1. Centre for Human Movement and Rehabilitation, University of Salford, Salford M6 6PU, UK
2. Hawkin Dynamics, Inc., Westbrook, ME 04092, USA
3. School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA 6027, Australia
4. Chichester Institute of Sport, University of Chichester, Chichester PO19 6PE, UK