1 Department of Sports Medicine, Royal Netherlands Lawn Tennis Association, Amersfoort, The Netherlands.
2 Amsterdam Collaboration on Health and Safety in Sports, IOC Research Centre for Prevention of Injury and Protection of Athlete Health, VUmc/AMC, Amsterdam, Netherlands.
3 Johnson and Johnson Human Performance Institute, Orlando, Florida, USA.
4 London, London, UK.
5 International Tennis Federation, Valencia, Spain.