Inertial tennis is an art of creating the best conditions for the optimal work of nature's laws
BASIC PHYSICAL PHENOMENA mass, velocity inertia, accelerations, conservation laws
BIOMECHANICAL STRUCTURE straight kinematic chain branched kinematic chains
TOTAL NUMBER OF JOINTS x (depends on technique) x + 1, varies in time
ENERGY PRODUCTION as much as you can as much as is needed (but no more!)
ENERGY LOSSES who cares? reduced to minimum
MAIN POWER SOURCE muscles concentration of energy in space and time
COHERENT THEORETICAL CORE does not exist unified theory of all strokes & movement
TYPES OF TECHNIQUES specific for any stroke universal
Simplicity and aesthetics Optimal timing close to human neurological limits
Powerful and effortless strokes Certain percentage of mishits is physically irremovable
Smart physics and biomechanics Significant changes in timing of strokes and movement
Effective masking of intentions Counterintuitive direction of strokes initiation
Well-defined types of strokes Relatively slow global progress in learning at early stages
Time and place for corrections No coaches (yet)
Coherent theoretical core for all strokes (no myths!) Lack of easily accessible sources of knowledge (yet)
Deep integration of strokes and movement Not falsified by a vast community of players and coaches (yet)
Efficient footwork
Low risk of serious injuries
Flexibility more important than athletic power
Some technical elements easy to learn at early stages
Rapid progress in learning at advanced stages
(numbers were chosen arbitrarly to visualize the most important processes and do not have a physical meaning)
beginner > > > > advanced
YOUR ENERGY PRODUCTION      dE      100 110 120 130 140 150
ENERGY LOSSES      -dE      -40 -40 -30 -30 -30 -30
TIME OF ENERGY RELEASE dt 10 10 9 9 8 8
P 6
P = dE ___ dt
TIME OF ENERGY RELEASE dt 10 9 8 6 4 2
ENERGY LOSSES -dE -40 -30 -30 -20 -20 -10
YOUR ENERGY PRODUCTION dE 100 90 80 70 60 50
27.02.2011 After three years of naive attempts, copying of Roger Federer forehand technique gave highly unsatisfactory results. Inspired by talks with physicists from the Institute of Physical Chemistry of the Polish Academy of Sciences, Faculty of Physics of the Warsaw University and National Centre for Nuclear Research (former IPJ), the author desides to adapt some ideas from laser optics to create own theory of tennis techniques.

The search for physical principles of the theory begins.
12.2012 A physical and biomechanical core of the new theory is ready.

It is unclear, whether or not it will be possible to transform this new theoretical structure into a set of useful tennis techniques.
19.02.2013 First (unsuccessful) attempts in biomechanical execution of the physical principles.
11.10.2014 For the first time, timing adapted to inertial techniques was used in groundstrokes during a session against a wall.
18.12.2014 First fully controlled integration of strokes and movement during an on-court game.
27.01.2015 An inertial topspin backhand, a quite new groundstroke technique, was successfully used during a wall session.

This day inertial tennis was transformed from a hypothesis into a real structure.
21.01.2016 An inertial serve technique was executed for the first time (no ball).
30.06.2016 First implementation of a final sequence of inertial topspin forehand (no ball).
01.12.2017 Invention of the inertial chalice grip.
17.12.2017 Inertial tennis techniques were presented to several world-class coaches and physicists.
03.03.2018 Starting date of the official website.


Jarek Chrostowski, Polish physicist, popularizer of natural and technical sciences (over 30 years of experience), author of several hundred popular science articles in national media, science journalist and editor promoting in Poland and around the world achievements of the leading Polish scientific institutions, such as the Faculty of Physics of the University of Warsaw, the Institute of Nuclear Physics of the Polish Academy of Sciences, the Institute of Physical Chemistry of the PAS, the Institute of Experimental Biology of the PAS and others. He has been playing tennis since he was a child, always as a self-taught amateur who has never participated in any tennis lessons. Inspired by creative conversations with other physicists, in 2011-12 he created the inertial theory of tennis and within the next five years transformed it into the first in history of the game internally coherent set of tennis techniques, based on the phenomenon of inertia and conservation laws.

In the history of tennis, inertial tennis is the first complete, internally coherent set of techniques of movement and strokes, created from scratch on solid scientific foundations. Each element of inertial techniques has been designed for the most optimal use of the fundamental properties of physical reality within the biomechanical framework of the human body. The core of the inertial techniques is embedded in the inertia (both physical and biomechanical in nature)1.

The inertial theory2 of tennis was created in 2011-13. Until 2017, the physical principles of the theory have been implemented in the biomechanical framework and then transformed into a set of tennis techniques. Its usefulness was verified by the author during his own tests on the court and by frame-by-frame comparisons of his recorded sequences with the techniques of the best modern ATP players3.

Scientific foundations

Individual elements of the human kinematic chain can be moved by muscles, but also without their activity, yielding to external forces - and thus inertially in a biomechanical sense. In the latter case, the movements can be significantly faster and more dynamic than those performed via the activation of muscles. This is why the inertial movements, performed with the least possible muscle activity, are the core of inertial tennis. Techniques constructed on their basis naturally reduce player's energy costs, often to a radical extent.

Power is the energy released over time. Modern tennis techniques aim to enlarge the power of strokes by increasing the amount of released energy, what requires significant activation of muscles and strenuous building of appropriate athletic fitness by the player. Inertial tennis was built on the assumption that in order to generate powerful strokes it is much better to use smaller amounts of energy, provided that this energy is concentrated in the smallest possible area of space, released in the shortest possible time, and its losses - that inevitably arise during the transfer of the conserved quantities (energy, momentum, and angular momentum) through the human kinematic chain - are reduced to a minimum. This approach is perfectly in line with the requirement to minimize the player's muscle activity.

In inertial tennis, conservation laws and the phenomenon of inertia are responsible for the concentration of the conserved quantities in space and time. In each stroke, the motion of the involved kinematic elements is so designed that it leads to the freezing of the kinematic chain along a specific direction. The inertia of moving elements straightens the kinematic chain. Consequently, more and more its subsequent elements stop. Because the conserved quantities generated in individual elements cannot be lost without a trace, during freezing they are transferred to the further, still moving elements. In the final phase of freezing, the last moving element accumulates the conserved quantities of all elements. This leads to a significant increase in velocity and a particularly rapid acceleration of the furthest element of the kinematic chain: the head of the racquet.

The specific properties of the mechanism of freezing allow the player to modify the position of the contact point of the ball with the racquet head until the last moment before the impact. As a result, it is possible to change the direction of ball flight after the stroke by up to several dozen degrees. This means that the intentions of the inertial tennis player are particularly hard to read for the opponent.

Taking use of the frozen kinematic chain - i.e. one in which the segment involved in the stroke straightens gradually - means that the optimal contact point is relatively far from the tennis player. In case of an incorrect perception of the ball motion path or flight time, the inertial tennis player has both the place and time to adjust his/her technique and in critical situations can even transform the inertial stroke into a classical one, performed with a significant involvement of muscles. Active, muscles-based techniques of strokes therefore remain part of inertial tennis. In this sense, inertial tennis is a generalization of modern tennis techniques (such as, for example, integer numbers are a generalization of natural numbers).

In inertial techniques of strokes, inertia not only forces the freezing of the kinematic chain and the transfer of the conserved quantities to the racquet head but also stabilizes its orientation in space.

An integral part of inertial tennis are techniques of body movement. Instead of running from point to point, every now and then accelerating and practically stopping the whole body, the inertial tennis player tries to stay in a continuous smooth motion. Redirecting his/her momentum with the relatively small involvement of muscles, he/she adapts the rhythm of his/her movements to the actions of the opponent. Energy costs, associated with these actions, are significantly reduced, which helps to relax the muscles involved in the techniques of strokes. The body overloading is also significantly smaller.

In inertial tennis, the techniques of movement are inextricably linked to the techniques of strokes: they allow for adjustments of the position of the contact point and stabilize in space the segments of the kinematic chain that are crucial for the strokes techniques, thus reducing energy losses and increasing efficiency of strokes.

The specific construction of modern tennis techniques forces players to continuously control almost every aspect of the stroke sequences. Meanwhile, the inertial tennis player focuses on the most precise stroke preparation. Once the initial conditions are carefully established, it is not the player but the fundamental laws of nature, operating for billions of years, that are responsible for the final shape of the stroke - and the player's body just succumbs to them.

The above situations can be compared to sledding downhill on natural slopes and inside a bobsleigh track. In both cases, the tobogganers will go downhill, but the ordinary tobogganer has to actively control every aspect of the ride, while the bobsleigh moves in an earlier laboriously constructed ice track, where the task is not to fight gravity but to surrender to it as fully as possible.

To sum up: the inertial tennis player does not fight against the physics of the Universe and the biomechanical limitations of his/her body, as is often the case during the training of modern techniques. On the contrary, he/she uses this physics and these limitations to obey the laws of nature to the maximum extent. In this sense, inertial tennis is an art of creating the best conditions for the optimal work of the laws of nature within the human body.

Tennis for everyone (but ambitious)

Inertial tennis is a set of techniques that are physically and biomechanically optimal. However, this does not automatically mean that it is the "best" or "ultimate" type of tennis. Like every human creation, inertial tennis has its advantages and disadvantages, it also requires time for learning (internal coherency, however, speeds up this process: mastering one element in one technique significantly accelerates the learning of other techniques).

Techniques of inertial tennis are strictly rational structures. Unlike techniques developed blindly during many years of training, they are not associated with any innate talent. It is pure knowledge and thus it can potentially be acquired by everyone. Not only by athletes but also by amateur enthusiasts (if they are able to bring themselves to regular and reasonable work)4.

The simplicity of inertial techniques and the shift of their main accents from the athletic preparation supported by many hours of on-court training to timing and muscle relaxation cause that exercises performed without a ball and (at more advanced stages) with hitting a ball against a wall play the key role in the learning process. In practice, this means that tennis players can effectively train outside the court. The frequency of exercises can be significantly increased, which improves the efficiency of learning and reduces the costs and time spent.

Inertial tennis - or its elements - can be useful for the whole spectrum of sport enthusiasts, from leading ATP players to amateurs. It should be particularly interesting for the latter group. Precise knowledge about particular inertial techniques, a description of possible errors and easy to verify physical and biomechanical fundamentals allow the ambitious amateur with a sufficient dose of self-denial to learn inertial techniques without the help of a coach and to raise many elements of playing to the level being today reserved exclusively for the world's most outstanding tennis players. The proof of the rightness of this thesis is the author of inertial tennis, who has never been trained by any coach.

Land of opportunities

The structure of inertial tennis differs significantly from modern tennis techniques. This fact generates many challenges for the players. Soon, tennis enthusiasts will be able to take them: both the theory and techniques will be presented in the book Inertial Tennis: The Sources of Internal Power and made available to the general public5.

People interested in scientific aspects of tennis could design experiments that would verify the physical and biomechanical foundations of the inertial theory. New teaching methodologies, suitable for adepts of different ages and sexes, with different amount of time devoted to studying, are waiting for development. It is necessary to verify how inertial techniques affect the bodies of tennis enthusiasts of all ages, especially on longer time scales. Experts responsible for athletic preparation will be able to develop sets of exercises taking into account the specificity of inertial tennis. Manufacturers of racquets and balls also have a lot of possibilities: parameters of current products should be reviewed and adapted to the needs of inertial tennis. This applies especially to children's tennis. Today, young tennis players play with very light racquets and balls that provoke the use of only muscle-active techniques and creating habits unfavorable from the point of view of inertial techniques.

Unexpectedly, even for its author, inertial tennis turned out to be not a tiny island on the ocean of possibilities, but a quite new continent, totally unknown so far. A great land that is waiting patiently for its pioneers.

You may be one of them.

1 Biomechanical inertia - i.e. movements of limbs performed without muscle activation - should be distinguished from physical inertia, i.e. motions without accelerations. Biomechanically inertial movements of limbs always involve accelerations. In the physical sense, these movements can not be considered as inertial.

2 Inertial theory of tennis is not a mathematical structure. Derived from a few simple postulates, it is a set of causal sequences between well-documented physical and biomechanical facts.

3 Today, many elements of inertial techniques can be found in Roger Federer tennis - and only there. Given the way inertial tennis was created (from a rationally constructed theory, derived from physical and biomechanical foundations, to the real on-court techniques which have been falsified by comparison with the techniques of modern ATP players) it seems reasonable to say that Roger Federer tennis is technically so unique because of the large number of intuitively implemented inertial techniques. In other words, it is not inertial tennis that is a better or worse copy of Roger Federer techniques, but Roger Federer is the first professional tennis player on a large scale using self-developed inertial techniques (but he is not a complete inertial tennis player!).

4 This does not mean that every inertial tennis player will automatically play as good as Roger Federer. The knowledge about the theory is one thing, the ability to execute the techniques is another, and to control them to the extent that they can be successfully used in real matches is yet another. Neither will inertial techniques guarantee proper mental resilience, motivation or financial support necessary for tournament competition. However, it can be assumed that many tennis players - including amateurs! - will be able to master inertial techniques, raising their skills to a level previously considered to be inaccessible.

5 Once the book has been published, inertial tennis - the theory and the set of techniques - will be available to everyone, also for commercial use, provided that any further developments of its ideas will also be made available free to other tennis enthusiasts.