June 21, 2024


Exercise makes you strong

Overload / Underload Training: How It Works & Why Ball Players Should Use This Training Method

There are some, particularly online, who continue to spread incorrect and misleading information about weighted ball training. Our discussion here will deal with Overload/Underload (OU) training in general, and its application to baseball and softball in particular.

1. OU Training Defined

2. A Brief History of OU Research and Training

3. Other Sports That Use OU Training

4. The Benefits of OU Training

5. Other Baseball Experts Who Are Proponents of OU Training


Using weight-modified implements that are otherwise identical
to those used during competition

The weights of these modified tools weigh both more and less than the standard competitive weight.

Such tools allow athletes to train more precisely for their sport. Sport-specific strength and power are developed by movements with resistance or assistance that imitate the joint action of the skill – SPECIFIC RESISTANCE TRAINING. What makes this type of training so effective is that the weights of the modified tools used are heavy enough to produce a conditioning effect, yet light enough to not adversely affect the athlete’s mechanical skills.

Generally, OU Training is employed to increase an athlete’s POWER. Power is defined as the rate at which one can perform work, or the ability to exert muscle force quickly. This ability is related to, but distinct from strength, which is defined as the ability to exert muscle force.

As an example, strength is demonstrated as the ability to pick up a 30 oz. bat. Power is demonstrated by the ability to drive a baseball 400+ feet while swinging that 30 oz. bat.

As long as the tools used are not too heavy, mechanics are not affected, making OU Training what I call “skill-neutral.” According to published data (see below) the ideal weight range for conditioning and performance enhancement is up to 20% +/- the weight of the competitive implement. I do NOT recommend using baseballs weighing more than 6 oz., or softballs heavier than 8 oz. There is some data that indicates using much heavier balls can negatively affect throwing mechanics, possibly leading to arm problems. Extra motor-units are recruited while throwing these heavy balls that are then not used when the regular competitive ball is used. As relates to our discussion here, the modified implements ball players can use are weighted baseballs and softballs, and various weights of baseball/softball bats, and/or devices attached to these bats.

Conversely, this type of training would not be useful for training other athletic skill areas, for example, shooting or throwing accuracy. OU training could help a golfer drive their tee shots further, but it wouldn’t help eliminate their slice if they have one, or otherwise help them to hit straighter drives. OU training could help a young basketball player who is having trouble hoisting a basketball high enough to make a shot in a 10 foot hoop, but the shot still has to be accurate enough to go in. Accuracy training needed for a specific skill would therefore be performed apart from power work.

If I was working with a pitcher who had control problems, I would not break out the weighted baseballs and expect training of this type to help him throw strikes. I would look at his mechanics and make any needed adjustments, and possibly suggest some drill work to help reinforce the new concepts being taught. Such a player might also be working with weighted baseballs/softballs as part of their overall training regimen, but this would occur at a different time, and for the purposes of developing more power and speed behind his/her throws as well as conditioning the throwing structures of the arm.

A potential side-benefit of OU training is that a player could improve their accuracy by virtue of the increased number of reps or throws they are performing. This would be an artifact of the main goal of improving power, however, and not the main purpose of OU training.


The first research involving OU training was performed in the 1970s by the Soviet Union and East-European track and field teams. A great deal of this research has been published in prestigious, peer-reviewed journals around the world. Shot-putters, javelin, discus and hammer throwers, and sprinters were the early adopters of this training method.

Research with baseball players dates back to the 1960s. This is just a sampling of studies involving OU Training and baseball. There are dozens more relating to OU Training generally:

1) Coop DeRenne, Kwok W. Ho and James C. Murphy. 2001: Effects of General, Special, and Specific Resistance Training on Throwing Velocity in Baseball: A Brief Review. The Journal of Strength and Conditioning Research: Vol. 15, No. 1, pp. 148-156.

2) Escamilla et al. 2000: Sports Med Apr; 29 (4): 259-272

3) David J. Szymanski, MEd, CSCS, June 1998: The Effects of Various Weighted Bats on Bat Velocity – A Literature Review. Strength and Conditioning, pp. 8 – 11

4) Coop DeRenne, Barton P. Buxton, Ronald K. Hetzler and Kwok W. Ho. 1995: Effects of Weighted Bat Implement Training on Bat Swing Velocity. The Journal of Strength and Conditioning Research: Vol. 9, No. 4, pp. 247-250.

5) Coop DeRenne, Barton P. Buxton, Ronald K. Hetzler and Kwok W. Ho. 1994: Effects of Under- and Overweighted Implement Training on Pitching Velocity. The Journal of Strength and Conditioning Research: Vol. 8, No. 4, pp. 247-250.

6) Coop DeRenne, Kwok Ho and Alan Blitzblau. 1990: Effects of Weighted Implement Training on Throwing Velocity. The Journal of Applied Sport Science Research, 4, 16-19.

7) DeRenne, C., Tracy, R., and Dunn-Rankin, P. 1985: Increasing Throwing velocity. Athletic Journal, April, 36 – 39.

8) Bagonzi, J. A. 1978: The Effects of Graded Weighted Baseballs, Free Weight Training, and Simulative Isometric Exercise on the Velocity of a Thrown Baseball. Master’s thesis, Indiana University.

9) Litwhiler, D., and Hamm, L. 1973: Overload: Effect on Throwing Velocity and Accuracy. Athletic Journal, 53, 64-65.

10) Brose, D.E., and D.L. Hanson 1967: Effects of Overload Training on Velocity and Accuracy of Throwing. Research Quarterly. 38:528-533.

11) Elias, J. 1964. The Effect of Overload Training on Speed in Baseball Pitching. Unpublished Master’s thesis, Springfield College, Springfield, Massachusetts.

12) Egstrom, G.H., Logan, G.A., and E. L. Wallis 1960: Acquisition of Throwing skill Involving Projectiles of varying Weight. research Quarterly 31:420-425.


Over and underloaded implements and techniques are used very effectively by athletes in many sports to augment performance:

Track & Field: heavier and lighter discuses, javelins, shot balls (shot putters) and hammers; sprinting with resistance, such as pulling weighted sleds, wearing weighted vests, and downhill running on a slight downward slope, being towed while running, and running on a high speed treadmill (overSPEED training) .

Swimming: wearing swimming gloves that allow for more water to be pulled during an arm stroke; swimming while dragging an implement or otherwise artificially producing drag on a swimmer.

Heavier footballs (over the standard 15 oz) are thrown by quarterbacks; heavier basketballs are used by basketball players. Boxers train with different weights of boxing gloves.

Note that ALL of these training implements are used to improve POWER and/or SPEED through the joint range-of-motion (ROM) in the activity being trained, which can lead to enhanced performance.


Benefit #1

Appropriate strength and conditioning regimens, such as OU Training, can reduce and even prevent arm injuries related to throwing by increasing STRENGTH/ENDURANCE. Increased Strength – helps prevent injury. Increased Endurance – helps maintain throwing velocity, allows for more pitches to be thrown before tiring.

The muscles, tendons, ligaments and bones (even nerves) of the shoulder and arm in general will positively adapt to an appropriate increase in training load. They become tougher and more durable, able to handle greater workloads. Such training must conform to the following two guidelines:

1) The training load is sufficient to produce the desired training effect, yet not so great as to negatively impact throwing (or hitting) mechanics.

2) The thrower’s program introduces OU training gradually and systematically, employing a training principle known as Progressive Overload (Clarkson & Watson, 1990). This principle states that “strength and endurance cannot be increased unless the muscles are stressed beyond their normal workload. To increase the workload, increase the frequency, duration and intensity of your exercise program.”

To effectively and safely increase throwing velocity, intensity is increased by using 20% +/- OU balls, duration is increased by gradually increasing the number of OU throws performed with each workout, and frequency is increased by the number of days of throwing workouts. Arm/shoulder structures trained in this manner are more capable of handling the regular competitive game requirements, which are less than those imposed by the OU conditioning. An arm conditioned for making numerous throws with a 6 oz ball will more than likely out-perform an arm trained only to perform under a 5 oz. load (ability, mechanics and over-use considerations aside).

Dr. Mike Marshall, in his Pitching Book (Chapter 32, pp. 5 & 6), describes a concept he calls “Plioanglos Training” as a means of training the external rotator cuff muscles (decelerators). This is similar to the ideas expressed above:

“Plioanglos training means adding resistance to forward ballistically speeding pitching arms to increase capacities of lengthening deceleration muscles to stop.”

Perhaps this is best summed up by way of the well-known conditioning principle S.A.I.D. – Specific Adaptation to Imposed Demands (Wallis and Logan, 1964). This principle states that the body will adapt to stress imposed on it (as long as it is not excessive, in which case the body breaks down). One safe and effective way of doing this is with OU Training, employing the aforementioned guidelines.

Benefit #2

Improved on-field performance – increased throwing velocity (or bat speed).

Increased arm speed throughout the throwing Range of Motion (ROM). This attribute is developed by throwing a ball weighing 20% less than the competitive ball. Because the ball weighs less, the arm moves more quickly through its ROM, leading to increased throwing velocity. Throwing lighter balls has been shown (both clinically and on the ball field) to be one of the best means of increasing throwing velocity. Swinging appropriately lighter bats helps develop increased bat speed. This is also known as overSPEED training.

A note on “light” ball training, high school and older players: This can be an excellent way for pitchers in particular to get a good amount of throwing in between starts with less stress on the arm. For youth ball players – why do we make lighter bats for younger ball players, yet make them throw the same 5 oz ball that guys like Roger Clemens and Randy Johnson throw? That youth fields are smaller makes little difference when it comes to the length of some of the throws that young players have to make. These little arms still have to generate a great deal of force to propel the ball. Underweight balls (4 oz.) are a GREAT tool for players of all ages.

Benefit #3

Enhanced neuromuscular conditioning.

According to Vern Gambetta, Strength and Conditioning Coach for the Chicago White Sox, the primary source of fatigue in baseball pitching is not metabolic, but neural. The metabolic demands – conditioning – are just not that great in baseball or softball. Don’t misunderstand – I’m speaking here of the skills required to be a good hitter or pitcher. Being well conditioned is still important, as this will help prevent injury, but no doubt you’ve seen players like John Kruk, David Wells, Tony Gwynn, and others. High level performers who are not particularly well conditioned.

Neural fatigue occurs at the motor-unit level. In the act of pitching, for example, the Central Nervous System sends a nerve impulse to a motor unit (MU) in the shoulder involved in this process. The ability of these MUs to transmit these signals, with optimal frequency and speed, diminishes over time. This “breakdown” occurs at the nerve synapse/biochemical level, which THEN leads to slower and weaker muscle contractions.

In baseball pitching, throwing muscles and tendons in the shoulder are stretching and contracting repeatedly while accelerating and decelerating the arm during an overhand throw – constant biochemical activity at the neuromuscular junction. As neural fatigue sets in, it becomes manifest in mechanical problems. For example, a pitcher dropping their shoulder later in the game, leading to a loss of control or velocity. The tough thing is, this “fatigue” is usually not felt by the pitcher, but it occurs nevertheless.

This is where proper conditioning (OU Training) comes in. Research has shown that neurons adapt to stress much like muscles do. Motor neurons exposed to high-frequency impulses end up with more developed neuromuscular junctions which appear more capable of handling high-intensity impulses better than those not exposed to similar stress. The S.A.I.D. principle in effect again.

Does this mean OU Training is fool proof, and has never harmed a player? Of course not. Most any type of conditioning, performed incorrectly, can cause problems or injury. Throwing itself, be it footballs, baseballs, rocks or whatever, has harmed many a throwing arm. Running is the cause of many knee and ankle injuries. Shoulder problems amongst swimmers are common. Ice skaters often suffer from some very painful leg ailments. I could go on, but you get the point. All of these injuries and problems occur as a part of the athlete’s regular practice and competitive activities. Performing them properly minimizes the risk, of course. So does a variety of strength and conditioning methods, including OU Training.


Dr. John Bagonzi. Former pitcher with the Red Sox. Known as the “Pitching Professor” and author of the highly regarded book, “The Act of Pitching.”

Dr. Tom House. Former pitcher with the Rangers. Author/co-author of several books, including “The Winning Pitcher” and “Power Baseball.” Personal pitching coach to Nolan Ryan, Randy Johnson, Mark Prior, and others.

Dr. Mike Marshall. Former Cy Young Award winner with the Dodgers. Author of the book, “Coaching Pitchers” and the pitching training DVD, “Dr. Mike Marshall’s Pitching Instructional Video.”

Dr. Coop DeRenne. Former professional player, instructor and consultant to the Chicago White Sox and Texas Rangers. Probably this country’s leading baseball researcher, supervising 16 hitting and pitching warm-up, biomechanical, and visual research projects using over 600 amateur and professional hitters and pitchers as his subjects. Co-author (with Tom House) of the book, “Power Baseball” and other baseball training books.

ASMI – The American Sports Medicine Institute

All of these experts possess impeccable credentials and favor some type of weighted ball training.