity, this study examines whether other controllable swing mechanics influence exit velocity when these three variables are held constant.

Specifically, this research analyzes the relationships between exit velocity and three swing metrics: attack direction (the horizontal path of the bat at contact), attack angle (the vertical path of the bat at contact), and contact point relative to the batter’s center of mass. Data were collected from 226 active MLB players who averaged 3.1+ plate appearances per team game during the 2025 season (as of May 2025) using Statcast data. To control for confounding variables, players were divided into eight groups based on height, weight, and bat speed. Within each group, average exit velocity was compared to the average values for attack direction, attack angle, and contact point. Statistical analysis was conducted using correlation coefficients (r), t-statistics (t), and p-values (p) to assess the strength and significance of these relationships.1 The null hypothesis stated that changes in these swing metrics would not significantly affect exit velocity.

Results supported the null hypothesis across all groups and variables, with one exception: Group 7, comprising the fastest 50% bat speeds among the lightest 50% of the shortest players, showed a statistically significant correlation between increased attack angle and higher exit velocity. This suggests that, among smaller players with high bat speed, a more upward swing path may provide a situational benefit to exit velocity. However, for attack direction and contact point, no significant correlation to exit velocity was found.

These findings suggest that while exit velocity remains an important contributor to hitting performance, isolated swing mechanics may have limited independent effects when controlling for bat speed and anthropometric factors. Consistent with emerging biomechanical literature, hitting performance is likely multifactorial, with swing path, kinetic sequencing, and bat speed playing more substantial roles than individual mechanical variables alone. Further research with a larger sample size, longer timeframe, and more comprehensive analysis of swing path and full-body mechanics is warranted to better understand their influence on batted-ball outcomes.

INTRODUCTION

In the sport of baseball, the ability of a batter to hit the baseball at a fast exit velocity is greatly desired. Hitting the ball at a greater exit velocity can lead to more hits, due to less reaction time for fielders, and farther ball flight.2 Several intrinsic and extrinsic factors have been associated with a player’s ability to generate a fast exit velocity on a hit baseball. One of the most well-known factors in increasing exit velocity for hitters is increasing one’s bat speed. The faster the bat travels through the hitting zone at impact, the greater the force applied to the baseball. The result leads to a greater exit velocity of the ball. Typically, a baseball’s exit velocity is between 1.2 to 1.4 times harder than the bat speed on the same hit.3 Additionally, a player’s height and weight have been linked to increased exit velocity. Taller athletes generally have more surface area to develop muscle mass, and greater muscle mass, being denser than fat, contributes to higher body weight.5,6

There is ongoing interest in identifying controllable elements of the baseball swing that can enhance exit velocity. While swing speed, closely linked to a player’s height and weight, is a key factor, there is significant interest in uncovering mechanical components of the swing that can be adjusted independently of a hitter’s size and strength to generate higher batted ball exit velocities.7 Three swing variables that are of interest in professional baseball are: contact in front of the batter’s center of mass, the attack direction of the swing, and the attack angle of the swing. The attack direction is defined as the horizontal angle at which the sweet spot of the bat is traveling at impact. The attack angle is defined as the vertical angle at which the “sweet spot” of the bat is traveling at impact.

The purpose of this study is to utilize hitting metrics from a public Major League Baseball (MLB) database to seek correlation between these three swing mechanics and a player’s average exit velocity on batted balls pertaining to their height, weight, and bat speed. It is hypothesized that variation in the modifiable swing mechanics will demonstrate no significant change in average exit velocity.

METHODS

An IRB waiver was obtained for this study through primary investigators’ home institution. Data were obtained via an open Internet search using MLB’s Statcast database. The participant field used for this study was every current batter in the 2025 MLB season that averaged 3.1 plate appearances per game played by the team. To control for the three factors contributing to exit velocity (bat speed, height, and weight), the 226 players were separated into eight groups based on height, weight, and average bat speed (Figure 1).

 

The eight groups are as follows:

1. Fastest 50% of average bat speed of the heaviest 50% of the tallest 50% of qualified players (n=27)

2. Slowest 50% of average bat speed of the heaviest 50% of the tallest 50% of qualified players (n=28)

3. Fastest 50% of average bat speed of the lightest 50% of the tallest 50% of qualified players (n=27)

4. Slowest 50% of average bat speed of the lightest 50% of the tallest 50% of qualified players (n=28)

5. Fastest 50% of average bat speed of the heaviest 50% of the shortest 50% of qualified players (n=32)

6. Slowest 50% of average bat speed of the heaviest 50% of the shortest 50% qualified players (n=32)

7. Fastest 50% of average bat speed of the lightest 50% of the shortest 50% of qualified players (n=28)

8. Slowest 50% of average bat speed of the lightest 50% of the shortest 50% of qualified players (n=26)

Once grouped, each manipulatable swing aspect “attack angle, attack direction, and contact point in front of center of mass” was individually compared to the exit velocity for that group. The correlation coefficient (r) was first found between each respective group and exit velocity. Then, the equation:

was used to solve for the t–statistic (t). The t–statistic is a value that is used to quantify the difference between a sample’s estimated value and an assumed value. The t–statistic was then used to determine the p–value using (p) the Excel function “T.DIST.2(t, n-2)”. The p-value was then determined and used to either prove or reject the null hypothesis. A p-value of <.05 correlated with a rejection of the null hypothesis. A p-value of >.05 correlated with an acceptance of the null hypothesis.

RESULTS

Under the search parameters set for, 226 active MLB players qualified for this study during the 2025 season. The first swing metric compared to average exit velocity was attack direction, which is the horizontal angle at which the sweet spot of the bat makes contact with the baseball. Across all eight groups there was no significant relationship found between a player’s average exit velocity and attack direction (Table 1). This was confirmed by the p-values across all eight groups being greater than .05, thus accepting the null hypothesis. The null hypothesis for this group states there is no significant relationship between average exit velocity and attack direction.

The next swing metric compared to average exit velocity was the attack angle, which is the vertical angle of the bat as it comes into contact with the baseball. The only group of players which demonstrated a significant relationship between these two metrics was group 7, which comprised the fastest 50% of average bat speed of the lightest 50% of the shortest 50% of qualified players. This was indicated by a p-value of less than .05, which rejects the null hypothesis that there is no significant correlation between attack angle and average exit velocity. For all the other 7 groups, there was no significant relationship found between these two variables based on a p-value greater than .05 (Table 2). This accepts the null hypothesis that there is no significant relationship between average exit velocity and attack angle.

The final swing metric compared to average exit velocity was the contact point in front of a batter’s center of mass, which is the point in front of the batter’s center of mass, measured in inches, at which the bat makes contact with the ball. Across all eight groups there was no significant relationship found between a player’s average exit velocity and contact point in front of their center of mass (Table 3). This was confirmed by the p-values across all eight groups being greater than .05, thus accepting the null hypothesis. The null hypothesis for this group states there is no significant relationship between average exit velocity and contact point in front of a batter’s center of mass.

 

CONCLUSION

In baseball, one of the most valuable qualities a hitter can possess is the ability to generate high exit velocity. A player’s batting average is one of the strongest indicators of offensive success in the MLB, yet it is notoriously difficult to predict.9 Research has shown, however, that higher average batted-ball exit velocity is directly linked to improved hitting outcomes, including increased batting average, slugging percentage, and extra-base hit production. Therefore, the ability to produce a higher average exit velocity as a hitter is highly desirable. While a player’s height and weight are generally non-modifiable variables, the ability to manipulate a hitter’s swing mechanics is often desirable in search of greater productivity.10

In the present study, we examined the effects of a batter’s attack angle, attack direction, and contact point in front of the center of mass in regard to their effect on average exit velocity of a batted ball. Significance was found between attack angle and average exit velocity amongst one subset of players (Group 7: fastest 50% of average bat speed of the lightest 50% of the shortest 50% of qualified players). Rationale for this may suggest that for shorter, lighter players with above-average bat speed, a greater upward bat path at contact may contribute to increased exit velocity. This finding supports the concept that optimal swing mechanics may vary depending on player-specific characteristics.11 However, it is important to note that this relationship was not observed across the majority of player groups.

Additionally, while anthropometric characteristics such as height and weight have historically been associated with performance, the findings of this study support the growing body of literature suggesting their contribution to hitting outcomes is limited. While trends in professional baseball have shown increases in player size over time (11,12), these factors alone do not appear to strongly dictate exit velocity or overall hitting success.12,13 This is further supported by Orishimo et al., who demonstrated that lower extremity kinematics and kinetic sequencing contribute more significantly to bat speed and swing efficiency than static anthropometric measures.14

Another important consideration is that while this study evaluated attack angle and attack direction independently, these variables are components of the broader concept of swing path, which likely plays a more critical role in determining batted-ball outcomes. Nakashima et al. highlighted that swing path directly influences timing precision and contact quality, emphasizing that hitting performance is dependent on a multifactorial interaction between bat trajectory, timing, and coordination rather than isolated swing parameters.15 This may explain why limited significant relationships were identified in this study when evaluating individual swing metrics in isolation.

The remainder of modifiable swing mechanics failed to reach statistical significance across the remaining player subgroups. While the current study encompassed 226 players, dividing them into eight subgroups resulted in relatively small sample sizes (N range 26–32), which may limit statistical power. The authors believe that increasing the number of seasons analyzed could provide a larger dataset and greater insight into subgroup-specific trends (13).

Furthermore, while this study confirms that hitters are more likely to increase their average exit velocity by focusing on known contributors such as increased bat speed (2) and increased muscle mass gain (3), these relationships are already well established in the literature. The more meaningful implication of this study is that isolated adjustments to swing mechanics, such as attack angle, attack direction, or contact point, may not independently result in improved hitting performance for most players. Instead, improvements in batted-ball outcomes likely require a comprehensive approach that incorporates bat speed development, efficient kinetic sequencing, and individualized swing mechanics.

In conclusion, the adjustment of attack angle may benefit a small subgroup of hitters based on the findings of this study, while adjustments to attack direction and contact point in front of the center of mass are unlikely to independently increase exit velocity. Future research should incorporate larger sample sizes, longer timeframes, and a more integrated analysis of swing path and full-body mechanics to better understand their relationship with hitting performance. 

RYAN MARRA is a medical student at Duquesne University and a former collegiate baseball player at Brown University. He has a passion for sports medicine and baseball and hopes to practice medicine in a field that allows him to stay active within the baseball community.

 

Notes

1. Mohammadreza Hojat and Gang Xu. “A Visitor’s Guide to Effect Sizes—Statistical Significance Versus Practical (Clinical) Importance of Research Findings.” Advances in Health Science Education: Theory and Practice 9, 241–49 (2004).

2. Jake Singleton. “Exit Velocity and a Player’s Offensive Value | Sports Analytics Group at Berkeley.” Sports Analytics Group Berkeley, November 2, 2017. https://sportsanalytics.studentorg.berkeley.edu/articles/mlb-exit-velocity.html.

3. Alan M. Nathan, “Dynamics of the baseball-bat collision,” American Journal of Physics, November 1, 2000, 979–90. https://pubs.aip.org/aapt/ajp/article-abstract/68/11/979/1055418/Dynamics-of-the-baseball-bat-collision.

4. Yungchien Chu, Karen Keenan, Katelyn Allison, Scott Lephart, and Timothy Sell, “The positive correlation between trunk, leg, and shoulder strength and linear bat velocity at different ball locations during the baseball swing in adult baseball hitters,” Isokinetics and Exercise Science, 23:4, November 1, 2015, 237–44.

5. “Statcast Swing Path/Attack Angle.” Baseball Savant, Major League Baseball, 2025, http://baseballsavant.mlb.com/leaderboard/bat-tracking/swing-path-attack-angle?sortColumn=avg_intercept_y_vs_batter&sortDirection=desc. Accessed 25 June 2025.

6. Michael E. Houston, Gaining Weight: The Scientific Basis of Increasing Skeletal Muscle Mass, Canadian Science Publishing, August 1999.

7. Jordan N. Kohn, Liam Lochhead, Jiren Feng, Ryan Bobb, and L. Gregory Appelbaum. Strength, speed, and anthropometric predictors of in-game batting performance in baseball. Journal of Sports Sciences 42:8, (2024) 720–27.

8. B.S. Everitt and A. Skrondal, The Cambridge Dictionary of Statistics. 4th ed., Vol. 1, (Cambridge, Cambridge University Press, 2010).

9. Sarah R. Bailey, Jason Loeppky, and Tim B. Swartz, “The Prediction of Batting Averages in Major League Baseball,” MDPI, April 3, 2020. https://www.mdpi.com/2571-905X/3/2/8.

10. Dhanjoo Ghista, Applied Biomedical Engineering Mechanics (Boca Raton: CRC Press, 2008).

11. William Carvajal, Andrés Ríos, Ivis Echevarría, Miriam Martinez, Julio Miñoso, and Dialvis Rodríguez, “Body type and performance of elite Cuban baseball players,” MEDICc Review, April 2009, 11:2, 15–20.

12. Ryan L. Crotin, Charles M. Forsythe, Thomas Karakolis, and Shivam Bhan, “Physical size associations to offensive performance among major league leaders,” Journal of Strength and Conditioning Research, September 2014, 28:9, 2391–6.

13. Ryan L. Crotin, Christian M. Conforti, David J. Szymanski, and Jordan Oseguera, “Anthropometric Evaluation of First Round Draft Selections in Major League Baseball,” Journal of Strength and Conditioning Research, August 2023, 37:8, 1609–15.

14. Karl F. Orishimo, Ian J. Kremenic, Edward Modica Jr., Takumi Fukunaga, Malachy P. McHugh, and Srina Bharam, “Lower extremity kinematic and kinetic factors associated with bat speed at ball contact during the baseball swing,” Sports Biomechanics, December 2024, 23:12, 3406–17.

15. Hirotaka Nakashima, Gen Horiuchi, Arata Kimura, and Shinji Sakurai, “Acceptable range of timing error at bat-ball impact in baseball depends on the bat swing path,” Frontiers in Sports and Active Living, March 2025. https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2025.1557145/full.