Retired Racehorses

which are more closely based on the biomechanical motion of interest are considered not simply a
measure which is convenient to perform like the Clegg hammer (Barry and Milburn 2000 and Cawley et
al. 2003).
Dynamic Penetrometer
The most widely used tool for the characterizing of racing surfaces is the dynamic penetrometer.
This device is made by Gill Engineering in Australia among other companies. Unlike the blunt weight of
the Clegg hammer, this device penetrates the surface with a sharp tapered tool which measures the
penetration resistance of the surface. The dynamic penetrometer has been used primarily in areas
where turf racing overwhelmingly predominates. This is because this type of device presupposes that to
the depth of penetration the surface is essentially homogeneous. The strong layering you see in any
type of dirt or most synthetic surfaces will mean that the characteristics of recent maintenance will
control the depth of penetration. However, for these types of homogeneous surfaces which exist for the
turf health as well as part of the surface design, this is a well established tool which is supported in the
literature (Murphy et al. 1996). However, it is necessary to correct these measurements for soil type and
moisture in order to create useful data which will help to provide an understanding of the performance
of a horse on a surface. Modeling of the surface interaction of the penetrometer makes it possible to
create a general rating of turf conditions which can be compared between locations (Thomas et al.
1996).
The primary limitations to the dynamic penetrometer are the inability to deal effectively with a
layered surface such as most dirt and synthetic racing surfaces. Little discussion has also occurred
regarding the applicability of the tool to some warm weather grasses which can create a layered root
zone. The existence of a horizontal root system and perhaps even the existence of reinforcing fibers or
grids in the surface can result in erroneous and highly variable readings from the penetrometer. In
general, the characteristic length of any of the constituent materials in the surface should be several
times smaller than the measurement device. For example, turf grids which are of the same size as the
penetrating probe of the penetrometer will result in a measurement of the existence or absence of a
turf grid under the probe, not a measurement of the strength of the soil. However, recognizing the
limitations of the measurement and assuming proper calibration of the penetrometer to the soil type,
along with simultaneous measurement of moisture, the dynamic penetrometer is a good tool for in‐situ
measurement of turf surfaces and one of the few methods with solid support in the published literature.
Automation of the penetrometer data acquisition to eliminate the operator judgment currently required
and linking of the data to GPS coordinates would provide a very promising tool for characterizing turf
racing surfaces.
Agricultural Penetrometer
In North America, the term penetrometer is generally used to refer to a pointed probe which is
pressed into the soil while the penetration force is measured. For agricultural applications this is an
important measurement since crop yield is related to the compaction of the soil in the root zone and the
profile of the soil compaction can be measured. Depending on the crop to be grown in a soil, the
allowable compaction or penetration resistance at a depth may be well characterized. Because the
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