Shoe-surface friction in tennis: influence on plantar pressure and implications for injury

Purpose. The different strategies employed by tennis players as a result of changes in friction properties of the playing surface are likely to influence injury incidence. Lower risk of injuries on surfaces that allow sliding has been reported. The aim of the present study was to characterise in-shoe pressure during tennis specific movements performed on a hard court and artificial clay in two surface-specific shoes.Methods. Two tennis surfaces were compared: artificial clay and cushioned acrylic hard court. Participants wore two different pairs of court-specific shoes on each surface. Seven (five males, two females) competitive tennis players performed three movements - open stance forehand, forehand plant (incorporated into a drill) and side jump. In-shoe plantar pressure distribution was recorded using the Pedar (Novel, Munich) insole system.Results. Significantly lower mean and peak pressure were measured during the side jump and running forehand plant on clay compared to hard court. Running forehand plant on artificial clay was characterised by a longer step duration and larger number of unloading episodes than on acrylic. Footwear did not influence peak pressures.Conclusions. A change in surface has a greater effect on plantar pressures than a change in shoe. The higher pressures on a hard court support an association for increased levels of overuse injuries. On clay, limiting areas of high pressure and a longer braking step could facilitate sliding by preventing sticking. Unloading episodes could also be part of the strategy aiming at sliding on clay. These differences are relevant to understand surface-specific mechanisms of injuries.