A COMPARISON OF SHOCK ABSORBENCY BETWEEN NATURAL AND LONG PILE ARTIFICIAL TURF
1Hiroyuki Nunome, 2 Koichiro Inoue and 1 Yasuo Ikegami
Research Centre of Health, Physical Fitness and Sports, Nagoya Univ., Japan
2Graduate School of Education and Human Development, Nagoya Univ., Japanemail: nuome@htc.nagoya-u.ac.jp
1

SUMMARY
To compensate inadequacies of the standard test (DIN180322) for evaluating the shock absorbency of long pile artificial
turf (3-g turf), we proposed a new testing procedure which
precisely reproduces acute, high loading likely caused byhuman sports action. The present study was designed tocompare the shock absorbency of 3-g turf with that of natural
turf using the new testing procedure. As the acceleration
change of the impact head precisely reflects the loading force(R2 =.990), the shock absorbency of natural turf was measured
from the surface in the field. This nature was compared withthose of 3-g turfs with different infills: sand, rubbers (large,medium and small grain) and sand/rubber, and with
underneath shock pads (rubber/urethane combined andpolythene foamed). In contrast to our conventional
understanding, most types of 3-g turf showed smaller peakacceleration and milder jerk than those of the natural turf.
Moreover, a 3-g turf with unusual infill component withrubber/urethane shock pad demonstrated a quite similar jerk
with that of natural turf. This result may reinforce the needs
for reconsideration of appropriate shock absorbency for 3-gturf.

The present study was designed to compare the shock
absorbency of 3-g turf with that of natural turf using the newtesting procedure.

INTRODUCTION
Use of artificial turf is becoming very common for sports thatare usually played on natural lawn, in particular for footballcodes (Soccer and Rugby). After alternations of artificial turf
generation, it seems that 3-g turf actualized more “naturalturf” like appearance and properties, such as: ball-surface andshoes-surface interaction. Major soccer (FIFA and UEFA)and rugby organizations (IRB) recently accepted the use of the3-g turf for official and international tournaments.
In contrast to the report for the earlier generation of artificial
turf, cohort studies [5,7,8] reported no clear differences forinjury risk of between 3-g turf and natural turf. However, there
still exists an indistinct anxiety among coaches and playersthat some mechanical characteristics of artificial sports
surfaces may link acute or chronic sports injuries. Soccer
players still had negative overall impression and felt greater
physical efforts when they play on 3-g turf [1].
Of various aspects, the cushioning ability is a key feature. To
date, “Shock Absorbency” of the 3-g turf has been approvedby a simple mechanical testing (DIN18032-2). However, it
has been suggested that the current, conventional testingprocedure does not reflect actual loading action occurring insports movements [3,4,10]. To compensate these inadequacies,
a new testing procedure has been proposed [11].

Acceleration (g)METHODS
Several types of 3-g turf tray with different infill components:
sand, rubbers (large, medium and small grain) and sand/rubber,and with underneath shock pads (rubber/urethane combined
and polythene foamed) were prepared. Each tray was designed
to have the same infill depth (35 mm).
To measure the shock absorbency of natural turf from thesurface, an accelerometer was attached to the impact head of
the testing rig, and an attempt was made to examine howmuch the acceleration change precisely reflects the loading
force measured from the bottom of the tray using force
platform. The acceleration change were precisely reflects thechange of the loading force (R2 = 0.990) (Figure 1). After theverification of linearity between the changes of accelerationand loading force the shock absorbing property of natural turf
and 3-g turfs were measured in the field where a professionalsoccer team regularly use for training..

R2 = 0.990

Force (N)Figure 1: Linearity verification of between the changes ofacceleration and loading force during testing.

Acceleration (g)(a)

Acceleration (g)Natural turf
3-g with sand3-g with sand/rubber
3-g with rubber
3-g new type3-g with sand/rubber 2Time (ms)(b)

Time (ms)Figure 2: Changes (±SD) in accelaration of natural turf and 3-g turfs. Panel (a) shows the changes
without underneath rubber/urethane shock pad and panel (b) shows the changes with the shouck pad.
RESULTS AND DISCUSSION
The average (±SD) changes of acceleration measured fromthe surface of natural and 3-g turf were shown in Figure 2. It
can be seen that most types of 3-g turfs except for the one withsand infill, demonstrated milder rate of acceleration (jerk)
during loading (Figure 2, panel a). The peak acceleration
become even smaller when underneath rubber shock pad was
installed (Figure 2, panel b). A 3-g turf with unusual infill
component (sand only) with rubber shock pad demonstrated
quite similar jerk with that of natural turf.
It can be assumed that most types of 3-g turf have excessive
shock attenuation property than that of natural turf in contrast
to our conventional understanding. This property likely
induces larger energy absorption when soccer specific actions
such as running, stopping and jumping were done on thesurface. This may explain why soccer players are demanded
greater physical efforts when they play on 3-g turf [1].
CONCLUSION
The present study clarified that most types of 3-g turf haveexcessive shock attenuation property than that of natural turf.
This result may reinforce the needs for reconsideration ofappropriate shock absorbency for 3-g turf.

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