Force Reduction on Tennis Court Surfaces

NGI Sports specializes in surfaces that provide optimum playability and cushioning properties. At NGI Sports material science is becoming one of the largest areas for innovation in tennis surface engineering and technology. Force reduction through cushioning and shock attenuation is not only an important property of a tennis court surface, it is also considered a key indicator of the performance, safety, comfort, and suitability of the surface for play.

A tennis player’s lower body is subject great stress and abuse through movements that create different forces on the lower extremities. Rapid stopping or foot planting creates some of the highest forces in tennis. There are frequent center of gravity adjustments where the body's center of gravity needs to be adjusted in any direction quickly and in a controlled manner, the direction of the forces placed on the foot and leg are forward, backwards, vertical as well as lateral. The body encounters more than just its own weight worth of forces from the energy returned from the tennis court. The surface therefore is important in reducing the impact of those forces to your lower leg and back.

As a designer and manufacturer of tennis court surfaces we use impact tests to measure and evaluate the effects surfacing design and surface design changes have on the impact forces generated on the body from the surface.

Testing results assist owners and players in making an informed, efficient, and empirical decision concerning a replacement tennis surface and for decisions regarding new surface selection. Puhulla et al (1999) defines hardness as “the ability of the surface to absorb shock imparted by the colliding object”. The most promising piece of equipment to measure surface hardness in the field is the Clegg Impact Hammer ®. This apparatus is an accelerometer device that relates to the deceleration of a falling weight on impact (Sifers and Beard, 1992; Neylan et al 1998).

We have conducted impact tests on numerous court surfaces. The impact forces simulated in the test method are intended to represent those produced by the lower extremities of a tennis player during play and impact on the tennis court. The Clegg machine fitted with electronic sensing instrumentation. Results are expressed in G Max values from 100 to 500. Benchmark figures for our use were based on concrete, asphalt and clay pavements.

In most cases clay (fast-dry) court play on courts two (2) to six (6) years old is thought to provide for a very comfortable and forgiving surface. Of course, the slide or foot release factor is not considered in this test. Results are based on an average of numerous sites tested with varying site conditions. Note that a larger numerical value reported represents less force reduction, a surface harder on the body.

Post Tension Concrete color only 732
Concrete slab tennis court with filler coats & acrylic color 495.1
Asphalt tennis court with acrylic color 334.3
Fast-Dry tennis court (4 yrs old) 244.6
Fast-Dry tennis court (8+ yrs old) 327
ProBounce all weather surface 245.3 (over cracked asphalt, 8 years old)
ProClay Tennis Court Surface 181.1 (over crushed stone base, 6 years old)
ProCourt XP (Granule In-filled Synthetic Turf Court) 132.4 (over cracked asphalt, 6months old)
ProXtreme (Urethane Cushioned Court) 249.5 (over cracked asphalt, 1 year old)
TitanTrax Shield with DecoTurf Cushion 292.1 (over concrete slab)

NOVA’PRO SURFACE PERCENTAGE OF GREATER FORCE REDUCTION FOR NGI SPORTS' SURFACE AS COMPARED TO CONCRETE
  CONCRETE ASPHALT FAST-DRY
PROBOUNCE 50% 27% 0%
PROCOURT 73% 60% 46%
PROCLAY 63% 46% 26%
XTREME 50% 48% 30%
THE NUMBERS INDICATE THE % IMPROVEMENT IN FORCE REDUCTION OF THE NOVA’PRO SURFACE AS COMPARED TO THE COURT SURFACE

These tests indicate a significant decrease in stress or advantage in force reduction for the NGI Surfaces. This appears true in all cases when compared to tennis courts built with hard pavement; thin cushioned finishes and as good as or better than clay courts in good condition.

We are continuing this study to build a database that compares the most prevalent courts in use today.