The Production Of Tennis Strokes: What’s Changed, What Hasn’t and Why?

Sound tennis strokes are produced by a balanced and synchronized combination of angular and linear forces because we strike a ball by moving  in coordinated arcs that produce straight paths.

The underlying  physics are: Rotational inertia of the racket (moment of inertia ) leads to centrifugal force which then moves the racquet linearly at a tangent to this rotation.

When We Swing, The Racquet Slings

While it’s true that athletes are bigger stronger and faster today,  the fundamental principles of physics have not changed since tennis was first played. What has changed is how we utilize the swing  using slingshot physics to play better. Physics has not changed, bio-mechanics has not changed; technology has changed.

The players of the pre-tennis technology revolution seemed to be more rigid and less segmented. Their movements had a greater linear component than what we see today. The players of the post-tennis technology revolution seem to rotate in greater separated segments. While I can’t dismiss the idea that these changes were primarily the result of a shift in coaching philosophy that just coincidently were parallel to these technique changes, it seems counter to the traditionalist philosophy that permeates tennis instruction even today.

I propose a hypothesis that uses the fewest assumptions as well as the greatest congruence to explain the revolution in tennis technique. Such changes were directly driven by changes in equipment. This is seen in these most significant areas:

The first change is that racquets today are lighter.

In physics this matters because lighter objects with less mass have less resistance to linear acceleration. So with a lighter racquet we can rotate our bodies and racquet with greater velocity to produce greater centrifugal acceleration which moves at a linear tangent to our rotation. With a lighter racquet, we can swing faster and sling truer.

The second change is the stiffness or restitution frequency of both racquets and strings

Synthetic materials used in modern equipment not only CAN be managed to swing faster, we NEED to swing faster to optimize the potential of the equipment we use. Think of a thick, rubber band. It has greater elastic potential, but it requires greater energy to stretch to its full elastic potential. So older, flexible racquets strung with less elastic strings, transfer forces at a lower frequency and in a less linear path especially when moved at high speeds just as old heavy rickety cars rattle and sway when driven fast. Heavy racquets like heavy cars without power steering are also more difficult to move and control at high velocities.

Force equals mass times acceleration. So a heavy racquet can create equal force at a slower velocity than a lighter racquet. Heavy flexible racquets with less elastic strings demand a slower swing velocity to match its lower restitution frequency. Further unless we have a great degree of strength we will likely want  to be less elastically segmented when we swing a heavier object.

Lighter, stiffer racquets with more elastic strings demand a faster swing velocity and require less strength/stability body management demands so we can relax and time our movements to segment more separated.

With equipment that transfers energy at a higher coefficient of restitution or vibration resonance we not only can swing  faster, we need to swing faster to optimize.

The handle and grip of a racket has changed

Old racquet handles were hard and slippery. They didn’t conform to our hands the way racquets of today do. You had to grip them firmly, very firmly. It’s easier to hold a fuzzy, pliable tennis ball than it is to hold a smooth, cast iron ball that weighs more. A tight grip results in a more rigid arm leading to less body relaxation and segmentation. This results in less manageable movement speed, and even less variation in grips (try holding a more western grip very tightly and see how well that works?)

A Tight Grip Results In A Rigid, Slower Movement

We have always used elasticity, rotation and sequencing in a sling like pulling action to propel the racquet. Athletes have evolved but technology has revolutionized which has transfigured many of the techniques we use today to swing the racquet.