Feature Presentation

I had the great pleasure of interviewing Professor Howard Brody, physicist, educator and tennis scientist extraordinary. Among his many accomplishments he has written over 75 technical papers on tennis, appeared on television many times from the children's science show, "Newton's Apple" and Australia's "Beyond 2000" to the physics of football trajectories for the National Football League. He is featured on an instructional video with Vic Braden called "Science and Myths of Tennis" and was even recently interviewed by Time magazine regarding his work in tennis racquet science. A tennis player for almost 60 years, the author of "Tennis Science for Tennis Players" talked with us about tennis physics - what's known today and what he envisions for the future.

We asked Howard to start "from the beginning" and tell us about himself and how he became interested in science and involved in tennis science.

"I grew up in Newark, New Jersey. Even as a young boy, I loved building things. I had erector sets, Lincoln Logs, chemistry sets. I really enjoyed electric trains and learned a lot about electricity that way. I think you learn all the basics of electricity by hooking electric trains up and making everything work together."

Professor Brody attended the Massachusetts Institute of Technology (MIT) and earned an SB in physics in 1954 and a Ph.D. from the California Institute of Technology (Cal Tech) in High Energy Physics in 1959. He has been on the faculty of the University of Pennsylvania since 1959.

"It was interesting the way I became involved in physics and then tennis science. I couldn't have been more than 10 or 12 years old at the time. My uncle came back from the war and he had small "pocketbooks" that he gave to me. One of them was called "Atoms in Action" by George Russell Harrison. And I was just fascinated with this book and that was when I first thought that I wanted to become a physicist when I grew up."

The story has another unique twist to it though. "When I later attended MIT the dean of science was named George Russell Harrison and he ran one of the science labs. I was really excited when I realized it was the same person and told him the story about reading his book when I was a boy and how it had inspired me to become a physicist. I think it made him feel very good to know that his book had encouraged someone to become a physicist."

"When I first moved to Penn, I could actually see the tennis courts from my office. One day about 20 years ago I noticed an oversized racket. I asked several teaching pros about it and they could not give me any answers about it. Why is it better? So I decided to find out for myself. I got a copy of the US Patent, wrote to Howard Head (the racket's inventor), and did some simple experiments in my lab. Then, I published a technical paper on tennis rackets in the American Journal of Physics. The response was so encouraging, that I slowly shifted my line of research from high energy, elementary particle physics to sports (tennis) physics."

We asked the professor - exactly what is physics, what is tennis science and how does one relate to the other? "Physics is the study of forces and matter. What are the basic forces of nature? What are the basic constituents of matter? How do the forces and matter interact?"

"Tennis science is the application of the laws of physics to the game of tennis. For example, what happens when the ball interacts with the racket or the ball interacts with the court; what effects the trajectory of the ball through the air; how the various parameters of the racket such as mass, length, mass distribution, width, stiffness, head size, string tension, influence how the racket "plays"."

Is there an overlap in physics and biomechanics? "Yes", he told us. "While physics usually studies inanimate objects, biomechanics applies the basic laws of physics (Newtonian mechanics) to the human body and its motions. Therefore, to study biomechanics, you must have an understanding of physics"

What type of work and projects does a tennis sport scientist conduct? Prof. Brody is a member of the Technical Committee and the Sports Science Committee of the USTA, a member of the International Tennis Federation's Technical Committee, and the science advisor for the USPTR.

"The USPTR is an organization of tennis (teaching) professionals devoted to improving the game. I am their science advisor. I lecture, write articles and answer questions for them concerning science and tennis."

"The members of the USTA Sport Science Committee deal with various technical, scientific and biomechanical questions that allow us to aid the USTA in the growth of the game of tennis. Their goal is to help players - from beginner to the elite - to play better, longer and with less injury. Members of the committee include: physicians, biomechanists, biochemist, physicist, sports psychologist, the medical physician from the US Open, orthopedic surgeons, and specialists in exercise, flexibility, nutrition, and even hydration. The USTA Technical Committee deals with the equipment such as court surfaces and net tension."

"The International Tennis Federation is the ruling body of all of tennis. The Technical Committee looks at rackets, stringing, balls, courts and tries to maintain the basic character of the game of tennis."

The professor shared some interesting insights with us. "One of the ITF's functions is to determine if an equipment invention violates the rules. The ITF can also originate rules. The ITF is now taking a very proactive position in equipment evaluation. For example, believe it or not there are no rules that say a tennis ball must be perfectly round. The ITF is automating the ball testing to determine standards for stiffness and bounce direction. There are rules that say that a ball must rebound a certain height, but not in a certain direction!"

"For court surfaces, the ITF is developing methods for measuring friction, traction, how level a court is and developing criteria for lighting. The only rules about a tennis court are its dimensions. It need NOT be level, flat, uniform, smooth, even, etc. to be a legal tennis court. Tennis, as we know it today, was originally played on grass (lawn tennis) and as it spread, various other surfaces were used (wood, cement, asphalt, clay, cow dung, dirt, canvas, carpets). Some surfaces are "fast" (grass and wood) while some surfaces are "slow" (clay). You must modify the way you play tennis to take into account the surface and its properties."

"At present, there is a worry in tennis that the rackets are getting too powerful and this will destroy the game as we know it. The present rules of tennis place no restrictions on racket power - only dimensions of the frame. The ITF is studying whether power rules for the racket can be formulated to control the game of tennis. We are also proposing a larger ball on fast courts to slow the game down due to greater air resistance."

We were curious and asked the professor to tell us what prompted him to write Tennis Science for Tennis Players? "I had written several very technical articles on tennis", he said, "and I had learned a great deal more - much of which was not appropriate for technical journals. I took off 6 months and wrote the book in an attempt to explain the science of tennis to non-scientist tennis players."

"What are the biggest changes in the game that you have witnessed since you've been working in the field?", we asked. "The biggest change in the game has been the size of the racket/racket head and the material (graphite reinforce composite) that rackets are made of. This has allowed players to change their style of play to a more aggressive, open style."

"Although a knowledge of tennis science is not necessary to be a good player, the findings of tennis science have been incorporated into the instructions that tennis players receive from coaches, tennis pros, teachers, and the literature of tennis. Players are using the science findings without knowing that they are doing so. Tennis like a lot of sports is "trial and error" - an accumulation of knowledge of what works, what doesn't work and adapting."

We asked, "What one piece of information do you feel tennis coaches and trainers should be aware of?" The surprising answer was: "The tightness of your grip on the rackets has almost no effect on the resulting trajectory of the ball. You only hold onto the handle with enough force to allow you to get the racket where you want it, when you want it there and with the speed you desire."

"In this regard, one of my favorite results was showing that a tennis racket had almost the same vibrational characteristics when free or when hand held - and very different from the results when the handle was clamped. This means that a hand held racket can be modeled by a free racket as opposed to a clamped frame."

What is the most common tennis science/physics error you believe players at all levels make? "Most people think that a shot down the line is more difficult than cross court because the net is higher there. It turns out that since the cross court shot must go further to reach the net, the minimum angle needed to clear the net is the same both ways. It is the depth of court that gives the cross court its advantage over down-the-line."

How to you use physics to test, for example, a tennis racket? "By measuring the physical properties of tennis rackets and balls, and applying the laws of physics, one should be able to predict the performance of that racket in actual play. I measure the weight (mass) and mass distribution of a racket, its flexibility, its rotational properties (moments of inertia), the string plane deformation (tension) and get information about the "sweet spots" of a racket (where it feels good when you hit the ball). I also determine the power (ball speed off of the racket) of a racket, the ease of swinging a racket and the maneuverability of a racket. I also correlate the lab testing of a racket with how that racket will play on the court."

Have the questions studied in tennis science changed over the years? Or is it the same questions with different manufacturers' products? "Anything that can be explained through physics is known. Sweet spots, what happens when a racket is made longer or wider - we understand all these things now."

"There are two major areas for investigation in my opinion. First, biomechanics. What causes tennis elbow and its cure is still an open unanswered question in biomechanics. The human body is so complicated to study. So many things go on at the same time. Second, material science. There have been a lot of different damping devises to attempt to minimize vibration. None have solved the problem. What is needed is a material that will damp the racket itself."

We asked Howard what he plans to do when he retires this coming January. "When I "retire" I will still be doing exactly what I do now - only not teaching classes. I will probably be at my desk and computer most days."

Finally, how does Professor Brody see the game of tennis changing in the next 5-10 years. "I hope in 5 to 10 years tennis is essentially what it is today - the basic nature of the game not changing due to technology."

The Aerodynamics in Sports team would like to thank Professor Brody for this interview and his assistance during our project.