Week 4: Mechanincal and Biomechanics Testing of Surfaces

Question 1

Why might artificial surfaces be used in sport? (Nigg and Yeadon 1987)

Answer 1

1. Reduced maintenance costs
2. Reduced influence of adverse weather conditions of performance = increases playing opportunity throughout the year
3. Provides surface consistency and durability

Question 2

What factors have linked artificial surfaces with increased risk of injury?

Answer 2

Increased impact and altered kinematics

Question 3

What are the characteristics of an Area Elastic Surface?

Answer 3

high bending strength and an area larger than the contact area of the object deforms and distributed the force of the impacting object.

Question 4

What are the characteristics of a Point Elastic Surface?

Answer 4

Deforms under the contact area of the impacting object with only slight deformity surrounding the local force.

Question 5

What is a benefit of Mechanical testing of sports surfaces?

Answer 5

Can test and compare the impact or force reduction properties of a surface

Question 6

Give two examples of mechanical testing apparatus:

Answer 6

1. The Artificial Athlete Stuttgard
   reflects the ground contact time of the running foot-strike which is relevant in many sports. it also mimics the active phase of running
2. The Artificial Athlete Berlin
   A modification of the AAS to simulate impact forces. AAB provides a measure of force reduction (%) in comparison to a baseline surface.

Question 7

What are the aims and results of the Dixon and Stiles (2003) running on Tennis Surface study.

Answer 7

The study aimed to investigate the relative role of typical shoes and surfaces to provide cushioning during running.

Mechanical tests found significant differences between surfaces used in the tests

Biomechanical tests found no significant differences in peak impact force

Question 8

What are the disadvantages of mechanical testing in biomechanics?

Answer 8

There is no consideration for subject-surface interaction.

There is no consideration for kinematic adaptation or altered joint stiffness

Question 9

Outline the results of the Stiles and Dixon (2006) study on the influence of different playing surfaces on the biomechanics of a tennis running forehand foot plant.

Answer 9

The mean values of the peak impact forces were similar with no significant difference on each surface
The only difference was the baseline surface had significantly lower baseline force than the tennis surfaces.
Reverse of what mechanical testing found.

Kinematic adjustments: No difference in initial foot angle between either group.
No difference was found in initial knee angle between groups
No difference was found in heel impact velocity between either group

Question 10

What are the characteristics of a forehand foot plant in tennis?

Answer 10

A large deceleration step which requires stability to plant the foot while hitting the ball.

Question 11

Which researchers found that impact forces were maintained when cushioning properties were changed?

Answer 11

Nigg and Yeadon 1987

Dixon et al 2000

Question 12

Which researchers found that changing cushioning properties altered kinematics?

Answer 12

Bobbart et al 1992

Hamill et al 1999

Dixon et al 2000

Question 13

What future research was suggested as a result of the Stiles and Dixon (2006) study on the influence of different playing surfaces on the biomechanics of a tennis running forehand foot plant.

Answer 13

What factors influence cushioning?
What factors were controlled during this study?
What factors may be complicating the results and interpretation of the data?

Question 14

How did the Stiles and Dixon (2007) study of the biomechanics response to systematic changes in surface cushioning properties while performing a tennis specific movement in a basic neutral shoe
build upon the 2006 study?

Answer 14

the 2007 study was a more controlled approach to understand whether variations in the cushioning properties of these shoes could influence the biomechanics test findings.
It removed the influence of changes in surface friction by systematically altering the surface cushioning properties.
it removed the influence of a sports shoe by having the participant run in plimsoles.

Question 15

What were the ground reaction force results seen in the Stiles and Dixon 2007 study?

Answer 15

There was a large range of surface impact reduction. There were three characteristic peaks during the impact phase but these began to smooth out in both the foam conditions.

Peak Impact force: higher peak impact forces were seen in the foam conditions which provided mechanically higher amounts of cushioning.

Peak impact force time of occurrence: the time to peak impact force was delayed in the foam conditions which influenced the loading rates

Peak loading rate: lower peak loading rates occurred in the foam conditions- more sillier to mechanical testing

Peak heel pressure: peak heel pressures followed similar trends to the peak loading rate - lower in foam surfaces

Cushioning perception: baseline was perceived to have the lowest level of cushioning and thicker levels gave higher cushioning - matched biomechanics variables

Question 16

Define: task orientated movement

Answer 16

A certain pattern of movement is performed in order to accomplish a task. The pattern is not open to change, otherwise the task performance may be compromised.

Question 17

What is the mechanical test for surface friction?

Answer 17

A rubber foot swings like a pendulum and hits the surface.

Gives the coefficient of friction.