One of the more complex tests performed on a sports surface is the measurement of shock absorption and deformation. The measurements made with an Advanced Artificial Athlete (AAA) attempt to characterise the responses between athlete/surface interaction during a run, stop or cut.

The complex biomechanics involved whenever a foot, ankle, knee, and hip engage at contact is simplified in a machine by normalising the plane of travel into a metal leg that incorporates a spring to simulate the body’s ability to absorb impact. This device is then connected to an accelerometer to collect the Max G on impact.

A version of this equipment, in one form or another, has been used to assess a wide variety of sports surfaces since 1972. For several decades, the data generated from these devices has influenced the development of sports surfaces,  on everything from athletics tracks to artificial pitches. Global governing bodies use the results the device generates to regulate the performance of sports surfaces and, in particular, artificial pitches.

Biomechanical Interactions of Athletes

The interaction between an athlete and a surface varies significantly depending on how fast the athlete is moving, whether they are cutting to make a turn, or simply running and passing a ball. At a basic level, this interaction can be simplified into two phases. The Stance Phase is where the foot is in contact with the ground and the Swing Phase is when the foot is not touching a surface. In the Stance Phase, the heel is normally the first part of the foot to make contact with the ground, followed by the midfoot, and then the ball of the foot followed by pushing off with the toes. This rolling motion from heel to toe means that each part of the foot is only in contact with the ground for a fraction of a second and at varying angles of contact.

AAA - Simplified Model

The Advanced Artificial Athlete is used to measure several surface qualities, namely shock absorption, energy restitution, and deformation.  The mechanics of the equipment can be understood as a simple spring-mass system. A mass attached to a spring is dropped, makes contact with the ground, and rebounds. Calculations such as energy restitution and deformation can be made by knowing the mass, initial drop height, rebound height, ground contact time, initial speed, and rebound speed of the spring-mass system shock.

Results Generated by AAA

The AAA provides useful measurements of shock absorption, deformation, and energy restitution. Currently, no other portable device provides this level of feedback from a surface. Some research tools can but they are not portable and are often operated by academia, making them inaccessible as a routine testing tool. The device measures properties we understand as engineers which allows us to feedback to manufacturers of sports floor and turf systems and coaches/athletes on how to tailor the surface to their requirements. This is not an exact science with this devices at this time, but it is possible to do this.

AAA Issues

There is an ongoing discussion that raises a concern that the AAA does not precisely simulate human interaction with a surface, and the point is well made. However, because the AAA has been in use for many years, a great deal of knowledge has been gained from its use as a reliable tool for measuring the performance of a surface. Based on an empirical approach, surfaces regulated by the AAA are not fundamentally unsuitable for athletes, but rather comparisons with the best natural fields suggest that this tool regulates surfaces about right for athletes. Improving the analysis of the surface needs not only improved testing protocols but we need to include player feedback and the comparison of the feedback to testing data to make the next leap in making artificial turf acceptable to elite athletes.

Benefits of the AAA

It is reasonably quick-to-use, provides easy-to-understand results, is well understood by Labs, NGB’s, manufacturers and suppliers, and it is a good differentiator of soft and hard surfaces. Additionally, it is versatile and used by many Governing Bodies in their standards.

Demerits

It is not easy to transport and it does not collect biomechanically correct data. The method also involves dropping the device three times on the same spot, which is different from an athlete's/surface interaction.

I give it an 8/10

While not perfect, the AAA plays a significant role in sports surface assessments and it will take some time before it can be replaced. With some modifications to the methodology employed, the device can be given a new life providing meaningful data to engineers, manufacturers and coaches/athletes.