Bat Speed
Power Development System
The Most effective Bat Speed Tool on the market!

The Overload/Underload Power development system is an innovative training
method that was developed around the concept of Overload Underload training in
order to make dramatic improvements in bat speed in the least amount of time
possible.  The program was developed to be effective for players looking to get a foot
up on the competition in Little League all the way to players at the professional
level looking to get that little edge needed to play with the planet's most talented

The concept of Overload Underload training is a simple concept that has been used
since the 1970’s by Olympic athletes to get dramatic performance increases in
relatively short amounts of time.  Unfortunately, the concept still remained a
mystery to the majority of the general public until recent years.  Overload
Underload training is a training concept that uses resistances slightly above and
below what one would encounter in his/her respective sport.  So, for baseball that
would mean swinging a baseball bat or throwing a baseball that is roughly 20%
over and 20% under the normal weight one would usually encounter.  This concept
was studied extensively by the Soviet Union and other Eastern Bloc countries back
in the 1970’s.  These countries took great pride in their athletic accomplishments
and poured millions of dollars in research into more efficient ways to build better
athletes.  After experimenting with their Olympic throwers (shot put, javelin,
hammer, and discuss), they discovered that by increasing or decreasing the
resistance of the projectiles that were thrown in practice, they could produce
significant gains in throwing distance (and velocity) with objects of regulation
weight.  This was a huge find since strength and power gains from traditional
weight training often doesn’t always transfer well to more complex sporting
motions such as throwing and hitting.

The Soviets also found out that when greater than 20% resistance was added or
subtracted from the training implements, it not only didn’t increase performance
but it actually decreased it.  By using too much or too little resistance you will be
putting in a lot of effort and time to make yourself better, but it is actually time and
effort wasted.  This again goes back to the fact that timing and bio-mechanics are
essential to sports which require a high technical component.  When objects 20%
heavier or lighter than the original objects are used, then the bio-mechanics of the
movement is changed.  That means in order to accommodate for the additional or
reduced load, the athletes would change their movement pattern--which means, in
baseball terms, they would change the way they swing or throw, making the
training essentially useless.  The phrase "practice makes perfect" is often used by
coaches, but in reality only perfect practice makes perfect.  That means someone
wishing to increase his bat speed must take each practice swing with perfect
technique at game speed in order to have the hope of making noticeable
improvements.  To become fast and explosive, you must train to be fast and
explosive.  Quality always wins over quantity.  A quick example would be looking at
a marathon runner vs. a sprinter.  A marathon runner runs for miles at a time in
training.  A sprinter runs a few short sprints.  They are both running but the
differences lie in a) intensity, b) volume of training, and c) rest intervals.  Changing
those 3 variables makes the outcome of the training drastically different.  The take-
home message is:  if you want to throw faster, you need to practice throwing FAST.  
If you want to increase your bat speed, you have to practice swinging as fast as
possible with perfect mechanics.  Once we had an idea of where to start in regards
to percentages with the overload-underload, we began experimenting with players
of different ages and ability levels.  The goal was to find the ideal percentage to
weigh the bat in order to get optimal performance increases (improved bat speed).    

Today, many of the world’s top athletes use Overload Underload training to gain the
edge on their competition.  Elite sprinters and swimmers have been effectively
using a form of Overload Underload training to blow away world records.  The
sprinters and swimmers attach themselves to cords that either provide resistance
from behind or a slight tow from in front of them to create a pace that is slightly
slower or slightly faster than their personal best.  This has provided excellent
results and was recently used by soccer phenom Freddy Adu who trains at IMG
Academies, a training academy that has a history of improving the performance of
the world’s best athletes.

Many throwers from track and field continue to use the Overload Underload concept
with great results.   Even baseball, which has a history of lagging behind the times in
improving sports performance through science, is beginning to catch on.  Many
pitchers have been using Overload Underload training to drastically improve their
throwing velocity as well as strengthen their arms for the wear and tear of a
professional season.

For a more detailed article with more real world examples check

Over the years there have been numerous studies done to determine the effects of
Overload Underload training on performance and safety.  The majority of Overload
Underload training research has been done with throwing a baseball.  The research
has all come back with stellar results.  Not only did the players participating in the
program make significant gains in velocity, but they also stayed healthy for the
following season, a difficult accomplishment considering the stress that throwing a
baseball puts on the muscles, tendons, and ligaments of the arm.  The most notable
study on the use of Overload Underload training for bat speed improvement comes
from Coop DeRenne, one of the world's premier research leaders in terms of
Overload Underload training for baseball.  DeRenne and colleagues came to the
same conclusion as many of the world's top sports scientists which is:  Overload
Underload training is simply one of the simplest and most effective ways to make
significant performance improvements in a short amount of time.  Here is a list of
pertinent literature pertaining to Overload Underload training and its effectiveness
on increasing performance.  Note - the vast majority of these studies deal with
training for improved bat speed or throwing velocity through the use of overload,
underload, or a combination of overload and underload techniques.  This is by no
means an exhaustive list; there are many more studies out there relating to
Overload Underload training.

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.

DeRenne, Coop EdD; Szymanski, David J PhD, CSCS*D
Effects of Baseball Weighted Implement Training: A Brief Review.  Strength and
Conditioning Journal:  April 2009 - Volume 31 - Issue 2 - pp 30-37

Bagonzi JA. The Effects of Graded Weighted Baseballs, Free Weight Training, and
Simulative Isometric Exercise on Velocity of a Thrown Baseball [master's thesis].
Indiana University, Bloomington, IN, 1978.

Brose DE and Hanson DL. Effects of overload training on velocity and accuracy of
throwing. Res Q 38: 528-533, 1967.

DeRenne C. Increasing bat velocity. Athletic J 62: 28-31, 1982.

DeRenne C. The donut: Does it improve bat velocity? Strength Cond J 13: 43-45,

DeRenne C and Branco D. Overload or underload in your on-deck preparation?
Scholast Coach 55: 32: 69, 1986.

DeRenne C, Buxton BP, Hetzler RK, and Ho KW. Effects of under- and overweighted
implement training on pitching velocity. J Strength Cond Res 8: 247-250, 1994.

DeRenne C, Buxton BP, Hetzler RK, and Ho KW. Effects of weighted bat implement
training on bat swing velocity. J Strength Cond Res 9: 247-250, 1995.

DeRenne C, Ho KW, and Blitzblau A. Effects of weighted implement training on
throwing velocity. J Appl Sports Sci Res 4: 16-19, 1990.

DeRenne C, Ho KW, Hetzler RK, and Chai DX. Effects of warm-up with various
weighted implements on baseball bat swing velocity. J Appl Sports Sci Res 6: 214-
218, 1992.

DeRenne C and Okasaki E. Increasing bat velocity (Part 2). Athletic J 63: 54-55,

Egstrom GH, Logan GA, and Wallis EL. Acquisition of throwing skill involving
projectiles of varying weight. Res Q 31: 420-425, 1960.

Elias J. The Effect of Overload Training on Speed in Baseball Pitching [master's
thesis]. Springfield College, Springfield, MA, 1964.

Fleisig GS, Phillips R, Shatley A, Loftice J, Dun S, Drake S, Farris JW, and Andrews
JR. Kinematics and kinetics of youth baseball pitching with standard and
lightweight balls. Sports Eng 9: 155-163, 2006.

Jarver J. Varied resistance in power development. Mod Athlete Coach 10: 5-8, 1973.

Sergo C and Boatwright D. Training methods using various weighted bats and the
effects on bat velocity. J Strength Cond Res 7: 115-117, 1993.

Southard D and Groomer L. Warm-up with baseball bats of varying moments of
inertia: Effect on bat velocity and swing pattern. Res Q Exerc Sport 74: 270-276,

Szymanski DJ, DeRenne C, and Spaniol FJ. Contributing factors for increased bat
swing velocity: A brief review. J Strength Cond Res February 27, 2009 [epub Ahead
of Print].

Van Huss WD, Albrecht L, Nelson R, and Hagerman R. Effect of overload warm-up
on the velocity and accuracy of throwing. Res Q 33: 472-475, 1962.

Vasiliev LA. Use of different weight to develop specialized speed-strength. Sov
Sports Rev 18: 49-52, 1983.

If you are interested in finding out more about the scientific studies on overload
underload training, a simple search at will reveal a large
number of studies.  To obtain the full study (not just the abstract) you might have to
go to a local library.  It’s important to point out again that numerous teams as well
as players from a wide variety of sports have already used Overload Underload
training and made drastic improvements.  The purpose of these studies is to show
that science is in agreement with what players in the “real world” have known for
years:  Overload Underload training works.  I point this out because oftentimes
people will make extraordinary claims about products or ideas being the next
miracle cure.  However, these products/ideas often have no science behind them
and within a year or two people who purchased these “scam” products will find out
they don’t work and learn that they have lost out on a significant amount of money.   

Bottom line:  
Overload-Underload Training works.  Whether you are looking to
improve bat speed or throwing speed it's tough to make a case against all the
overwhelming evidence!
Looking for drills to improve bat speed?  Drills can be an effective method for
improving hitting mechanics which can potentially improve a player's bat speed

But what happens if a player already has sound mechanics?  The drills will fail to
improve bat speed and it will be time spend practicing with nothing to show.  

With the power development system there are NO DRILLS.  Just grab the bat and
swing it.  The weight of the bat combined with a program that regulates training
volume will do the rest.  Players, regardless of level and mechanical efficiency, can
see results.  Not convinced?  Check out the what the research has to say below.