Flexible Studs in Prevention of Football Injuries

A Preliminary Laboratory Study

Andrea Ferretti

, Carlo Mapelli

, Silvia Barella

, Andrea Gruttadauria

, Davide Mombelli

Andrea Francesco Ciuffini

, Cosma Calderaro

and Daniele Mazza

Orthopaedic Unit, Sant’Andrea University Hospital, Rome, Italy

Department of Mechanics, Politecnico, Milan, Italy

Keywords: Football, Injuries, Prevention, Sports Equipment, Shoes, Studs.

1 INTRODUCTION

Lower limb injuries in football players can occur as

a result of shock and impulsive stresses that can

damage their organic tissues.

Despite increasing interest toward injury

prevention little attention has been drawn to athletes

equipment such as boots and studs, whose role in

players performance and safety has been considered

crucial.

The spikes and the sole of a shoe represent the

interface between the body of an athlete and the soil

and on this interface the applied forces and their

reactions are concentrated. The choice of a correct

stiffness of the spikes and of the sole allows the

dissipation of the energy involved in the motion

performed by the athletes. The spikes or the sole of a

shoes can be realized as a composite system, where

material featured by different mechanical

characteristics are coupled to assure a correct

mechanical reliability and stability and to realize the

dissipation of the energy. Such composite systems

have allowed the realization of spikes and sole

whose mechanical features have been tested by

instrumented machines in experimental laboratories

in order to point out mechanical stability and attitude

to energy dissipation possibly preserving athlete’s

health.

The purpose of this paper is to present

preliminary results of laboratory tests performed on

a new type of flexible studs designed to reduce risk

of injuries in football and other outdoor sports

(American football, rugby, field hockey etc.).

2 MATERIALS AND METHOD

The performances of the system designed and built

for absorbing the energy associated to the impact of

the athlete with the soil has been investigated by

laboratory equipment that allows a control and

systematic repeating of the loading cycle. The

energy absorption of a traditional shoe equipped by

a traditional sole and by a rigid aluminium spike has

been used as a reference condition. A tensile

machine has been modified in order to simulate the

most frequent loading mode of the shoe sole and of

the spikes imposed by the athlete motion. An

universal traction/compression machine (MTS

Alliance RF/150) equipped with dedicated devices

built to allow vertical and oblique compression

forces was used (see figures 1 and 2).

Figure 1. Figure 2.

Vertical and oblique forces were applied to either

hindfoot and barefoot (figure 3 and 4) A 2 KN

compression force has been applied at a speed of

10mm/min.

Ferretti, A., Mapelli, C., Barella, S., Gruttadauria, A., Mombelli, D., Ciufﬁni, A., Calderaro, C. and Mazza, D..

Flexible Studs in Prevention of Football Injuries - A Preliminary Laboratory Study.

Figure 3.

Figure 4.

The deformation of the inner side of the football

shoe in the two main direction (longitudinal and

transverse) has been measured by the application of

four extensometers (HBM 1-xy18-3/350) attached

on the inner side of the sole (figure 5).

Figure 5.

The sole deformation has been measured as a

function of the load and of the overall displacement

imposed by the tensile machine. After the definition

of such a reference condition, high deformable

(flexible) energy absorbing spikes mounted on a

traditional sole were tested using the same protocol.

Five set of tests were performed on shoes equipped

with both standard (aluminium) and flexible suds.

Statistical analysis was performed with a student t-

test; statistical significance was set with p<0.05.

3 RESULTS

Flexible studs significantly reduced stress and

deformation in all the performed tests and of the

inner sole as revealed by data collected by

extensometers in both directions (longitudinal and

transverse) (see tables 1,2,3).

Table 1: Mean sole deformation as a result of a vertical

load applied to the hindfoot (p<0.05).

Al 2kN

[mm/mm]

Saspik 2kN

[mm/mm]

1 Hindfoot Longitudinal 491 (11) 281 (17)

2 Hindfoot Trasversal 365 (13) -216 (13)

3 Barefoot Longitudinal 886 (19) 89 (5)

4 Barefoot Trasversal 237 (7) 218 (7)

Table 2: Mean sole deformation as a result of a vertical

load applied to the barefoot (p<0.05).

Al 2kN

[mm/mm]

Saspik 2kN

[mm/mm]

1 Hindfoot Longitudinal 255 (8) -78 (2)

2 Hindfoot Trasversal 302 (12) -17 (2)

3 Barefoot Longitudinal 198 (4) 41 (4)

4 Barefoot Trasversal 821 (6) 395 (12)

Table 3: Mean sole deformation as a result of an oblique

load applied to the hindfoot (p<0.05).

Al 2kN

[mm/mm]

Saspik 2kN

[mm/mm]

1 Hindfoot Longitudinal 608 (21) 262 (9)

2 Hindfoot Trasversal 1244 (45) 120 (9)

3 Barefoot Longitudinal 2250 (39) 480 (15)

4 Barefoot Trasversal 414 (25) 242 (15)

4 CONCLUSIONS

On the basis of these preliminary laboratory data, use of

flexible studs could result in a significant reduction of

stress absorbed by athletes during sports activity, possibly

reducing actual rate and severity of football and other

outdoor sports injuries.

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E.M. Henning. 2011. The influence of soccer shoe design

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H. Liebeskind. 2011. The biodynamics of soccer and

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C. Mapelli. 2012. Progettazione e prove meccaniche su

tacchetti compositi per il gioco del calcio. Tesi,

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