Centre for Sport and Exercise Sciences Faculty of Biological Sciences Shoe-Surface Interaction in Tennis Daniella Strauss Study Impetus • Tennis match-play – Year round season – Range of surfaces • Participation in tennis – Overall increase 14 • Injuries in tennis 12 injury 10 – Site specific incidences 8 (Absolute 6 – Proportionally twice as 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) Deflection 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 1.200 1.20 1.100 1.00 All Court Footwear act Force act Grass Court Shoe 0.80 p 1.000 Hard Court Shoe 0.60 0.900 Clay Court Shoe 0.40 Multi-Court Shoe 0.800 0.20 Norm Im pactForce alised 0.00 N o rm alised Im 0.700 grass hard clay multi 0.700 0.800 0.900 1.000 1.100 1.200 court court court court Normalised Shoe Weight Surface Type Relationship between tennis footwear Mean Normalised impact force weight and impact force (19 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 ) 150.000 Force Velocity Relationship on the 3 Court 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 350.000 0.5 300.000 0 250.000 01234 AMR 200.000 -1 CMR Velocity (ms ) 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?.