Few topics in pitching split coaches the way weighted balls do. Some programs treat them as the engine of every velocity jump. Some clinicians would rather nobody touched them. The published research supports neither extreme. It shows a tool that works for many pitchers, carries measurable risk, and depends heavily on how it is used.
This guide walks through what the studies actually found, who is a good candidate, how to fit the work into a throwing week without blowing up workload, and what a conservative first block can look like.
What weighted ball training is
Weighted ball training means throwing implements that are heavier or lighter than a regulation baseball, which weighs about 5 ounces. The terms you will see:
- Overload: balls heavier than 5 oz. In research, these range from slightly heavy (6 to 7 oz) up to 16 and 32 oz balls used for holds and short drills.
- Underload: balls lighter than 5 oz, usually 3 to 4 oz in studies, with some programs going as light as 2 oz.
- Weighted baseballs vs. plyo balls: Driveline describes leather weighted baseballs as tools for higher-intent throwing, and soft-shell PlyoCare balls as tools mainly for submaximal constraint drills and arm care.
The theory is that changing the load changes the movement. Heavier balls slow the arm down and may help a pitcher feel sequencing and arm path. Lighter balls let the arm move at or above game speed. Constraint drills like reverse throws and pivot picks isolate one piece of the delivery at a time.
What the research says about velocity
The velocity case is reasonably consistent. A 2000 review by Escamilla and colleagues looked at seven overweight and four underweight training studies lasting 6 to 12 weeks, with overweight balls from 5.25 to 17 oz and underweight balls from 4 to 4.75 oz. The authors concluded the data strongly supported training with these balls to raise regulation-ball velocity, while noting there was no injury data yet.
A 2019 systematic review by Caldwell, Alexander and Ahmad included 10 studies and found that weighted-implement training increased pitching velocity in the majority of them. It also rated the quality of evidence as very poor, with large differences in protocols, ball weights and populations, and found the injury data inadequate to judge risk.
The best-known trial is Reinold and colleagues (Sports Health, 2018). Thirty-eight healthy high school age pitchers (13 to 18 years, mean age 15.3) were randomized in the offseason. The training group did a 6-week program three times per week using 2, 4, 6, 16 and 32 oz balls from kneeling, rocker and run-and-gun positions, building from 75% to 100% intensity. Both groups lifted.
- The training group gained about 1.0 m/s (roughly 2.2 mph), a 3.3% increase. The control group gained about 0.3 m/s.
- The between-group comparison over time was not statistically significant (P = 0.06), even though the training group's own change was.
- About 80% of the training group got faster, but so did 67% of the control group.
A 2023 cross-sectional study of US high school pitchers by Bowman and colleagues found that 63% had used a weighted ball program, and those pitchers averaged about 71 mph versus 66 mph for non-users. That is an association, not proof the balls caused the difference.
Not every study finds a gain. Driveline's own research team (Marsh et al., PeerJ, 2018) followed 17 college and professional pitchers through a six-week individualized program that included weighted implements, lifting and other work. Across the group there was no significant change in pitching velocity. That honesty from a facility that sells weighted balls is worth noting.
What the research says about risk
This is where the story gets more serious, and it should be read carefully rather than ignored or exaggerated.
- Reinold 2018: 4 of the 17 pitchers who completed the weighted ball program (24%) had elbow injuries requiring medical attention: two olecranon stress fractures, one partial UCL injury, and one UCL injury where reconstruction was recommended. Two happened during the program and two in the following season. No control pitcher was injured. Shoulder external rotation range of motion rose by about 4 degrees in the training group.
- Reinold 2020: in 16 high school pitchers, a single session with overload balls (6 and 9 oz) raised shoulder external rotation by 3.3 degrees, and extreme overload (16 and 32 oz) raised it by 8.4 degrees. Underload balls produced no significant change. The authors advised using heavier balls with caution and monitoring range of motion.
- Shanley 2025: an interim analysis of 88 professional pitchers found higher arm injury rates in weighted ball users (11.8 per 1,000 game exposures) than non-users (7.5 per 1,000). It is a preliminary, one-season observational result, but it points the same direction.
The biomechanics studies add useful nuance. Fleisig and colleagues (Sports Health, 2017) tested 25 high school and college pitchers already experienced with weighted balls. A 4 oz ball and a regulation ball produced similar kinematics and kinetics, and arm torques generally decreased as ball weight went up. Flat-ground crow hop throws, though, produced higher shoulder internal rotation velocity and elbow varus torque than mound pitching. The authors described 14 and 32 oz holds as hybrid resistance exercises rather than pitching drills.
Driveline's 2022 study (O'Connell et al., Journal of Applied Biomechanics) with 26 college and professional pitchers found that 3 to 7 oz baseballs changed arm speed and some body positions without significantly changing arm joint kinetics.
Weighted balls in the 3 to 7 oz range do not appear to load the arm more per throw than a regulation ball in lab studies. Programs built around them still show injury signals in the field. The likely culprit is the program around the ball: high-intent volume, frequency, heavy implements, youth athletes, and work that is never counted as part of total load.
Who weighted ball training is for
The pitchers who tend to be good candidates share a few traits:
- Physically mature, typically late high school age or older. Most of the supportive biomechanics research used experienced high school, college or pro pitchers.
- Healthy and pain-free, with no recent arm injury.
- An established throwing base: several weeks of consistent catch play and long toss before adding high intent. Driveline's own guidance describes on-ramping first and having a solid throwing program "under their belt."
- A strength program running alongside it. Weighted balls do not replace lifting.
- Supervision from a coach who can watch movement quality and adjust volume.
Who should wait
- Youth and skeletally immature pitchers. The injuries in Reinold's trial occurred in 13 to 18 year olds, and a 2023 editorial in Arthroscopy argued weighted baseball training should be banned for youth athletes. Younger pitchers usually gain more from athletic development, strength, and a well-built throwing program.
- Anyone throwing with pain. Pain means stop and see a qualified clinician.
- Pitchers early in return to throw. Follow the clinician-guided interval program first.
- Pitchers with no base. Coming off a layoff or with a thin throwing history, build volume and tolerance before intensity.
Ball weights commonly used
| Weight | How it shows up in research | Practical note |
|---|---|---|
| 3 to 4 oz (underload) | Highest ball speed; kinematics similar to a regulation ball (Fleisig 2017; O'Connell 2022) | Treat as near-max intent work. Count every throw. |
| 5 oz (regulation) | Baseline in every study | Anchor each block with regulation throws so gains transfer. |
| 6 to 7 oz (light overload) | Arm torques similar or lower than regulation per throw (Fleisig 2017) | The most studied overload range for throwing. |
| 9 oz and heavier | Acute increases in shoulder external rotation, largest with 16 and 32 oz (Reinold 2020) | Use sparingly, for low-intent drills or holds, under supervision. |
Common drills
Most programs combine constrained drills with soft plyo balls and less constrained throws with weighted baseballs. Driveline's workload data found that more constrained drills like pivot pickoffs and roll-ins produced lower average elbow torques and are typically used on recovery days, while walking windups and janitors ran slightly higher.
- Reverse throws: facing away from the target and throwing backward, usually with a heavier plyo ball at low effort. Often used as a warm-up or recovery drill.
- Pivot picks (pivot pickoffs): start facing the target, pivot and throw. Isolates hip and trunk rotation into arm action.
- Roll-ins: a short rolling step into the throw that adds a little momentum while keeping the motion organized.
- Walking windups: a walking approach into a full throw. More momentum and more stress than the constrained drills.
- Plyo wall work: throwing soft plyo balls into a solid wall so a pitcher can get many reps without a partner. Effort is still effort, so wall throws count toward the day's total.
How to fit it into the throwing week
Treat weighted ball work as part of the throwing program, not a bonus on top of it. A few principles that line up with the research:
- Count every throw. Plyo drills, weighted throws and pulldowns all go into daily workload. If they are not logged, your acute vs. chronic picture is wrong.
- Watch the acute:chronic workload ratio (ACWR). A 2024 interval throwing program by Reinold and colleagues was built to keep ACWR in a 0.7 to 1.3 range for most of the program. Adding a weighted ball block on top of normal throwing is a classic way to spike the acute side. Try the pitching workload calculator to see where you are.
- Limit true high-intent days. Driveline lists over-programming high-intent days as a common way weighted ball training goes wrong. Keep them apart, and avoid stacking them next to bullpens or games.
- Let readiness steer the day. Poor sleep, high soreness, or a heavy arm are reasons to swap a high-intent day for a recovery or hybrid day.
- Remember that effort is underestimated. In a long toss study, throws pitchers rated as 50% effort still produced 87% of maximum elbow varus torque (Melugin 2019). "Easy" plyo throws are rarely as easy on the arm as they feel.
Sample 6-week progression (example template, not a prescription)
This is an example for a healthy, physically mature pitcher who has already completed several weeks of regular catch play and long toss. It is intentionally conservative. Volumes are per session, all on flat ground, with a full warm-up first. A qualified coach should adjust it to the athlete.
| Week | Sessions | Focus | Example content | Effort |
|---|---|---|---|---|
| 1 | 2 | Learn the drills | Reverse throws, pivot picks, roll-ins with plyo balls, about 2 x 5 each | Low to moderate |
| 2 | 2 | Add light overload | Week 1 drills plus walking windups with 6 to 7 oz balls, about 2 x 5 | Moderate |
| 3 | 2 | Introduce intent | Drill circuit, then 1 day of walking windups at moderately high effort with 4, 5 and 6 oz balls, about 3 to 4 throws each | Moderate to high |
| 4 | 2 to 3 | Build | One higher-intent day with 4 to 7 oz balls, the others as hybrid or recovery drill days | One high day |
| 5 | 2 to 3 | Peak exposure | Same structure as week 4, small volume increase only if readiness and arm feel are good | One to two high days |
| 6 | 2 | Deload and transfer | Cut volume roughly in half, finish with regulation-ball throws and a moderate bullpen | Moderate |
Keep regular catch play on the other days and log it. If ACWR climbs well above the range you have been living in, or readiness drops for several days, repeat a week instead of moving forward.
Red flags
- Pain in the elbow or shoulder during or after throwing, especially on the inside of the elbow.
- Soreness that lasts into the next day's throwing session or keeps building through the week.
- Velocity dropping or command falling apart across sessions.
- Numbness or tingling in the hand or fingers.
- A big jump in total throws, high-intent throws, or ACWR over a single week.
Pain means stop and see a qualified clinician. Soreness and fatigue are signals to pull back volume and intensity, not to push through.
Frequently asked questions
Do weighted balls really increase pitching velocity?
Most studies show velocity gains, including a 3.3% increase in a 2018 randomized trial. A 2019 systematic review found gains in most included studies but rated the evidence quality as very poor, and one Driveline study found no group-wide change, so results vary by athlete and program.
Are weighted balls safe?
They are not risk-free. In Reinold's 2018 trial, 24% of the weighted ball group had elbow injuries and no control pitchers were injured. Lab studies show 3 to 7 oz balls do not load the arm more per throw than a regulation ball, so dosing, intent, frequency, heavy implements and athlete readiness appear to matter most.
What age should a pitcher start weighted ball training?
There is no single research cutoff, but the injuries in Reinold's study occurred in 13 to 18 year olds and much of the supportive research used experienced high school, college and professional pitchers. Most young pitchers are better served by strength, athleticism and a solid throwing program first.
What weight balls should pitchers use?
The most studied range for throwing is 3 to 7 oz. Heavier balls such as 16 and 32 oz caused larger short-term increases in shoulder external rotation and are best kept to low-intent drills or holds under supervision.
Do weighted ball throws count toward workload?
Yes. Plyo drills, weighted throws and pulldowns should all be counted in daily throwing workload so your acute:chronic workload ratio reflects what your arm actually did.
Built around your week
Let Pitch AI fit intent work into your throwing week
Pitch AI builds your throwing week from your profile, season phase and schedule. Depending on your block, days can include plyo drills like reverse throws, pivot pickoffs, roll-ins and walking windups, weighted-ball command work, and pulldown days. New or returning throwers start with a base-building block where the week's one max-effort day is a bullpen. Logged throws, including weighted-ball throws, feed an acute:chronic workload ratio, and daily readiness check-ins adjust the volume and intensity of the plan.
Sources and further reading
- Reinold MM, et al. Effect of a 6-Week Weighted Baseball Throwing Program on Pitch Velocity, Pitching Arm Biomechanics, Passive Range of Motion, and Injury Rates. Sports Health, 2018
- Reinold MM, et al. Acute Effects of Weighted Baseball Throwing Programs on Shoulder Range of Motion. Sports Health, 2020
- Fleisig GS, et al. Biomechanical Analysis of Weighted-Ball Exercises for Baseball Pitchers. Sports Health, 2017
- Escamilla RF, et al. Effects of Throwing Overweight and Underweight Baseballs on Throwing Velocity and Accuracy. Sports Medicine, 2000
- Caldwell JE, Alexander FJ, Ahmad CS. Weighted-Ball Velocity Enhancement Programs for Baseball Pitchers: A Systematic Review. Orthopaedic Journal of Sports Medicine, 2019
- Melugin HP, et al. The Evidence Behind Weighted Ball Throwing Programs for the Baseball Player: Do They Work and Are They Safe? Current Reviews in Musculoskeletal Medicine, 2021
- Marsh JA, et al. (Driveline Baseball). Effects of a six-week weighted-implement throwing program on baseball pitching velocity, kinematics, arm stress, and arm range of motion. PeerJ, 2018
- O'Connell ME, et al. (Driveline Baseball). Weighted Baseball Training Affects Arm Speed Without Increasing Elbow and Shoulder Joint Kinetics. Journal of Applied Biomechanics, 2022
- Bowman EN, et al. Most high school baseball pitchers are using weighted ball throwing programs to increase ball velocity. JSES Reviews, Reports, and Techniques, 2023
- Shanley E, et al. Professional Baseball Pitchers Use of Weighted Ball Training, Injury Incidence, and Time Loss: A Preliminary Study. International Journal of Sports Physical Therapy, 2025
- Anz AW. Editorial Commentary: Weighted Baseball Training Should Be Banned for Youth Athletes. Arthroscopy, 2023
- Reinold MM, et al. An Interval Throwing Program for Baseball Pitchers Based upon Workload Data. International Journal of Sports Physical Therapy, 2024
- Melugin HP, et al. Baseball Pitchers' Perceived Effort Does Not Match Actual Measured Effort During a Structured Long-Toss Throwing Program. American Journal of Sports Medicine, 2019
- Driveline Baseball: How Different Drills and Ball Weights Affect an Athlete's Workload (2021)
- Driveline Baseball: Weighted Baseballs vs. PlyoCare Balls, What's the Difference?
- Driveline Baseball: Weighted Ball Training Gone Wrong (2017)
- Driveline Baseball: Weighted Baseball Training for Pitchers, A Get Started Guide