Yes, plyo ball (plyometric ball) training can increase pitching velocity. Studies on weighted ball programs consistently show velocity gains in the range of 2% to 4%, which translates to roughly 1.5 to 3.5 mph for most pitchers. But those gains come with a real tradeoff: significantly higher injury rates to the arm and trunk. Understanding how the training works, what the evidence actually shows, and who’s most at risk will help you decide whether it belongs in your program.
How Plyo Balls Increase Arm Speed
Plyo ball programs use an overload-underload principle. A standard baseball weighs 5 ounces. Heavier balls (typically 6 to 32 ounces) act like resistance training for the arm, forcing the muscles involved in throwing to work harder and get stronger. Lighter balls (under 5 ounces) do the opposite: they let the arm move faster than it normally would, training the nervous system to recruit fast-twitch muscle fibers more efficiently. Most programs alternate between both.
The biggest mechanical change is increased shoulder external rotation, the amount the arm lays back just before release. In one six-week study, pitchers using weighted balls gained about 5 degrees of external rotation compared to a control group. Separate research found that throwing heavier balls (16 to 32 ounces) at submaximal intensities produced an 8-degree increase in passive shoulder external rotation. More layback generally means more velocity, because the arm has a longer path to accelerate through before releasing the ball. Researchers believe this gain in shoulder range of motion is the primary reason weighted ball programs boost velocity.
What the Velocity Gains Actually Look Like
A prospective six-week study on high school pitchers found that the weighted ball group improved velocity by 3.3% more than the control group. An eight-week study on college pitchers showed a 2.4% increase, going from about 83.2 mph to 85.2 mph on average. A four-week program with adolescent players (ages 11 to 15) combining resistance training and interval throwing produced a 4% bump. These are meaningful gains, especially in a sport where a single mph can change draft stock or roster decisions, but they’re not dramatic overnight transformations.
The gains tend to come from throwing the plyo balls into walls or nets as part of structured drill work, not from casually tossing them around. Programs like Driveline Baseball use specific drills designed to target different parts of the throwing motion. Reverse throws train the back of the shoulder to absorb the forces that come with higher velocities. Pivot pickoff throws build forearm strength and improve the timing of pronation at release. Walking windups emphasize powerful hip drive into foot strike. Each drill isolates a specific link in the chain, and the plyo ball’s weight variation amplifies the training effect.
The Injury Problem
This is where the conversation gets serious. In one prospective study on weighted ball training, nearly 25% of subjects sustained an injury to the shoulder or elbow. That’s one in four pitchers hurt during the program itself.
A study of professional baseball pitchers found that those who used weighted ball training had an arm injury rate of 11.8 per 1,000 game exposures, compared to 7.5 for pitchers who didn’t use weighted balls. Trunk injuries were even more lopsided: 5.9 per 1,000 exposures versus 2.1. Overall injury prevalence was 39.1% in the weighted ball group versus 23.8% in the non-weighted ball group. Perhaps most telling, pitchers who trained with weighted balls lost nearly twice as many days to injury on average (44.4 days versus 23.2 days).
Elbow injuries were especially concerning. Among weighted ball users, 17.4% suffered an elbow injury compared to 7.1% of non-users. The biomechanical explanation is straightforward: throwing heavier balls increases the varus torque on the elbow, which is the inward rotational stress that loads the ulnar collateral ligament. Research has shown this stress increases as ball weight goes up, particularly in youth pitchers. Even underweight balls increase peak varus torque at the elbow compared to regular pitching. Weighted ball throwing appears to be equal to or more stressful than pitching off a mound.
Why the Stress on the Arm Increases
When you throw a heavier ball, your body compensates in predictable ways. Elbow extension torque, the force your arm produces to straighten during the throw, increases substantially with ball weight. Research on overhead throwers found that peak elbow extension torque roughly doubled when going from a standard-weight ball to one nearly three times heavier. Meanwhile, the stabilizing muscles around the elbow don’t ramp up proportionally. Elbow flexion torque and pronation torque stayed essentially the same regardless of ball weight, meaning the joint absorbs more force without more muscular protection.
The extra shoulder external rotation that drives velocity gains is also a double-edged sword. More layback means the shoulder capsule stretches further, and the ligaments and tendons around both the shoulder and elbow experience greater peak loads during deceleration. This is why researchers have consistently noted that the same adaptations responsible for velocity improvement are also responsible for increased injury risk.
Who Should and Shouldn’t Use Them
The American Sports Medicine Institute lists weighted ball throwing programs as a risk factor for pitching injuries, alongside pitching while fatigued, insufficient rest, and single-sport specialization. Youth pitchers face particular concern because their growth plates and connective tissue are still developing, and studies have documented increased varus torque in young throwers using balls as light as 3 to 6 ounces.
For older, physically mature pitchers with solid throwing mechanics and no history of arm trouble, a carefully structured plyo ball program can produce real velocity gains. The key variables are progression, volume, and intensity. Programs that jump straight to max-effort throws with heavy balls, or that pile plyo ball work on top of an already demanding throwing schedule, are where injuries cluster. The drills are designed to be performed at largely submaximal intensities, and the total volume in a typical session is modest, often around 27 throws with the heavier implements.
If you’re considering adding plyo balls to your training, the honest summary is this: they work for velocity, the gains are modest but real, and the injury risk is substantially higher than traditional throwing programs. That tradeoff is worth taking seriously, especially if your arm is your livelihood or your season depends on staying healthy.