Shoe-Surface Interaction in Tennis

Centre for Sport and Exercise Sciences Faculty of Biological Sciences

Daniella Strauss Study Impetus

• Tennis match-play – Year round season – Range of surfaces

• Participation in tennis – Overall increase

• Injuries in tennis 14 12 – Site specific injury 10 incidences 8 – Proportionally twice as (Absolute 6 values) 4 many lower limb injuries in 2 0 younger players Junior Senior Veteran Age classification

– Injury mechanism Trunk Upper Limb Lower Limb The Study

• Relationship between the mechanical properties of the independent systems and their combined effect on the tennis player –Surfaces • Deflection • Stiffness

– Shoes •Mass • Impact Force • Impact Velocity • Interaction Study – Surface comparison – Shoe comparison •Maximum Force •Peak Pressure •Impulse • Pressure-time integral Mechanical Properties: Surfaces

1400

1200

Deflection (um) 1000 Deflection*** 800 Co-efficient of 600 Court Type Variation (%) 400 200 Acrylic Court 23.37 0 A crylic Court Clay Court Grass Court Clay Court 22.37 Surface Type Grass Court 35.83

700

600

500 Stiffness***

Stiffness 400 (Elastic Co-efficient of Modulus) 300

200 Court Type Variation(%) 100 Acrylic Court 24.58 0 Acrylic Court Clay Court Grass Court Clay Court 21.66 Surface Type Grass Court 47.24 Mechanical Properties: Shoes

All Court Footwear 1.20 act Force act 1.200 Grass Court Shoe p 1.00 Hard Court Shoe 1.100 0.80

1.000 Clay Court Shoe 0.60 0.40 0.900 Multi-Court Shoe 0.20 0.800

Norm Im pactForce alised 0.00 N0.700 o rm alised Im

grass hard clay multi court court court court

Relationship0.700 0.800 between 0.900 tennis 1.000 footwear 1.100 1.200 Mean NormalisedSurface impact Type force weight andNormalised impact force Shoe (19 Weight shoes values for a range of tennis tested). footwear

No significant differences found in impact force between any of the tested shoes Interaction Study Variation in Maximum Force Across the 3 Court Surfaces during Open Stance Forehand Under the Multi-shoe Condition

250.000

) 200.000

Force Velocity Relationship on the 3 Court 150.000 AMO CMO Surfaces 100.000 GMO Force (%NBW Force 4 50.000 3.5 0.000 R2 = 0.5385 3 Condition R2 = 0.5954 2.5 R2 = 0.5633 2 Acrylic Court Variation in maximum Force Across the 3 Court 1.5 Clay Court Surfaces during a Running Forehand Under the Force (%bw) Force Multi-shoe Condition.*** 1 Grass Court

0.5 350.000 0 300.000 250.000 01234 AMR 200.000 CMR Velocity (ms-1) 150.000 GMR

Force (%NBW) Force 100.000

50.000

0.000

Condition The Study Findings

• Highly significant differences in surfaces • No significance differences in tennis footwear • Trends on surfaces in relation to the velocity of the movements and the subsequent force production • Significant differences are found for the maximum force experienced by players on the 3 surface types, this is only present in the higher velocity movements Comments

• Movement velocity is the determining factor for increases in maximum impact force experienced • Rather than the surface stiffness and/or footwear condition • The players are adapting to the surface change independently of the footwear However • Is the footwear ‘permitting’ the adaptation to take place? • Is there a change in distribution of force across the area of the foot in response to surface? Thank you for listening, any questions?